HomeMy WebLinkAboutAPA127 Exh E Chp 1 2 Feb 1983SUSITNA HYDROELECTRIC,PROJEC
,FERC LICENSE APPLICATION
PROJECT NO.7114-000
As accepted by FERC.July.27.198~
DATE DUE
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Alaska Resources
Library &Information Services
Anchorage.Alaska
ALASKA RESOURCES LIBRARY
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BEFORE THE d·\kT-
FEDERAL ENERGY REGULATORY COMMISSION
APPLICATION FOR LICENSE FOR MAJOR PROJECT
SUSITNA HYDROELECTRIC PROJECT
VOLUME SA
EXHIBITE
Chapters 1 &2
FEBRUARY 1983
Prepared by:
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Alaska Resources
.Inft ation Services
chorage,Alaska
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SUSITNA HYDROELECTRIC PROJECT
iVOLU~lE 5
EXHIB,IT E CHAPTER 1
GENERAL DESCRIPTION OF THE LOCALE
SUSITNA HYDROELECTRIC PROJECT
VOLUME 5
EXHIBIT E CHAPTER 1
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GENERAL DESCRIPTION OF THE LOCALE
TABLE OF CONTENTS
Page
1 -GENERAL DESCRIPTION OF THE LOCALE .••.•••.•.•.•.•••.•••••...E-1-1
1.1 -General Sett i ng ..••••••..•.•..•.•••..•••.•••••.••.••••E-1-1
1.2 -Susitna Basin ••..••.•.•.•..••.•..••..••••••••..••.•..E-1-2
1.2.1 -Physiography and Topography .••.•••••.••.••••.E-1-2
1.2.2 -Geology and Soils .•..••.••..•.•••...••••.•.••E-1-2
1.2.3 -Hydrology •••.•,.••..•.•..•••••.••••..••••.••.•E-1-4
1.2.4 -Cl imate ••.••.••.••.•••.•.••.•••••.••.•..•.•..E-1-5
1.2.5-Vegetation •.•.••.•••••••••...••.•••••••.••.••E-1-5
1.2.6 -Wildl ife .••.••.••••••••.••.••.••••••••••.••••E-1-6
1.2.7-Fish .••••.•.•.••••.••••••••.••••...•.•.•••.•.E-1-7
1.2.8 -Land Use .•.••.••,...••..•.••..•.••.••...••.••E-1-8
1.2.9 -Recreation •.•..••..••.•••••.••.••.••..•••••.•E-1-9
GLOSSARy ••.••.••.••.••••••.••..•.•••.•••••..•.••.•.••.••.••.•.•E-1-11
LIST OF FIGURES................••••••••...•.••.•.••..•..•.•••••i
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LIST OF FIGURES
Figure E.l.l -Location of the Proposed Susitna Hydroelectric Project
Figure E.1.2 -Vicinities of the Proposed Dam Sites,Susitna
Hydroelectric Project
Figure E.l.3 -Upper Susitna River Basin
Figure E.l.4 Susitna River Drainage Basin
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1 GENERAL DESCRIPTION OF THE LOCALE
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1.1 -General Setting
The locatiofl.of the proposed Susitna Hydroelectric Project is within
the east-to-west-flowing section of the Susitna River approximately 140
miles (230 km)north-northeast of Anchorage,Alaska,and 110 miles
(180 km)south-southwest of Fairbanks,Alaska (Figure E.1.1).Two pro-
posed dams would generate electrical power for the rail belt region of
Alaska;that is,the corridor surrounding the Alaska Railroad from
Seward and Anchorage to Fairbanks.The two proposed damsites,Watana
and Devil Canyon,are 152 (246 km)and 184 (300 km)river miles up-
stream from the river's mouth at Cook Inlet.The nearest settlements
(Gold Creek,Canyon,Chulitna)are along the Alaska Railroad,.approxi-
mately 12 miles (18 km)from Devil Canyon.
The project site is within the south-central region of Alaska.This
region is geographically bounded by the Alaska Range to the north and
west,the Wrangell Mountains to the east,and the Chugach Mountains and
the Gulf of Al aska to the south.Topography is varied and i ncl udes
rugged,mountainous terrain;plateaus;and broad river valleys.
Mount McKinley,the state's single most significant geographical fea-
ture,is located on the region's northwest border.Denali National
Park,Denali State Park,and the diversity of landscapes and resources
offer a wide variety of recreational opportunities.Spruce-hemlock and
spruce-hardwood forests,wetlands,and tundra are the predominant vege-
tative types.A wide variety of wildlife and fish species are present,
including moose,car"ibou,bear,and salmon.
Approximately 50 percent of Alaska's population lives in south-central
Alaska.Anchorage is the state1s largest city with a civilian popUla-
tion in 1980 of 174,400.Fairbanks,north of the present site and out-
side south-central Alaska,is the state1s second largest urban center
with a population of 30,000.The region's economy is based on support
services,commercial fishing,mining,forestry,petroleum,and
touri sm.
South-central Alaska contains the most highly developed transportation
system in the state interconnected by paved highways and grave1secon-
dary roads.An extensive airport system ranging from the international
1eve1 to gravel stri ps and water bodies permit pl ane access into more
remote areas.The Alaska Railroad and ferry systems also serve large
portions of the region.
Air quality in the region is good.All areas outside Anchorage and
Fairbanks meet all the National Ambient Air Quality Standards.Thus,
the area is classified as attainment,and any facility which exceeded
threshold levels for pollutant emissions would be subject to the re-
quirements of the Prevention of Significant Deterioration program under
the Clean Air Act.
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1.2 -Susitna Basin
1.2.1 -Physiography and Topography
The 19,400-square-mile (50,440 km 2 )Susitna River basin is
bordered by the Al aska Range to the north,the Chul itna and
Talkeetna Mountai ns to the west and south,and the northern
Talkeetna plateau and Gulkana uplands to the east.This area is
largely within the Coastal Trough province of south-central
Alaska,a belt of lowlands extending the length of the Pacific
Mountain System and interrupted by the Talkeetna,Clearwater,and
Wrangell Mountains.
The basin has distinct and diverse combinations of landforms and
waterforms.The deep V-shaped canyon of the Sus itna Ri ver and
tributary valleys the Talkeetna Mountains-,and upland plateau to
the east are the dominant topographic forms.Elevations in the
basi n range from approximately 700 feet (210 meters)to over
6000 feet (1800 meters).Distinctive landforms include tundra
highlands,active and post-glacial valleys,and numerous lakes.
In the vicinity of the proposed impoundments (Figure E.l.2),the
river cuts a narrow,steep-walled gorge up to 1000 feet (300
meters)deep through the C1 arence Lake Upl and and Fog Lakes
Upland,areas of broad,rounded summits 3000 to 4200 feet (900 to
1260 meters)in elevation.Between these uplands,the gorge cuts
through an extensi on of the Talkeetna Mountai ns,where rugged
peaks are 6900 feet (2070 meters)high.Downstream from its
confluence with the Chulitna and Talkeetna rivers,near
Talkeetna,the Susitna traverses the Cook Inlet-Susitna Lowland,
a relatively flat region generally less than 500 feet (150
meters)in elevation.A portion of the proposed transmission
facilities,between Healy and Fairbanks,would follow the narrow
valley of the Nenana River through the northern foothills of the
Alaska Range,traverse the Tanana-Kuskokwim Lowland in a flat
region generally less than 650 feet (200 meters)in elevation
(the Tanana Flats),and then parallel a ridge on the edge of the
Yukon-Tanana Upland.
1.2.2 -Geology and Soils
The regional geology of the Susitna Basin area has been exten-
sively studied and is documented.The upper Susitna Basin lies
within what is geologically called the Talkeetna Mountains area.
This area is geologically complex and has a history of at least
three periods of major tectonic deformation.The oldest rocks
exposed in the region are volcanic flows and limestones which
were formed 250 to 300 million years before present (m.y.b.p.)
and which are overlain by sandstones and shales dated approxi-
mately 150 to 200 m.y.b.p.A tectonic event approximately 135 to
180 m.y.b.p.resulted in the intrusion of Jarge diorite and
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1.2 -Susitna Basin
granite plutons,which caused intense thermal metamorphism.This
was followed by marine deposition of silts and clays.The
argi 11 ites and phyll ites whi ch predomi nate at Devil Canyon were
formed from the silts and clays during faulting and folding of
the Talkeetna Mountains area in the Late Cretaceous period (65 to
100 m.y.b.p.).As a result of this faulting and uplift,the
eastern portion of the area was elevated and the oldest volcanics
and sediments were thrust over the younger metamorphics and sedi-
ments.The major.area of deformation during this period of
act i vity was southeast of Devil Canyon and i ncl uded the Watana
area.The Talkeetna Thrust Fault,a well-known tectonic feature
which has been identified in the literature,trends northwest
through this region.This fault was one of the major mechanisms
of this overthrusting from southeast to northwest.The Devil
Canyon area was probably deformed and subjected to tectonic
stress during the same period,but no major deformations are
evident at the site.
The diorite pluton that forms the bedrock of the Watana site was
intruded into sediments and volcanics about 65 m.y.b.p.The
andesite and basalt flows near the site have intruded the pluton.
During the Tertiary period (20 to 40 m.y.b.p.)the area surround-
i ng the sites was again upl ifted by as much as 3000 feet (900
meters).Si nce then,widespread erosion has removed much of the
older sedimentary and volcanic rocks.During the last several
million years,at least two alpine glaciations have carved the
Talkeetna Mountains into the ridges,peaks,and broad glacial
plateaus seen today.Postglacial uplift has induced downcutting
of streams and rivers,resulting in the deep,V-shaped canyons
that are evident today,particularly at the Vee and Devil Canyon
damsites.This erosion is bel ieved to be still occurring,and
virtually all streams and rivers in the region are considered to
be actively downcutting.This continuing erosion has removed
much of the glacial debris at high elevations,but very little
alluvial deposition has occurred.
The resulting 1andscape consists of barren bedrock mountai ns,
glacial till-covered plains,and exposed bedrock cliffs in can-
yons and along streams.Cl imatic conditions have retarded the
development of topsoil.Soils are typical of those formed in
cold,wet climates and have developed from glacial till and out-
wash.They include the acidic,saturated,peaty soils of poorly
drained areas;the acidic,relatively infertile soils of the
forests;and raw gravels and sands along the river.The upper
basin is generally underlain by discontinuous permafrost.
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1.2 -Susitna Basin
1.2.3 -Hydrology
The entire drainage are2 of the Susitna River is about 19,400
square miles (50,440 km ),of which the basin above Gold Creek
comprises approximately 6160 square miles (16,016 km 2 )(Figures
E.1.3 and E.1.4).Three glaciers in the Alaska Range feed forks
of the Sus i tna Ri ver and flow southward for about 18 mil es (29
km)before joining to form the mainstem of the Susitna River.
The river flows an additional 55 miles (88 km)southward through
a broad valley,where much of the coarse sediment from the gla-
ciers settles out.The river then flows westward about 96 miles
through a narrow valley with the constrictions in the Devil Creek
and Devil Canyon areas creating violent rapids.Numerous small,
steep-gradient,clear-water tri butaries flow to the Susitna in
this reach of the river.Several of these tributaries cascade
over waterfall s as they enter the gorge.As the Susitna curves
south past Gold Creek,12 miles (19 km)downstream from Devil
Canyon,its gradient gradually decreases.The river is joined
about 40 miles (64 km)beyond Gold Creek in the vicinity of
Talkeetna by two major rivers,the Chulitna and Talkeetna.From
this confluence,the Susitna flows south through braided channels
about 97 miles (155 km)until it empties into Cook Inlet near
Anchorage,approximately 318 miles (509 km)from its source.
(a)Flows
The Susitna River is typical of unregulated northern glacial
rivers with high,turbid summer flow and low,clear winter
flow.Runoff from snowmelt and rainfall in the spring
causes a rapid increase in flow in May from the low dis-
charges experi enced throughout the wi nter.Peak annual
floods usually occur during this period.ApprOXimately 80
percent of the annual flow occurs between May and September.
At Gold Creek,average fl ows approach 6000 cubi c feet per
second (cfs)in October,the start of the water year.The
flow rapidly decreases in November and December as the river
freezes.Low flows of about 1000 cfs occur in March and
April.At breakup,flows are over 13,000 cfs in May and
peak at about 27,700 cfs in June.Flows gradually decrease
to 24,000 cfs in July,22,000 cfs in August,and 13,000 cfs
in Se ptember.
Associated with the higher spring flows is a 100-fold in-
crease in sediment transport whi ch persists throughout the
summer.The large,suspended sediment concentration in the
June-to-September time period causes the river to be highly
turbid.Glacial silt contributes most of the turbidity of
the river when the glaciers begin to melt in late spring.
Rainfall-related floods often occur in August and early
September,but generally these floods are not as severe as
the spring snowmelt floods.
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1.2 -Susitna Basin
As the weather begins to cool in the fall,the glacial melt
rate decreases and the flows in the river gradually decrease
correspondi ng1y.Because most of the ri ver suspended sedi-
ment is caused by glacial melt,the river also begins to
clear.Freeze up normally begins in October and continues
to progres s up river through ear 1y December.The river
breakup generally begins in late April or early May near the
mouth and progresses upstream with breakup at the damsite
occurring in mid-May.
(b)Water Quality
The Susitna River is a fast-flowing,cold-water glacial
stream of the calcium bicarbonate type containing soft to
moderately hard water during breakup in summer,and moder-
ately hard water in the winter.Nutrient concentrations
(name 1y,nitrate and orthophosphate)exi st in 10w-to-
moderate concentrations.Oi ssol ved oxygen concentrat ions
typically remain high,averaging about 12 mg/l during the
summer and 13 mgj1 during winter.Percentage saturation of
di sso 1ved oxygen generally exceeds 80 percent and averages
near 100 percent in the summer.Winter saturation levels
decline slightly from the summer levels.Typically,pH
values range between 7 and 8 and exhibit a wider range in
the summer compared to the wi nter.Our i ng summer,pH
occasionally drops below 7,which is attributed to organic
acids in the tundra runoff.True color,also resulting from
tundra runoff,disp1 ays a wider range duri ng summer than
winter.Values have been measured as high as 40 color units
in the vicinity of the damsites.Temperature remains at or
near DOC during winter,and the summer maximum is 14°C.
Alkalinity concentrations,with bicarbonate as the dominant
anion,are 10w-to-moderate during summer and moderate-to-
high during winter.The buffering capacity of the river is
relatively low on occasion.
The concentrations of many trace e1 ements monitored in the
river were low or within the range characteristics of nat-
ural waters.However,the concentrations of some trace ele-
ments exceeded water quality guidelines for the protection
of freshwater aquatic organisms.These concentrations are
the result of natural processes because,with the exception
of some placer mining activities,there are no man-induced
sources of these elements in the Susitna River Basin.
Concentrations of organic pesticides and herbicides,
uranium,and gross alpha radioactivity were either .1ess than
their respective detection limits or were below levels con-
sidered to be potentially harmful to aquatic organisms.
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1.2 -Susitna Basin
1.2.4 -Climate
As in most of Alaska,winters are long,summers.are short,and
there is considerable variation in daylight between these sea-
sons.Higher elevations in the upper basin are characterized by
a continental climate typical of interior Alaska.The lower
floodplain falls within a zone of transition between maritime and
continental climatic influences.From the upper to the lower
basin,the climate becomes progressively wetter,with increased
cloudiness and more moderate temperatures.
At Talkeetna,which is representative of the lower basin,average
a nnua 1 preci pitat ion is about 28 inches,of whi ch 68 percent
falls between May and October,and annual snowfall is about 106
inches.Monthly average temperatures range from gOF (-l3°C)in
December and January to 58°F (14°C)in July.
1.2.5 ~Vegetation
The Susitna Basin occurs within an ecoregion classified as the
Alaska Range Province of the Subarctic Division.The major vege-
tation types in the upper basin are low mixed shrub,woodland and
open bl ack spruce,sedge-grass tundra,mat and cushion tundra,
and birch shrub.These vegetation types are typical of vast
areas of interior Alaska and northern Canada,where plants exhi-
bit slow.or stunted growth in response to cold,wet,and short
growi ng seasons.Deciduous and mixed conifer-deciduous forests
occur at lower elevations in the upper basin,primarily along the
Susitna River,but comprise less than three percent of the upper
basi narea.These forest types have more robust growth charac-
teristics than the vegetation types at higher elevations and are
more comparable to vegetation types occurring on the floodplain
farther downstream.
The floodplain of the lower river is characterized by mature and
decadent balsam poplar forests,birch-spruce.forest,alder
thickets,and willow-balsam poplar shrub communities.The
willow-balsam poplar shrub and alder communities are the earliest
to establish on new gravel bars,followed by balsam poplar for-
ests and,eventually,by birch-spruce forest.
Each of the transmission corridors cro_ses several vegetation
types.The Healy-to-Fa irbanks transmi ss i on corri dor i ncl udes
ridges,wetlands,and rolling hills with areas of open spruce
forests,open deciduous forests,mixed forests,shrublands,and
wet tundra.The Willow-to~Anchorage transmission corridor passes
through closed birch forests,mixed conifer-deciduous forest,wet
sedge grass marshes,and open and closed spruce stands.The
Willow-to-Healy transmission corridor traverses a wide variety of
vegetat i on types,from closed spruce-hardwood forests in the
south to tundra and shrubland in the north.
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1.2.6 -Wildlife
Big gcrne in the upper basin include caribou,moose,brown bear,
black bear,wolf,and Dall sheep.Caribou migrate through much
of the open country in the upper basin,and important calving
grounds are present outs ide the impoundment zone.Moose are
fairly cornmon in the vicinity of the proposed project,but high
qual ity habitat is rather 1 imited.Moose al so frequent the
floodplain of the lower river,especially in winter.Brown bear
occur throughout the project vicinity,while black bear are
1 argely confined to the forested habitat along the river;popul a-
tions of both species are healthy and productive.Several wolf
packs have been noted using the area.Dall sheep generally in-
habit areas higher than 3000 feet (910 meters)in elevation.
Furbearer species of the upper basin include red fox,wolverine,
pine marten,mink,river otter,short-tail ed weasel,1east
weasel,lynx,muskrat,and beaver.Beavers becomeincreas'ingly
more evident farther downstream.Sixteen species of small mcrn-
mal s that are characteristic of interior Al aska are known to
occur in the upper basin.
Bird popul ations of the upper basin are typical of interior
Al aska but sparse in comparison to those of more temperate
regions.Generally,the forest and woodland habitats support
higher densities of birds than do other habitats.In regional
perspective,ponds and lakes in the vicinity of the proposed im-
poundments support rel ativel y few waterbirds.Ravens and rap-
tors,including bald and golden eagles,are conspicuous in the
upper basin.Bald eagles also nest along the lower river.No
known peregrine falcon nests ex ist in or near the reservoir area,
although one nest exists near the northern leg of the transmis-
sion corridor.This nest has not been known to be active since
the early 1960s.
1.2.7-Fish
Fi shery resources in the Susitna River comprise a major portion
of the Cook Inlet commercial salmon harvest and provide sport
fishing for Anchorage and the surrounding areas.
Anadromous fish in the Susitna basin include all five species of
P·acific salmon:pink (humpback);chum (dog);coho (silver);
sockeye (red);and chinook (king)salmon.The Susitna River is a
migrational corridor,spawning area,and juvenile rearing area
for the five species of salmon from its point of discharge into
Cook Inlet to Devil Canyon,where salmon appear to be prevented
from moving upstream by the water velocity at high flow.Spawn-
ing occurs primarily in the tributaries,sloughs,and side
channels;limited spawning occurs in the mainstem.Preliminary
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1.2 -Susitna Basin
data indicate that the majority of the 1981 Susitna River escape-
ment of sockeye,pink,chum,and coho salmon spawned above the
Yentna River confluence and below Curry Station.Data also show
that sloughs between Devil Canyon and Talkeetna provide spawning
habitat for pink,sockeye,and chum salmon.Field data show that
juvenile chinook and coho salmon occur throughout the lower
river,concentrating at slough and mainstem habitat during winter
and at tributary mouths during summer.
Grayl i ng abound in the cl ear-water tri butari es of the upper
basin;these populations are relatively unexploited.Grayling as
well as lake trout also inhabit many lakes.The mainstem Susitna
has populations of burbot and round whitefish,often associated
with the mouths of clear-water tributaries.Dolly Varden,hump-
back whitefish,sculpin,sticklebacks,and long-nosed suckers
have also been found in the drainage.Rainbow trout,like the
anadromous species,have not been found above Devil Canyon.
1.2.8 -Land Use
Because of limited access,the project area in the upper basin
has retained a wilderness character.There are no roads to the
project vicjnity,but there are several off-road vehicle and sled
trails.Although rough,dirt landing strips for light planes are
not uncommon,floatplanes provide the principal means of access
via the many lakes in the upper basin.
Perhaps the most significant land use over the past three decades
has been the study of hydropower potential of the Susitna River.
The area is also used by hunters,white-water enthusiasts,fish-
ermen,trappers,and miners.Raft float trips are taken from the
Dena 1i Hi ghway on the Sus i tna or Tyone Ri vers down to either Vee
or Devil Canyons.Both guided and non-guided hunting occur with-
in the project area,part icul arly near Stephan,Fog,Cl arence,
Watana,Deadman,Tsusena,and Big Lakes.A few wilderness rec-
reationlodges and private cabins,single and in small clusters,
are scattered throughout the basin,especially on the larger
1 akes.
Most of the lands in the project area and on the south side of
the ri ver have been sel ected by the Natives under the Al aska
Native Claims Settlement Act.Lands to the north are generally
federal and are managed by the Bureau of Land Management.The
state has selected some lands on the north side of the river,and
there are many small,scattered private holdings in the upper
basin.The U.S.Department of the Interior has preserved part of
the area withi n the project impoundment zones as a Power Site
Classification (No.443).
Mineral exploration and mining have been limited in the immediate
project area.Mining in the upper Susitna River Basin has been
low in claims density and characterized by intermittent activity
since the 1930s.
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The transmission corridors outside the dam and impoundment areas
(Willow to.Anchorage and Healy to Fairbanks)traverse lands with
a somewhat hi gher degree of use.Most of the 1and withi n the
corridors.however.is undeveloped.
Wetlands cover large portions of the Upper Susitna River Basin.
including riparian zones along the mainstem Susitna.sloughs and
tributary streams.and numerous lakes and ponds on upland pla-
teaus.In addition.extensive areas of wet sedge-grass tundra
are classified as wetlands by the U.S.Army Corps of Engineers
for purposes of Section 404 permitting.The U.S.Soil Conserva-
tion Service has determined that there are no prime farmlands.
rangelands.or forests within the upper Susitna Basin.
1.2.9 -Recreation
The large diversity of landscapes and resources in south-central
Alaska offer a wide variety of outdoor recreational opportuni-
ties.The region's largest and most popular attraction is the
Denal i National Park and Preserve.Adjacent to this park is
Denali State Park.one of 53 state parks in the south-central
region of Alaska.Other state parks in the vicinity include
Nancy Lake State Park.70 m"i1es (112 km)from Anchorage.and
Chugach State Park.10 mi 1 es (16 km)east of Anchorage.All of
the above parks offer facilities for h"iking.camping.fishing.
and picnicking.Other government land near the project area
i nc1 udes the Sus itna Fl ats State Game Refuge and the Chugach
National Forest.
North of the Susitna project site.the U.S.Bureau of Land Man-
agement maintains the 4.4-mi11ion-acre Denali Planning Block.
The bureau maintains several small campgrounds and picnic areas.
boat launches.and a canoe trail.
Numerous private facil ities "in the region provide additional for-
mal and informal recreation opportunities.These include remote
lOdges.cabins.restaurants.airstrips.and flying and boat
servi ces •
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GLOSSARY
Alluvial deposition -fine grained material left by rivers
Anadromous fi sh -fi sh that ascend freshwater ri vers from the ocean
in order to breed
Argillites - a compact rock derived from either mudstone or shale
Conifer -forest containing both evergreen trees (pine.spruce.etc.)
and those that lose their leaves on an annual basis
Diorite plutons -igneous rocks formed at considerable depth interme-
diate in composition between acidic and basic rocks
Escapement -the process by which adult anadromous fish migrate from
the ocean to their freshwater spawning sites
Igneous -formed by solidification from a molten or partially molten
state
Phyllites -an argillaceous rock commonly formed by regional
metamorphism and intermediate in grade between slate and mica
schist
Schist - a medium or coarse-grained metamorphic rock with subparallel
orientation of the mica material
Tectonic -pertaining to rock structure and external forms resulting
from the deformation of the earth1s crust
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\.
~~~-.........,
\\,
L~
)
...-/.
.""..
t7
~
LOCATION MAP
LEGEND:
---PRIMARY PAVED UNDIVIDED HIGHWAY
IIIIIIIIII.RAILROAD
_...-WATERWAY
&DAMSITES
o 20 40MILES
SCALE
LOCATION OF THE PROPOSED
SUSITNA HYDROELECTRIC PROJECT FIGURE E.I.I
WATANA ,VIEW UPSTREAM
DEVIL CANYON,VIEW UPSTREAM
VICINITIES OF THE PROPOSED
DAM SITES)SUSITNA HYDROELECTRIC PROJECT
FIGURE E.1.2
LEGEND:
~DAMSITES
'~oI'.,.
~.....'7-
~.~
~,...~~
,A
,.~
~
.,-.'--.........r·'"""
./..;\f-..I(..<-(".
>l.--."\../........~....)~.,\.'\::~".y I·''"O~.\
-,,--"'.7 (~CR,._.1\...--.'......,.,0£[.~c::-~
.V )'''v''-./'('.--".r~(,'-...'..-.-"~~-......
."./-:-...._----v"\\c,.'\.,/\.r I~..\.,,-...~.~............,---.._...-",.../\
./".'";'~pO-."~~).,...,---.~~"
,.',•.,!?~...,~..J /~p ,.1/,.~/-,'-7°>."'...---,.-'<>tV"..r "..~//~.""'''''~.J I
---./................(.~.-:-...,..r----...~"'~.-r'../~~..~
./t.v-~\·\.,·.......·_./·"-.........·v -/',d./<')
.f "----=.~"+.
"J '\J',1 .."~~.Lo~"........./7-.(..~\-:1
r'r "\.\'\,,\...--.J/j (/,\~o ~)r(\~~_)
'1 ---:~\~\.LAKE (
. .~I "---..:~LAICE LOUISE
\\.R\Y£O h ~'.~\
'.".Q~,~\)L....J)\((I /~-_._._.
\.(.f--.r-._."...,J
'L.~'StAll v 10 ZO MILES!
SUSITNA RIVER BASIN UPSTREAM OF GOLD CREEK
FIGURE E.!.!
COOK INLET
\
BASIN
;;
(
",,-
/
/
/
/
/
/
I
/
/
/
/
/
/'
"'"/'
SUSITNA RIVER "'"
DRAINAGE BASIN ~/'
",,-/"'"",,-/
.",,-
.",,-
..-"'-
,."..,."..~"'-
""-,,,,-"'-
//LOWER DRAINAGE
",,-
/'
/
/'
/
/
I
I
/
I
I
I
/
/
I
/
I
/
/
/
/
I
/
/
I
I
I
(
\(LOWER DRAIN~~~~N,~/'",/.~"/~..,..""/''/,'''''','--"'-,",,
'\
\
\
\
SUSITNA R
UPPER DRAINAGE
BASIN
/----------
'"--,/......._-----'"--......./.....
/,
/,
\
\
l
I
I
I
/
/6'/
I
/
/
MIDDLE
I
\
\
\
\
6<7 V \\
\
\
)I \
Q \
\
\
I
I
/,.,...-------_.---/
/
//'"/
////
..................-,,/---
..--
o 10 20 MILES
SCALE !"'.~~~~iiiiiiiiiiiiiiiiiiiiiiiiii
IVER DRAINAGE BASIN
FIGURE E 1.4
-.
S'USITNA HYDROELECTRIC PROJECT
.VOLUME SA
EXHIB IT E CHAPTER 2
WATER USE AND QUALITY
SUSITNA HYDROELECTRIC PROJECT
-VOLUME 5A
EXHIBIT E CHAPTER 2
.-
r
T
WATER USE AND QUALITY
TABLE OF CONTENTS
1 -INTRODUCTION •.••••.••••.••..••••••••••.•••••.••••.•••••••.E-2-1
2 -BASELINE DESCRIPTION ••••••••••••••••••••••••••••••••••••••E-2-3
2.1 -Susitna River Morphology ••..•••••••••••••••.••••••••E-2-4
2.1.1 -Mainstem ••••••••.•••••••••••.••••••••.••••.•E-2-4
2.1.2 -Sloughs ..•••••..•••••.•.•••.••..•.•••.••••••E-2-10
2.2 -Susitna River Water Quantity ••.•••.••.•••••••••.••••E-2-10
2.2.1 -Mean Monthly and Annual Flows •••••••••••••••E-2-10
2.2.2 -Floods -...........•....,•...•....•..•.E-2-14
2.2.3 -Flow Vari abil ity ••••••••••••••••••••••••••••E-2-15
2.2.4 -Water Levels .•.............•.......•........E-2-17
2.3 -Susitna River Water Quality •.••.••••.••••••.•••••••.E-2-18
2.3.1 -Water Temperature •••••••••••••••••••••••••••E-2-20
2.3.2 -Ice ..•.......................................E-2-22
2.3.3 -Bedload and Suspended Sediments •••••••••••••E-2-25
2.3.4 Turbidity •••••••..•..•.•.•.••.••••••.•••••.•E-2-30
2.3.5 -Vertical Illumination •••••••••••••••••••••••E-2-31
2.3.6 -Dissolved Gases ••••.••••••••••••••••.•••••••E-2-31
2.3.7 -Nutrients .•.••..•.••.•••.•••.••••••••...•...E-2-32
2.3.8 -Other Parameters ••••.•••••.•••••••••••.•.•••E-2-33
2.3.9 -Water Quality Summary 1:-2-38
2.4 -Basel ine Ground Water Conditions •••••••••••••••.••••E-2-39
2.4.1 -Description of Water Table and Artesian
Conditions ...••.•..••.....•....•..•••••.••.•E-2-39
2.4.2 -Hydraul ic Connection of Ground Water and
Surface Water ..•••.•••••..••..•.••..••..•..•E-2-40
2.4.3 -Locations of Springs,Wells,and Artesian
Flows .•.•...••.•.••••..•••..•..••••.••••...•E-2-40
2.4.4 -Hydraulic Conn€ction of Mainstem and Sloughs.E-2~40
2.5 -Existing Lakes,Reservoirs,and Streams •••••••••••••E-2-41
2.5.1 -Lakes and Reservoirs •.•••••••••.•••••••..•••1:-2-41
2.5.2 -Streams E-2-42
2.6 -Existing Instream Flow Uses •••••••••.••••••••••.••••£-2-43
2.6.1 -Downstream Water Ri ghts ••••••.••..•••...•..•E-2-43
2.6.2 -Fi shery Resources E-2-44
2.6.3 -Navigation and Transportation ••••••••••.••••-E-2-44
2.6.4 -Recreati o-n E-2-48
2.6.5 -Riparian Vegetation and Wildlife Habitat .•••£-2-48
2.6.6 -Waste Assimilative Capaclty •••••••••••••••••E-2-48
2.6.7 -Freshwater Recruitment to Cook Inlet
Estuary .••..••..•...•••.••......••...•..••.••E-2-49
TABLE OF CONTENTS
2.7 -Access Plan ..••••.•.••••...••.•.•.••.•••.•.•••..•••.
2.7•1 -Flow 5 •••••••••••••••••••••••••••••••••••••••
2.7.2 -Water Quality •.•..••.••.••...•.•..•••.••••.•
2.8 -Transmission Corridor •••••••••••••••••••••••••••••••
2.8.1 -Flows ..............•..•....•..•..•..........
2.8.2 -Water Quality ••..................••••.••••••
3 -PROJECT OPERATION AND FLOW SELECTION ••••••••••••••••••••••
3.1 -Project Reservoirs •••.••..••.••.••••••••.••.•..•...•
3.1.1 -Watana Reservoir Characteristics ••••••••••••
3.1.2 -Devil Canyon Reservoir Characteristics ••••••
3.2 -Simulation Model and Selection Process •••••.••••••••
3.3 -Pre-project Flows ..........•.....•...•••.••.••••••..
3.4 -Project Flows ••.••..•..•.•••.•.•........•..........•
3.4.1 -Range of Flows ...•.••..••.•..••.•••.••••...•
3.4.2 -Timing of Flow Releases ••••••••••••.••••••••
3.5 -Energy Production and Net Benefits •••••••••.••••••••
3.6 -Fishery and Instream Flow Impacts on Flow Selection.
3.6.1 -Susitna River Fishery Impacts •••••••.••••••••
3.6.2 -Tributary Fishery Impacts •.•••••••••••••••••
3.6.3 -Other Instream Flow Considerations ••••••.•••
3.7 -Operational Flow Scenario Selection •••••••••••••••••
3.8 -Maximum Drawdown Selection •.•••••••••••••.••••••••••
4 -PROJECT IMPACT ON WATER QUALITY AND QUANTITy ••••••••••••••
4.1 -Watana Development •••••••••••••••••••••••.••••••••••
4.1.1 -Watana Constructi on •••••.•••••••••••••••••••
4.1.2 -Impoundment of Watana Reservoir •••••••••••••
4.1.3 -Watana Operation •.••••••.••••••.••••••••••••
4.2 -De vil Ca nyon De ve 1 opment ••••••••••••••••••••••.•••••
4.2.1 -Watana Operation/Devil Canyon Construction ••
4.2.2 -Watana Operation/Devil Canyon Impoundment •••
4.2.3 -Watana/Devil Canyon Operation •••••••••.•••••
4.3 -Access Pl an ...................•..........•.....••...
4.3.1 -Flows ..................•......•...........•.
4.3.2 -Water Quality .
4.4 -Transmission Corridor ••.•••••••••••••.••••••.••••••.
5 -AGENCY CONCERNS AND RECOMMENDATIONS •••••••••••••••••••••••
6 -MITIGATION~ENHANCEMENT,AND PROTECTIVE MEASURES •••••••••.
6.1 -Introduction .
6.2 -Mitigation -Construction •••.•.•••••••••••••••••••••
6.2.1 -Borrow Areas ••s •••••••••••••••••••••••••••••
6.2.2 -Contamination by Petroleum Products ••••••.••
6.2.3 -Concrete Contamination •••••.••••••.•••••••••
6.2.4 -Support Facilities ••••••••••••••••••••••••••
6.2•5 -Ot he r 5 ••••••••••••••••••••••••••••••••••••••
6.3 -Mitigation -Watana Impoundment ••••••••••••••••••.••
Page
E-2-50
f>2-50
E-2-51
E-2-51
E-2-52
E-2-52
E-2-55
E-2-55
E-2-55
E-2-55
E-2-55
E-2-56
E-2-57
E-2-57
E-2-58
E-2-58
E-2-59
E-2-59
E-2-60
E-2-60
E-2-62
E-2-62
E-2-65
E-2-65
E-2-65
E-2-78
E-2-101
E-2-140
E-2-140
E-2-148
E-2-154
E-2-174
E-2-175
E-2-175
E-2-176
E-2-179
E-2-181,
E-2-181
E-2-181
E-2-182
E-2-183 ,-
E-2-183
E-2-184
E-2-185
E-2-185
.....
TABLE OF CONTENTS
Page
6.4 -Mitigation -Watana Operation E-2-186
6.4.1 -Flows E-2-186
6.4.2 -River Morphology E-2-187
6.4.3 -Temperature ....................•............E-2-187
6.4.4 -Total Dissolved Gas Concentration E-2-187
6.5 -Mitigation -Devil Canyon Construction E-2-188
6.6 -Mitigation -Devil Canyon Impoundment E-2-188
6.7 -Mitigation -Devil Canyon/Watana Operation E-2-189
6.7.1 -Flows E-2-189
6.7.2 -Temperature E-2-189
6.7.3 -Total Dissolved Gas Concentration E-2-189
6.8 -Mitigation -Access Road and Transmission Lines ...•.E-2-189
-
REFERENCES
GLOSSARY
LIST OF TABLES
E-2-195
.....LIST OF FIGURES...............................................iv
LIST OF PHOTOGRAPHS ..............................•............xiii
APPENDIX E.2.A -Relationship Between Main Channel Flow
and Slough Physical Habitat Variables
"""
LIST OF TABLES
,~
-
.....
.....
-
E.2.1
E.2.2
E.2.3
E.2.4
E.2.5
E.2.6
E.2.7
E.2.8
E.2.9
E.2.10
E.2.11
E.2.12
E.2.13
E.2.14
E.2.15
E.2.16
E.2.17
E.2.18
E.2.19
E.2.20
E.2.21
E.2.22
E.2.23
E.2.24
Susitna ~ver Reach Definitions
Periods of Record for Gaging Stations
USGS Streamflow Summary
Fi lled Streamflow Summary
Modi fi ed Streamflow Summary
Watana Pre-Project Monthly Flow Modified Hydrology
Devi 1 Canyon Pre-Project Monthly Flow Modified Hydrology
Gold Creek Pre-Project Monthly Flow Modi fi ed Hydrology
Sunshine Pre-Pr~ject Monthly Flow Modified Hydrology
Susitna Pre-project Monthly Flow Modified Hydrology
Instantaneous Peak Flows of Record
Distribution Statistics for Annual Instantaneous Peak Flows
Compari son of Susitna Regional Flood Peak Estimates with
USGS Methods for Gold Creek
HEC-2 Water Surface Elevations
Deadman Creek to Devi 1 Creek for Select Watana Flows
HEC-2 Water Surface Elevations
Dev;1 Canyon to Talkeetna for Select Gold Creek Flows
Detecti on Li mi ts and Cri teri a for Water Quali ty Parameters
Parameters Exceedi ng Cri teri a by Stati on and Season
Locati on of Open Leads Observed Between Portage Creek and
Talkeetna During Mid-Winter 1982
1981 Bedload Transport Data Susi tna Ri ver Basi n
Suspended Sed;ment at Go 1d Creek
May to September 1952
1982 Turbidity and Suspended Sediment Analysi s
Susitna River at Gold Creek -Monthly Summary of Suspended
Sediment!WY 1953
Si gni fi cant Ion Concentrati ons
Lakes Potenti ally Impacted by Access Roads and/or
Tr ansmi ssi on Li nes
i
E.2.25
E.2.26
E.2.27
E.2.28
E.2.29
E.2.30
E.2.31
E.2.32
E.2.33
E.2.34
E.2.35
E.2.36
E.2.37
E.2.38
E.2.39
E.2 .40
E.2.41
E.2.42
E.2.43
E.2 .44
E.2.45
E.2.46
E.2.47
E.2.48
E.2.49
Streams and Sloughs to be Parti ally or Completely
Inundated by Watana Reservoir
Streams and Sloughs to be Partially or Completely
Inundated by Devi 1 Canyon Reservoi r
Downstream Tributaries Potenti ally Impacted by Project Operation
Summary of Surface Water and Ground Water Appropri ati ons
I~ater Ri ght Appropri ati ons Adjacent to the Susi tna Ri ver
Susitna River -Limitations to Navigation
Temporal Salinity Estimates for Select Cook Inlet Locations
Esti mated Low and Hi gh Flows at Access Route Stream Crossi ng s
Avai lable Streamflow Records for Major Streams Crossed
by Transmission Corridor
Monthly Flow Requirements at Gold Creek
Net Benefits for Susitna Hydroelectric Project Operating
Scenari os
Minimum Downstream Flow Requirements at Gold Creek
Watana Flows for Three Fi lli ng Cases
Gold Creek Flows for Three n lling Cases
Monthly Pre-Project and Watana Fi 11i ng Flows at Gold Creek,
Sunshine and Susitna Station
Monthly Operating Rule Curves at Watana and Devi 1 Canyon
Watana Operation -Monthly Minimum Energy Demands
Wat ana Post-Project Month ly Flow
Watana Operation
Monthly Maximum,Minimum,and Mean Flows at Watana
Gold Creek Post-Project Monthly Flow
Watana Operation
Monthly Maximum,Minimum,and Mean Flows at Gold Creek
Sunshine Post-Project Monthly Flow
Watana Operation
Monthly Maximum,Mi nimum.and Mean Flows
at Sunshi ne
Susitna Post-Project Monthly Flow
Watana Operation
Monthly Maximum,Minimum,and Mean Flows at Susitna
i i
.-E.2.50 Watana Fi xed Cone Valve Operati on
E.2.51 Watana/Devi 1 Canyon Operati on -Monthly Mi nimum Energy Demand s
E.2.52 Watana Post-Project Monthly Flow
Watana/Devi 1 Canyon Operati on
-E.2.53 Devi 1 Canyon Post-Project Monthly Flow
Watana/Devi 1 Canyon Operati on
E.2.54 Gold Creek Post-Project Monthly FlowrWatana/Devi 1 Canyon Operati on!
E.2.55 Monthly Maximum,Minimum,and Mean Flows at,..,.Devi 1 Canyon
E.2.56 Sunshine Post-Project Monthly Flow-Wat an a/Devi 1 Canyon Operati on
E.2.57 Susitna Post-Project Monthly Flow
....Watana/Devi 1 Canyon Operati on
E.2.58 Devi 1 Canyon Fixed Cone Valve Operation
....
P-
I
....
-
-iii
,."'".LIST OF FIGURES
-
E.2.1
E.2.2
E.2.3
E.2.4
Ee2.5
E.2.6
E.2.7
E.2.8
E.2.9
E.2.1O
E.2.11
E.2.12
E.2.13
E.2.14
E.2.15
E.2.16
E.2.17
E.2.18
E.2.19
Eo 2.20
E.2.21
Eo 2.22
E.2.23
E.2.24
E.2.25
E.2.26
E.2.27
E.2.28
E.2.29
Streamflow Gaging and Water Quality Monitoring Stations
Single-Channel River Pattern
Split-Channel River Pattern
Braided-Channel River Pattern
Multi-Channel River Pattern
Susitna River Thalweg and Water Surface Profil es -
Deadman Creek to Devil Creek
Susitna River Thalweg and Water service Profiles -
Devil Canyon to RM 126
Susitna River Thalweg and Water Surface Profiles-RM 126 to Talkeetna
Susitna River Thalweg Profile-Sunshine to Cook Inlet
Cross-Section Number 32 Near Sherman (River Mile 129.7)
Susitna River Plan Index Map
Susitna River Plan RM 152 to RM 145
Susitna River Plan RM 145 to RM 139
Susitna River Plan RM 138 to RM 132
Susitna River Plan RM 131 to RM 125
Susitna River Plan RM 124 to RM 118
Susitna River Plan RM 117 to RM 111
Susitna River Plan RM 110 to RM 104
Susitna River Plan RM 103 to RM 101
Susitna River Plan RM 100 to RM 97
Slough 9 Thalweg Profile
Slough 9 Cross Section
Low-Flow Frequency Analysis of Mean Annual Flow at Gold Creek
1964 Natural Flows -Cantwell,Watana,and Gold Creek
1967 Natural Flows -Cantwell,Watana,and Gold Creek
1970 Natural Flows -Cantwell,Watana,and Gold Creek
Annual Flood Frequency Curve -Susitna River Near Denali
Annual Flood Frequency Curve -Susitna River near Cantwell
Annual Flood Frequency Curve -Susitna River at Gold Creek
iv
E.2.30
E.2.31
E.3.32
E.2.33
E.2.34
E.2.35
E.2.36
E.2.37
E.2.38
E.2.39
E.2.40
E.2.41
E.2.42
E.2.43
E.2.44
E.2.45
E.2.46
E.2.47
E.2.48
E.2.49
E.2.50
E.2.51
E.2.52
E.2.53
E.2.54
E.2.55
E.2.56
E.2.57
E.2.58
Annual Flood Frequency Curve -Maclaren River near Paxson
Annual Flood Frequency Curv~-Chulitna ~ver near Talkeetna
Annual Flood Frequency Curve -Talkeetna River near Talkeetna
Annual Flood Frequency Curve -Skwentna River near Skwentna
Design mmensionless Regional Frequency Curve -
Annual Instantaneous Flood Peaks
Watana -Natural Flood Frequency Curve
Devi 1 Canyon -Natural Flood Frequency Curve
Susitna River at Gold Creek Flood Hydrographs -May -July
Susitna River at Gold Creek Flood Hydrographs -August -October
Monthly and Annual Flow Duration Curves -Susitna River near Denali,
Susitna ~ver near Cantwell,Susitna ~ver at Gold Creek
Monthly and Annual Flow Duration Curves -Susitna River at
Susitna Station
Monthly and Annual Flow Duration Curves -Maclaren River at Paxson
Monthly and Annual Flow Duration Curves -Chulitna River near
Talkeetna,Talkeetna ~ver near Talkeetna
Susitna River at Gold Creek -High-Flow Frequency Curves -January
Susitna ~ver at Gold Creek -Hi gh-Flow Frequency Curves -February
Susitna River at Gold Creek -High-Flow Frequency Curves -March
Susitna ~ver at Gold Creek -~gh-Flow Frequency Curves -April
Susitna River at Gold Creek -High-Flow Frequency Curves -May
Susitna River at Gold Creek High-Flow Frequency Curves June
Susitna River at Gold Creek -High-Flow Frequency Curves -
July and August
Susitna River at Gold Creek -High-Flow Frequency Curves -
September and October
Susitna Ri ver at Gold Creek -High-Flow Frequency Curves -November
Susitna River at Gold Creek -High-Flow Frequency Curves -December
Susitna River at Gold Creek -Low-Flow Frequency Curves -January
Susitna River at Gold Creek -Low-Flow Frequency Curves -February
Susitna Ri ver at Gold Creek -low-Flow Frequency Curves -March
Susitna ~ver at Gold Creek -low-Flow Frequency Curves -Apri 1
Susitna Ri ver at Gold Creek -low-Flow Frequency Curves -May
Susitna River at Gold Creek -low-Flow Frequency Curves -June
v
-
E.2.59
E.2.60
E.2.61
E.2.62
E.2.63
E.2.64
E.2.65
E.2.66
E.2.67
E.2.68
E.2.69
E.2.70
E.2.71
E.2.72
E.2.73
E.2.74
E.2.75
E.2.76
E.2.77
E.2.78
E.2.79
E.2.80
E.2.81
E.2.82
Susitna River at Gold Creek -Low-Flow Frequency Curves -
July and August
Susitna River at Gold Creek -Low-Flow Frequency Curves -
September and October
Susitna River at Gold Creek -Low-Flow Frequency Curves -November
Susitna River at Gold Creek -Low-Flow Frequency Curves -December
Mainstem Water Depths -Devil Canyon to RM 126
Mainstem Water Depths -RM 126 to Talkeetna
Backwater Profiles at the Mouth of Slough 9
Observed Water Surface Elevations at Mouth of Slough 9 for
Associated Mainstem Discharges at Gold Creek
Susitna River Water Temperatures -Summer 1980
Susitna River Water Temperatures -Summer 1981
Susitna River at Watana -Weekly Average Water Temperature -
1981 Water Yea r
Susitna River -Water Temperature Gradient
Data Summary -Temperature
Location Map for 1982 Midwinter Temperature Study Sites
Comparison of Weekly Diel Surface Water Temperature Variations
in Slough 21 and the Mainstem Susitna River at Portage
Creek -1981
Susitna River,Portage Creek,and Indian River Water Temperatures -
Summer 1982
Compari son of 1982 Talkeetna,Chul itna,and Sus itna Ri ver
Water Temperatures
Ice and Open Water Stage -Discharge Relationship,LRX-9,RM 103.2
Bed Material Movement Curves LRX-28,29,31,35
Data Summary -Total Suspended Sediments
Suspended Sediment Rating Curves -Middle and Upper
Susitna River Basins
Suspended Sediment Size Analysis -Susitna River
Data Summary -Turbidity
Turbidity vs.Suspended Sediment Concentration
vi
E.2.83
E.2.84
E.2.85
E.2.86
E.2.87
E.2.88
E.2.89
E.2.90
E.2.91
E.2.92
E.2.93
E.2.94
E.2.95
E.2.96
E.2.97
E.2.98
E.2.99
E.2.100
E.2.101
E.2.102
E.2.103
E.2.104
E.2.105
E.2.106
E.2.107
E.2.108
E.2.109
E.2.110
E.2.111
E.2.112
E.2.113
E.2.114
E.2.115
E.2.116
E.2.117
Oat a Summary -Di sso 1ved Oxygen
Data Summary -Di ssolved Oxygen %Saturation
Total Di ssolved Gas (%Saturation)vs.Oi scharge
Data Summary -Total Phosphorus
Oat a Summary -Orthophosphate
Oat a Summary -Nitr ate Nitrogen
Data Summary -Total Di ssolved Solids
Data Summary -Conductivity
Oat a Summary -Su If ate
Data Summary -Chloride
Data Summary -Calcium (d)
Data Summary -Magnesi urn (d)
Data Summary -Sodi urn (d)
Data Summary -Potassi urn (d)
Data Summary -Hardness
Oat a Summary -pH
Data Summary -Alkalinity
Oat a Summary -Free Carbon Di oxi de
Data Summary -Total Organic Carbon
Data Summary -Chemi cal Oxygen Demand
Data Summary -True Color
Oat a Summary -A1umi n urn (d)
Data Summary -Aluminum (t)
Data Summary -8i smuth (d)
Data Summary -Cadmium (d)
Data Summary -Cadmium (t)
Data Summary -Copper (d)
Data Summary -Copper (t)
Data Summary -Iron (t)
Oat a Summary -Lead (t)
Data Summary -Manganese (d)
Data ~ummary -Manganese (t)
Data Summary -Mercury (d)
Data Summary -Mercury (t)
Data Summary -Ni ekel (t)
vii
-
~,
-
,F"I
.....
-
E.2.118
E.2.119
E.2.120
E.2.121
E.2.122
E.2.123
E.2.124
E.2.125
E.2.126
E.2.127
E.2.128
E.2.129
E.2.130
E.2.131
E.2.132
E.2.133
E.2.134
E.2.135
E.2.136
E.2.137
E.2.138
E.2.139
E.2.140
E.2.141
E.2.142
E.2.143
E.2.144
E.2.145
E.2.146
Data Summary -Zinc (d)
Data Summary -Zinc (t)
Slough 8A -GroundWater Contours
Slough 9 -Ground Water Contours
Sally Lake Area -Capacity Curves
Water Bodies to be Inundated by Watana Reservoir
Water Bodies to be Inundated by Devil Canyon Reservoir
Township Grids Investigated for Water Rights in the
Susitna River Basin
Select Locations of Cook Inlet Salinity Estimates
Temporal Salinity Estimates for Cook Inlet near the
Susitna River Mouth
Watana Reservoir Volume and Surface Area
Devil Canyon Reservoir Volume and Surface Area
Minimum Operational Target Flows for Alternative Flow Scenarios
Potential Watana Borrow Sites
Watana Quarry Site L
Watana Borrow Site D
Watana Borrow Site E
Watana Borrow Site I
Minimum Flow Requirements at Gold Creek
Three-Year.Mean Discharge at Gold Creek
Watana Water Levels and Gold Creek Flows During Reservoir Filling
Flow V,ariability at Gold Creek During Watana Filling
Schematic of the Potential Effects of the Susitna River
on a Typical Tributary Mouth
Watana Filling:Downstream Temperatures -October to January
Watana Fi 11 ing:Downstream Temperatures -January to April
Watana Filling:Downstream Temperatures -October to January -
.Low Winter Flows
WatanaHll ing:Downstream Temperatures -January to April
Low Winter Flows
Watana:Second Year of Filling Downstream Temperatures -Summer
Watana:Second Year of Filling Downstream Temperatures -Summer-
6,000 cfs in August
viii
E.2.147
E.2.148
E.2.149
E.2.150
E.2.151
E.2.152
E.2.153
E.2.154
E.2.155
E.2.156
E.2.157
E.2.158
E.2.159
E.2.160
E.2.161
E.2.162
E.2.163
E.2.164
E.2.165
E.2.166
E.2.167
E.2.168
E.2.169
E.2.170
E.2.171
E.2.172
Eklutna Lake Light Extinction In Situ Measurements
Watana -Unit Effi ci ency and Di scha rge Operati ng Range
(at Rated Head)
Watana Reservoir Water Levels (Watana Operation)
Watana Simulated Reservoir Operation
Watana Operation:Monthly Average Water Surface Elevations
at River Mile 142.3
Watana Operation:Monthly Average Water Surface Elevations
at River Mile 130.9
Watana Operation:Monthly Average Water Surface Elevations
at River Mile 124.4
Watana Flood Discharges and Reservoir Surface Elevations
Gold Creek Annual Flood Frequency Curve -Watana Operation
1964 Watana and Gold Creek Flow Simulation Using 1995 Demand
1967 Watana and Gold Creek Flow Simulation Using 1995 Demand
1970 Watana and Gold Creek Flow Simulation Using 1995 Demand
Monthly and Annual Flow Duration Curves -Susitna River at Watana
Monthly and Annual Flow Duration Curves -Susitna River at Gold Creek
Monthly and Annual Flow Duration Curves -Susitna River at Sunshine
Monthly and Annual Flow Duration Curves -Susitna River at
Susitna Station
Annual Flow Duration Curve -Susitna River at Gold Creek -
Pre-Project and Watana Operation
Water Temperature Profiles -Bradley Lake,Alaska
Eklutna Lake Observed and Predicted Temperature Profiles -
June -July
Eklutna Lake Observed and Predicted Temperature Profiles -
August -September
Eklutna Lake Observed and Predicted Temperature Profiles -
October -December
Lake Williston Temperature Profiles -April 14-15,1982
Watana Mult il eve 1 Intake
Eklutna Lake Reservoir Temperature Simulation -June to September
Eklutna Lake Reservoir Temperature Simulation -October to December
Watana Reservoi r Temperature Profi 1es -June to August
ix
"""
-
.....
E.2.173
E.2.174
E.2.175
E.2.176
E.2.177
E.2.178
E.2.179
E.2.180
E.2.181
E.2.182
E.2.183
E.2.184
E.2.185
E.2.186
E.2.187
E.2.188
E.2.189
E.2.190
E.2.191
E.2.192
E.2.193
E.2.194
E.2.195
E.2.196
E.2.197
Wat ana Reservoi r Temperature Profi 1es -September to December
Watana Reservoi r Inflow and Outflow Temperatures -June to September
Watana Reservoir Inflow and Outflow Temperatures -
October to December
Watana Operat i on:Downstream Temperatures -June to August
Watana Operati on:Downstream Temperatures -September
Watana Operati on:Downstream Temperatures -October to December
Comparison of 1981 .Observed Water Temperatures near Sherman and
1981 Temperature Si mul ati on of Watana Operati on
Watana Operati on:Downstream Temperatures -October to January
Outflow Temperature 4°C
Watana Operati on:Downstream Temperatures -January to Apri 1
Outflow Temperature 4°C
Watana Operati on:Downstream Temperatures -October to January
Outflow Temperature 4 to 2°C
Watana Operati on:Downstream Temperatures -January to Apri 1
Outflow Temperature 4 to 2°C
Watana Operati on:5i mul ated Ice Thi ckness and Ice Front Locati on
Watana Operati on:Ri ver Stage Increase Due to Ice Cover
Devi 1 Canyon -Flood Frequency Curve
Devi 1 Canyon -Borrow 5i te G
Devi 1 Canyon -Borrow Site Map
Devi 1 Canyon -Quarry Site K
Devi 1 Canyon -Uni t Effi ci ency and Di scharge Operati ng Range
(at Rated Head)
Watana Reservoi r Water Level s (Watana and Devi 1 Canyon in Operati on)
Devi 1 Canyon Reservoi r Water Leve 1s
Watana and Devi 1 Canyon Simulated Reservoir Operation
Watana and Devi 1 Canyon Si mul ated Reservoi r Operati on
~tana/Devi 1 Canyon Operation:Monthly Average Water Surface
El evati ons at Ri ver Mi 1e 142.3
Watana/Devi 1 Canyon Operati on:Monthly Average Water Surface
Elevati ons at Ri ver Mi le 130.9
Watana/Devi 1 Canyon Operati on:Monthly Average Water Surface
El evati ons at Ri ver Mi 1e 124.4
x
E.2.198
E.2.199
E.2.200
E.2.201
E.2.202
E.2.203
E.2.204
E.2.205
E.2.206
E.2.207
E.2.208
E.2.209
E.2.210
E.2.211
E.2.212
E.2.213
E.2.214
E.2.215
E.2.216
E.2.217
E.2.218
E.2.219
E.2.220
Devi 1 Canyon Flood Di scharges and Reservoi r Surface El evati ons
Gold Creek Annual Flood Frequency Curves -Watana/Devi 1 Canyon
Operati on
1964 Devi 1 Canyon and Gold Creek Flow Simulation Using 2002 Demand
1967 Devi 1 Canyon and Gold Creek Flow Si mul ati on Usi ng 2002 Demand
1970 Devi 1 Canyon and Go ld Creek Flow Si mul ati on Usi ng 2002 Demand
1964 Devi 1 Canyon and Gold Creek Flow Simulation Using 2010 Demand
1967 Devi 1 Canyon and Gold Creek Flow Simulation Usinq 2010 Demand
1970 Devil Canyon and Gold Creek Flow Simulation Using 2010 Demand
Monthly and Annual Flow Duration Curves -Susitna River at Watana
Monthly and Annual Flow Durati on Curves -Susi tna Ri ver at
Devi 1 Canyon
~~onthly and Annual Flow Duration Curves -Susitna Ri ver at Gold Creek
Monthly and Annual Flow Durati on Curves -Susi tna Ri ver at Sunshi ne
Month ly and Annual Flow Durati on Curves -Susitna Ri ver at
Susitna Station
Annual Flow Duration Curve -Susitna Ri ver at Gold Creek
Pre-Project and Watana/Devi 1 Canyon Operation
Watana/Devi 1 Canyon Operati on Gold Creek Di scharges for Vari ous
Probabi li ti es of Exceedance
Devil Canyon Reservoir Temperature Profi les -June to September
Devi 1 Canyon Reservoir Temperature Profi les -October to December
Devi 1 Canyon Reservoir Inflow and Outflow Temperatures -
June to September
Devi 1 Canyon Reservoir Inflow and Outflow Temperatures -
October to December
Wat ana/Devi 1 Canyon Operati on Downstream Temperatures -
June to October
Wat ana/Devi 1 Canyon Operati on Downstream Temperatures -
October to December
Watana/Devi 1 Canyon Operati on Downstream Temperatures -
October to January -Outflow Temperature 4°C
Watana/Devi 1 Canyon operati on Downstream Temperatur€s -
January to Apri 1 -Outflow Temperature 4°C
xi
.-
~
i
E.2.221 Watana/Devi 1 Canyon Operation Downstream Temperatures
October to January -Outflow Temperatures 4 to 2°C
E.2.222 Wat an a/Devi 1 Canyon Operation Downstream Temperatures -
Januar y to Apri 1 -Out flow Temperatures 4 to 2°C
xii
LIST OF PHOTOGRAPHS
'II"'"
-
,-
E.2.1
E.2.2
E.2.3
E.2.4
E.2.5
E.2.6
E.2.7
E.2.8
Frazi 1 Ice Upstream from Watana
Ice Cover Downstream from Watana Showing Natural Lodgement
Point
Slough 9 Approximately 3500 Feet Upstream from Slough Mouth,
December 1982
Slough 8A Freezeup,December 1982
Slough 8A Near LRX-29 Looking Upstream
Slough 8A
Slough 8A Showing Flooding During Freezeup
Enlargement of Photo E.2.7 Showing Turbulent Flow
xiii
!"""l
i
I,,
-
-
.....
1 -INTRODUCTION
The Report on Water Use and Quality is divided into six sections:
1 -Introduction;
2 Baseline Conditions;
3 -Project Operation and Flow Selection;
4 -Project Impacts;
5 -Agency Concerns and Recommendations;and
6 -M,Higative,Enhancement,and Protective Measures.
Within the sections on baseline conditions and project impacts,~mpha
sis is placed on river morphology,flows,water quality parameters,
ground water conditions and i nstream fl ow uses.The importance of
flows and instream flow uses cannot be overstressed.For this reason,
mean flows,flood flows,low flows and flow variability are discussed
in detail.
The primary focus of the water qual ity discussion is on those para-
meters determined most critical for the maintenance of habitat for fish
populations and other aquatic organisms.Detailed discussions are pre-
sented on wate r temperature,ice,suspended sediments turbi dity,di s-
solved oxygen,total dissolved gas supersaturation and nutrients.
These parameters have previously been identified as areas of greatest
concern.
Mainstem surface water-slough ground water interaction downstream from
Devil Canyon is important to successful salmonid spawning in the
sloughs and is discussed.
The primary instream flow uses of the Susitna are for fish,wildlife
and riparian vegetation.Since these are discussed in Chapter 3,they
are only briefly discussed in this Chapter.Other instream flow uses
including navigation and transportation,recreation,waste assimilative
capacity,and freshwater recruitment to Cook Inlet estuary are dis-
cussed.Since minimal out-of-river use is made of the water,limited
discussions have been presented on this topic.
In the section on Project Operation and Flow Selection,the character-
istics of the Watana and Devil Canyon reservoirs are described and the
alternative operating flow scenarios are discussed.The rationale for
the selected operational flow regime is presented.
Project impacts have been separated by development.Impacts associated
with each development are presented in the following chronological
order:construction,impoundment,and operation.
The agency concerns and recommendations that were received during the
ongoing consultation process have been addressed.Section 5 of this
chapter highlights the major concerns.Detailed responses to indi-
vidual comments are addressed in Chapter 11 of Exhibit E.
E-2-1
1 -Introduction
The mitigation plans incorporate the engineering and construction meas-
ures necessary to minimize potential impacts,given the economic and
engineering constraints.
E-2-2 P'
-
"i'
I
2 -BASELINE DESCRIPTION
The entire drainage area of the Susitna River is about 19,400 square
miles,of which the drainage area above Gold Creek comprises approxi-
mately 6160 square miles (Figure E.2.1).Three glaciers in the Alaska
Range feed forks of the Susitna River,which flow southward for about
18 miles (30 km)and then join to form the Susitna River.The river
flows an additional 55 miles (90 km)southward through a broad valley
where much of the coarse sediment from the glaciers settles out.The
ri ver then f1 ows westward about 96 mn es (154 km)through a narrow
valley,with constrictions at the Devil Creek and Devil Canyon areas
creating violent rapids.Numerous small,steep gradient,clear-water
tributaries flow into the Susitna in this reach of the river.Several
of these tributari es cascade over waterfall s as they enter the gorge.
As the Susitna curves south past Gold Creek,13 miles (21 km)down-
stream from the mouth of Devil Canyon,its gradient gradually
decreases.The river is joined about 40 miles (64 km)beyond Gold
Creek in the vicinity of Talkeetna by two major tributaries,the
Chul itna and Talkeetna Rivers.From this confluence,the Susitna flows
south through braided channels for 97 miles (156 km)until it empties
into Cook Inlet near Anchorage,approximately 318 miles (512 km)from
its sou rce.
For ease of discussion,the watershed has been divided into three
drainage basins.The upper drainage basin extends from the glacial
headwaters of the Susitna River to the confluence of the Tyone River.
The middle basin extends downstream from this point to Talkeetna and
contains the Watana and Devil Canyon damsites.The middle reach is
where the major project-related impacts will occur.The lower basin is
defined as the drainage basin from Talkeetna to Cook Inlet.The
approximate boundaries of the three basins are shown in Figure E.2.1.
The Susitna River is typical of unregulated northern glacial rivers
with high,turbid summer flow and low,clear winter flow.Runoff from
snow melt and rainfall in the spring causes a rapid increase in flow in
May from the low discharges experienced throughout the winter.Peak
annual floods usually occur in June.
Associated with the higher spring flows is a 100 fold increase in sedi-
ment transport which persists throughout the summer.Between June and
September,the large suspended sediment concentration causes the river
to be highly turbid.Glacial silt,released by the glaciers when they
begin to melt in late spring or re-entra"ined from the river banks by
high flows,is responsible for much of the turbidity.
Rainfall-related floods often occur in August and early September,but
generally these floods are not as severe as the spring (May-June)snow-
melt f1 oods.
As the weather begins to cool in the fall,the glacial melt rate de-
creases and the flow in the river correspondingly decreases.Because
most of the suspended sediment is caused by glacial outwash,the
E-2-3
2 -Ba se 1 in e De sc ri pt i on
river also begins to clear.Freezeup normally begins in October and
continues through early December,progressing upstream from one natural
lodgement point in the river to the next upstream lodgement point.
Freezeup generally begins at the upper basin lodgement points first.
The river breakup generally begins in late April or early May near the
mouth,and progresses upstream with breakup at the damsites occurring
in mid-May.
2.1 -Susitna River Morphology
2.1.1 -Mainstem
The Susitna River originates in the glaciers of the southern
slopes of the central Alaskan Range,flowing 318 miles (512 km)
from Susitna Glacier to the river's mouth at Cook Inlet.
Throughout its course,the Susitna River is characterized by
several reach types.These are defined and ill ustrated in
Fig u res E•2.2 t hr 0 ug h E.2.5.
(a)Morphological Characteristics Upstream of Devil Canyon
The headwaters of the Susitna River and the major upper
basin tributaries are characterized by broad,braided,
gravel floodplains below the glaciers,with several melt-
streams exiting from beneath the glaciers before they can-
bine further downstream.The West Fork Susitna River joins
the main river about 18 miles (29 km)below Susitna Glacier.
Below the West Fork confluence,the Susitna River develops a
spl it-channel configuration with nllllerous i sl ands.The
river is generally constrained by low bluffs for about 55
miles (89 km).The Maclaren River,a significant glacial
tributary,and the non-glacial Tyone River,which drains
Lake Louise and the swampy lowlands of the southeastern
upper basin,both enter the Susitna River from the east.
Below the confluence with the Tyone River,the Susitna River
flows west for 96 miles (154 km)through steep-walled can-
yons before reaching the mouth of Devil Canyon.The reach
contains the Watana and Devil Canyon damsites at River Mile
(RM)184.4 and 151.6,respectively.River gradients are
high,averaging nearly 14 feet per mile (4 m per km)in the
54 mil e (87 km)reach upstream of the Watan a damsite wherein
the Watana reservoir will be located.Downstream from
Watana to Devil Creek,the river gradient is approximately
10.4 feet per mile (3.2 m per km)as illustrated in the pro-
file contained in Figure E.2.6.In the 12 mile (19 km)
reach between Devil Creek and Devil Canyon,the river
gradient averages 31 feet per m"ile (9.5 m per km).
E-2-4
2.1 -Susitna River Morphology
This 96 mile-long (154 km)reach is primarily a single
channel with intermittent islands.Cross sections presented
in the Hydraulic and Ice Studies Report (R&M 1982b)illus-
trate the single channel configuration.Bed material mainly
consists of large gravel cobbles.The mouth of Devil Can-
yon,at RM 149 forms the lower limit of this reach.
(b)Morphological Characteristics Downstream from Devil Canyon
Between Devil Canyon and the mouth at Cook Inl et,the ri ver
has been subdivided into nine separate reaches (R&M 1982d).
These reaches are i dent ifi ed in Tabl e E.2.1,together wi th
the average s10pes and predomi nant channel pat terns.The
thal weg profil es betw~en Portage Creek and Talkeetna and
between Sunshine and Cook Inlet are shown in Figures E.2.7,
E.2.8,and E.2.9.Figure E.2.10 illustrates the cross sec-
tion at RM 129.7 near Sherman.Additional cross section
data are contained in the Hydraul ic and Ice Studi es Report
(R&M 1982b).Aerial photographs of the Susitna River
between Portage Creek and Talkeetna are presented in Figures
E.2.11 through E.2.20.The nine reaches are discussed
below.
(i)RM 149 to RM 144
Through this reach,the Susitna flows predominately
ina single channel confined by valley walls.At
locations where the valley bottom widens,deposition
of gravel and cobble has formed mid-channel or side-
channel bars.Occasionally,a vegetated island or
fragmentary floodplain has formed with elevations
above normal flood levels,and has become vegetated.
Presence of cobbles and boulders in the bed material
aids in stabilization of the channel geometry.
-
......
(i i )RM 144 to RM 139
-A broadeni ng of the valley bottom throl1gh thi s reach
has allowed the river to develop a split channel with
intermittent,well-vegetated islands.A correlation
exi sts between bankfull stage and mean-annual flood.
Where the main channel impinges on valley walls or
terra~es,a cobble armor layer has developed with a
top elevat ion at roughly bankfull flood stage.At RM
144-,a periglacial alluvial fan of coarse sediments
confines t~e river to a single channel •
E-2-5
2.1 -Susitna River f>brphology
(iii)RM 139 to RM 129.5
This river reach is characterized by a well-defined
split channel configuration.Vegetated islands sep-
arate the main channel from side channels.Side
channels occur frequently in the alluvial floodplain
and are inundated only at flows above 15,000 to
20,000 cfs.There is a good correlation between
bankfull stage and the mean annual flood.
Where the main channel impinges valley walls or ter-
races,a cobble armor layer has developed with a top
elevation at roughly bankfull flood stage.The main
channel bed has been frequently observed to be well
armored.
Primary tributaries include Indian River,Gold Creek
and Fourth of July Creek.Each has formed an allu-
vial fan extending into the valley bottom,constrict-
ing the Susitna to a single channel.Each constric-
tion has establ ished a hydraul ic control point that
regul ates water surface profil es and assoc iated
hydraul ic parameters at varying discharges.
(iv)RM 129.5 to RM 119
River patterns through thi s reach are simil ar to
those in the previous reach.Prominent characteris-
tics between Sherman and Curry include the main
channel flowing against the west valley wall and the
east floodplain having several side channels and
slo~ghs.The alluvial fan at Curry constricts the
Susitna to a single channel and terminates the above
patterns.A fair correlation exists between bankfull
stage and mean annual flood through this reach.Com-
parison of 1950 and 1980 aerial photographs reveal
occasional local changes in bankl ines and island
morphology.
The west valley wall is generally nonerodible and has
occasional bedrock outcrops.The resistant boundary
on one side of the main channel has generally forced
a uniform channel configuration with a well armored
perimeter.The west valley wall is relatively
straight and uniform except at RM 128 and 125.5.At
these 1 ocati ons,bedrock outc rops defl ect the main
channel to the east side of the floodplain.
E-2-6
""'"I
-
2.1 -Susitna River MJrphology
(v)RM 119 to RM 104
Through this reach the river is predominantly a very
stable,single incised channel with a few islands.
The channel banks are well armored with cobbles and
boulders,as is the bed.several large boulders
occur intermittently along the main channel and are
bel ieved to have been transported down the vall ey
during glacial ice movement.They provide local
obstruction to flow and navigation,but do not have a
significant impact on channel morphology.
(vi)RM 104 to RM 95
At the confluence of the Susitna,Chulitna and
Tal keetna Rivers,there is a dramatic change in the
Su~itna from a spl it channel to a braided channel.
Emergence from conf"ined mountainous basins into the
unconfined 1owl and basin has enabled the river sys-
tems to develop 1 aterally.Ampl e bedload transport
and a gradient decrease also assist in establishing
the braided pattern.
The glacial tributaries of the Chul itna River are
much closer to the confluence than the Susitna
glacial tributaries.As the Chul itna River emerges
from an incised canyon 20 miles (32 km)upstream of
the confl uence,the river transforms into a braided
pattern wi th moderate v egetati on growth on the inter-
mediate gravel bars.At about a midpoint between the
canyon and the confl uence,the Chul itna exhibits a
highly braided pattern with no vegetation on inter-
mediate gravel bars,which is evidence of recent
lateral instability.This pattern continues beyond
the con fl uence,g iv ing the impressi on that the
Susitna is tributary to the dominant Chul itna River.
The split channel Talkeetna River is a tributary to
the dominant braided pattern.
Terraces generally bound the broad fl oodpl ain,but
provide little control over channel morphology.
General fl oodpl ain instabil ity resul ts from the
three-river system striv ing to bal ance out the com-
bined flow and sediment regime.
-
-
(v i i)RM 95 to 61
Downstream from the three-river confl uence,the
Susitna continues its braided pattern,with multiple
channels interlaced through a sparsely vegetated
fl oodpl ain.
E-2-7
2.1 -Susitna River Morphology
The channel network consists of the main channel,
usually one or two subchannels,and a nllTlber of minor
channel s.The main channel meanders i rregul arly
through the wide gravel floodplain and intermittently
flows against the vegetated floodplain.It has the
abil ity to easily migrate laterally within the active
gr av e 1 flood P1a in,as t he ma inc han neli s si In ply
reworking the g ravel that the system prev iously
deposited.When the main channel flows against vege-
tated bank 1 ines,erosi on is retarded due to the
vegetation and/or bank material s that are more resis-
tant to erosion.Flow in the main channel usually
persists throughout the entire year.
Subchannel s are usually positioned near or against
the vegetated fl oodpl ain and are generally on the
opposite side of the fl oodpl ain from the main
channel.The subchannel s normally bifurcate from the
main channel when it crosses over to the opposite
side of the fl oodpl ain and terminate where the main
channel meanders back across the fl oodpl ain and
intercepts them.The subchannel s have small er geo-
metric dimensions than the main channel,and their
thalweg is generally about 5 feet (1.5 m)higher.
Their flow regime is dependent on the main channel
stage and hydraul ic flow control s the point of bifur-
cation.Flow mayor may not persist throughout the
year.
Minor channels are relatively shallow,wide channels
that traverse the gravel floodplains and complete the
interlaced braided pattern.These channels are very
unstable and generally short-lived.
The main channel and subchannel s are intermittently
controlled laterally where they flow against ter-
races.Since the active fl oodpl ain is very wide,the
presence of terraces has 1 ittl e significance except
for determining the general orientation of the river
system.Jln exception occurs where the terraces con-
strict the river to a single channel at the Parks
Highway bridge.Minor channels react to both of the
1 arger channe--l s'behaviors.
(viii)RM 61 to RM 42
Downstream from the Kashwitna River confluence,the
Susitna River branches into multiple channels separ-
ated by islands with established vegetation.This
E-2-8
-I
"
i
1"""\, I
2.1 -Susitna River MJrphology
reach of the river is known as the Delta Islands
because it resembles the distributary channel network
common with large river deltas.The multiple chan-
nels are forced together by terraces just upstream of
Kroto Creek (Deshka River).
Through this reach,the very broad floodplain and
channel network can be divided into three cate-
gories:
-Western b raided channel s;
-Eastern spl it channel s;and
-Intermediate meandering channels.
The western braided channel network is considered to
be the main portion of this very complex river
system.Although not substantiated by river surveys,
it appears to constitute the 1 argest flow area and
lowest thalweg elevation.The reason for this is
that the western braided channel s constitute the
shortest distance between the point of bifurcation to
the confl uence of the Del ta Island channel s.There-
fore it has the steepest gradient and highest poten-
tial energy for conveyance of water and sediment.
-
( i x)RM 42 to RM 0
Downstream from the Delta Islands,the Susitna River
gradient decreases as it approaches Cook Inlet
(Figure E.2.9).The river tends toward a split
channel configuration as it adjusts to the lower
energy slope.There are short reaches where a ten-
dency to braid emerges.Downstream of RM 20,the
river branches out into delta distributary channel s.
Terraces constrict the fl oodpl ain near the Kroto
Creek confluence and at Susitna Station.Further
downstream,the terraces have little or no influence
on the river.
The Yentna River joins the Susitna at RM 28 and is a
major contributor of flow and sediment.
Tides in Cook Inlet rise above 30 feet (9 m)and
therefore control the water surface profi 1 e and to
some degree the sediment regime of the lower river.
A river elevation of 30 feet (9 m)exists near RM 20
which corresponds to the location where the Susitna
begins to branch out into its delta channel s.
E-2-9
2.2 -Susitna River Water Quantity
2.1.2 -Sloughs
Sloughsare spring-fed,overflow channels that exist along the
edge of the floodplain,separated from the river by well-vegeta-
ted bars.An exposed all uvi al berm often separates the head of
the sloughs from the mainstem or side-channel flow.The control-
ling streambank elevations at the upstream end of the sloughs are
less than the mainstem water surface elevations during median and
high flow periods.At intermediate and low flows,the sloughs
convey clear water from small tributaries and upwelling ground
water (ADF&G 1982a).
Differences between mainstem water surface elevations and the
streambed elevation of the sloughs are notably greater at the
upstream entrance to the sloughs than at the mouth of the
sloughs.The gradients within the sloughs are typically greater
than the adjacent mainstem because of their shorter path length
from the upstream end to the downstream end,than along the rnai n-
stem.The upstream end of the sloughs generally has a higher
gradient than the lower .end.This is evidenced ;In Figure E.2.21,
which illustrates the thalweg profile of a typical slough.
The sloughs vary in length from 2,000 to 6,000 feet (610 to
1829 m).Cross-sections of sloughs are typically rectangular
with fl at bottoms as ill ustrated in Fi gure E.2.22.At the head
of the sloughs,substrates are dominated by boulders and cobbles
[8 to 14 inch (20 to 36 cm)diameter].Progressing downstream
towards the slough mouth,substrate particles reduce in size with
gravel s and sands predomi nating (Figure E.2.21).Beavers fre-
quently inhabit the sloughs.Active and abandoned dams are
visible.Vegetation commonly covers the banks to the water's
edge with bank cutting and slumping occurring during spring
break-up flows and high summer flows.
The importance of the sloughs as salmon spawning habitat is dis-
cussed in detail in Chapter 3.
2.2 -Susitna River Water Quantity
2.2.1 -Mean Monthly and Annual Flows
Continuous historical streamflow records of various record length
(7 to 32 years through water year (WY)1981)exist for gaging
stations on the Susitna River and its tributaries.USGS gages
are located at Denali,Cantwell (Vee Canyon),Gold Creek and
Susitna Station on the Susitna River;on the Maclaren River near
Paxson;at Chulitna Station on the Chulitna River;at Talkeetna
on the Talkeetna River;and at Skwentna on the Skwentna Ri ver.
E-2-10
-I
-
I""'l
I
-
-
2.2 -Susitna River Water Quantity
In 1980 a USGS gaging station was installed on the Yentna River
and in 1981 a USGS gaging station was installed at Sunshine on
the Susitna River.Statistics on river mile,drainage area and
years of record are shown in Tabl e E.2.2,and a summary of the
maximum,mean and minimum monthly flows for the respective
periods of record are shown in Table E.2.3.Because of the short
duration of the stream flow records at Sunshine and on the
Yentna,summaries for these two stations have not been included.
The station locations are illustrated in Figure E.2.1.
With the exception of the Yentna station,compl ete 30 year
streamflow data sets for each USGS stream gagjft9 station illus-
trated in Table E.2.2,were generated through a correlation
analysis,whereby missing mean mo~thly flows were estimated
(Acres 1982b).The analysis was based on the program FILLIN
developed by the Texas Water Developillent Board (1970).The pro-
cedure adopted is a rnultisite regression technique which analyzes
monthly time seri es data and fi 11 sin mi ssi ng port ions in the
incomplete records.The program evaluates statistical parameters
which characteri ze the data set (i .e.,seasonal means,seasonal
standard devi at ions,1ag-one auto-correl at ion coeffi ci ents and
multi-site spatial correlation coefficients)and creates a
filled-in data set in which these statistical parameters are pre-
served.For the analysis,all streamflow data up to September
1979 were used (30 years of data at Gold Creek).Recorded data
for water years 1980 and 1981 have been subsequently added to
provide 32 years of record.The resultant maximum,mean and min-
imum monthly and annual flows for the 32 years of record are pre-
sented in Table E.2.4.
Using an annual volume frequency analysis,the 1969 drought was
determined to have a recurrence interval of approximately 1:1000
years,as illustrated in Figure E.2.23.This was considered too
extreme an event for an energy simulation analysis and was modi-
fi ed a ccordi ngly to a once in 30 yea r event based on the long
term average,monthly flow distribution.(For a more detailed
discussion refer to Section 3.3 pre-project flows).A summary of
the resulting 32-year modified hydrology for Gold Creek,Sun-
shine,and Susitna Station is presented in Table E.2.5.
Mean monthly flows at the Watana and Devil Canyon damsites were
estimated using a linear drainage area-flow relationship between
the Gold Creek and Cantwell (Vee Canyon)gage sites.The result-
ant maximum,mean,and minimum monthly and annual flows are also
presented in Tables E.2.4 and E.2.5.
Monthly -flows for'each month of the 32-year modified record for
Watana,Devil Canyon,Gold Creek,Sunshine and Susitna Station
are presented in Tables E.2.6 through E.2.10.
E-2-11
2.2 -Susitna River Water Quantity
Comparison of mean annual flows in Table E.2.4 indicates that 39
percent of the streamfl ow at Gold Creek originates above the
Denal i and Macl aren gages.It is in thi s catc hllent that the
glaciers which contribute to the flow at Gold Creek are located.
The Susitna River above Gold Creek contributes 19 percent of the
mean annual flow measured at Susitna Station near Cook Inlet.
The Chul itna,and Talkeetna Rivers contribute 20 and 10 percent
of the mean annual Susitna Station flow respectively.The Yentna
provides 40 percent of the flow,with the remaining 11 percent
originating in miscellaneous tributaries.
The variation between summer mean monthly fl ows and winter mean
monthly flows is greater than a 10 to 1 ratio at all stations.
This large seasonal difference is due to the characteristics of a
glacial river system.Glacial melt,snow melt,and rainfall pro-
vide the majority of the annual river flow during the summer.At
Gold Creek,for example,88 percent of the annual streamflow
volume occurs during the months of May through September.
A comparison of the maximum and minimum monthly flows for May
through September indicates a high flow variability at all sta-
tions from year to year.
(a)Effect of Glaciers on Mean Annual Flow
The gl aciated portions of the Susitna River Basin above Gold
Creek pl ay a signi ficant rol e in the hydrology of the area.
Located on the southern slopes of the Al aska Range,the
g1ac i ated reg ion s receive the greatest amount of snow and
rainfall in the basin.During the sllllmer months,these
regions contribute significant amounts of snow and glacial
melt.The glaciers,covering about 290 square miles (750
square kilometers),act as reservoirs that produce most of
the water in the basin above Gold Creek during drought
periods.The drainage area upstream of the Denal i and
Maclaren gages comprises 19.9 percent of the basin above
Gold Creek,yet contributes 39 percent of the average annual
fl ow at Gol d Creek (47 percent of the flow at Watana).
Stated another way,the area upstream of the Dena:!i and
Maclaren gages contributes 3.1 cubic feet per second (cfs)
per square mile,and the area downstream to Gold Creek con-
tributes 1.2 cfs per square mi 1 e.In the record droug ht
year of 1969,the proportion of fl ow at Gold Creek contri-
buted from upstream of the Denal i and Maclaren gages
increased to 53.4 percent.
There is strong evidence from East Fork Glacier,a small
glacier of 13.6 square miles (35.2 square kilometers),that
glacier wasting has cOl'ltributed to the runoff at Gold Creek
since 1949 (R&IVl 1982a;R&M 1981b).However,the magnitude
E-2-12
,....,
I
-
-
,....
2.2 -Susitna River Water Quantity
of the runoff from gl acier wasting has not been well docu-
mented.Potentially significant errors exist iii the ice
loss estimate at East Fork Gl acier due to the 1 ack of ade-
quate survey control.Consequently,errors of 60 feet
(18 m)may exist in the estimate of 163 feet (50 m)of sur-
face altitude loss.
Extrapol ation of resul ts from East Fork Gl acier to the other
'275 square miles (712 square kill)(or 95 percent)of the
glaciers in the basin is speculative at best.Glaciers
react differently to changes "in climate.Gulkana Glacier,
43 miles (69 km)to the east of East Fork macier,wasted at
a rate of 1.1 feet (0.3 m)per year from 1966 to 1977,com-
pared to the estimated rate of 5.3 feet (1.6 m)per year
from 1949 to 1980 for East Fork Glacier.In the Washington
Cascades,North ~awatti Glacier lost about 27 feet (8 m)of
ice between 1947 and 1961,while adjacent Klawatti Glacier
gained 19 feet or 6 m (Meier 1966).
Even though there is evidence that the glaciers have been
wasting since 1949,there is little data available to deter-
mine what the impact of wasting has been on the recorded
fl ow at Gol d Creek or what will occur in the future.Large
glaciers,such as those in the Susitna Basin,take decades
to attain equil ibriul11 after a change in cl imate.The
Susitna glaciers may have reached their most recent maximum
extent during the "Little Ice Age"which occurred in the
early 1800's and may still be responding to the change in
climate since then (Harrison personal communication).If
the estimated rate of glacier wasting of East Fork Glacier
were al so appl ied to Susitna and West Fork Glaciers,almost
36 percent of the recorded streamflow (990 cfs)at Denali
and 22 percent (220 cfs)at Macl aren would have been from
glacier melt.That is,12.5 percent of the annual flow at
Gold Creek and 15 percent of the annual flow at Watana would
be from glacier wasting.These values should be considered
as high estimates.
Using the above estimate of glacier wasting,the contribu-
tion in the drainage area upstream of the Denali and
Macl aren gages woul d be 2.1 cfs per square mil e without the
contribution from glacier wasting.
It is difficult to predict future trends.If the glaciers
were to stop wasting due to,perhaps,a climate change,
there could be impl ications in hydrological changes through-
out the basin.On the other hand,the wasting of the
glaciers could easily continue over the life of the project.
There is no way to judge whether wasting will continue into
E-2-13
2.2 -Susitna River Water Quantity
the future;hence,no mechanism presently exists for analyz-
ing what will occur during the life of the project.
2.2.2 -Floods
The most common causes of floods in the Susitna Ri ver Basin are
snow melt or a combination of snow melt and rainfall over a large
area.This type of flood occurs between May and July with the
majority occurri ng in June.Floods attri butabl e to heavy rai ns
have occurred in August and September.These floods are aug-
mented by snow melt from higher elevations and glacial runoff.
Examples of flood hydrographs can be seen in the daily dis-
charges for 1964,1967,and 1970 for Cantwell,Watana,and Gold
Creek which are illustrated in Figures E.2.24,E.2.25 and £.2.26.
The daily flow at Watana has been approximated using the linear
drainage area-flow relationship between Cantwell and Gold Creek
that was used to detennine Watana average monthly flows.
Figure E.2.24 shows the largest snow melt flood on record at Gold
Creek.The 1967 spring flood hydrograph shown in Figure £.2.25
has a daily peak equal to the mean annual daily flood peak.In
addition,the summer daily flood peak of 76,000 cfs is the second
largest flood peak at Gold Creek on record.Figure E.2.26
(WY 1970)illustrates a low flow spring flood hydrograph.
The maximum recorded instantaneous flood peaks for Denal i,
Cantwell,Gold Creek,and Maclaren,recorded by the USGS,are
presented in Table E.2.11.Instantaneous peak flood frequency
curves for individual stations are illustrated in Figures E.2.27
to £.2.33.Distribution statistics are presented in Table £.2.12
(R&M 1981f).In the majority of cases the three parameter log-
normal distribution provides the best fit to the data.Conse-
quently,the three parameter log-normal distribution has been
selected to model peak flows due to its simple construction and
adequacy in modeling the sample data parameters.
A regional flood frequency analysis was conducted using the
recorded floods in the Susitna River and other Cook Inlet tribu-
tar ies (R&M 198lf)•Th ere suIt ing dime ns ion 1ess re gion a1 f re -
quency curve is depicted in Figure £.2.34.A stepwise multiple
1 inear regression computer program was used to relate the mean
annual instantaneous peak flow to the physiographic and climatic
characteristics of the drainage basi ns.The mean annual i nstan-
taneous peak flows for the Watana and Devil Canyon damsites were
computed to be 40,800 cfs and 45,900 cfs respectively.The
regional flood frequency curve was compared to the station
frequency curve at Gold Creek (Table E.2.13).Because the Gold
Creek single station frequency curve yielded more conservative
flood peaks (i.e.larger),it was used to estimate flood peaks
E-2-14
-
-
"'"'
......
-
-
2.2 -Susitna River Water Quantity
at the Watana and Devil Canyon damsites for floods other than the
mean annual flood.The ratio of a particular recurrence interval
flood at Gold Creek to the mean annual flood at Gold Creek was
multiplied by the mean annual flood at Watana or Devil Canyon to
obtain the flood for the given recurrence interval.For example,
the ratio of the 1:10,000-year flood to mean annual flood at Gold
Creek is 3.84.With the use of this factor,the 1:10,000-year
floods at Watana and Devil Canyon were computed to be 157,000 cfs
and 176,000 cfs respectively.The flood frequency curves for
Watana and Devil Canyon are presented in Figures E.2.35 and
E.2.36.
Dimensionless flood hydrographs for the Susitna River at Gold
Creek were developed for the May -July snow melt floods and the
August -October rainfall floods using the five largest Gold
Creek floods occurring in each period (R&M 1981f).Flood hydro-
graphs for the 100,500,and iO,OOO year flood events were con-
structed using the appropriate flood peak and the dimensionless
hydrograph.Hydrographs for the May -July and August -October
flood periods are illustrated in Figures E.2.37 and E.2.38 res-
pectively.
Probable maximum flood (PMF)studies were conducted for both the
Watana and Devil Canyon damsites for use in the design of project
spillways and related facilities (Acres 1982b).The PMF floods
were determi ned by usi ng the SSARR watershed model developed by
the Portland District,U.S.Army Corps of Engineers (1975)and
are based on Susitna Basin climatic data and hydrology.The
probable maximum precipitation was derived from a maximization
study of historical storms.The studies indicate that the PMF
peak at the Watana damsite is 326,000 cfs.
2 •.2.3 -Flow Vari abil ity
The variabil ity of flow in a river system is important to all
instream flow uses.To illustrate the variability of flow in the
Susitna River,monthly and annual flow duration curves showing
the proportion of time that the discharge equals or exceeds a
given_value were developed for the four mainstem Susitna River
gaging stations (Denal i,Cantwell,Gold Creek and Susitna
Station)and three major tributaries (Maclaren,Chulitna,and
Talkeetna Rivers)(R&M 1982f).These curves,based on mean daily
flows,are illustrated in Figures E.2.39 through E.2.42.
The shape of the monthly and annual flow durati on curves is
similar for each of the stations and is indicative of flow from
northern glacial rivers (R&M 1982f).Streamflow is low in the
E-2-15
2.2 -Susitna River Water Quantity
winter months,with little variation in flow and no unusual
peaks.Ground water contributions are the primary source of the
small but relatively constant winter flows.Flow begins to
increase slightly in April as breakup approaches.Peak flows in
May are an order of magnitude greater than in April.Flow in May
also shows the greatest variation for any month,as low flows may
continue into May before the high snow melt/breakup flows occur.
June has the highest peaks and the highest median flow for the
mi ddl e and upper bas in stations.The months of Jul y and August
havere1at i vel y f 1at flo w du rat ion cur ves•Th iss it uat ion is
indicative of rivers with strong base flow characteristics,as is
the case on the Susitna with its contributions from snow and
glacial melt during the summer.More variability of flow ;s
evident in September and October as cooler weather becomes more
prevalent accompanied by a decrease in glacial melt and hence
discharge.
From the flow duration curve for Gold Creek (Figure E.2.39),it
can be seen that flows at Gold Creek are less than 20,000 cfs
from October through April.As a result of the spring breakup in
May,fl ows of 20,000 cfs are exceeded 30 percent of the time.
During June and July,the percent of time Gold Creek flows exceed
20,000 cfs increases to 80 percent.This percentage decreases to
65 percent in August and further decreases to only about 15 per-
cent in September.On an annual basis,a flow of 20,000 cfs is
exceeded 20 percent of the time.
The I-day,3-day,7-day and 15-day high and the I-day,3-day,
7-day and -14-day low flow values were determined for each month
of the year for the period of record at Gold Creek and from May
through October for the periods of record at the Chul itna River
near Talkeetna,the Talkeetna River near Talkeetna and the
Susitna River at Susitna Station (R&M 1982f).The high and low
flow values are presented for Gold Creek in the form of frequency
curves in Figures E.2.43 through E.2.62.May exhibits substan-
tial variability.Both low winter flows and high breakup flows
usually occur during May and thus significant changes occur from
year to year.June exhibits more variability than July.Flow
variability increases again in the August through October period.
Heavy rai nstorms often occur in August,with 28 percent of the
annual floods occurring in this month.Flow variability in the
wi nter months is reduced cons i derab ly refl ect i ng the low base
flow.
The da-i ly hydrographs for 1964,1967,and 1970 shown in Fi gures
E.2.24,E.2.25 and E.2.26 illustrate the daily variability of the
Susitna River at Gold Creek and Cantwell.The years 1964,1967,
and 1970 represent wet,average and dry hydrological years on an
annual flow basis.
E-2-16
2.2 -Susitna River Water Quantity
2.2.4 -Water Levels
(a)Mai nstem
Water surface 'elevations for various Watana discharges in the
reach between Deadman Creek (RM 186.8)and Devil Creek (RM
162.1)are listed in Table E.2.14.The elevations were determin-
ed wi th the use of the HEC-2 computer program "Water Surface
Profiles",developed by the U.S.Army Corps of Engineers.The
water surface elevations at the discharge of 42,200 cfs would be
similar to those of the mean annual flood of 40,800 cfs.The
water levels for an 8100 cfs discharge,which is similar to the
winter operational flow at Watana,are shown in Figure E.2.6.
The HEC-2 program was also used to predict water levels for the
reach between Devil Canyon and Tal keetna.The water surface
elevations are presented in Table E.2.15.The water levels pre-
sented for the Gold Creek flow of 52,000 cfs would be slightly
higher than those associated with the mean annual flood of 49,500
cfs.Water levels for a flow of 13,400 cfs at Gold Creek,which
is similar to the project operational flow at Gold Creek during
August and early September,are illustrated in Figures E.2.7 and
E.2.8.
In addition to the water levels presented in Table E.2.15 for
the selected flow cases,the HEC-2 program was used to determine
water 1eve 1s for the 1:100 year flood and the PMF in the reach
between Devil Canyon and Talkeetna.The 1:100 year flood plain
boundary is illustrated in Figures E.2.12 through E.2.20.The
water surface profile associated with the 1:100-year flood and
the PMF water surface profile are presented in Figures E.2.7 and
E.2.8.
(b)
With the use of the data in Table E.2.15 and the corresponding
thalweg elevations,water depths were determined at the river
cross section locations in the Devil Canyon to TaHeetna reach.
This information is shown in Figures E.2.63 and E.2.64.
Sloughs
The water surface elevation of the mainstern generally causes a
backwater effect at the mouth of the sloughs1/.The back-
water effects in slough 9,resulting from several mainstem
Susitna discharges is shown in Figure E.2.65.The backwater pro-
files were determined using the stage-discharge relationship
shown in Figure E.2.66 and the HEC-2 program.The stage-
discharge curve was obtained from 1982 field data.
.....,
....
"""
liThe relationships between mainstem flows and hydraulic character-
istics of three sloughs upstream of Ta"'keetna and one slough down stream
of Talkeetna are presented in Appendix E.2.A to Chapter 2 of Exhibit E.
E-2-17
2.3 -Susitna River Water Quality
Upstream of the backwater effects,the sloughs function like
sma 11 stream systems conveyi ng water from local runoff and
ground water upwelling during low flow periods and mainstem
water during high flow periods when the upstream end of the
slough is overtopped by the mainstem flow.
2.3 -Susitna River Water Quality
As previously described in Section 2,the Susitna River is charac-
terized by large seasonal fluctuations in discharge.These flow varia-
tions,along with the glacial origins of the river,essentially dictate
the water quality of the river.
Water quality data collected by the U.S.Geological Survey (USGS)and
R&[v]Consultants (R&M),have been compiled for the mainstem Susitna
River from monitoring stations located at Denali,Cantwell (Vee
Canyon),Gold Creek,Sunshine,and Susitna Station.In addition,data
from the tributary Chulitna and Talkeetna Rivers,have also been com-
pi 1ed.Water quality mon itori ng stat i on i nformat i on is presented in
Table E.2.2.Locations of the respective stations are depicted in
Fig ure E.2.1.
Water quality data were compiled according to season:breakup,summer
and winter.Breakup is usually short and extends from the time ice
begins to move down river until the recession of spring runoff.
However,it was often difficult to assess the termination of spring
runoff so for the purpose of this report,breakup water qual ity data
were cons i dered to be data collected duri ng the month of May.The
summer data peri od was cons i dered to extend from the end of breakup
(June 1)until the water temperature dropped to essentially DoC (32°F).
W"inter data were compiled from the end of summer to the beginning of
breakup (May 1).In the event that no water temperature data were
available to delineate the termination of summer and the onset of the
winter period,October 15 was utilized as the cutoff.The water
quality parameters measured,and the respective detection limits of the
methods used to analyze the samples,are provided in Table E.2.16.
Water quality was evaluated using criteria and guidelines set forth in
the following references:
-ADEC.1979.Water Quality Standards.Alaska Department of Environ-
mental Conservation,Juneau,Alaska.
-EPA.1976.Quality Criteria for Water.U.S.Environmental Protec-
tion Agency,Washington,D.C.
-McNeely,R.N.,V.P.Neimanism and K.Dwyer.1979.Water Quality
Sourcebook--A Guide to Water Quality Parameters.Environment Canada,
Inland Waters Directorate,Water quality Branch Ottawa,Canada.
E-2-18
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"....
-
2.3 -Susitna River Water Quality
-Sittig,M.1981.Handbook of Toxic and Hazardous Chemicals.Noyes
Publications,Park Ridge,New Jersey.
-EPA.1980.Water Quality Criteria Documents:Availability.Environ-
mental Protection Agency,Federal Register,45,79318-79379.
The'criteri a used for each parameter were chosen based on a pri ori ty
system.The Alaska Department of Environmental Consideration's Water
Quality Standards (1979)were the first choice,followed by criteria
presented in EPAls Quality Criteria for Water (1976).If a criterion
expressed as a specific concentration was not presented in either of
these references,the other references were used.
A second priority system was necessary for selecting the criteria used
for each parameter.This was required because the various references
cite levels of parameters that provide for the protection of water
quality for specific uses,such as (1)the propagation of fish and
other aquatic organisms;(2)water supply for drinking and food prepar-
ation,(3)industrial processes and/or agriculture;and (4)water
recreation.Given the limited direct human use of the river,the first
priority was to present the criteria that apply to the protection of
freshwater aquati c organi sms.The second pri ority was to present
levels of parameters that are acceptable for water supply and the third
priority was to present other guidelines if available.Criteria and
guideline values are provided in Table E.2.16 and in each of the indi-
vidual water quality data summary figures to be discussed later in this
document.
Although the Susitna River is a pristine area,22 parameters exceeded
t hei r respective criteri a.These parameters,the 1ocat i on and the
season during which the criteria were exceeded,and the respective
source of the criteria limits,are identified in Table £.2.17.In
addition,reasons for establishment of the criteria levels are provided
in the individual water quality data summary figures.
Note that water quality standards apply to man-induced alterations and
constitute the degree of degradation which may not be exceeded.
Because there are no industries except for placer mining operations,no
significant agricultural areas,and no major cities adjacent to the
Susitna,Talkeetna,and Chulitna Rivers,the measured levels of these
parameters are considered to be natural conditions.In addition,the
Susitna River basin supports diverse popul ations of fish and other
aquati c 1ife.Consequently,it was concl uded that the parameters
exceeding their criteria probably do not have significant adverse
effe·cts on aquatic organisms.As such,limited additional discussions
will be given to criteria exceedance.
E-2-19
I
2.3 -Susitna River Water Quality
In the following sections,breakup data will generally not be discussed
since the limited amount of data available normally indicate transition
values between winter and summer extremes.Breakup data are provided
in the water quality data summary figures.When available,summer and
winter data are briefly highlighted at one monitoring station in each
of the three Susitna River reaches (i.e.,upper,middle,and lower).
Typically the three monitoring stations discussed are Denali,Gold
Creek,and Susitna Station.Levels of water quality parameters dis-
cussed in the following sections are extracted from updated information
in R&M (1982g)unless otherwise noted.
2.3.1 -Water Temperature
(a)Mainstem
Generally during winter (October through April),the entire
mainstem Susitna River is at or near O°C (32°F).However,
there are a number of small discontinuous areas with ground
water inflow at a temperature of approximately 2°C (35.6°F).
As spri ng breakup occurs the water temperature begi ns to
rise,with the downstream reaches of the river warming
first.
During summer (June through September),glacial melt is near
O°C (32°F),when it leaves the glaciers,but as it flows
across the wide gravel floodplains downstream from the
glaciers,the water begins to warm.As the water winds its
way downstream to the Watana damsite,temperatures are as
high as 14°C (57.2°F).Further downstream there is addi-
tional warming but,temperatures are cooler at some loca-
tions due to the effect of tributary inflow.Maximum
recorded temperatures at Gol d Creek and Susitna Stat i on are
15°C (59°F)and 16.5°C (61.7°F).respectively.In August,
temperatures begin to drop,reaching O°C (32°F),in late
September or October.
The seasonal temperature variation on a daily average basis
for the Susitna River at Denali and Vee Canyon during 1980,
and for Denali and Watana during 1981 are displayed in
Figures E.2.67 and E.2.68.Weekly averages for Watana dur-
ing 1981 are shown in Figure E.2.69.The shaded area in
this figure is indicative of the range of temperatures
measured on a mean daily basis.The temperature variations
for ei ght summer days at Denali,Vee Canyon and Su si tna
Station are compared in Figure E.2.70.
The recorded variations in water temperatures at seven USGS
gaging stations are displayed in Figure E.2.71.The data in
this figure represent discrete measurements recorded by the
E-2-20
p'
r"',
-.
2.3 -Susitna River Water Quality
USGS and thus,do not refl ect the cont i nuously recordi ng
thermographs located at Denali,Vee Canyon,Gold Creek,
Chulitna or Sunshine.Because of the influence of the Gold
Creek tributary inflow on the location of the Gold Creek
thermograph prior to 1982,and since all seven stations did
tlot have continuous recording equipment,the USGS discrete
measurements were used to provide both accuracy and consis-
tency in this figure.
Additional data on water temperature are available in the
annual reports of the USGS (Surface Water Records for
Alaska;Water Resources Data for Alaska),the Alaska Depart-
ment of Fish and Game (ADF&G),Susitna Hydroelectric Project
data reports (Aquat ic Habitat and Instream Flow Proj ect -
19B1,and Aquatic Studies Program -1982a),and in R&M
Consultants reports (Water Qual ity Annual Reports -1981h,
1981i).
-
(b)Sloughs
The sloughs downstream of Devil Canyon have a temperature
regime that differs from the mainstem.During the winter of
1982,intergravel and surface water temperatures were
measured in sloughs 8A,9,11,19,20 and 21,the locations
of which are illustrated in Figure E.2.72.The measurements
indicated that intergravel temperatures were relatively con-
stant at each location through February and March but
exhibited some variability from one location to another.At
most stations intergravel temperatures were v>lithin the 2-3°C
(35.6-37.4°F)range.Slough surface temperatures sho~ied
more vari abil ity at each location and were generally lower
than intergravel temperatures duri ng February and March
(Trihey 1982c).
During the spring and summer periods of high flow,when the
heads of most sloughs are overtopped,slough water tempera-
tures correspond closely to mainstem temperatures.However,
when flow at the heads of the sloughs is cut off,spring and
summer slough temperatures tend to differ from mainstem
temperatures.
Figure E.2.73 compares weekly diel surface water temperature
variations during September,1981 in Slough 21 with the
mainstem Susitna River at Portage Creek (ADF&G 1982a).The
slough temperatures show a marked diurnal variation caused
by increased solar warming of the shallow slough water dur-
ing the day and sUbsequent long wave back radiation at
night.Thermograph measurements taken in slough 21 during
the summer of 1981 illustrated a diurnal temperature fluctu-
ation ranging from 4.5 -8.5°C (40.1-47.3°F)at the water
E-2-21
2.3 -Susitna River Water Quality
surface wi th a constant i ntergrave 1 water temperature of
3°C (37.4°F).Mainstem water temperatures are more constant
because of the bufferi ng capabil ity offered by the 1 arge
volume of the river and the extensive mixing that occurs.
(c)Tributaries
The tributaries to the Susitna River generally exhibit
cool er water temperatures than does the mai nstem.Continu-
ous water temperatures have been monitored by both the USGS
and ADF&G in the Chulitna and Talkeetna Rivers near
Talkeetna,and by ADF&G in Portage,Tsusena,Watana,Kosina,
and Goose Creeks,and the Indian and Oshetna Rivers.
The 1982 mean daily temperature records for Indian River and
Portage Creek are compared in Figure E.2.74 (ADF&G 1982c).
Portage Creek was consistently cooler than Indian River by
0.7 to 109°C (1.3-3.4°F).The flatter terrain in the lower
reaches of the Indian River valley is apparently more con-
ducive to solar and convective heating than the steep-walled
canyon of Portage Creek.Figure E.2.74 also presents water
temperature data from the mainstem Susi tna for the same
period,showing the consistently warmer temperatures in the
mainstem.There are noticeable diurnal fluctuations in the
tributary temperatures,though not as extreme as in the
sloughs.
The major tributaries joining the Susitna at Talkeetna show
uniform variation in temperature from the mainstem as illus-
trated in Figure E.2.75.Compared to the Susitna River,the
Talkeetna River temperature is 1-3°C (1.8-5.4°F)cooler on
an average daily basis.The Chul itna River,being closer to
its glacial headwaters,is from a to 2°C (0 to 3.6°F)cooler
than the Talkeetna River,and has less diurnal fluctuation.
Winter stream temperatures are usually very close to O°C
(32°F),as all the tributaries become ice covered.Ground
water inflow at some locations creates local conditions
above freezing,but the overall temperature regime is domi-
nated by the extremely cold ambient air temperatures.
2.3.2 -Ice
(a)Freezeup
Air temperatures in the Susitna basin increase from the
headwaters to the lower reaches.While this temperature
E-2-22
-
-
-
-
......
2.3 -Susitna River Water Quality
gradient is partially due to the two-degree latitudinal span
of the river,for the most part it is due to the 3,300-foot
(lOOO-m)e 1evat i on difference between the lower and upper
bas ins,and the cl imate-moderat i ng effect of Cook In 1et on
the lower river reaches.The gradient results in a period
(late October -early November)during which the air temper-
atures in the lower basin are above freezing,while upper
basin temperatures are subfreezing.
Frazil ice (Photograph E.2.1)forms in the upper segment of
the river first in October,due to the initial cold tempera-
tures of glacial melt and the earlier cold ambient air tem-
peratures.Additional frazil ice is generated in the fast-
flowing rapids between Vee Canyon and Devil Canyon.The
frazil ice generation normally continues for a period of 3-5
weeks before a solid ice cover forms in the river downstream
of Devil Canyon.
The frazil-ice pans and floes jam at natural lodgement
points,which usually are constrictions with low velocity.
One such lodgement point is illustrated in Photograph E.2.2.
Border ice formati on along the ri ver banks al s.o serves to
restri ct the channel to all ow the ice cover closures,or
bridgings to form.
From the natural lodgement points,the ice cover progresses
in an upstream direction as additional ice is supplied from
further upriver.However,before the ice cover can progress
upstream,a leading edge stabil ity criterion must first be
satisfied.This translates to a velocity at the upstream
end of the ice front that is sufficiently low to allow the
flowing ice to affix itself to the ice front,causing an
upstream progression of the ice front.If the velocities
upstream of the ice front are too high (i .e.leading edge
stability criterion not satisfied),the ice flowing down-
stream will be pulled underneath the ice front and deposited
downstream on the under side of the establ ished cover.In
reaches where the velocity permits ice deposition,a
thickening of the ice cover will occur.The thickening ice
cover constricts the flow downstream of the ice front by
increasing the resistance and thus creating a backwater
effect.The velocity upstream of the ice front is thereby
reduced until tne leading edge stability criterion is
satisfied.Experience has shown that in the thickening
process,the maximum velocity attained underneath the ice
deposits is about three feet per second.
During freezeup,the upstream progression of the ice front
on the Susitna Ri ver often rai ses water level s by 2 to 4
feet (0.6 to 1.2 m),but higher stages have al so been
E-2-23
2.3 -Susitna River Water Quality
observed.Figure E.2.76 illustrates the open water rating
curve for cross section 9 at RM 103.2 and the observed
increase "in stage as the ice front progressed upstream of
this location in December 1980.Once the ice cover has
consolidated,the rating curve will be approximately paral-
lel with the open water discharge as indicated by the hypo-
thetical ice cover rating curve.However,the water level
increase in a particul ar reach of the river is dependent
upon the prevail ing discharge at which the ice cover was
formed in that reach.
The variabil ity in discharge at freezeup,and hence water
level increase,coupled with the varying berm elevations at
the upstream ends of sloughs results in some sloughs being
overtopped during freezeup,other sloughs occasionally being
overtopped,and still others not being overtopped.For
example,Photograph E.2.3 shows the flow through slough 9
during the 1982 freezeup and photographs E.2.4 through E.2.8
illustrate the increased water level and flow through slough
SA during the same freezeup.It is estimated that slough 8A
was overtopped with a discharge of 150 cfs.
The Susitna River is the primary contributor of ice to the
river system below Talkeetna,contributing 70-80 percent of
the ice load in the Susitna-Chulitna-Talkeetna Rivers (R&M
1982d).Ice formation on the Chulitna and Talkeetna Rivers
normally commences several weeks after freezeup on the
middle and upper Susitna River.
(b)Winter Ice Conditions
Once the sol id ice cover forms,open leads still occur in
areas of high-velocity or ground water upwelling.These
leads shrink during cold weather and are the last areas in
the main channel to be completely covered by ice.Ice
thickness increases throughout the winter.The ice cover
averages over 4 feet (1.2 m)thick by breakup (R&M 1982d),
but thicknesses of over 10 feet (3 m)have been recorded
near Vee Canyon.
Some of the side-channels and sloughs above Talkeetna have
open leads during winter due to ground water upwell ing.
Table E.2.18 is a preliminary compilation of open leads that
were observed during mid-winter 1982,(Trihey personal
communication 1982).They are illustrated in Figures E.2.12
through E.2.20.All open leads identified in Table E.2.18
are bel ieved to be thermally induced from ground water
upwelling.Winter ground water temperatures,generally
varying between 2°C and 4°C (35.6 and 39.2°F),contribute
enough heat to prevent the ice cover from formi ng (Tri hey
1982a).These areas are often salmonid egg incubation
areas.
E-2-24
2.3 -Susitna River Water Quality
I~
(c)Breakup
The onset of warmer air temperatures occurs in the lowe r
basin several weeks earlier than in the middle and upper
basins due to the temperature gradient previously noted.
The low-elevation snowpack melts first,causing the river
discharge to increase.The rising water level puts pressure
on the ice,causing fractures to develop in the ice cover.
The severity of breakup is dependent on the snow melt rate,
the depth of the snowpack and the amount of rainfall,if it
occurs.A light snowpack and warm spring temperatures
result in a gradual increase in river discharge.During
these conditions,strong forces on the ice cover do not
occur to initiate ice movement,resulting in a mild breakup
as occurred in 1981 (R&M 1981e).Conversely,a heavy snow-
pack and cool air temperatures into late spring,followed by
a sudden increase in air temperatures may result in a rapid
rise in water level.The rapid water level increase ini-
t i ates ice movement and when coupl ed wi th ice 1eft ina
strong condition due to the cooler early spring tempera-
tures,can lead to numerous and possibly severe ice jams
which may result in flooding and erosion,as occurred in
1982 (R&M 1982h).Local veloclties during severe ice jams
may reach 10 fps.
These breakup floods result in high flows through the side-
channels and sloughs in the reach above Talkeetna.The
flooding and erosion during breakup are bel ieved to be the
primary factors influencing river morphology in the reach
between Devil Canyon and Talkeetna (R&M 1982d).The follow-
ing is an excerpt from the Winter 1981-82,Ice Observations
Report (R&I"1 1982h)."By May 7 even mi nimum dai ly tempera-
tures averaged 4°C (39.2°F)and ice movement began.Jams
occurred inmost of the areas descri bed in 1981 but wi th
greater consequences,ranging from scarring and denuding of
vegetation to flooding and washing away railroad ties from
under the tracks.In several areas below Talkeetna,massive
amounts of soil were removed from cutbacks,jeopardizing at
least one residence."
2.3.3 -Bedload and Sus~er,ded Sediments
(a)Bedload
Bedload data were collected in 1981 and 1982 in the Susitna,
__Chul itna,and Ta'i keetna Ri vers by the USGS.Data were col-
lected monthly in 1981 during July,August,and September
and weekly for June-August 1982 with two samples in
-E-2-25
--f'"-"'AU);ALASKA T"-,\\',>c'""-'".L\>
U.S.DEPT.oF.lNTERlOB
2.3 -Susitna River Water Quality
September.The 1981 data,presented in Table E.2.19,indi-
cates that the Chulitna River is the primary contributor of
bedload at the confluence.Preliminary results from 1982
bedload measurements confi rm this.Susitna Ri ver bedload
above the confluence was about 80,000 tons (72,730 tonnes)
during 1982,whereas bedload in the Chulitna River was
1,200,000 tons (1,090,900 tonnes).That is,the Chulitna
River has an estimated bedload volume 15 times greater than
the Susitna River near the confluence.
Gravel-bed streams such as the Susitna Ri ver are essenti ally
inactive most of the time (Parker 1980).The surface bed
material must be moved in order for the bed to be mobilized.
Parker indicates that the conditions necessary for mobiliza-
tion of a gravel bed typically occur for only several days
or weeks during the year associated with the high flow
periods.The gravel pavement is maintained between trans-
port events.
The stability of a particle resting on the bed or channel
bank is a function of stream velocity,depth of flow,the
angle of incl ined surface on which it rests and its geo-
metric and sedimentation characteristics (Stevens and Simons
1971).However,the interaction of the above factors is
quite compl ex,and obtaining data for all parameters is
often impractical under natural conditions.In order to
determine at what flow rates the various reaches of the
Susitna River above Talkeetna would be stable,an engineer-
ing approach to the design of stable alluvial channels was
used.
Two major variables affecting channel stability are velocity
and s hear stress.Determi ni ng the shear stress is quite
difficult.Consequently,velocity is often used as the most
important factor in assessing stable alluvial channels.
Various techniques have been developed which estimate the
maximum channel velocity so that no scouring occurs for
values of velocity equal to or less than the maximum velo-
city.However,the maximum permissible velocity varies with
the sediment carrying characteristics of the channel.
Fortier and Scobey (1926)recognized this problem,and
introduced an increase in their listed values of maximum
permissible velocities when water was transporting colloidal
silt.
Various engineering formulas for maximum permissible velo-
city were presented by Simons and Senturk (l977).The
formula selected for analysis was that derived by Neill
(1967).Neill's formula uses data readily available for the
Sus itna Ri ver,and gi ves result sin the s arne range as
Fortier and Scobey's.The formula as presented by Neill
;s:
E-2-26
....
2.3 -Susitna River Water Quality
is/,-gD
Where:
=~~.-0.20
2.5
d
u =maximum permissible velocity,ft/sec
9=density of water,lb/ft 3
"...Is =density of sediment,lb/ft 3 (assumed to be 165
1 b/ft3 )
g =gravitational constant,32 ft/sec 2
r~D =bed material di ameter,ft
d =average depth of flow,ft
,~
The above stability criterion was developed for use on uni-
form bed material or on the median (D50)size in mixed
bed material with moderate size dispersion.Neill (1968)
later indicated that the bed material mixture remained
fairly stable until the 050 size became mobile,at which
time general movement of the bed would occur.The stability
criteria was designed to use vertically-averaged local velo-
cities (mean column velocities),thus identifying bed sta-
bility on only a short segment of the river cross-sectional
width.However,only average velocity at each cross sec-
tion is available for the Susitna River.The results from
the equation would thus indicate when bed movement across
the entire cross-section is imminent.Bedload normally does
not move uniformly across the width of a river,but is con-
centrated in a relatively narrow band.Therefore,the
results of this analysis are not strictly accurate,but do
provide an adequate indicator of bed movement occurrence.
In order to estimate the D50 size of bed material which
woul d be at the poi nt of movement at a parti cul ar cross
section for a given flow rate,the above formula was
rearranged so that bed materi a 1 di ameter was the unknown
value.The average velocity and average depth were obtained
from runs of the HEC-2 model for different flow rates.The
formula in its rearranged version is:
o =
465.43d O•25
E-2-27
2.3 -Susitna River Water Quality
Using the above formula and hydraulic parameters obtained
from runs of HEC-2,estimates were made of the median mate-
ri al size at the poi nt of movement for flow rates of 9,700;
17,000;34,500;and 52,000 cfs.The median bed material
size at the point of movement for selected cross sections is
described in Figure E.2.77.Additional information on bed
material movement can be found in the River Morphology
Report (R&M 1982d).Included in Figure E.2.77 are the bed
material size distribution in the reach described.To
assist in classifying the size range of sediment which is
being moved,a sediment grade scale is included in the bed
movement figure.
By comparing the bed material movement curves to the bed
material size distribution,predictions can be made of the
effect of reducing the streamflow,i.e.,reducing the mean
annual flood at Gold Creek.Once the median bed material
size is moved,general movement of the bed would occur.In
general,bed material size ranges from coarse gravel to
cobbl e throughout most of the river.Some movement of the
median bed material size (from the grid samples)could occur
above 35,000 cfs throughout much of the river,although
these samples were primarily taken along the upper shore.
It is believed that an armor layer consisting of cobbles and
boulders exists throughout most of the river (R&M 1982d).
(b)Suspended Sediments
The Susitna Ri ver and many of its major tributari es are
glacial rivers which experience extreme fluctuations in sus-
pended sediment concentrations as the result of both glacial
melt and runoff from rainfall or snow melt.The West Fork,
Susitna,East Fork,and Maclaren Glaciers are the primary
sources of suspended sediment in the river.
Commencing with spring breakup,suspended sediment concen-
trations begin to rise from their average winter levels of
approximately 10 mg/l.During the summer,values as high as
5690 mg/l have been recorded at Denali,the gaging station
nearest the gl aci ally-fed headwaters.In the rea.ch down-
stream from the mouth of the Maclaren River to the Chulitna
River,there are no significant glacial sediment sources.
Hence,concentrations decrease due to both the settling of
the coarser sediments and dilution by the inflow from
several clear-water tributaries.However,at high flows
when erosion is more prevalent,the tributaries can become
significant suspended sediment contributors.Maximum summer
concentrations of 2620 mg/l have been observed at Gold
Creek.Table E.2.20 illustrates the suspended sediment con-
centrations at Gold Creek observed from May to September in
WY 1952.
E-2-28
....
,-
2.3 -Susitna River Water Quality
Immediately downstream from Talkeetna,concentrations are
increased because of the contribution of the sediment-laden
Chul itna Ri ver whi ch has 28 percent of its drai nage area
covered by year round ice.Maximum values of 3510 mg/l have
been recorded downstream at the Sunshine monitoring station.
Downstream from Talkeetna,the Yentna River is the only
other major glacial river entering the Susitna River.Other
sediment sources in the Susitna River include bank erosion,
tal us sl ides,and resuspension of sediments.Resuspension
of sediments from sand and gravel bars,as ri ver fl ows
increase,can be a significant source of sediment,espe-
cially in the wide,braided portions of the river.When the
flows decrease,the sediments are redeposited on bars down-
stream.
A summary of suspended sediment concentrations is presented
in Figure E.2.78.Table E.2.21 illustrates suspended sedi-
ment data collected at Chase (RM 103),at Sunshine (RM 83),
on the Chulitna River,and on the Talkeetna River during the
summer of 1982.
The 1982 suspended sediment data presented in Table E.2.21,
indicates that the suspended sediment load for the Susitna
River above the confluence was 3,700,000 tons (3,363,600
tonnes)wh i 1e the suspended sediment load for the Chul itna
River was 7,100,000 tons (6,454,500 tonnes).That is,the
suspended load in the Chulitna River was approximately twice
that of the Susitna River above the confluence.
Suspended sediment discharge has been shown to increase with
river discharge (R&M 1982c).This relationship is illus-
trated for four middle and upper Susitna gaging stations in
Figure E.2.79.Table E.2.22 shows the increase in suspended
sediment discharge at Gold Creek with the river discharge of
WY 1953.
Estimates of the average annual suspended sediment load for
three locations on the middle and upper Susitna River are
provided in the following table (R&M 1982c).
Gaging Station
Susitna River at Denali
Susitna River near Cantwell
Susitna River at Gold Creek
Average Annual
Suspended Sediment
Load (Tons/Year)
2,965,000
6,898,000
7,731,000
(Tonnes/
Year)
2,695,500
6,270,900
7,028,200
-
The suspended sediment load enteri ng the proposed Watana
reservoi r from the Susitna Ri ver is assumed to be that at
the gaging site for the Susitna River near Cantwell,or
6,898,000 tons/year (6,210,900 tonnes/year)(R&M 1982c).
E-2-29
2.3 -Susitna River Water Quality
A suspended sediment size analysis for four upper and middle
Susitna River monitoring stations is presented in Figure
E.2.80.This analysis indicates that between 20 and 25
percent of the suspended sediment is 1ess than 4 mi crons
(.004 millimeters or 0.157 mils)in diameter.
2.3.4 -Turbidity
(a)Mainstem
The Susitna River is typically clear during the winter
months with turbidity values at or near zero.Turbidity
values measured by the USGS in January and April 1982 were
1.1 Nepholometric Turbidity Units (NTU)or less at Gold
Creek,Sunshine,and Susitna Station.Turbidity increases
as snow melt and breakup commence.Peak turbi dity val ues
occur during summer when glacial input is greatest.
As presented in Table E.2.21,during 1982,measurements of
up to 720 and 728 NTU were recorded at Vee Canyon and Chase,
respectively.At the USGS gaging station on the glacially-
fed Chulitna River,a value of 1920 NTU was observed.In
contrast,the maximum recorded value on the Talkeetna River,
with its minimal gl acial input,was 272 IHU.Downstream on
the Susitna River,turbidity values decrease,with maximums
of 1056 and 790 NTU measured at Sunshine and Susitna
Station,respectively.
A summa ry of the turbi dity data is presented in Fi gure
E.2.81.Figure E.2.82 shows the relationship between sus-
pended sediment concentration and turbidity as measured on
the Susitna River at Cantwell,Gold Creek,and Chase
(Peratrovich,Nottingham and Drage 1982).
(b)Sloughs
Turbidity values for sloughs 8A,9,16B,19,and 21 were
measured by ADF&G during June,July,and September 1981
(ADF&G 1981).June measurements were taken on June 23,24,
and 25 at a Gold Creek discharge of approximatley
17,000 cfs.No sloughs were overtopped with rnainstem flow
and turbidity in all the sloughs ~'/as less than 1 NTU.The
corresponding turbidity at Gold Creek was 100 NTU.
During the July measurements,Gold Creek flow was in excess
of 35,000 cfs and the upstream ends of sloughs 8A,9,16B
and 21 were overtopped.However,slough 19 was not.Tur-
bidity values in the overtopped sloughs were 130,130,43,
E-2-30
.-
.-
2.3 -Susitna River Water Quality
and 150 NTU,respectively.Turbidity in slough 19 was 2.5
NTU and turbidity at Gold Creek was 170 NTU.
September measurements were taken with a Gold Creek dis-
charge of about 8500 cfs.Maximum slough turbidity was 1.1
NTU and the turbidity of Gold Creek was 5.5 NTU.
These data indicate that sloughs are generally clear with
low turbidity until the upstream ends are overtopped.Dur-
ing overtopping,slough turbidities reflect mainstem values.
Even with overtopping,some sloughs maintained lower turbid-
ity due to the dilution effect of ground water or tributary
i nfl ow.
2.3.5 -Vertical Illumination
In general,vertical illumination through the water column varies
directly with turbidity and hence follows the same temporal and
spatial patterns described above.Although no quantitive assess-
ment was conducted,summer vertical illumination is generally a
few inches.During winter months,the river bottom can be seen
in areas without-ice cover,since the river is exceptionally
clear.However,vertical illumination under an ice cover is
inhibited especially when the ice is not clear or when a snow
cover is present.
2.3.6 -Dissolved Gases
(a)Dissolved Oxygen
Dissolved oxygen (D.O.)concentrations generally remain
high throughout the drainage basin.Winter values average
11.6 to 13.9 mg/l,while average summer concentrations are
between 11.5 and 12.a mg/l.These average concentrations
equate to summer saturation levels between 97-105 percent.
Winter saturation levels decline slightly from summer
levels,averaging 98 percent at Gold Creek and 80 percent at
Susitna Station.
Figures E.2.83 and E.2.84 contain additional dissolved
oxygen data.
(b)Total Dissolved Gas Concentration
Total dissolved gas (nitrogen)concentrations were monitored
in the vicinity of Devil Canyon during 1981 and 1982.
Limited 1981 data revealed saturated conditions of approxi-
mately 100 percent above the Devil Creek rapids.However,
downstream concentrations immediately above and below the
E-2-31
2.3 -Susitna River Water Quality
Devil Canyon damsite were measured in the supersaturated
range of 105-117 percent,respectively (Schmidt 1981).
From August 8,to October 6,1982,a continuous recording
tensionmeter was installed immediately downstream of Devil
Canyon.As noted in Fi gure E.2.85,the data reveal s a
linear relationship between dissolved gas concentration and
discharge at Gold Creek.Gas concentrations ranged from 106
to 115 percent for discharges from 11,700 to 32,500 cfs
(ADF&G 1983).Computations have yielded decay rates which
suggest variations in the rate of decay of supersaturation
with discharge,distance downstream,and channel slope and
morphology characteristics (ADF&G 1983;and Peratrovich,
Nottingham and Drage 1983).
Alaska water quality statutes allow a maximum dissolved gas
concentration of no higher than 110 percent.
2.3.7 -Nutrients
Of the four major nutrients:carbon,silica,nitrogen and phos-
phorus;the limiting nutrient in the Susitna River is phosphorus
(Peterson and Ni chol s 1982).Although total phosphorous concen-
trations regularly exceed established criteria (Figure [.2.86),
the majority of this nutrient is in a form not available for use
by the microflora.
Studies of glacial lakes in Alaska (ADF&G 1982b)and Canada (St.
John et ale 1976)indicate that over 50 percent of the total
phosphorus concentration in the lakes studied was in the biologi-
cally inactive particulate form (Peterson and Nichols 1982).
The bio-available phosphorous,namely orthophosphates,are 0.1
mgjl or less throughout the drainage basin.Although one mea-
surement at Vee Canyon was 0.49 mgjl,this value was disregarded
since it was considered unrealistic (R&M 1982g).Data is
depicted in Figure E.2.87.
Nitrate nitrogen concentrations exist in low to moderate concen-
trations «0.9 mgjl)in the Susitna River.Gold Creek summer
1evel s vary between 0.02 mgjl and 0.86 mgjl.Du ri ng wi nter,the
range of variability is reduced with the concentration varying
between 0.05 and 0.34 mgjl.Maximum recorded concentrations "in
the watershed of 1.2 mg/l are from the Talkeetna River monitoring
station during the summer.Nitrate data for six gaging stations
are illustrated in Figure E.2.88.
E-2-32
(0"--
....
2.3 -Susitna River Water Quality
2.3.8 -Other Parameters
(a)Total Dissolved Solids
Total dissolved solids (TDS),or dissolved salts as they are
often referrd to,are higher during the winter low-flow
peri ods than duri ng summer.The TDS concentrations
generally decrease in a downstream direction.
At Gold Creek,TDS winter values are 100-188 mg/l,while
summer concentrations are between 55 and 140 mg/l.Down-
stream,measurements at Susitna Station range from 109-139
mg/l duri ng wi nter,and between 56 and 114 mg/l in the
summer.Figure E.2.89 presents the data collected.
Salinity data for Cook Inlet are presented in Section
2.6.7.
,....
I
I
....
.....
(b)
(c)
Specific Conductance (Conductivity)
Conductivity values,which generally show an excellent cor-
relation with TDS concentrations provided salinity contents
are reasonably low (Cole 1975),are also higher during the
winter and lower during the summer.In the upstream reaches
of the Susitna,conductivity values are generally higher
than downstream values.
At Denali,values range from 351-467 umhos/cm in the winter
to 121-226 umhos/cm in the summer.Gold Creek conductivi-
ties vary from 84-300 umhos in the winter to 75-227 umhos/cm
in the summer.Spec Hi c conductance 1evel s at Susitna
Station range from 182-225 umhos/cm during winter to 90-160
umhos/cm during summer.Figure E.2.90 provides the
conductivity data for the seven USGS gaging stations.
Significant Ions
Concentrations of the seven significant ions;namely bicar-
bonate,sulfate,chloride,and the dissolved fractions of
calcium,magnesium,sodium and potassium;which comprise a
major portion of the total dissolved solids,are generally
low to moderate,with summer concentrations lower than win-
ter values.The ranges of concentrations recorded upstream
of the project at Denali and Vee Canyon,and downstream of
the project at Gold Creek,Sunshine and Susitna Station are
compared in Table Eo2.23.The ranges of anion and cation
E-2-33
2.3 -Susitna River Water Quality
concentrations at each monitoring station are presented in
Figures £.2.91 to £.2.96.Data on bicarbonate are presented
in the discussion of Total Alkalinity.
(d)Total Hardness
Waters of the Susitna River are moderately hard in the
wi nter t and soft to moderately hard duri ng breakup and
summer.In addition t there is a general trend towards
softer water in the downstream direction.
Total hardness t measured as the sum of the calcium and mag-
nesium hardness and reported in terms of CaC03t ranges
from 60-121 mg/l at Gold Creek during winter to 31-107 mg/l
in the summer.At Susitna Station t values are 73-96 mg/l
and 44-66 mg/l during the winter and summer t respectively.
Figure £.2.97 presents the available data.
(e)E.!!
Average pH values tend to be slightly alkaline with averages
ranging between 6.9 and 7.7.Maximum pH levels occasionally
exceed 8.0 t while a value as low as 6.0 has also been re-
corded.Low pH levels are common in Alaskan streams and are
attributable to the acidic tundra runoff.
At Denali t pH variations between 7.1 and 7.6 occur during
winter t while the summer fluctuation is 7.2 to 7.9.Winter
pH levels at the Gold Creek station are between 7.0 and 8.1.
The range of summer values is 6.5 to 7.9.Figure £.2.98
displays the pH data for the seven stations.
(f)Tot a1 A1 kali ni ty
Total alkalinity concentrations t with bicarbonate typically
the only form of alkalinity present t exhibit moderate to
high levels during winter and low to moderate levels during
.summer.In addition t upstream concentrations are generally
higher than downstream concentrations.
Concentrations at Denali during winter are 112-161 mg/l t and
42-75 mg/l during summer.At Gold Creek t winter values
range between 46 and 88 mg/l t whil e summer concentrations
are in the range of 23-87 mg/l.In the lower river at
Susitna Station t winter concentrations are 60-75 mg/l t and
summer levels are 36-57 mg/l.
Figure £.2.99 provides total alkalinity data in the form of
CaC03'
E-2-34
r-'
2.3 -Susitna River Water Quality
-
....
"""
(g)Free Carbon Dioxide
Free carbon dioxide (C02)in combination with carbonic
acid and the previously discussed bicarbonates (alkal inity)
constitute the total inorganic carbon components present in
the Susitna River.
In the upper basin,summer measurements of free CO~at
Denali yield values that range from 1.5 to 5.2 mg/l.Wlnter
data indicates levels from 5.5 mg/l to 25 mg/l.
At Gold Creek,the summer and winter ranges are virtually
identical.Minimum values are 1.1 mg/l during summer,and
1.2 mg/l during winter.Maximum concentrations are 20 mg/l
during both seasons.
In the lower river basin at the Susitna Station,summer data
indicate a variability between 0.6 and 8 mg/l.Winter data
range from a minimum of 1.8 mg/l to a maximum of 17 mg/l.
,....
Free C02 data are illustrated in Figure E.2.100.
(h)Total Organic Carbon
Total organic carbon (TOC)varies with the composition of
the organic matter present (McNeely et al 1979).
At Gold Creek,summer TOC levels vary from 1.4 to 3.8 mg/l.
Winter concentrations range from 1.0 mg/l to 5.5 mg/l.
Downstream at Susitna Station,TOC ranges between 2.7 and
11.0 mg/l and 0.4 and 4.0 mg/l,duri ng summer and wi nter,
respectively.
Criterion for TOC has been suggested by McNeely et al.
(1979)as 3.0 mg/l,since water with lower level s have been
observed to be relatively clean.However,as is evidenced
above,streams and rivers in Alaska receiving tundra runoff
frequently exceed this criterion (R&M 1982g).
A summary of the TOC data is presented in Figure E.2.101.
(i)Chemical Oxygen Demand
Chemical oxygen demand (COD)data are limited to observa-
tions at Vee Canyon and Gold Creek.Summer concentrations
at Vee Canyon range between 8 and 39 mg/l.Wi nter val ues
are 6-13 mg/l.Below the proposed reservoirs,at the Gold
Creek moni tori ng stat ion,summer 1eve 1s vary from 1.3-24
mg/l,while winter concentrations are in the range of 2-16
mg/l.
E-2-35
2.3 -Susitna River Water Quality
The available COD data are presented in Figure E.2.102.
(j)True Color
True color~measured in platinum cobalt units,typically
displays a wider range during summer than winter.This
phenomenon is attributable to organic acids (especially
tannin)characteristically present in the summer tundra
runoff •
Data gathered at Denal i,with its dominant glacial onglns,
ranged between 0 and 5 units and 0 and 10 units,during win-
ter and summer~respectively.However,color levels at Gold
Creek~with its significant tundra runoff,vary between 0
and 40 color units during winter and 0 to 110 units in sum-
mer.Although they are extremely high,it is not uncommon
for color levels in Alaska to reach 100 units for streams
receiving tundra runoff (R&M 1982g).
Figure E.2.103 displays the data collected.
(k)Meta 1s
The concentrations of many metals monitored in the river
were low or within the range characteristic of natural
waters.In addition~15 parameters were below detectable
limits when both the dissolved (d)fraction and the total
recoverable (t)quantities are counted.For antimony.
boron,gold,platinum,tin,radium,and zirconium,both (d)
and (t)were below detection limits.The dissolved fraction
of molybdenum was also not detectable.
The concentrations of some trace elements,however~exceeded
water qual ity guidel ines for the protection'of freshwater
organisms (Table E.2.17).These concentrations are the
result of natural processes,since with the,exception of
some placer mining activities,there are no man-induced
sources of these elements in the Susitna River basin.
Metals which exceeded criteria include both dissolved and
total recoverable aluminum~cadmium,copper,manganese,
mercury,and zinc.In addition,the dissolved fraction of
bismuth,and the total recoverable quantities of iron,lead,
and nickel also exceeded criteria.
Figures E.2.104 through E.2.119 summarize the data for those
metal s that exceeded criteria.Information pertaining to
metals,that did not surpass established or suggested guide-
lines are presented by R&M (1982g).
E-2-36
r"'.
2.3 -Susitna River Water Quality
(1)Chlorophyll-a
Chlorophyll-a,as a measure of algal biomass,is low due to
the poor light transmissivity of the sediment laden waters.
The only chlorophyll-a data available for the Susitna River
were collected at the Susitna Station gage.Values up to
-1.2 mg/m 3 (chlorophyll-a periphyton uncorrected)were
recorded.However,when the chromospectropic technique was
used,val ues ranged from 0.004 to 0.029 mg/m 3 for three
samples in 1976 and 1977.All recorded values from 1978
through 1980 were less than detectable limits when analyzed
using the chromographic fluorometer technique.
As previously noted,no data on chlorophyll-a are available
for the upper basin.However,with the high suspended sedi-
ment concentrations and turbidity values,it is expected
that chlorophylla values are low.
(m)Bacteri a
No data are available for bacteria in the upper and middle
river basins.However,because of the glacial origins of
the river and the absence of domestic,agricultural,and in-
dustrial development in the watershed,bacteria levels are
expected to be low.
Limited data on bacterial indicators are available from the
lower river basin,namely for the Talkeetna River since
1972,and from the Susitna River at Susitna Station since
1975.Indicator organisms monitored include total coli-
forms,fecal coliforms,and fecal streptococci.
Total col iform counts were generally low,with the three
samples at Susitna Station and 70 percent of the samples on
the Talkeetna River registering less than 20 colonies per
100 ml.Occasional high values have been recorded during
sum~er months,with a maximum value of 130 colonies per 100
ml.
Fecal coliforms were also low,usually registering less than
20 col oni es per 100 ml.The maximum recorded summer val ues
were 92 and 91 colonies per 100 ml in the Talkeetna and
Susitna Rivers,respectively.
..-
-
Fecal streptococci data also display the same pattern;low
values in winter months,with occasional high counts during
the summer months •
E-2-37
2.3 -Susitna River Water Quality
All recorded values are believed to reflect natural varia-
tion within the river,as there are no significant human
influences throughout the Susitna River basin that would
affect bacterial counts.
(n)Miscellaneous
Concentrations of organic pesticides and herbicides,ura-
nium,and gross alpha radioactivity were either less than
their respective detection limits or were below levels con-
sidered to be potentially harmful.No significant sources
of these parameters are known to exist in the drainage
basin,with the exception of herbicides (amitrole,2-4,D,
bromicil and Garlon)used along the railroad right-of-way.
Since no pesticides,herbicides,or radioactive materials
will be used during the construction,filling or operation
of the project,no further discussions will be pursued.
2.3.9 -Water Quality Summary
The Susitna River is a fast flowing,cold water river with
glacial origins and large seasonal flow variations that greatly
influence its character.During winter,river temperatures re-
main at or near DoC (32°F)throughout the mainstem.Local ized
areas,especially sloughs,experience ground water upwelling
which maintains winter temperatures slightly above freezing.
Maximum summer mainstem temperatures at Gold Creek reach 15.0°C
(59.0°F).Ice formation commonly begins during October in the
upper reaches of the river.Breakup usually occurs in the
project area during May.Suspended sediment concentrations and
turbidity levels experience extreme seasonal fluctuations as the
result of glacial melt,snow melt and rainfall.Suspended
sediment measurements up to 5690 mg/l have been documented at
Denali.
Dissolved oxygen concentrations are high throughout the basin
with wi nter val ues near 13 mg/l.Summer measurements average
near 12 mg/l.Dissolved oxygen saturation in the middle and
upper basin averages near 100 percent.Total dissolved gas
concentrations exceed criteria levels below the Devil Canyon
rapids with supersaturated values up to 117 percent recorded.
Nutrient concentrations,namely nitrates and orthophosphates,
exist in low to moderate concentrations throughout the basin.
Total dissolved solids (TDS)concentrations are higher during the
winter low-flow periods than dur"ing summer.Correspondingly,
conductivity values are also higher during the winter,and lower
during summer.Concentrations of the seven significant ions are
generally low to moderate with lower levels during summer.The
E-2-38
.....
-
1"""1I
-
2.4 -Baseline Ground Water Conditions
Sus itna is moderately hard duri ng wi nter and soft to moderately
hard during breakup and summer.Typically,pH values range be-
tween 7 and 8,although values often fall below 7 due to the
organic nature of tundra runoff.Total alkalinity concentrations
are moderate to high during winter,and low to moderate during
summer.
Total organic carbon and true color both exceed their respective
criteria because of the influence of tundra runoff •
(
The concentrations of many trace elements monitored in the river
were low or within the range characteristic of natural waters.
However,the concentrations of some trace elements exceeded water
quality guidelines for the protection of freshwater aquatic
organi sms.These concentrat ions are the resu lt of natural pro-
cesses since there are no man-induced sources of these elements
in the Susitna River basin,with the exception of some placer
mining activities.
Chlorophyll-a measurements are low as a result of the poor light
transmissivity of the sediment-laden waters.Bacterial indi-
cators exhibit generally low concentrations.
Concentrations of organic pesticides and herbicides,uranium,and
gross alpha radioactivity were either less than their respective
detection limits or were below levels considered to be poten-
tially harmful to aquatic organisms.
2.4 -Baseline Ground Water Conditions
2.4.1 -Description of Water Table and Artesian Conditions
The landscape of the upper and middle basin consists of rela-
tively barren bedrock mountains with exposed bedrock cliffs in
canyons and along streams,and areas of unconsolidated sediments
(outwash,till,alluvium)with low relief,particularly in the
valleys.The arctic climate has retarded development of topsoil.
Unconfi ned aqu ifers exi st in the unconso 1 i dated sed iments,how-
ever there are no water table data in these areas except in the
relict channel at Watana and the south abutment at Devil Canyon.
Winter low flows in the Susitna River and its major tributaries
are fed primari ly from ground water storage in these unconfi ned
aquifers.The bedrock within the basin is comprised of crystal-
line and metamorphic rocks.No significant bedrock aquifers have
been identified or are anticipated.
Below Talkeetna,the broad plain between the Talkeetna Mountains
and the Alaska Range generally has higher ground water yields,
with the unconfined aquifers immediately adjacent to the Susitna
E-2-39
2.4 -Baseline and Ground Water Conditions
River having the highest yields.Potential ground water yields along
the ri ver are 100-1000 gallons per mi nute (gpm)(379-3795 1 iters per
minute),whereas upstream of Talkeetna,the ground water yields adjac-
ent to the river are 20-50 gpm (76-189 liters per minute)(Freethey
and Scu lly 1980).
2.4.2 -Hydraulic Connection of Ground Water and Surface Water
Much of the ground water in the system is stored in unconfined
aquifers in the valley bottoms and in alluvial fans along the slopes.
Consequently,there is a direct connection between the ground water
and surface water.Confi ned aqu ifers may exi st withi n some of the
unconsolidated sediments,but no data are available as to their
extent.
2.4.3 -Locations of Springs,Wells,and Artesian Flows
Due to the wilderness character of the basin,there are no data on
the location of springs,wells,and artesian flows other than within
the sloughs.Winter aufeis buildups have been observed between Vee
Canyon and Fog Creek,i nd i cat i ng the presence of ground water di s-
charges.Ground water is the main source of flow durin~winter
months,when precipitation falls as snow and there is no glaclal melt.
It is believed that much of this water comes from the unconfined
aquifers (Freethey and Scully 1980).
2.4.4 -Hydraulic Connection of Mainstem and Sloughs
The sloughs downstream from Devil Canyon are used by salmonid species
for spawning,and provide valuable rearing habitat for anadromous and
resident fish.Ground water upwelling within the sloughs provides
appropriate conditions for egg incubation.
Ground water studies at Sloughs 8A and 9 indicate that there is a
hydraulic connection between the mainstem Susitna River and the
sloughs.Ground water observat i on well measurements demonstrate that
the ground water upwelling in the sloughs is caused by ground water
flow from the uplands and from the mainstem Susitna.The higher per-
meability of the valley bottom sediments (sand-gravel-cobble-
alluvium),compared with the till mantle and bedrock of the valley
sides,indicated that the mainstem Susitna River is the major source
of ground water inflow in the sloughs.This is illustrated in Figures
E.2.120 and E.2.121.The contours indicate a flow direction along the
valley and laterally towards the sloughs.Prel iminary estimates of
the travel time of the ground water from the mainstem to the sloughs
indicate a time on the order of six months to a year or more.
Changes in water levels in observation wells in response to a 3.1
foot change in the mainstem stage during the September 14 to 22,1982
hydrograph event varied from 2.8 feet to 1.7 feet (0.85 to 0.52 m)at
distances of 50 feet (15 m)and 1200 feet (366 m),respectively,from
the river bank1/.
l/See Appendix E.2.A for a description of groundwater levels and main-
stem discharges.
E-2-40
,~
.fII¥iIl'.
-
2.5 -Existing Lakes,Reservoirs,and Streams
Preliminary investigations show that ground water upwelling tem-
peratures in sloughs reflect the long-term average water tempera-
ture of the Susitna River,which is approximately 3°e (37.4°F).
These conclusions are based upon the investigations that have
been undertaken to determi ne the mechani sms controll i ng slough
upwelling.Drilling and soil sampling,installation of observa-
tion wells,monitoring of ground water levels and temperatures,
analysis of field data,and numerical and analytical modeling of
the ground water have been performed.The results indicate that
hydrodynamic dispersion and heat exchange between the ground
water and soil are the dominant mechanisms responsible for the
near constant upwell ing temperatures.Annual ground water tem-
peratures within the range 3 +1.5°e (37.4 +2.7°F)are calcu-
1ated for ground water traver di stances greater than 100 feet
(30 m)from the mainstem,based on best estimates for the
controlling parameters (Acres 1983).
The dominant parameter in the analysis is the hydraulic conduc-
tivity of the alluvial sediments.However,hydraulic conductiv-
ity is spatially variable.Values an order of magnitude,higher
or lower than the best estimate used in the calculations are
quite possible.The sensitivity of temperature fluctuations to
an order of magnitude increase in hydraulic conductivity has been
exami ned.Thi sind i cates that temperatures withi n the range
3+1.5°e (37.4 +2.7°F)would occur at distances greater than
24,000 feet (7317 m)along a flow line.The flow line lengths
between the mainstem and the sloughs are typically 1000 to 4000
feet (305 to 1220 m).Thus,the di spersi on and heat exchange
mechanisms appear capable of significant damping of the seasonal
mainstem temperature fluctuations even for hydraulic conductivi-
ties significantly higher than have been calculated from avail-
able field data.
A technique for measuring upwelling water flows has been devel-
oped.However,sufficient measurements have not yet been taken
to determine the magnitude and spatial variation of ground water
flow.Gaging of flows in Slough 9 has been undertaken and these
data indicate that the ground water component was 0.74 and
1.00 cfs on the two occasions measured.This represented 36 and
61 percent of the total flow at the downstream end of the
slough.
2.5 -Existing Lakes,Reservoirs,and Streams
2.5.1 -Lakes and Reservoirs
There are no reservoirs on the Susitna River or on any of the
tributaries flowing into either the Watana or Devil Canyon reser-
voirs.A few small lakes at and upstream of the damsites will be
affected by the proj ect.No 1akes downstream of the reservoi rs
will be directly impacted by project construction,impoundment,
or ope rat i on.However,secondary impacts resulting from
increased access from the access road or transmission line
E-2-41
2.5 -Existing Lakes,Reservoirs,and streams
maintenance road could occur.The major lakes and lake complexes
potentia11y affected are listed in Table E.2.24,along with the
potential impacts.
The normal maximum operating level of 2185 feet (666 m)"in the
Watana reservoi r wi 11 1ead to the i nundati on of a number of
lakes,none of which are named on USGS topographic maps.Most of
these are sma11 tundra lakes and are located along the Susitna
River between RM 191 and RM 197 near the mouth of Watana Creek.
The largest of these lakes is Sally Lake.It is situated at geo-
graphic location S/32N/07E/29.Surface area of this lake is 63
acres (25 ha).It has a maximum depth of 27 feet (8 m)and a
mean depth of 11.6 feet (3.5 m).The shoreline length is 10,500
feet (3200 m).The water surface elevation is approximately at
elevation 2050 feet (625 m).The area-capacity curves for Sally
Lake are illustrated in Figure E.2.122.
There are 27 1 akes 1ess than 5 acres (2 ha)in surface area and
one between 5 and 10 acres (2 and 4 ha),all on the north side of
the river between RM 191 and RM 197.In .addition,a sma11 lake
(less than 5 acres [2 haJ)lies on the south shore of the Susitna
at RM 195.5 and another of about 10 acres (4 ha)in area lies on
the north side of the river at RM 204.Most of these 1akes
appear to be perched,but fi ve are either connected by small
streams to Watana Creek or empty directly into the Susitna River
mainstem.
A small lake (2.5 acres or 1 ha)lies on the south abutment near
the Devil Canyon damsite at RM 151.3,at approximately elevation
1400 feet (427 m).No other 1akes exi st withi n the proposed
Devil Canyon reservoir.
2.5.2 -Streams
Numerous streams in each reservoi r wi 11 be compl etely or par-
tially inundated during project filling and operation.The
streams to be inundated within the respective reservoirs and
appearing on the 1:63,360 scale USGS maps,are illustrated "in
Figures E.2.123 and E.2.124 and listed in Tables E.2.25 and
E.2.26.Provided in these tables are the map name of each
stream,Susitna River mile locations,the existing elevation of
the stream mouths,the average stream gradient of the reach to be
inundated and the 1ength of the stream to be inundated.El eva-
tions of 2190 feet (668 m)and 1455 feet (444 m)were used for
these determinations for the Watana and Devil Canyon reservoirs,
respectively.
Withi n the Watana reservoi r,there are two sloughs located at
approximately RM 212.Near Jay Creek,there are two sloughs,one
just upstream (RM 208.7)and the other just downstream (RM 208.0)
from the mouth of Jay Creek.Additional sloughs are located at
RM 205.7,RM 200.9 and just downstream of Watana Creek at
RM 193.6.Within Devil Canyon reservoir,there are ten sloughs
E-2-42
.....
2.6 -Existing Instream Flow Uses
at RM 180.1, 179.1, 177.0, 173.9,172.2,172.0,171.5,171.5,
169.5,and 168.0,which will be totally inundated.The locations
of the sloughs to be inundated are also shown on Figures E.2.123
and E.2.124.
Aside from the streams to be inundated by the two project im-
poundments,there are several tributaries downstream of the proj-
ect which may be affected by changes in the Susitna River flow
regime.Since post-project summer stages in the Susitna will be
several feet lower than pre-project levels,some of the creeks
may either degrade to the lower elevation or remain perched above
the river.Analyses were done on 19 streams between Devil Canyon
and Talkeenta which were determined to be important for fishery
reasons or for maintenance of existing bridge crossings by the
Alaska Railroad (R&M 1982f).These streams are listed in Table
E.2.27,with their river mile locations and the reason for
concern.
2.6 -Existing Instream Flow Uses
Instream flow uses are uses made of water in the river channel as
opposed to water withdrawn from the river.Instream flow uses include
hydroelectric power generation;commercial or recreational navigation;
waste assimilation;downstream water rights;water requirements for
riparian vegetation,fisheries and wildlife habitat;recreation;fresh-
water recru itment to estuari es;and water requ ired to ma i nta in the
desirable aesthetic characteristics of the river itself.Existing
instream flow uses on the Susitna River involve all of these uses
except hydroelectric power operation.
2.6.1 -Downstream Water Rights
In 1966,liThe Alaska Water Use Act"was established.This legis-
lation,which was amended in 1979,authorized the Alaska Depart-
ment of Natural Resources (ADNR)to determine and adjudicate
water rights for use of the state's water resources (ADNR 1981).
Existing water rights users at that time were eligible for
"gran dfather rights"and were required to formalize their inter-
ests as of April 1968.Currently,the statutory procedure for
formalization of water rights requires the filing of an Applica-
tion for Water Rights with the Commissioner of the ADNR.After
issuance of a permit and subsequent to the beneficial utilization
of th~water as noted in the permit,ADNR personnel may elect to
conduct a field investigation.Provided the ADNR concur that the
water rights have been perfected,a Certificate of Appropriation
is then issued.This certificate provides legal rights against
confl i cti ng users of the water who do not have water ri ghts or
are junior in priority (ADNR 1981).
Existing surface and ground water rights in the Susitna River
basin were investigated by Dwight (1981).To facilitate this
E-2-43
2.6 -Existing Instream Flow Uses
search,the basin was divided into 18 township grids (Figure
E.2.125).The investigation noted that the only significant surface
water rights exist in the headwaters of the Willow Creek (18.3 cfs)
and Kahiltna (125 cfs)township grids where placer mining operations
occur on a seasonal basis (Table E.2.28).Neither of these areas
will be affected by the project.
The only appropriation on record in the area of the proposed reser-
voirs (Susitna Reservoir township grid)is permit ADL-203386 current-
ly held by the A1ask a Power Authority for the 44 man Watana camp.
The permit for the camp,from which field work for the project has
been conducted,is for 3000 gpd (0.00465 cfs or 11,355 liters per
day)from a nearby unnamed lake.
Downstream of the proposed facilities,in the Susitna township grid,
surface water rights amount to 0.153 cfs while ground water appropri-
ations total 0.56 acre-feet/year or 0.0498 cfs (Table E.2.29).No
surface water rights on file with the ADNR withdraw directly from the
Susitna River malnstem.In addition,an analysis of topographic maps
and overlays denoting the specific location of each recorded appro-
priation indicate that all surface water diversions from tributaries,
as well as all ground water withdrawals from wells,are located at
elevations that will be unaffected by water level changes and/or flow
regulation resulting from the construction,filling,and operation of
the proposed Susitna Hydroelectric Project (Dwight 1981).As such,
no further discussions regarding potential impacts to existing down-
stream water rights appropriations will be presented.
2.6.2 -Fishery Resources
The Susitna River supports populations of both anadromous and resi-
dent fish.Important commercial,recreational,and subsistence
species include pink,chum,coho,sockeye and chinook salmon,
eulachon,rainbow trout,Arctic grayling,burbot,and Dolly Varden.
Natural flows presently provide for fish passage,spawning,incuba-
tion,rearing,overwintering,and outmigration.These activities are
correlated to the natural hydrograph.Salmon migrate upstream and
spawn on the receed i ng 1imb of the spri ng hydrograph and throughout
most of the summer,the eggs incubate through the 1ow-fl ow Wl nter
period,and fry out-migratlon occurs in association with spring
breakup1/.Rainbow trout and grayling spawn during the high
flows oT the breakup period with embryo development occurring during
the early summer.Further detail on the fishery resources is pre-
sented in Chapter 3.
2.6.3 -Navigation and Transportation
(a)Boat Navidation and Transportation
Navigation and transportation on the Susitna River from the
headwaters to the Dev il Canyon dams ite is 1imited,bei ng
1!See Appendix E.2.A for a description of mainstem flow relationships
to hydraulic and hydrologic characteristics of sloughs.
E-2-44
-
-I
2.6 -Existing Instream Flow Uses
primarily related to hunters 'and fishers·access to the
Tyone River (RM 247)after launching at the Denali Highway
(RM 291).However,some use is made of recreational kayak-
ing,canoeing and rafting.Downstream of the Tyone River,
Vee Canyon rapids (RM 226-232)offer some of the fi nest
rafting and white-water kayaking in Alaska,and are rated
Cl ass IV white-water.
Farther downstream are the Devil Creek and Devi 1 Canyon
rapids which offer 11 miles (18 km)of some of the most
challenging kayaking in the world.The first successful
running of these rapids,which are rated Class VI white-
water occurred in 1978.Less than 40 kayakers from through-
out the world have attempted the rapids since then,and at
least five people have died trying.
Oownstream of Devil Canyon,the Susitna River is considered
navigable by the U.S.Department of the Interior,Bureau of
Land Management (BLM)from its mouth to a distance 7.5 miles
(12 km)upstream of Gold Creek (TES 1982).However,the
river is used for navigation up to Portage Creek (RM 149).
This entire reach is navigable under most flow conditions
although abundant floating debris during extreme high water
and occasional shallow areas during low water can make navi-
gation difficult.
The Susitna River downstream of Devil Canyon is used for
sport fishing,hunting,recreational boating,sightseeing,
and transportation of some supplies.Access to the river is
gained from four principal boat launching sites,Talkeetna
(RM 97),Sunshine Bridge at the Parks Highway (RM 84),
Kashwitna Landing (RM 61),and Willow Creek (RM 49);from
several of the minor tributaries between Talkeetna and Cook
Inlet;and from Cook Inlet.Other primary tributaries
accessible by road are Willow Creek,Sheep Creek,and
Montana Creek.
A very substanti al increase in the use of the ri ver and its
tributaries has been noted within recent years.Dwight and
Trihey (1981)reported a 50 percent increase in the use of
certain salmon streams in past years.During 1976,500
boats were 1aunched at the Kashwitna Landi ng.Mi d-summer
1981 estimates of launches at the Kashwitna Landing approxi-
mated 5000.One Friday,during the 1981 king salmon season,
147 craft were launched (TES 1982).An aerial survey of the
river during moose season,Thursday,September 17,1981,
noted 22 craft on the mainstem below Talkeetna and 102 craft
on its respective tributaries.
£-2-45
2.6 -Existing Instream Flow Uses
Under the existing flow regime,the ice on the river breaks
up and the river becomes ice-free for navigation in mid to
late May.Flows typically rema'in high from that time
through the summer until September or early October,when
freezeup begins.During freezeup frazil ice restricts boat
operat ion,but often a frazil-free peri od of 1 to 2 weeks
follows the initial stages of freezeup and navigation is
again possible.The next sequence of frazil generation
generally leads to continuous freezing of the river,prohib-
iting open-water navigation until after the following spring
breakup.
In 1982,investigations were conducted on potential naviga-
tion problems downstream of the proposed hydroelectric dams
on the Susitna River during the ice-free months (ADNR 1982).
A review was made of river cross-sectional data,simulated
water surface profil es determi ned by the HEC-2 program and
aerial photographs for the reach between Portage Creek and
Talkeetna.Figures E.2.63 and E.2.64 present the results of
the simulation,converted to depths at each cross section
for the various discharges considered.Figure E.2.63 shows
that the major area of concern is a broad shallow reach 1 to
3 miles (1.6 to 4.8 km)below Sherman,where the main chan-
nel of the Susitna River crosses the floodpl ain.A repre-
sentative cross section of the reach is depicted in Figure
E.2.10.Water surface elevations for each of the discharges
simulated and the estimated water surface elevation for a
flow of 6000 cfs are presented.The water surface el eva-
tions are considered accurate to ~1 foot (0.3 m).
Using the stage-discharges relationship for cross section 32
presented in Figure E.2.10,the Alaska Department of Natural
Resources (ADNR)determi ned that a di scharge of 6500 cfs
would be required to maintain a navigable depth of 2.5 feet
(0.8 m).The 2.5 foot (0.8 m)depth was established as the
navigation criterion even though 1.5 feet (0.5 m)was con-
sidered as an adequate depth for navigation,because of the
1 foot (0.3 m)potential error in the HEC-2 water surface
prediction.Extrapolation of the stage-discharge rating
curve to a 1.5 foot (0.5 m)depth indicates that the equiva-
lent discharge would be approximately 3000 cfs.
A reconnaissance conducted on October 14,1982 (R&M 1982j)
when the Gold Creek discharge was 6000 cfs indicated that
the reach downstream of Sherman was navigable if the center
channel was used.
E-2-46
-
~,
2.6 -Existing Instream Flow Uses
Downstream from Talkeetna,the ADNR study used personal
interviews,aerial photographs and topographic maps to
determine potential navigation problems.Four areas were
designated as potentially adversely affected by reduced
discharges.
1.A braided area on the east side of the Susitna River,
about 6 river miles (10 km)downstream from Talkeetna
near RM 91.
2.A braided area of the east side of the Susitna River,
adjacent to and extending about 1 mile (1.6 km)down ...
stream from Kashwitna.Thi sis at approximate1 y RM 60
to 61.
3.The Susitna River near its confluence with Willow Creek
at about RM 48 to 49.
4.On A1 exander Slough (a1 so known as the west channel),
just as it divides off the mainstem of the Susitna River
(also known as the east channel downstream of this
point).This is near RM 19.
The ADNR analysis indicates the following mlnlmum discharges
at Sunshine gage were necessary to maintain 1.5 foot and 2.5
foot (0.5 m and 0.8 m)depths,respectively.
Near Talkeetna <1000 cfs,<1000 cfs
Kashwitna Landing Upstream 2750 cfs,7200 cfs
Kashwitna Landing Downstream 3550 cfs,8100 cfs
Near Willow Creek 10,400 cfs,16,200 cfs
Near Willow Creek Middle Channel 6500 cfs,11,000 cfs
Mi nimum di scharges cou1 d not be determi ned for A1 exander
Slough.
Identified restrictions of open-water navigation over the
full length of the river are tabulated in Table E.2.30.
(b)Other Navigation and Transportation Uses
The Susitna is used by several modes of non-boat transporta-
tion at various times of the year.Fixed-wing aircraft on
floats make use of the river for landings and take-offs dur-
ing the open water season.These are primarily at locations
in the first 50 m"iles (80 km)above the mouth.The previ-
ously mentioned aerial survey conducted during moose season
(September 17,1981),located 12 planes on the mainstem and
its tributaries below Talkeetna (TES 1982).Among the most
common 1andi ng sites for f1 oatp1 anes are Kashwitna Ri ver,
Willow Creek,Little Willow Creek,Deshka River (Kroto
E-2-47
2.6 -Existing Instream Flow Uses
Creek),Susitna River near the mouth of Alexander Creek,and
Alexander Slough near the mouth of the river.Floatplane
access also occurs on occasion within the middle and upper
Susitna reaches.
After the river ice cover has solidly formed in the fall,
the river is used extensively for transportation access by
ground methods in several areas.Snow machines and dogsleds
are commonly used below Talkeetna;the Iditarod Trail
crosses the river near the Yentna River confl uence and is
used for an annual dogsled race in February.Occasional
crossings are also made by automobiles and ski,primarily
near Talkeetna and near the mouth.
2.6.4 -Recreation
The summer recreat i on uses of the Sus itna Ri ver i ncl ude recrea-
tional boating,kayaking,canoeing,sport fishing,hunters·
access,and sightseeing.In winter,recreation uses include snow
machines and dogsleds.These uses were discussed in Section
2.6.3.
2.6.5 -Riparian Vegetation and Wildlife Habitat
Wetlands cover large portions of the Susitna River basin,includ-
ing riparian zones along the mainstem Susitna,sloughs,and trib-
utary streams.Wetl ands are bi 01 09i ca lly important because they
generally support a greater diversity of wildl ife species per
unit area than most other habitat types in Alaska.In addition,
ri pari an wetlands provi de wi nter browse for moose and,duri ng
severe winters,can be a critical survival factor for this
species.They also help to maintain water quality throughout
regional watersheds.Detailed information on riparian wetlands
and wildlife habitat can be found in Chapter 3.
The processes affecting riparian vegetation include freezeup,
spring ice jams and flooding.As noted in Section 2.3.2(c),
spring ice jams can have a devestating impact on vegetation.
However,ice jams are generally confined to specific areas.In
the Devil Canyon to Talkeetna reach,both flooding and freeze up
are believed to be important factors affecting vegetation.
Because of the braided channel pattern downstream of Tal keetna,
flooding is expected to be the dominant factor influencing
riparian vegetation.
2.6.6 -Waste Assimilative Capacity
Revi ew of the Alaska Department of Envi ronmenta 1 Conservation
II Inventory of Water Poll ut i on Sources and Management Actions,
E-2-48
-
--
-
2.6 -Existing Instream Flow Uses
Maps and Tabl es"(1978)indicates that the primary sources of
pollution to the Susitna River watershed are placer mining opera-
tions.Approximately 350 sites were identified although many of
these claims are inactive.As the result of these operations,
1 arge amounts of suspended sediment may be i nt roduced into the
watershed.However,no biochemical oxygen demand (BOD)is placed
on the system,and therefore,the waste assimil ative capacity
remains unaffected by these mining activities.
As for BOD discharges in the watershed,the inventory did identi-
fy one municipal discharge in Talkeetna,two industrial waste-
water discharges at Curry and Tal keetna,and three sol id waste
dumps at Talkeetna,Sunshine,and Peters Creek.No volumes are
available for these pollution sources.
Personal communication (1982)with Joe LeBeau of the Alaska
Department of Environmental Conservation (ADEC)revealed that no
new wastewater discharges of any significance are believed to
have developed since the 1978 report.Further,it was noted that
the sources that do exist are believed to be insignificant.
Mr.Robert Fl int of the ADEC indicated that,in the absence of
regulated flows and significant wastewater discharges,the ADEC
has not establ i shed minimum flow requi rements necessary for the
maintenance of the waste assimil ati ve capacity of the river
(personal communication 1982).
2.6.7 -Freshwater Recruitment to Cook Inlet Estuary
The Susitna River is the most significant contributor of fresh-
water to Cook In 1et and,as such,has a majo r i nfl uence on the
salinity of Upper Cook Inlet.High summer freshwater flows asso-
ciated with the occurrences of snow melt,rainfall,and glacial
melt cause reduced sal inities.During winter,low flows permit
the more saline ocean water to increase Cook Inlet salinities.
A second major factor influencing the salinity levels in Cook
Inlet are the large tidal variations that occur.These tides,
which are amongst the largest in the world,cause increased
mixing of freshwater and saltwater.
A numerical water quality model of Cook Inlet was developed for
the U.S.Army Corp of Engineers (Tetra Tech,Inc.1977).The
results of this model were found to compare quite well with the
available Cook Inlet surface salinity data from May 21-28,1968;
August 22-23,1972;and September 25-29,1972 (COE 1979).
Using this model,Resource Management Associates (1983)simulated
pre-project monthly salinity concentrations throughout the Inlet
E-2-49
2.6 -Existing Instream Flow Uses
using average freshwater flows from the Cook Inlet tributaries.
Figure E.2.126 shows 5 select locations where salinities were
computed.Near the mouth of the Susitna Ri ver (Node 27),the
study results indicated a natural salinity of 5800 mg/l in August
and 21,000 mg/l during April,or a range of 15,200 mg/l (Table
E.2.31).The temporal salinity variation at this location is
provided in Figure E.2.127.
In the center of Cook Inlet near East Foreland,approximately 45
miles southwest of the Susitna River mouth (Node 12),normal sal-
i nity values were estimated to vary between 21,100 mg/l duri ng
September and 26,800 mg/l in Apri 1,or a range of 5700 mg/l.
Near the mouth of Cook Inlet (Node 1)the annual salinity range
is 2100 mg/l with maximum and minimum average monthly vallJes of
30,200 mg/l in April and 28,100 mg/l in August.
In addition to these three locations,estimated pre-project sal-
inity values for the centers of Turnagain and Knik Arms (Nodes 55
and 46,respectively)are also provided in Table E.2.31.
Sa 1i nity measurements were recorded at the mouth of the Sus i tna
River during spring tides on August 18 and 19,1982 to determine
if,and to what extent saltwater intruded upstream.No saltwater
intrusion was detected.Flow was approximately 90,000 cfs at the
mouth of the Susitna River at the time the measurements 'Were
made.Additional salinity measurements were made on February 14,
1983 to determine if saltwater penetration occurs upstream of the
mouth of the river during low flow periods.Salinity was moni-
tored over a tidal cycle at approximately RM 1.No sal inity was
detected.
2.7 -Access Plan
2.7.1 -Flows
The flow regime of the streams to be crossed by the access road
is typical of subarctic,snow-dominated streams,in which a snow
melt flood in spring is followed by generally moderate flows
through the summer,punctuated by periodic rainstorm floods.
Between October and April,precipitation falls as snow and
remains on the ground.The annual low flow occurs during this
period,and is predominately base flow.
Streamflow records for these small streams are sparse.Conse-
quently,regression equations developed by the U.S.Geological
Survey (Freethey and Scully 1980)have been utilized to estimate
the 30-day low flows for recurrence intervals of 2,10,and 20
years,and the peak fl ows for recurrence i nterva 1s of 2,10,25,
and 50 years.These flows are tabulated in Table E.2.32 for the
E-2-50
r-:--
-
-
2.8 -Transmission Corridor
three access route segments:(1)Denal i Highway to Watana D.am;
(2)Watana Dam to Devil Canyon Dam;and (3)the Devi 1 Canyon to
Gold Creek railroad.Only named streams are presented.
2.7.2 -Water Quality
At present,1 ittle water qual ity data are available for the
streams in the vicinity of the proposed access routes.
However,as noted in the fisheries discussions in Chapter 3,many
of the major streams scheduled for crossing are known to support
popul ations of Arctic grayl ing.Arctic grayl i ng are generally
residents of clear,cold streams (Scott and Crossman 1973)and as
a result it is theorized that water quality is generally good.
In contrast,water quality conditions associated with tundra run-
off are also expected.Among the conditions that might be anti-
cipated are pH levels in the 6-7 range,total organic carbon con-
centrations exceeding the suggested criterion level of 3.0 mgjl
(McNeely et al.1979),and true color values as high as 100
un i ts •
During periods of high flow conditions resulting from spring snow
melt and summer rainstorms,elevated suspended sediment and tur-
bidity levels are expected.
2.8 -Transmission Corridor
-The transmission corridor consists of four segments:
Willow 1 ine and the Fai rbanks-Healy 1 ine (called
WillOW-Healy Intertie,and the Gold Creek-Watana line •.
the Ancho rage-
"Stubs"),the
,....
I
..,..
The Intertie will extend from Willow to Healy,where it will ultimately
connect with Susitna Hydroelectric Project features referred to as
"Stubs."The Intertie is planned to be constructed in 1983.It will
be a l70-mile (274 km)long facility constructed basically of guyed
steel "X"poles.Angle structures will be three separate vertical pole
structures with single-pole hillside structures.At initial construc-
tion,the intertie line will be energized at 138 kV.
When the l~atana Project comes on line in 1993,a second parallel line
will be added to the Intertie,the "Stubs"will be constructed at the
two ends,the lines will be energized to 345 kV,and a switchyard built
near Gold Creek to connect with Watana power.In 2002,when Devil
Canyon comes on line,a third parallel line will be built on the Gold
Creek to Willow portion of the line,and the Willow to Anchorage stub
will also have a third line •
E-2-51
2.8 -Transmission Corridor
2.8.1 -Flows
Water bodies in each of the four sections will be crossed by the
transmission line.Most of these are small creeks in remote
areas of the regi on,but each segment has some maj or st ream
crossings.Data are limited on the small streams,both with
respect to water quantity and water qual ity.Most of the major
crossings,however,have been gaged at some point along their
length by the USGS.Major stream crossings are identified below.
Pertinent gage records are summarized in Table E.2.33.
The Anchorage-Willow segment will cross Kn ik Arm of Cook In 1et
with a submarine cable.Farther north~major stream crossings
include the Little Susitna River and Willow Creek,both of which
ha ve been gaged.
The Fairbanks-Healy line will make two crossings of the Nenana
River and one of the Tanana River,both large rivers and gaged.
The intertie route between Willow and Healy will
dozen small creeks,many of I"hich are unnamed.
include the Talkeetna~Susitna,and Indian Rivers;
and Middle Fork of the Chulitna River;the Nenana
Fork of the Nenana River;and Healy Creek.
cross several
Maj or st reams
the East Fork
River;Yanert
The final leg of the transmission corridor,from Gold Creek to
Watana Dam,will cross only one major river:the Susitna.Two
smaller but sizeable tributaries that will be crossed are Devil
Creek and Tsusena Creek~neither of which have been gaged.
2.8.2 -Water Quality
Water quality data are limited for those streams and rivers that
exist in close proximity to the proposed transmission corridors.
A literature search by Dwight (1982)directed towards USGS sus-
pended sediment data coll ecti on i dentifi ed one conti nuous
sampling location on the Nenana River at Healy.In addition,
sparse periodic data are available for monitoring stations at the
following locations:Nenana River near Windy,Healy Creek near
Suntrana~Healy Creek at Suntrana,Healy Creek 0.1 mile (0.2 km)
above french Gulch near Usibelli~Lignite Creek 0.5 mile (0.8 km)
above mouth near Healy,Lignite Creek near Healy and Francis
Creek 100 feet above Lignite Creek near Suntrana.
E-2-52
-
.....
I
2.8 -Transmission Corridor
At the USGS Stat ion 15518000 on the Nenana Ri ver near Healy,
13 years of continuous records revealed mean daily summer sedi-
ment concentrat ions rangi ng up to 8330 mgjl.Al though no wi nter
data were available,late September and October measurements were
approachi ng concentrations of near zero.These data are i ndi ca-
tive of the glacial origins at the river's headwaters.Although
no additional water quality parilineters were investigated by
Dwight 1982,it is assumed that previously noted characteristics
associated with tundra runoff will also be present in the Nenana
and its tributaries •
E-2-53
.....
.....
!
-
.....
3 -PROJECT OPERATION AND FLOW SELECTION
3.1 -Project Reservoirs
3.1.1 -Watana Reservoir Characteristics
The Watana Reservoir will be operated at a normal maximum operat-
ing level of El 2185 ft (666 m)above mean sea level,but will be
allowed to surcharge to El 2190 ft (668 m)in late August during
wet years.Average annual drawdown will be to £1 2093 ft (638 m)
with Watana operation and El 2080 ft (665 m)with Watana/Devi 1
Canyon operati on.The maximum drawdown for either operati on
scenario will be to El 2065ft (630m).During extreme flood
events,the reservoir will rise to £1 2193.3 ft (668.7 m)for the
1:10,000 year flood and £1 2200.5 ft (670.9 m)for the probable
maximum flood.
At El 2185 ft (666 m),the reservoir will have a surface area of
38,000 acres (15,200 ha)and a total volume of 9.47 million acre-
feet as indicated in the area-capacity curves in Figure E.2.128.
Maximum depth wi 11 be 735 feet (223 m)and the mean depth wi 11 be
250 feet (76 m).The reservoir will have a retention time of
1.65 years.The shorel"ine length will be 183 miles (295 km).
Withi n the Watana reservoi r area the substrate cl ass ifi cat ion
varies greatly.It consists predominantly of glacial,colluvial,
and fluvial unconsolidated sediments and several bedrock litholo-
gies.Many of these deposits are frozen.
3.1.2 -Devil Canyon Reservoir Characteristics
Devil Canyon reservoir will be operated at a normal maximum oper-
ating level of £1 1455 ft (441 m)above mean sea level.Average
annual drawdown will be 28 feet (8.5 m)with the maximum drawdown
equalling 50 feet (15 m).At El 1455 ft (441 m)the reservoir
has a surface area of 7800 acres (3120 hal and a volume of 1.09
mi llion acre-feet.Figure E.2.129 illustrates the area capacity
curve of the reservoi r.The maximum depth wi 11 be 565 feet
(171 m)and the mean depth wi 11 be 140 feet (42 m).The
reservoir will have a retention time of 2 months.Shoreline
length will total 76 miles (123 km).Materials forming the walls
and floors of the reservoi r area are composed predomi nant ly of
bedrock and glacial,colluvial,and fluvial materials.
3.2 -Simulation Model and Selection Process
A multi-reservoir energy simulation model was used to evaluate the
opti mum method of operating the Sus itna Hydroe 1ectri c project for a
range of post-project flows at the Gold Creek gaging station 15 mi les
(24 km)downstream from the Devil Canyon damsite.
The simulation model incorporates several features which are satisfied
according to the following hierarchy:
£-2-55
3.2 -Simulation Model and Selection Process
-Minimum downstream flow requirements;
-Minimum energy demand;
Reservoir operating rule curve;and
-Maximum usable energy level.
The physical characteristics of the two reservoirs,the operational
characteristics of the powerhouses,and either the monthly or weekly
average flow at each damsite and Gold Creek for the number of years to
be simulated are required as input to the simulation program.The pro-
gram operates the two reservoirs to produce the maximum possible aver-
age annual usable energy whi le satisfying the criteria listed above.
First,the minimum flow requirement at Gold Creek is satisfied.Next,
the minimum energy requirement is met.The reservoir operating rule
curve is checked and if "extra water"is in storage,the "extra water"
is used to produce additi ona 1 energy up to the maxi mum usab le energy
level.There is a further consideration that the reservoir cannot be
drawn below the maximum allowable drawdown limit.The energy produced,
the flow at the damsites and at Gold Creek,and the reservoir levels
are determined for the period of record input to the model.
The process that led to the selection of the flow scenario used in this
license application includes the following steps:
-Determination of the pre-project flows at Gold Creek,Cantwell,
Watan a,and Devi 1 Canyon for 32 years of record;
-Selection of the range of post-project flows at Gold Creek to be
included in the analysis;
-Selection of timing of flow releases to match downstream fishery
requirements;
-Determination of the 1n,ergy produced and net benefits for the seven
flow release scenarios_I being studied;
-Consideration of the influence of instream flow and fishery needs on
the selection of project operational flows;
Selection of a range of acceptable flows based on economic factors,
fishery,and instream flow considerations;and
-Selection of the maximum drawdown at Watana.
A summary discussion of the detailed analysis is presented in the
following paragraphs.
3.3 -Pre-project Flows
As discussed in Section 2.2.1 of Chapter 2,the 32-year discharge
record at Gold Creek was combined with a regional analysis to develop a
l/Three additional flow regimes were investigated with respect to
project economics.These regimes are discussed in Exhibit B,
pp.B-2-123 through B-2-128 and are identified as Cases E,F,and G.
E-2-56
r
3.3 -Pre-Project Flows
32-year record for the Cantwe 11 gage near Vee Canyon at the upper end
of the proposed Watana reservoir.The flow at Watana and Devi 1 Canyon
was then calculated using the Cantwell flow as the base and adding an
incremental flow proportional to the additional drainage area between
the Cantwell gage and the damsites.
The avai 1ab le 32-year record was cons i dered adequate for determi ni ng a
statistical distribution of annual energies for each annual demand
scenario considered,and hence,it was not considered necessary to
synthesize additional years of record.
The 32-years of record contained a low flow event (water year 1969)
with a recurrence interval of approximately 1000 years as illustrated
in Figure E.2.23.This water year (WY)was adjusted to reflect a low
flow frequency of 1:30-years since a 1:30-year event represents a more
reasonable return period for firm energy used in system reliability
tests.
Although the frequency of the adjusted or modified year is a 1:30-year
occurrence,the two year low flow frequency of the modified WY 1969 and
the succeeding low flow WY 1970 is approximately 1:100 years.The
unmodified two year low flow frequency is approximately 1:250 years.
This two-year low flow event is important in that,if the reservoir is
drawn down to its minimum level after the first dry year,the volume of
water in storage in the reservoi r at the start of the wi nter season of
the second year of the two-year sequence,will be insufficient to
sati sfy the mi n imum energy requirements.Hence,the modifi ed record
was adopted for use in the simulation studies (refer to Section 3.8 for
the effect of this change on firm energy and average energy).
The 1:30 year annual volume was proportioned on a monthly basis accord-
ing to the long term average monthly distribution.This increased the
WY 1969 average annual discharge at Gold Creek 1600 cfs,from 5600 cfs
to 7200 cfs,and the average annual discharge at Gold Creek for the 32
years of record by 0.5 percent.The resulting monthly flows at Watana,
Devil Canyon,and Gold Creek are presented in Tables E.2.6,E.2.7,and
E.2.8.
3.4 -Project Flows
3.4.1 -Range of Flows
A range of project operational target flows from 6000 to 19,000
cfs at Gold Creek were analyzed.The flow at Gold Creek was
selected because it was judged to be representative of the Devi 1
Canyon -to-Tal keetna reach where downstream imp acts wi 11 be the
greatest.Additi ona 11y,the flows can be di rect ly compared with
the 32 years of discharge records at Gold Creek.
E-2-57
3.4 -Project Flows
The range of project flows analyzed included the operational flow that
wou ld produce the maxi mum amount of usab le energy from the project,
neglecting all other considerations (referred to as Case A)and the
operational flow which would have resulted in essentially no impact on
the downstream fishery d~/ing the anadromous fish spawning period
(referred to as Case 0)-.Between these two end points,five
additional flow scenarios were analyzed.
In Case A,the minimum target flow at Gold Creek for the month of
August and the first half of September was established at 6000 cfs.
Flow was increased in increments of 2000 cfs for the August-September
time period,thereby establishing the target flow for Cases AI,A2,C,
Cl,and C2.The August-September flow for Case 0 was established at
19,000 cfs.The resulting seven flow scenarios were adequate to define
the change in project economics resulting from a change in project flow
requirements.The monthly minimum target flows for all seven flow
scenarios are presented in Table E.2.34 and Figure E.2.130.
3.4.2 -Timing of Flow Releases
In the reach of the Susitna River between Ta"lkeetna and Devil Canyon,
it is percei ved that an important aspect of mai ntai ni ng natural sockeye
and chum salmon reproduction is providing access to the slough spawning
areas hydraulically connected to the mainstem of the river.Access to
these slough spawning areas is primarily a function of flow (water
level)in the main channel of the river during the period when the sal-
mon must gain access to the spawning areas.Field studies during 1981
and 1982 have shown that the most critical period for access is August
and early September.Thus,the project operational flow has been
scheduled to satisfy this requirement;i.e.,the flow will be increased
the last week of July,held constant during August and the first two
weeks of September,and then decreased to a level specified by energy
demands in mid September.Alternative modes that release the same vol-
ume of water but as short-term augmented flows are also being
evaluated.
3.5 -Energy Production and Net Benefits
The reservoir simulation model was run for the seven flow cases.Monthly
energies were determined for the 32 years of simulation assuming the year
2002 energy demand for Watana operation and 2010 for Watana/Devi 1 Canyon
operation.It was assumed that the distribution of energies obtained in the
year 2002 simulation would apply for years 1993 to 2002 and the 2010 simula-
tion would apply for the years 2002 to 2010.Beyond year 2010,the demand
was assumed to remain constant.
l/Three additional flow regimes were investigated with respect to pro-
ject economi cs.These regimes are di scussed in Exhi bit B,p.B-2-123
through 8-2-128 and are i dent ifi ed as Cases E,F and G.
E-2-58
3.6 -Fishery and Instream Flow Impacts on Flow Selection
To determi ne the net economi c value of the energy produced by the Sus itna
Hydroelectric Project,the mathematical model commonly known as OGP 5
(Optimized Generation Planning Model,Version 5,General Electric Co.
1979),was used to determine the present worth cost (1982 dollars)of the
long-term (1993-2051)productions costs (LTPWC)of supplying the Rai lbelt
energy needs by various alternative means of generation.A more detailed
description of the OGP 5 model is contained in Exhibit B,Section 1.5.The
analysis was performed for the "best thermal option"as well as for the
seven flow scenarios for operating Susitna.The results are presented in
Table E.2.35.
The net benefit presented in Table E.2.35 is the difference between the
LTPWC for the II best thermal option II and the LTPWC for the vari ous Sus itna
options.In Table E.2.35,Case A represents the maximum usable energy
option and results in a net benefit of $1234 million.As flow is transferr-
ed from the winter to the August-September time period for fishery and in-
stream flow mitigation purposes,the amount of usable·energy decreases.
This decrease is not significant until the flow provided at Gold Creek dur-
ing August reaches the 12,000 to 14,000 cfs range.For a flow of 19,000 cfs
at 'Gold Creek,a flow scenario that represents minimum downstream fishery
impact,approximately 46 percent of the potential project net benefits have
been foregone.
3.6 -Fishery and Instream Flow Impacts on Flow Selection
3.6.1 -Susitna River Fishery Impacts
As noted earlier,the primary function controlled by the late summer
flow is the ability of the salmon to gain access to their traditional
slough spawning grounds.Instream flow assessment conducted during
1981 (the wettest Ju ly-August on record)and 1982 (one of the dri est
Ju ly-August on record)has indi cated that for flows of the Case A
magnitude,severe impacts would occur which cannot be mitigated except
by compensation through hatchery construction and operationl/.
For flows in the 12,000 cfs range (flows similar to those that occurr-
ed in August,1982)the salmon can,with difficulty,obtain access to
their spawning grounds.To insure that the salmon can always obtain
access to spawning areas during a flow of 12,000 cfs,a series of
habitat alteration techniques are incorporated into the mitigation
plan presented in Section 2.4.4(a)of Chapter 3,Exhibit E.Because
Case A,AI,and A2 flow scenarios are not expected to allow habitat
alteration to mitigate the impacts caused by the changed flows,the
lowest acceptable flow range was established at approximately 12,000
cfs (Case C)at Gold Creek during August.
liThe relationship between mainstem discharge and hydraulic character-
istics of the sloughs is described for four sloughs in Appendix E.2.A.
E-2-59
3.6 -Fishery and Instream Flow Impacts on Flow Selection
3.6.2 -Tributary Fishery Impacts
Since three salmon species (chinook,coho,and pink)use the clear
water tributaries for essentially all their spawning activities and
chum use the tributaries for most of their spawning,a second primary
concern relative to post-project flow modifications is maintaining
access into the tributaries:i.e,the mouths of the tributaries cannot
be permitted to become perched as a result of reduced mainstem stages.
However,a tributary1s response to perching is a function of its flow
and the size of bed material at its mouth,neither of which will be
affected by the post-project change in mainstem flow.Thus,perching
of tributaries is more dependent on tributary characteristics than on
the operational scenario selected.
Recent studies (R&M 1982f)have shown that for post-project flows,most
of the tributaries will not become perched (Table E.2.27).However,
eight tributaries showed potential for perching.Of these three named
tributaries,Little Portage Creek (RM 117.8),Deadhorse Creek (RM
121.0),and Sherman Creek (RM 130.9),and two unnamed tributaries are
not considered to be significant salmon streams (ADF&G comments on the
November 15,1982 Draft Exhi bit E).If one of the three tri but ari es
that provide some spawning potential does become perched,the entrance
to the stream will be regraded so that salmon can gain access to tradi-
tional spawning areas.
3.6.3 -Other Instream Flow Considerations
(a)Downstream Water Rights
Water rights in the Susitna basin are minimal (see Section 2.6.1).
Therefore,since all flow scenarios provided more than enough flow
to meet downstream water rights,it was not a factor in minimum
flow selection.
(b)Navigation and Transportation
As discussed in Section 2.6.3(a),an impact on navigation during
the open water period cou ld occur in the Sherman area with Gold
Creek flows of 6000 cfs.However,if navigation problems develop,
mitigation measures will insure that navigation is not affected
(Section 6.3).Since minimum flows in May through September for
Cases C,C1, C2,and 0 are 6000 cfs and since mitigation measures
will be implemented if necessary,navigation was not considered to
be a factor in selecting an approprit}e operating flow scenario
from among Cases C,Cl,C2,and 0-=-.Cases A,AI,and A2
have minimum flows that are less than 6000 cfs and the minimum
flows for these cases could lead to increased mitigation
difficulty .
.U In Exhibit B,pp.121 through 128,three additional regimes,Cases E,
F,and G were considered.
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3.6 -Fishery and Instream Flow Impacts on Flow Selection
From a navigation perspective Cases A,AI,and A2 are less
acceptable than Cases C,Cl,C2,and D.
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(c)Recreation
Recreation on the Susitna River is closely associated with
navigation and transportation,and the fishery resource.
Since the Susitna River below Devil Canyon will be navigable
during the summer months at all minimum flow scenarios
because of the incorporated mitigation measures,the boating
aspect of recreation was not a factor in the flow selection
process.However,from a fishery perspective,if fishery
habitat is lost,this could reduce the recreational poten-
tial of the fishery.At the Case A,AI,and A2 flows,there
is some impact on the sockeye and chum fi shery.For flows
equal to or greater than Case C flows,the fishery impact
can be mitigated.Hence,Case C or greater flows should be
selected as the minimum operational flow based on recrea-
tional considerations.
The summer water quality improvement in turbidity,which
will enhance the recreation potential of the area would be
the same for all cases and thus was not a factor in flow
selection.
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(d)Riparian Vegetation and Wildlife Habitat
Riparian vegetation is affected by one or more of the
following:floods,freezeup,and spring ice jams.Minimum
flow selection for the cases considered is unrelated to any
of these factors.Hence,riparian vegetation effects were
not considered in minimum project flow selection.
Riparian vegetation is likely affected by the freezeup pro-
cess,ice jams,and spring floods in the Devil Canyon-to-
Talkeetna reach (Section 2.6.5).In the Talkeetna-to-Yentna
and Yentna-to-Cook Inlet reaches,spring flooding likely has
the major impact on riparian vegetation.S·ince spring
floods in the Susitna River will be reduced from Watana to
Cook Inlet (Section 4.l.3(a)(iii)),it may be desirable to
maintain-riparian vegetation by simulating spring floods for
a short period of time.However,the spring runoff storage
is a key element of the project.Large releases for even a
few days would have a severe economic impact on the project.
~ence,no minimum flood discharges were considered.
E-2-6l
3.8 -Maximum Drawdown Selection
If late August or September floods have an effect on ripar-
ian vegetation,there would essentially be no difference
between the flow cases.This is because minimum flows would
not govern operation of the reservoir because the reservoir
would be full and outflow would be set equal to inflow up to
the capacity of the release facilities,thereby providing
occasional high flows downstream during late August and
September.
(e)Water Qual ity
The pre-and post-project downstream summer temperatures
will be essentially the same for all cases,although the
lower discharges would be slightly warmer during summer and
would exhibit a faster temperature response to climatic
changes.
The waste assimil ative capacity for all cases will be ade-
quate at a flow of 4000 cfs.All other water qual ity para-
meters will essentially be the same for all flow scenarios.
(f)Freshwater Recruitment to Cook Inlet Estuary
The change in salinity in Cook Inlet will essentially be the
same for all seven flow scenarios although the higher mini-
mum flows (Case D)will exhibit a salinity pattern closer to
the natural condition.This was not considered significant
in the flow selection process.
3.7 -Operational Flow Scenario Selection
Based on the economic analysis discussed above,it was judged that,
while cases A,AI,and A2 flows produced essentially the same net bene-
fit,the loss in net benefits for Case C is of acceptable magnitude.
The loss associated with Case Cl is on the borderline between accept-
able and unacceptable.However,as fishery and instream flow impacts
(and hence mitigation costs associated with the various flow scenarios)
are refined (see Table E.3.39 in Chapter 3),the potential decrease in
mitigation costs associated ~~ith higher flows will not offset the loss
in net benefits.Thus,selecting a higher flow case such as C1 cannot
be justified by savings in mitigation costs.The loss in net benefits
associated with Cases C2 and 0 are considered unacceptable and the
mitigation cost reduction associated with these higher flows will not
bring them into the acceptable range.
3.8 -Maximum Drawdown Selection
The Watana reservoi r is used to redi stri bute the flow from the summer
runoff peri od to t he wi nter hi gh energy demand peri od.The maxi mum
reservoi r drawdown is used to produce fi rm energy duri ng a low flow
E-2-62
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3.8 -Maximum Drawdown Selection
sequence t which is usually one to two years in duration for the Susitna
Ri ver above Gol d Creek.The drawdown of the Devi 1 .Canyon reservoi r is
used either to provide the specified minimum downstream fishery flow
during August and early September or to produce firm energy in April or
early May during those years when the Watana reservoir has reached its
maximum drawdown limit.
During the Susitna Hydroelectric Feasibility Study (Acres 1982b)the
maximum drawdown of the Watana reservoir for power generation purposes
was selected as 140 feet (43 m)and for the Devil Canyon reservoir as
50 feet (15 m).The 140-foot (43 m)drawdown was determined to be
optimal for the Case A operational flow scenario.However t the maximum
drawdown was re-evaluated for two reasons.As more flow is released
for instream flow purposes during the summer season t less 1 ive storage
volume is required on an annual basis to redistribute the remainder of
the summer runoff into the wi nter high energy demand peri ode On the
other hand t during a low flow year,less flow is available from reser-
voir storage because of the additional downstream flow requirements.
The net effect may i nfl uence the maximum drawdown requi red and was
therefore reassessed.
In addition,in the Case A scenario presented in the Susitna Hydroelec-
tric Feasibility Study (Acres 1982b)t the maximum drawdown was required
for two years in the 32-year simulation period.For the other 30
years,the maximum drawdown was approximately 100 feet (30 m).There-
fore,the frequency of the two-year low flow sequence that was control-
1 ing the maximum drawdown was reexamined to determine if the severity
of the two-year dry spell was too conservative a basis for determina-
tion of the maximum drawdown.As discussed in Section 3.3,WY 1969 was
modified to reflect a more representative planning period.
Taking into account the minimum downstream flow considerations t the
average annual and fi rm energy producti on,and the intake structure
cost,the reevaluation process resulted in the selection of 120 feet
(37 m)as the maximum drawdown for the Hatana reservoi r with the Case C
scenari o.Because the Devi 1 Canyon maximum drawdown is controll ed by
technical considerations,the 50-foot (15 m)drawdown was not reconsi-
dered and has been retained as the limit for Devil Canyon.
The modified record had 1 ittle effect other than on maximum drawdown
which is controlled by the minimum annual (or firm)energy production t
and vice versa.It has minimal effect on average flow t increasing the
flow at Gold Creek by 0.5 percent over the unmodified record.Average
annual energy increased by the same 0.5 percent.Project operation
differed from the unmodified record only during the two-year low flow
period and the succeeding one-year recovery period.
E-2-63
3.8 -Maximum Drawdown Selection
The downstream flow requirement at Gold Creek will be met at all times
unless both the Watana and Devil Canyon reservoi rs are drawn down to
their minimum level and the natural flows at Gold Creek are less than
the flow requirement.The possibility of this occurring in the summer
months is remote.Even if a two-year low flow event with a recurrence
interval greater than 100 years occured,downstream flows would be
provided at all times.Only during a late spring breakup,occuring
after a severe two-year low flow event when both reservoirs are
drawdown to their minimum elevation would there be a possibility of not
meeting the downstream flow requirement.
E-2-64
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4 -PROJECT IMPACT ON WATER QUALITY AND QUANTITY
4.1 -Watana Development
For details of the physical features of the Watana development,refer
to Section 1 of Exhibit A.
4.1.1 -Watana Construction
(a)Flows and Water Levels
During construction of the diversion tunnels,the flow of
the mainstem Susitna will be unaffected.Upon completion of
the diversion facil ities in the autumn of 1986,closure of
the upstream cofferdam will be comp1 eted and flow will be
diverted through the lower diversion tunnel without any
interruption in flow.Although flow will not be inter-
rupted,a I-mile (1.6 km)section of the Susitna River will
be dewatered.(The fishery impacts resulting from this
action are discussed in Chapter 3).
Flows,velocities,and associated water levels upstream from
the proposed Watana damsite wi 11 be unaffected duri ng con-
struction except for approximately one-half mile (0.8 km)
upstream from the upstream cofferdam during winter,and 1
mil e (3 km)upstream during summer flood flows.Duri ng
wi nter,ponding to E1 1470 ft (449 m)will be requi red to
form a stab1 e ice cover.However,the vol ume of water con-
tained in this pond will be insignificant relative to the
total river flow.
During the summer,the diversion intake gates will be fully
opened to pass the natural flows resulting in a run-of-river
diversion.All flows up to approximately 30,000 cfs will be
passed through the lower diversion tunnel.Average veloci-
ties through the tunnel will be 13 and 26 feet per second
(fps)(4 to 8 m per sec)at discharges of 15,000 and 30,00U
cfs,respectively.The mean annual flood of 40,800 cfs will
cause higher than natural water level s for approximately 1
mile (1.6 km)upstream from the cofferdam.At the upstream
cofferdam,the water 1 eve 1 wi 11 ri se from a pre-di versi on
natural river level of El 1468 ft (448 m)to El 1500 ft
(457 m).One mile (1.6 km)upstream,the water level will
be about 2 feet (0.6 m)higher than the natural level during
the mean annual flood.
The two diversion tunnels are designed to pass the routed
1:50-year flood of 87,000 cfs with a maximum water surface
elevation of 1536 ft (468 m).For flows up to the 1:50 year
flood event,water levels and velocities downstream of the
diversion tunnels will be the same as pre-project levels.
E-2-65
4.1 -Watana Development
Floods greater than the 1:50-year event coul d overtop the
Watana cofferdams and cause failure of the cofferdams.If a
flood event of a magnitude 1 arge enough to overtop the
cofferdam did occur,the only location within 80 miles down-
stream from the cofferdam where damage would occur is the
main dam construction site.If the main dam height is less
than the cofferdam when ove rtoppi ng occurs,si gnifi cant
losses would occur.However,if the main dam is somewhat
higher than the cofferdam when overtopping occurs,no damage
is anticipated.Although damage could occur further down-
stream,the relatively small volume of the head pond and the
attenuation of the flood wave as it moves downstream would
significantly reduce the potential for downstream flooding.
(b)River Morphology
Since changes in flow will be negligible during Watana con-
struction,impacts on river morphology will be confined to
the dam and borrow sites.As previously stated.a one-mile
segment of the Susitna River will be dewatered for construc-
tion of the main dam.The morphology at the primary borrow
areas,Borrow Sites E,I,and L,will incur the greatest
impacts.They are illustrated in Figure E.2.131.Borrow
Sites J,if developed,and L will be inundated by the Watana
reservoir.Borrow Site E will become a deep pool in the
ri ver.The ri ver at Borrow Site I wi 11 become a deeper and
wider channel.These areas will have no opportunity to fill
with sediment once reservoir impoundment begins.Local mor-
phological changes may occur near these sites in the period
between Watana construction and Devil Canyon construction.
However,both sites will be inundated once Devil Canyon Dam
is constructed.
(c)Water Quality
(i)Water Temperature
Since the operation of the diversion structure will
essentially be run-of-river,no impact on the temper-
ature regime will ·occur downstream from the tunnel
ex it.A small amount of pondi ng wi 11 occur ea rly in
the freezeup stage to enhance the formation of a
stable ice cover upstream from the tunnel intake.
This will have no detectable effect on water tempera-
tures.
(i i )Ice
During freezeup,the formation of a stable upstream
ice cover facil Hated by the use of an ice boom and
E-2-66
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4.1 -Watana Development
some ponding to reduce approach velocities,will
serve to protect the diversion works from ice damage
or blockage and maintain its flow capacity.The ear-
ly formation of the ice cover at this point will
cause a more rapid ice front progressi on upstream
from the damsite.The ice generated in the upper
reach,which nonnally feeds the downstream ice
growth,will no longer be available.However,be-
cause of the presence of a natural lodgement poi nt
immediately downstream from Watana (Photograph
E.2.2),frazi1 ice upstream from Watana does not
significantly contribute to the ice cover formation
downstream from thi s lodgement poi nt under the
natural regime.Hence,no appreciable impact on ice
format i on downstream from Watan a wi 11 occur as a
result of the diversion scheme.The major contribu-
tor of frazi1 ice will continue to be the rapids
through the Devil Creek to Devil Canyon reach as it
is now (R&M 1982d).
The ice cover upstream from the dalllsite will therm-
ally decay in place,since its movement downstream
will be restricted by the diversion structure.Down-
stream from Devil Canyon,the ice cover volume will
be the same as baseline conditions,and breakup will
likely be similar to natural occurrences.
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(i i i )Suspended Sediments/Turbidity/Vertical Illumination
During construction,suspended sediment concentra-
tions and turbidity levels are expected to increase
within the impoundment area,and for some distance
downstream.This will result from the necessary con-
struction activities within and immediately adjacent
to the river,including drag1ine excavation of gravel
from borrow areas E and I,gravel processing,con-
struction of the diversion tunnels,placement of
cofferdams,~earing the construction site of vegeta-
tion and spoil material,and clearing the reservoir
area of vegetation prior to impoundment.
The excavati on of the materi a1 from the proposed
borrow sites will create the greatest potential for
problems due to increased suspended sediment and tur-
bidity.The originally considered borrow sites are
identified in Figure E.2.131.However,the primary
borrow sites currently envisioned include D,L,E and
1.The ba1 ance of the sites have been abandoned
because of envi ronmenta1 reasons,economi c or engi-
neering constraints,'or are now being considered only
as backup sites.
E-2-67
4.1 -Watana Development
Quarry Site L,located adjacent to the upstream
cofferdam (Figure E.2.132),is considered a potential
source for rock.Located wholly within the proposed
reservoir,this 20-acre site is estimated to contain
2.5 million cy of rock.With careful removal of the
vegetative and organic layers,the absence of work in
the river channel and no tributaries in the immediate
area,not siltation problems are envisioned.
Borrow Site D (Figure E.2.133)is the selected source
of impervious and semi-pervious materials consisting
of glacial tills for use in the cores of the main
dam,cofferdam,freeboard dike.and the emergency
spillway fuse pl ug.The site covers approximately
1150 acres and contains an estimated 180 million cy
of alluvial material,from which 8.5 to 9 million cy
of opt imum materi al s woul d be mi ned.Borrow Site H
is an alternative for this material;however,Site 0
is more desirable because of lower moisture content,
less permafrost,material stratification,and its
close proxi mity to the dams ite and support fac i 1 i-
ties.
Selecting mining of the material will occur during
the summer months (May-September)ut"il i Z"j ng blocks of
material that have been pre-drained with lateral
perimeter ditches.All runoff wi 11 be coll ected and
directed towards settling ponds prior to discharge
into Deadman Creek or the Susitna River.No work is
scheduled in or immediately adjacent to Deadman
Creek,and therefore,no significant erosion control
problems are anticipated.However,several small
1 akes withi n the area wi 11 be drai ned as a resul t of
the mining activities.
The organic layer will be stripped and stockpiled
prior to construction.Subsequent to disturbance,
the mined-out pits ~ill be continuously reclaimed
with appropriate materials and techniques.Portions
of the site will be withi n the annual reservoi r draw-
down zone and will be stabil i zed to control sl ump-
i ng.
Borrow Site E (Figure E.2.134),with an areal extent
of approximately 800 acres,is proposed as the pri-
mary source of aggregate (52,000,000 cubic yards or
40 mi 11 ion cubi c meters)for the gravel fi lters and
shells of the dam and concrete.Borrow Site I,loca-
ted immedi ately downstream as noted in Fi gure
E.2.135,will also be used to obtain adequate
supplies of aggregate.
E-2-68
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4.1 -Watana Develo~nent
Mining is scheduled to begin just upstream from the
natural (bedrock)flow restriction weir in Borrow
Site I.A large dragline will be operated from the
north shore,extending across the river and excavat-
"ing up to 100 feet below river level.Subsequent
mining will proceed upriver and to the north into the
floodplain.River mining will only be conducted dur-
ing the summer when high levels of suspended sedi-
ments and turbidity already exist.In addition,once
this large pool is excavated,the impacts from subse-
quent upstream work should be significantly reduced
by the sedimentation that will occur in this instream
settl·ing basin.
Assum"ing a one percent loss in material to the river
during the summer construction period,there would be
about a 4 percent increase in suspended sediment load
over 1982 levels.Stockpiling of gravel will alle-
viate the need for wet excavation during winter when
the impact from siltation to incubating eggs would be
greatest.As a result of the proposed schedul i ng of
activities,impacts will be minimized.However,it
is inevitable that there will be some increases in
suspended sediments and turbi dity duri ng wi nter,but
these w"il 1 be short term and local i zed.Downstream
from Talkeetna,turbidity and suspended sediment
levels should remain essentially the same as baseline
conditions.
Decreases in winter vertical illumination.are expec-
ted to be commensurate with any increased suspended
sediment concentrations.However,because summer
vertical illumination is naturally limited by high
suspended sediment concentrations,elevated levels of
suspended sediments and turbidity resulting from
construction activities will have essentially no
effect on summer vertical illumination.
The second major potential source of suspended sedi-
ments is the processing and deposition of borrow ma-
terial.The primary processing operation of granular
materials for dam construction will produce,over a 6
year period,10 to 15 million cubic yards (7.6 to
11.4 million cubic meters)of waste materials ranging
in size from oversize rock to silt and clay.Most of
this material will be moved from the process plant by
E-2-69
4.1 -Watana Development
truck or belt conveyer and used to selectively back-
fill portions of the borrow area by placing the ma-
terial at a depth to avoid entrainment in the river.
About 2 to 3 million cubic yards (1.5 to 2.3 million
cubic meters)will be suspended silt and clay in the
wash water.
The wash water wi 11 be directed into a seri es of
settling ponds.Considerable silt will settle out
immediately after discharge,hence control of the
di scharge end wi 11 be necessary to spread the mate-
rial.Silt and clay remaining in suspension will be
settled by passing the water through additional
settling ponds before discharging into the river.
Control of flow between ponds will be regulated
through gated culvert pipes.It is expected that
much of the water wi 11 re-enter the Susi tna by seep-
i ng through the granul ar soi 1 in di kes between the
disposal area and the river.This in itself will
ensure that fines are removed from the water.
A secondary processing plant for concrete aggregates
and filter gravel s will be located at Borrow Site E.
A 1 imited amount of spoil wi 11 be produced by this
aggregate processing plant which will be controlled
by runni ng the wash water into sett1 i ng ponds as
described above.It is estimated that 200,000 to
300,000 cubic yards (150,000 to 230,000 cubic meters)
of fine sand,silt and clay will be produced by this
operation.These wastes will be completely disposed
of within the excavation area in a manner that will
preclude their introduction into the river.
Summer flows will be passed through the diversion
tunnel with no impoundment.Hence,no settl ing of
suspended sediments being carried naturally by the
river is expected to occur.The insignificant head
pond that will be maintained during winter is not
expected to affect the low suspended sediment and
turbidity levels present during the winter season.
(iv)Nutrients and Organics
Increased concentrations of nutrients and organic
compounds could occur as a result of the disturbance
of vegetation and soil cove r and the subsequent ero-
sion of overburden and spoil materials.These poten-
tial impacts will be minimized by the careful removal
and either burning or stockpiling by methods that
will preclude their introduction into the watershed.
E-2-70
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4.1 -Watana Development
These spoil materials will latter be reused to reha-
bilitate construction impacted areas.
(v)Metal s
Increases in the concentration of trace metal swill
result from construction disturbances to soils and
rock on the river bank and in the riverbed.As noted
in Section 2.3.8(k),many metals currently exceed
established criteria.As such,increases are not
expected to create adverse conditions in the aquatic
ecosystem.
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(vi)
(vi i )
Contamination by Petroleum Products
Acci dental spi 11 age and 1eakage of petrol eum products
could contaminate surface water and ground water dur-
ing construction.Lack of maintenance and service of
vehicl es coul d increase the 1eakage of fuel,1 ubri ca-
ting oil,hydraulic fluid,and antifreeze.In addi-
tion,improper storage and handl ing techniques could
lead to accidental spills.Large quantities of
petroleum products,especially diesel fuel,will be
stored on site.Gi ven the dynam ic nature of the
Susitna River,the contaminated water from small oil
spills would be quickly diluted.However,spills in
the small er cl earwater streams coul d be del eteri ous
to aquatic residents.In addition,spills that occur
during winter are extremely difficult to contain.
All state and federal regul at ions governi ng the pre-
vention and reclamation of accidental spills,includ-
i ng the development andimpl ementati on of a Spill
Prevention,Containment and Countermeasure Pl an
(SPCC),will be adhered to as described in Sections
6.2 and Chapter 3,Section 2.4.3(e)(ii).
Concrete,Contamination
Construction of the Watana project will create a
potential for concrete contamination of the Susitna
Ri ver.The ~'lastewater and waste concrete associ ated
with the operation of a concrete batch plant,if
directly discharged to the river,could seriously
degrade downst ream water qual i ty and resul tin
substantial mortality of fish.
E-2-71
4.1 -Watana Development
Approximately 500,000 cubic yards (cy)(380,000 cubic
meters)of concrete will be placed at Watana.The
use of an efficient central batch plant will reduce
problems with waste concrete.
The production of concrete for the various permanent
structures will produce 10,000 cy (7600 cubic meters)
of waste material.Approximately one-half this quan-
tity will be rejected concrete which will be disposed
either by haulage directly to an upstream rock dispo-
sal area or dumped,allowed to harden and disposed in
an excavated area.
The other one-half of the waste will be material
washed from mixing and haul ing equipment.This waste
concrete wi 11 be processed through a washer/separa-
tor/classifier to provide aggregates for reuse.The
wash water will be stored in a lined pond until its
specific gravity drops to a point which allows its
reuse as mixing water for batching new concrete.
This system will minimize the waste water effluent to
be returned to the river.
At concrete placement areas the wash water resulting
from the cleanup of placing equipment,curing and
green cutting will be collected in sumps and pumped
to a series of settling ponds to remove most of the
suspended materials before the effluent is discharged
into the river.Ponds will generally be unl ined,
with sand fi 1ters to ensure removal of most waste
products.Neutral i zati on of wastewater vJill be con-
ducted as required to obtain proper pH levels.It is
expected that control of toxic chemicals in the
effl uent wi 11 be accomp 1 i shed through ca reful se 1ec-
tion of concrete additives,the provision of filters
for effluent and the close monitoring of operations
by the Construction Manager.
Airborne particulates are a second potential pollu-
tion problem related to concrete batching plants.No
significant dust problems are anticipated since a
modern control batch plant fully enclosed for winter
operational requirements is envisioned.In addition,
the transfer of materials will be facilitated through
pipes,hence,dust should be further contained.
(viii)Other
No additional water quality impacts are anticipated.
E-2-72
-4.1 -Watana Development
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,...
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(d)
(e)
Ground Water Conditions
Si nce there will be no change in ma i nstem di scharge and no
change in water 1evel other than in the local i zed a rea of
the project,no ground water impacts are expected either up-
stream or downstream from the construction area.However,
in the construction area,ground water impacts will likely
result from the construction activity.
The relict channel at Watana has previously been identified
as an area of potent i al ground water seepage probl ems after
Watana Reservoir is filled (Acres 1982b).It lies within
the drainage between Deadman Creek to the east,the Susitna
River to the south,and Tsusena Creek to the west and north-
west.Ground water gradients in the unconsol i dated sedi-
ments of the channel are principally towards Tsusena and
Deadman Creeks with the diorite pluton at the damsite acting
as a ground water barrier to the south.
The ground water regime in the relict channel is complex and
poorly understood due to the presence of intermittent perma-
frost,aquicludes,perched water tables,and confined aqui-
fers.Possible artesian or confined water tables exist in
several of the stratigraphic units while other units appear
to be unsaturated.
Perrneabil ity testing indicate the range of average perme-
ability in the more gravelly materials is about 10-3
cm/sec (3 ft/day),while the tills and lacu~trine deposits
'can be estimated at about 10-
4 to 10-cm/sec (0.3
to 0.03 ft/day).
Assuming worst case conditions,an estimated maximum seepage
rate through the rel ict channel under full reservoir condi-
tions would be approximately 9-10 cfs,which is not con-
sidered significant to the project operation.
Construction activities related to the rel ict channel will
therefore,be 1 imited to construction of the la-foot (3 m)
freeboard dike.However,during filling,the reli~t channel
will be monitored with piezometers and at the outfall.If
necessary,the outfall will be treated with a filter blanket
to minimize the risk of piping.
Lakes and Streams
As noted in (c)(iii)above,there will be impacts at the
mouth of Tsusena Creek caused by excavation of material from
E-2-73
4.1 -Watana Development
Borrow Site E.Figure E.2.134 provides a map of the area
tentatively scheduled for disturbance.
The construction,operation,and maintenance of facilities
to house and support construction personnel are expected to
impact the Tsusena and Deadman Creek drai nage bas ins and
some of the small lakes located between the two creeks near
the damsite.For more detailed di scussions of these impacts
refer to Support Facilities,Section (g)below.
(f)Instream Flow Uses
For all reaches of the Susitna River,except for the immedi-
ate vicinity of the Watana damsite,no impacts on naviga-
tion,transportation,recreation,fishery resources,rip-
arian vegetation,wildlife habitat,waste load assimilation
or the freshwater recruitment to Cook Inlet will occur for
flows less than the 1:50-year flood event.
(i)Fi shery Resources
During winter,the diversion gate will be partially
closed to maintain a headpond at El 1470 ft (948 m).
This will cause velocities greater than 20 fps
(6 m/sec)at the gate intake.This velocity coupled
with the 50-foot (15 m)depth at the intake wi 11 act
as a barrier to resident fish passage.
During summer,the diversion gates will be fully
opened.This will permit downstream fish movement
during low flows of about 10,000 cfs (equivalent vel-
ocity of 9 fps (3 m/sec).Upstream migration is not
anticipated.Higher flow rates and hence,velocities
may lead to fish mortality.
The impacts associ ated with both wi nter and summer
diversion tunnel operation are discussed in Chapter
3.
(ii)Navigation and Transportation
Since all flow will be diverted,there will be an
impact on navigation and transportation only in the
immediate vicinity of Watana dam and the diversion
tunnel.The cofferdams W"j 11 form an obstacle to nav-
igation which will be difficult to circumvent.How-
ever,since this stretch of river has very 1 imited
use because of the rapi ds u pst ream a nd downstream
from the site,impact will be minimal.
E-2-74
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-4.1 -Watana Development
Existing shoreline vegetation immediately upstream
from the cofferdam will be inundated approximately 30
feet (9 m)to El 1500 ft (457 m)during the mean.
annual flood.This flooding will be confined to a
I-mile (1.6 km)reach with the depth of flooding
lessening with distance upstream.Since the flooding
will be infrequent and temporary in nature and since
the flooded 1ands are withi n the proposed reservoi r,
the impact is not considered significant.Further
information on the impacts to riparian vegetation can
be found in Chapter 3.
Support Facilities
-
.....
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(g)
(iii)Riparian Vegetation
(~
The constructi on of Watana wi 11 requi re the constructi on,
operation,~nd maintenance of support facilities capable of
providi ng the basi c needs for a maximum popul at ion of 4720
people (3600 in the construction camp and 1120 in the vil-
lage).The facilities,including roads,buildings,utili-
ties,stores,recreation facilities,airport,etc.,will be
constructed in stages during the first three years (1985-
1987)of the proposed ten-year construction period.The
camp and village will be located approximately 2.5 miles
(4 km)northeast of the Watana damsite,between Deadman and
Tsusena Creeks.The location and layout of the camp and
village facilities are presented in Plates F34,F36,and F37
of Exhibit F.
-
(i )Water Su pp 1y
Nearby Tsusena Creek will be utilized as the major
source of water for the commun ity (Pl ate F34).In
addition,wells will be drilled in the Tsusena Creek
alluvium as a backup water supply.
During construction,the required capacity of the
water treatment plant has been estimated at 1,000,000
gallons per day,700 gallons per mi nute 0 r 2650
liters per minute (1.5 cfs)(Acres 1982a).With the
use of the USGS regression equation described in
Table E.2.32,a 30-day minimum flow with a recurrence
interval of 20 years was estimated for Tsusena Creek
near the water supply intake.This flow was estima-
ted to be 17 cfs for the approximately 126 square
miles (326 square km)of drainage basin.As a
result,no significant adverse impacts are anticipa-
ted from the maximum water supply withdrawal of 1.5
cfs.Furthennore,a withdrawal of this magnitude
E-2-75
4.1 -Watana Development
will,not occur during the low-flow winter months,
since construction personnel will be reduced by
approximately two-thirds fran peak summer levels.
The water supply will be treated by chemical addi-
tion,flocculation,filtration,and disinfection
prior to its use.Di sinfection will probably be
facilitated by the use of ozone to avoid the need for
later dechlorination.In addition,the water will be
demineralized and aerated,if necessary_
A water ri ghts appropri at i on permit from the ADNR
will be applied for.Presently,water rights appro-
priation permit ADL 203386-P (amended)is held by the
Al aska Power Authority for use of 3000 gpd (11,350
liters per day)from a nearby unnamed lake for the
44-man Watana camp.
(ii)Wastewater Treatment
A secondary wastewater treatment facility will treat
all wastewater prior to its discharge into Deadman
Creek.
Treatment will reduce the BOD and TSS concentrations
to levels acceptable to the Alaska Department of
Environmental Conservation (ADEC)and the u.s.Envi-
ronmental Protection Agency (EPA).The levels are
1 ikely to be 30 mg/l BOD and 30 mg/l TSS.In addi-
tion,wastewater will be treated with chlorine if
necessary,to ensure that fecal col iform bacteria
levels meet ADEC and EPA criteria.The maximum
volume of effluent,1 million gallons per day (3.8
milnon liters per day)or 1.5 cfs,will be dischar-
ged into Deadman Creek which has a winter low flow of
27 cfs (see below).Under the worst case flow condi-
tions (maximum effluent and low flow in Deadman
Creek),this will provide a dilution factor of about
17,thereby reducing BOD and TSS concentrations to
about 2 mg/l after complete mixing.Thorough mixing
will occur rapi dl yin the creek because of its turbu-
1 ent natu reo
The effl uent is not expected to cause any degrada-
tion of water quality in the 1-1/2 mile (2.4 km)sec-
t i on of Deadman Creek between the wastewater dis-
charge poi nt and the c reek 's confl uence with the
Susitna River.Furthermore,no water quality pro-
blems are anticipated within the impoundment area or
downstream on the Su sitna Ri ver as a result of the
input of this treated effluent.
E-2-76
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4.1 -Watal1a Development
With the use of the USGS regression analysis,the
1:20-year~3D-day low flow for Deadman Creek at the
confluence with the Susitna was estimated at 27 cfs.
Flow at the point of discharge,which is less than
2 miles (3.2 km)upstream,is not expected to differ
significantly.
Constructi on of the wastewater treatment facil ity is
expected to be completed in the first 12 months of
the Watana construction schedule.Prior to its oper-
ation,all waste will be stored in a 1 agoon system
for treatment at a later date.No raw sewage will be
dis~harged to any water body.
Chemical toilets located throughout the construction
areas will be regularly serviced to ensure proper
treatment and disposal.
The applicant will obtain all the necessary ADEC,
EPA,and ADNR permits for the water supply and waste-
water discharge facilities.An ADEC wastewater dis-
posal permit (WP 80-9)that allows the discharge of
4000 gpd (15,150 1 iters per day)of treated waste-
water is presently held by the Alaska Power Authority
for the existing Watana field camp.
Additional details pertaining to the proposed water
supply and wastewater discharge facilities are avail-
able in the Susitna Hydroelectric Project Feasibility
Report,Design Development Studies,Appendix B (Acres
1982a.
(iii)Constru£tion,Maintenance,and Operation
Construction of the Watana camp,village,airstrips
etc.will cause impacts to water quality similar to
many of those OCCU rri ng fr{)ffi dam construct i{)n.
Increases in suspended sediment and tu~bidity levels
are anticipated in the local drainage bas~ns (Le.,
Tsusena and Deadman Cree.ks).-Even with extensi ve
safety controls,acchlental spil leage an-d 1eakage of
petroleum products c-ouldoc<:JJr,creating localized
contamination wit-hi n the watershed.Add4 t i onal dis-
cussions ~n the water quality impacts ~ssociated with
faci 1ities constructi on,operation,and mai ntenance
are provided in Chapter 3,Sec'tion 2.:3.11a)(ii).
£-2-7:1
4.1 -Watana Development
4.1.2 -Impoundment of Watana Reservoir
(a)Reservoir Fill ing Criteria
The filling of the Watana reservoir is scheduled to commence
in May 1991 and will take three summer runoff periods before
being completed.During filling,downstream flow require-
ments wi 11 be met and a flood sto rage safety factor rna i n-
ta i ned.Testing and commi ss i oni ng of the powerhouse units
will begin after the second summer of filling.
(i)Minimum Downstream Target Flows
Because of the naturally occurring low flows during
winter,little water is available for filling the
Watana reservoir during the winter season.There-
fore,natura 1 river flows wi 11 be mai ntai ned fran
November through Apri 1.Du ri ng summer,runoff will
be captured and stored in the reservoir in a manner
similar to that which will occur during project
operation.Therefore,the downstream flow require-
ments selected for project operation from May through
September were adopted for the Watana reservoir
filling period [see Sections 3.4.2 and 3.7J.The
primary difference wi 11 be that the downstream flow
requirements will be met by passage of water through
the low level outlet rather than the powerhouse.
Filling will continue during the month of October
with the flow volume in excess of the downstream flow
requirement being stored.
Table E.2.36 and Figure E.2.136 illustrate the tar-
geted minimum Gold Creek flows.From May to the last
week of Jul y,the ta rget flow wi 11 be increased to
6000 cfs to allow for navigation and mainstem fishery
movement.
The 6000 cfs Gold Creek flow will provide a minimum
river dePth of 2 feet (0.6 m)for mainstem fishery
movement at all 65 surveyed cross sections between
Talkeetna and Devil Canyon as discussed in Section
2.6.3.
Ouring the last 5 days of July,flow will be in-
creased from 6000 cfs to 12,000 cfs in increments of
approximat"ely 1000 cfs per day.Flows will be main-
tained at 12,000 cfs from August 1 through mid-
September to coincide approximately with the sockeye
and churn spawni ng season in the sloughs upstream from
E-2-78
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4.1 -Watana Development
Tal keetna.Adverse impacts to the fi shery resource
resulting from this flow regime are discussed in
Chapter 3.
Starting September 15,flows will be reduced to 6000
cfs in daily increments of 1000 cfs and then held
constant until October when they wi 11 be further
reduced to 2000 cfs.In November,natural flows will
be released.
The minimum target flows at Gold Creek will be
attained by releasing that flow necessary from the
Watana impoundment which,when added to the flow con-
tribution from the intervening drainage area between
Watana and Gold Creek,will equal the minimum Gold
Creek target flow.The mi nimum flow rel ease at
Watana from May through September wi 11 be 1000 cfs.
During filling,flows at Gold Creek will be monitored
and the flow at Watana adjusted as necessary to pro-
vide the required Gold Creek flow.
(ii)Flood Storage Protection
Taking into account the 30,000 cfs discharge capabil-
ity of the low-level outlet,sufficient storage will
be made available during the filling sequence so that
fl ood vol umes for all floods up to the 2S0-year
recurrence interval flood can be temporari ly stored
in the reservoi r wi thout endangering the rnai n dam.
Whenever this storage criterion is violated,dis-
charge from the Watana reservoir will be increased up
to the max imum capacity of the outl et to lower the
reservoir level behind the dam.
""""
(b)Flows and Water Levels
,..,.
(i )Simulation of Reservoir Filling
Taki ng into account the reservoi r fi 11 i ng criteri a,
three reservoir fill ing sequences were simul ated to
deterrninethe mean or likely filling sequence and
probable deviations if wet or dry hydrologic
sequences o-ecurred duri ng fill ing.Si nce approxi-
mately three years will be required to br"ing the
reservoi r to its normal operati ng 1evel,three-year
moving averages of the total annual flow vol ume at
Gold Creek were computed from mean monthly flows.
The probability of occurrence for each of the three
4.1 -Watana Development
year average values was then determined (Figure
E.2.137).The annual flow volumes,with a 10 per-
cent (wet),50 percent (mean),and 90 percent (dry)
change of exceedence,were then proportioned accord-
ing to the long term average monthly Gold Creek flow
distribution.This produced a synthesized Gold Creek
monthly flow distribution.The same process was used
to synthesize the 10,50,and 90 percentile vol umes
and flow distributions at Watana.The intermediate
flow contribution was taken as the difference between
the Watana and Gol d Creek monthly flows.The Watana
and Gold Creek monthly flows for each of the three
cases are identified as "pre-project'l in Tables
E.2.37 and E.2.38.The downstream flow criteria and
the flow val ues at Watana and Gol d Creek were then
used to determine the fill ing sequence for each of
the three cases by repeating the annual flow sequence
for each percentil e flow until the reservoi r was
fill ed.
Hle Watana reservoir water levels for each of the
three filling cases considered are illustrated in
Figure E.2.138.Under average conditions (50 percent
case),the reservoir would fill sufficiently by
autumn 1992 to allow testing and commissioning of the
units to begin.However,the reservoir would not be
filled to its normal operating level until the fol-
lowing summer.If the dry sequence were to occur,
(90 percentile case)the reservoir would not be
sufficently full to permit unit testing and commis-
sioning until late spring 1993.If a wet sequence
were to occur (10 percenti le case)only about one
month woul d be saved over the average fill ing time
because the flood protection criterion would be vio-
lated and flow would be released rather than stored.
The dry sequence and wet sequence each have a prob-
ability of occurrence of approximately 10 percent.
The Watana discharges for the high (10 percent),mean
(50 percent),and low (90 percent)flow cases con-
sidered are compared to the Hatana inflow in Table
E.2.37.For the average hydrologic case,the
May-October mean monthly flows are reduced up to 95
percent during the filling period.From November
through April there is no change in flow during the
filling period.
As previously stated,Gold Creek flows are considered
representative for the Devil Canyon to Talkeetna
E-2-80
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4.1 -Watana Development
reach.Percent changes in the flow at Gold Creek are
similar to those at Watana but are somewhat reduced
because of tributary inflow between Watana and Gold
Creek.For the 50 percentile case t maximum mean
monthly flow reduction is 78 percent (see Tab1 e
E.2.38 and Figure E.2.138).
Flow will be altered in the Talkeetna to Cook Inlet
reach t but because Df significant tributary contribu-
tions t the impact on summer flows will be greatly
reduced with distance downstream.Table E.2.39 is a
comparison of mean pre-project monthly flows and
monthly flows during reservoir filling at Sunshine
and Susitna Station.Pre-project flows are based on
the long-term average ratio between the respecti ve
stations and Gold Creek.Filling flows are pre-
project flows reduced by the quantity of water stored
in the reservoir.The maximum monthly flow reduction
is 34 percent at Sunshi ne and 17 percent at Susitna
Station.
(i i )Floods
The reservoir filling criteria dictates that avail-
able storage volume in the reservoir must provide
protecti on for all floods up to the 250-year recur-
rence i nterva 1 flood.Thus t the reservoir mu st be
capable of storing the flood volume of a 1:250-year
flood less the flow which can be discharged through
the outlet facilities during the flood event.The
maximum discharge of the outlet facilities at Watana
is 30 t OOO cf5.The maximum flow of 30 t OOO cfs repre-
sents a substantial flood peak reduction.These
flood peak reductions will be approximately main-
tained downstream to Cook Inlet.For examp1e t the
1:50-year flood at Gold Creek would be reduced from
106,000 cfs to approximately 49 t OOO cfs.
After the flood event t the outlet facil ity wi 11 con-
tinue to discharge at its maximum capacity until the
storage volume criterion ;s reestablished.This will
cause the flood du rati on to be extended beyond its
normal duration although at a greatly reduced
discharge.
(iii)Flow Variability
Under natural conditions t substantial changes in flow
can occur dai 1y.Thi s flow vari abil ity wi 11 be
E-2-81
4.1 -Watana Development
reduced during the filling process.Using August
1958 a san ex am p1 e,Fig ure E.2.139 show s the dail y
fl ow variation that occurs naturally.The August
1958 average flow of 22,540 cfs was close to the long
term average monthly discharge of 22,000 cfs.Super-
imposed on Figure E.2.139 are the flow variations
that woul d occur under fill ing conditions assuming
the August 1958 flow occurred during the filling
process.To obtain Curve (1)in Figure E.2.139,it
was assumed that the reservoi r storage criterion was
violated (i.e.,30,000 cfs discharge at Watana).The
second curve was obtained assuming the reservoir was
capable of accommodating the entire inflow volume.
80th Gold Creek filling hydrographs have reduced
flood peaks.
In filling Sequence (1),outflow is greater than
infl ow at Watana on the receding 1 imb of the hydro-
graph in order to reestabl ish the reservoir storage
volume criterion.Hence,during this time period,the
Gold Creek flow is greater than the natural flow.In
this example,it was assumed that ongoing construc-
tion did not permit additional storage in the reser-
voir.In reality,the dam height will be increasing
and additional storage woul d be permitted,thus re-
ducing the required outflow from Watana.This would
correspondingly reduce the Gold Creek discharge.
In filling Sequence (2),the Gold Creek flow is
constant at 12,000 cfs.To mai ntai n thi s constant
flow,the flow release at Watana during the filling
sequence woul d only be 4400 c fs at the natural Go 1d
Creek flood peak of 47,800 cfs because flow from the
drai nage a rea between Watana and Gol d Creek woul d
contribute 7600 cfs to the flow at Gold Creek.The
Watana contribution would be about 10,000 cfs when
the natural Gold Creek flow drops to 12,000 cfs.
Farther downstream,the daily variation in flow for
both sequences ~"ill increase and become simi 1 ar to
natural conditions,but would remain less than under
natural conditions.The percent change from natural
fl ow wi 11 become 1ess because of the added tri butary
inflow.
(c)Testing and Commissioning
As reservoir filling nears completion and the reservoir
level is above the minimum drawdown elevation,testing and
E-2-82
4.1 -Watana Development
commi ssioning of the powerhouse units will commence.This
process may take several months and will require a number of
tests for each unit.Every attempt will be made to commis-
sion the units so that the impact on downstream flow will be
a minimum.The most severe fluctuations in flow could occur
duri ng the full load to off or off to full load tests when
the flow through the turbine being tested will be quickly
reduced from approximately 3500 cfs to 0 or increased from 0
to 3500 cfs,respectively.However,this will be compensa-
ted for by openi ng orcl osi ng the outl et'faci 1 ity gates or
other units which have previously been tested in an effort
to stabilize flow downstream.If testing is done during
late summer,the additional downstream flow required from
Watana and released through the outlet facilities will help
to stabilize the flow.The natural attenuation of flow
variation with distance downstream will also serve to stabi-
1 i ze the flow.
If testi ng occurs in winter and flow is 1 ess than 3500 cfs
at Watana,flow will be gradually increased to 3500 cfs over
a one day peri od and ma i nta i ned at that 1evel through the
testing period.If testing is temporarily halted,flow will
be gradually reduced to the natural flow.
r-
I
i!""i,
(d)River Morphology
During filling of the Watana reservoir,the trapping of bed-
load and suspended sediment by the reservoir (Section (e)
(iii)below)will greatly reduce the sediment being trans-
ported by the Susitna River in the Watana-Talkeetna reach.
Except for isolated areas,bedload movement will remain
limited over this reach because of the armor layer and the
reduced flows.This is indicated by the bed material move-
ment curves shown in Figure E.2.77 and in the River Morphol-
ogy report (R&M 1982d).Bed materi al movement may occur in
the regions of River Mile 124,131-133,and near the conflu-
ence with the Chulitna River where bed material size is in
the coarse gravel range,i.e.,somewhat smaller than in most
of the river between Devil Canyon and Talkeetna.The 1ack
of suspended sed iments will si gnifi cantly reduce sil tati on
in calmer areas.The Susitna River main channel will tend
to become better defined with a narrower channel in this
reach.The main channel river pattern will strive for a
tighter,better defined meander pattern within the existing
banks.A trend towards channel width reduction by encroach-
ment of vegetation will begin.Tributary streams,including
Portage Creek,Indian River,Gold Creek,and Fourth of July
Creek,will extend their alluvial fans into the river.
E-2-83
4.1 -~atana Development
Figure £.2.140 illustrates the influence of the mainstem
Susitna Ri ver on the sedimentation process that occurs at
the mouth of the tributaries.
An analysis of 19 tributaries between Devil Canyon and
Talkeetna was undertaken to determine which,if any,tribu-
taries would become perched (R&M 1982f).The analysis indi-
cated that ei ght tributari es showed a potential to perch
(Table E.2.27).This is primarily the result of the large
si ze bed materi al at the mouths of the tributaries.The
remaining tributaries are expected to degrade.
Overflow into most of the side channels will not occur,as
high flows will be reduced to a maximum of 30,000 cfs at
Watana.The backwater effects at the mouths of side
channel s and sloughs will al so be reduced.These factors
will lead to vegetation encroachment in the side channels
and sloughs.However,side channels and sloughs that are
presently overtopped duri ng the freezeup process wi 11 con-
tinue to be overtopped during freezeup and,hence,will have
scouri ng flows of up to 3 feet per second (0.9 m/sec)
[Section 2.3.2(a)and Section (e)(iii)below].
At the Chulitna-Susitna confluence,tne Chulitna River is
expected to expand and extend its alluvial deposits.Re-
duced summer flows in the Susitna River may allow the
Chulitna River tD extend its alluvial deposits to the east
and south.However,high flows in the Chul itna Ri ver may
cause rapid channel changes,inducing the main channel tD
migrate to the west.This would tend to relocate the depo-
sition to the west (R&M 1982d).
Downstream from the Susitna-Chul itna confluence,the pre-
project mean annual bankfull flood will now have a recur-
rence interval of five to ten years.This will tend tD
decrease both the frequency and amount of bed material move-
ment and,consequently,the frequency of changes in braided
channel shape,form and network.A trend toward relatively
stabilized floodplain features will begin,but this would
occur over along period of time perhaps several decades
(R&M 1982d).
(e)\~ater Qual ity
Beg i nni ngwith the filling of the reservoi r,many of the
physical,chemical,and biological processes common to a
lentic environment should begin to appear.Some of the more
important processesi-ncl ude sedimentati on,1 ea:ching,nutri-
ent en6chment~strat i fi catiDn,and ice cover fonnation.
£-2-84
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4.1 -Watana Development
These processes are expected to interact to alter the water
qual ityconditionsassociated with the natural riverine
conditions.A summary discussion of the processes and their
interactions is provided in.Peterson and Nichols (1982J.
(i)Water Temperature
-Watana Reservoi r
During Ute first summer of filling,the temperature
·inthe Watana reservoir will be essentially a com-
posi te of the inflow temperature,increased some-
what near the surface by the effects of sol ar heat-
ing.The reservoir will fill very rapidly (to
about a 400-foot depth (El 1875 ft,or 568 m)by
the end of the fi rst summer)and the effects of
surface heat exchange will not penetrate to the
depth at which tne intake is located (El 1490-1528
ft,or 451-493 m).Therefore,outlet temperatures
duri ng the fi rst summer of fill ing wi 11 be an
average of the existing river water temperatures
with some lagging behind the inflow water tempera-
tures.
During fall,the reservoir will gradually cool to
4°C (39.2°F).()lce at this temperature,the low-
level outlet will discharge water at just above 4°C
(39.2°F)until the reservoir water level has in-
creased suffi ci ently to permit operati on of the
outlet facilities (fixed-cone valves).
The volume of water stored in the reservoir after
October of the first summer of filling will be
about 2.2 million acre-feet.From November through
April,0.5 million acre-feet of 4°C (39.2°F)water
will be discharged from the reservoi r and be re-
placed with O°C (32~F)water which was contributed
as inflow during this time.The O°C (32°F)water,
because it is less dense than the 4°C (39.2°F)
water,will enter the reservoi r as surface flow.
Although there will be some mix·ing of DoC (32°F)
and 4°C (39.2°F}water,mixing will be confined to
the upper 1 ayers.Even with coon ng before the ice
cover forms,little cooling wi11 occur below a
depth of 175 feet (53 m).It is the 0.5 million
acre-feet stored below this depth whi ch wi 11 be
discharged during winter.
E-2-85
4.1 -Watana Development
In spri ng the ice on the reservoi r su rface wi 11
melt and the reservoir will warm to 4°C (39.2°F),
probably by about the end of May.The surface will
continue to warm above 4°C (39.2°F)and slowly this
warmer layer will extend deeper into the reservoir.
Also,warmer Susitna River inflow will be stored in
the reservoir.Although there will be some mixing,
the warmer surface water,because it is less dense
that the 4°C (39.2°F)water,will enter the reser-
voir as surface flow.From 'May through mid-Septem-
ber,approximatley 1.8 million acre-feet of 4°C
(39.2°F)bottom water would be released from the
reservoir if the low level outlet continued to be
used.Thi s would still 1 eave a reserve of 4°C
(39.2°F)water in the bottom of the reservoir.
However,it is anticipated that sometime in August,
the reservoir will be sufficiently full to allow
discharge through the outlet facilities.
Once the outlet facil ities can be operated,down-
stream river temperatures should more closely
approximate natural conditions.During the second
winter of filling,outlet temperatures will be
closer to aoc (32°F).During the third summer of
filling,reservoir temperatures will be similar to
those during Watana operation,with the exceptions
that water will be discharged through the outlet
faci 1 iti es rather than the powerhouse and flows
will be slightly reduced from those during Watana
operation.A discussion on reservoir temperatures
during Watana operation can be found in Section
4.1.3(c)(i).
-Watana to Talkeetna
As discussed above,Watana outlet temperatures dur-
ing the first summer of filling will be similar to
natu ra 1 temperatures.Hence,downst ream tempera-
tures between Watana and Talkeetna should also be
similar to natural temperatures,except that there
will be some additional warming of the water with
distance downstream because of the reduced flows.
During winter,the outlet temperature will be con-
stant at 4°C (39.2°F).To assess the effects of
E-2-86
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-
....
-
4.1 -Watana Development
the warmer outlet water on water temperatures down-
stfeam,a downstream temperature analysis using the
computer model HEATSIM was undertaken.Information
on this model is contained in Appendix A,Hydrolo-
gical Studies,Susitna Hydroelectric Project Feasi-
bil ity Re port (Ac res 1982b).
With the use of the mean monthly natural flows and
the long-term average meteorol ogi cal data,down-
stream water temperature profiles were determined.
These a re shown for October to Janua ry in Fi gu re
E.2.141 arid for January to April in Figure E.2.142.
The resul ts show that temperatures will stay aboveooe(32°F)from Watana to Talkeetna until late
October,thus lagging natural temperatures by about
one month.However,as colder air temperatures
occur,the location Df ooe (32°F)water moves up-
stream.Even with the coldest winter temperatures,
a reach of approximately 18 mi 1es (29 km)below
Watana remai ns above ooe (32°F).In April,the
downstream temperatures increase and if no ice
cover were present,would remain above ooe (32°F)
downstream to Talkeetna.Si nce thi sis not the
case (i.e.,an ice cover wi 11 form,see (i i)
below),the water temperatures will actually be
near ooe (32°F)at Talkeetna du ri ng Apri 1.The
model does not consider tributary inflow which
would be at ooe (32°F).
A sensitivity analysis was also undertaken to
determine the effect of lower winter flows and is
presented in Figures E.2.143 and E.2.144.With
reduced flows,O°C (32°F)water will occur at a
given location earl ier in.the freezeup process;
however,a reach with water above O°C (32°F)will
conti nue to exist just downstream from the Watana
dam.
Downstream s ummel"temperatures were al so model ed •
This analysis used the median filling flows and the
1981 meteorological data recorded at Watana as
input.The·results are presented in Figure
E.2.145.Tempe ratures increased with di stance
downstream with temperatures reaching goe (48.2°F)
at Talkeetna during the lower flow period of June
and July.The sensitivity to meteorological data
is apparent given the variabil ity of downstream
temperatures at similar discharges.
E-2-87
4.1 -Watana Development
It is anticipated that the outlet facilities will
be operable sometime in August and thus able to
draw water from the surface of the reservoir.How-
ever,if a low flow year occurs,the outlet facili-
ties will not be useable and thus,downstream
August tempe ratures woul d be cons i derab ly lower
than natural temperatures.For exampl e,tempera-
tures at Gold Creek would be in the range of 5 to
6°C (41 to 42.8°F).Since this may have detrimen-
tal impacts on fisheries,a discharge sensitivity
analysis was performed using an August flow of 6000
cfs at Gold Creek (figure £.2.146).Gold Creek
temperatures increased by approximately 0.3 to
1.3°C (0.5 to 2.3°F)compared to the 12,000 cfs
flow case.Further downstream,the temperature
changes were larger.Note that since tributary in-
flows are warmer than the predicted temperatures,
they would tend to increase the Susitna tempera-
tures above these predicted values.
-Talkeetna to Cook Inlet
The contributions of the Talkeetna and Chul itna
Rivers will be much greater than the Susitna River
during summer filling.Hence,the temperature in
the mainstem,downstream of Talkeetna,will reflect
those of the Tal keetna and Chul i tna.Si nce thei r
temperatures are cooler than the Susitna (Figure
E.2.75),summer temperatures will be cooler than
natural conditions.However,because of the re-
duced discharge in this reach,the water tempera-
tures will warm faster than presently observed.
Downstream from the confluence with the Yentna
River,there will be no significant temperature
differences from natural conditions.
During October,the temperature of the Susitna is
likely to be above O°C (32°F)(figure E.2.141).
However,since the Chulitna and Talkeetna River
temperatures will be near O°C (32°F),there should
be 1itt 1e change from the natural temperatu re of
near O°C (32°F)downstream from Talkeetna.
(11.)Ice
-Reservoi r
An ice cover will normally form on Watana reservoir
in late November.Although the reservoir ice for-
mation duri ng fill ing has not been modeled,it
E-2-88
.....
....
4.1 -Watana Developnent
should be similar to the ice formation during
Watana operation,described in Section 4.1.3(c)
(i i ) .
-Watana to Talkeetna
Because of the approximate 4°C (39.2°F)water which
wi,ll be discharged from Watana,there wi 11 be a
del ay of 3-4 weeks in the ice format i on process.
From Figure E.2.141,the approximate location at
which ice generation begins (i .e.,first point of
DOC (32°F)water)can be determined.Until 1ate
November,there is little opportunity for ice
generation.At this time,ice will be generated
downstream from Devil Canyon.
By about mid-December ai r temperatures are low
enough for the water to be cooled to O°C (32°F)and
ice generation to begin upstream of Devil Canyon.
This will result in significant ice generation in
Devil Canyon.Because of the colder temperatures
at this time of year than during the natural
freezeup peri od,once begun,the ice front wi 11
move upstream rapidly because of the generation of
additional frazil ice.The freezeup staging will
be similar to natural conditions,but slightly
lower because of the natural reduction in flow as
the winter progresses.
Sloughs and side channels that are currently over-
topped will likely be overtopped during the winter
freezeup.Hence,the natural scouring that takes
place during freezeup will continue during.the
filling period.
The maximum upstream extent of the ice cover will
be in the vicinity of Devil Canyon.Upstream from
Devil Ca,nyon,.openwater will exi'st year round.
In March and April,the'4°C (39.2°F)water being
released wilT not be cooled to DOC {32°FJ by the
time it reaches the ice front and will begin to
mel:tthe ice cover.This,coupled'with reduced
flows during breakup w·H l're'sult tr:rtess severe
breakl:lip cond:;tlofls tha'l1I current1yoccur.
E-2-89
4.1 -Watana Development
-Talkeetna to Cook Inlet
Because of the delay in ice formation in the Watana
to Talkeetna reach,the 70-80 percent contribution
to the downstream ice cover formation process that
is normally contributed by the Susitna upstream
from Talkeetna (R&M 1982d),will be delayed until
later in the year.Thus,the ice cover formation
downstream from Talkeetna will also be delayed.
(iii)Suspended Sediments/TurbidityjVertical Illumination
Watana Reservoir
As the reservoir begins to fill,velocities will be
reduced and deposition of the larger suspended
sediment particles will occur.Initially,all but
the larger particles will pass through the reser-
voir;but as more water is impounded,smaller dia-
meter particles will settle before reaching the
reservoir outlet.As the reservoir approaches nor-
mal operating levels,the percentage of particles
settling will be similar to that occurring during
reservoir operation.During the first year and
through sometime in August of the second year of
filling,water will be passed through the low-
level outlet which is at invert El 1490 ft (454 m).
During operation all water wi)l be drawn from above
El 2065 ft (630 m).As a consequence,1 arger par-
ticles are expected to pass through the reservoir
during the early stages of filling,than during
operat i on.(The depos it i on process du ri ng reser-
voir operation is discussed in detail in Section
4.1.3(c)[iii]).
During the filling process,reservoir turbidity
will decrease in conj unct i on wit h the sett 1 i ng of
suspended sediments.Turbidity will be highest at
the upper end of the reservoir where the Susitna
River enters.Turbid interflows and underflows may
occur during summer months,dependi ng on the rel a-
t i ve dens it i es of the reservoi r and the i ncomi ng
river water.Summer turbidity levels will be in
the 20-50 NTU range (Peratrovich,Nottingham,and
Drage 1982).Turbidity levels in the winter after
freezeup are expected to decrease to 10-20 NTU
(Peratrovich,Nottingham,and Drage 1982);however,
turbidity will be greater than the pre-project
winter levels.
E-2-90
rc--"
i~'
-
r-.
!
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"""
.-
"""
4.1 -Watana Development
Vertical illumination in the reservoir will de-
crease during breakup as higher flows begin to
b ri ng increased suspended sediment concent rat i on s
into the reservoir.Vertical illumination during
the summer will vary,dependi ng on where the i ncom-
ing river water finds its equilibrium depth (over-
flow,interflow,or underflow).Data from glacial-
ly fed Eklutna Lake indicate that vertical illumi-
nation wilT not exceed 4 meters (13.2 ft)during
the mid-summer months (Figure E.2.147)(R&M 1982"i).
Vertical illumination will gradually increase
during the autumn as glacial input decreases.
During reservoir filling,additional suspended
sediment will be introduced to the reservoir due to
slope instability along the shoreline.One of the
principal factors influencing slope instability
w"il 1 be the thawing of the permafrost soil s (Acres
1982c).A large portion of the reservoir shoreline
is susceptible to shallow slides,primarily of skin
and bimodal flow type with some shallow rotational
slides.Reservoir slopes which are totally submer-
ged or those with a break in slope below the reser-
voir surface will exhibit less stability problems
than those with the reservoi r surface at an inter-
mediate or low level on the slope.Flow slides
induced by perma frost thaw in fi ne-g rai ned soil s
can,however,occur on very flat slopes.
The effects of the reservoi r sl ides wi 11 primari ly
be confined to the area near the slides,and should
quickly dissipate.Quantitative estimates of the
total amount of sediment or the local changes in
suspended sediment concentration and turbidity are
not possible.However,the locations of potential
reservoir slope stability problems are discussed in
more detail in Appendix K of (Acres 1982c).The
period in which restabil ization of the slopes adja-
cent to the reservoir will occur is also unknown.
Construction activities,such as the removal of
timber from within the impoundment,are also ex-
.pected to contribute to increased suspended sedi-
ment concentrations and turbidity levels due to
erosion.Once removed,the lack of soil stabiliz-
ing vegetative cover will likely accelerate wall
sl ump ing •
E-2-91
4.1 -Watana Development
-Watana to Talkeetna
Maximum suspended particle sizes passing downstream
through the project area will decrease from about
500 microns (20 mils}during pre-project conditions
to about 5 microns (0.2 mils)as filling progres-
ses.As can be observed from the particle size
distribution curve in Figure Ee2.80,this results
in the retent i on of about 80 percent of the pre-
project suspended sediment at Watana.Because of
the clear water tributary fnflow in the Watana to
Talkeetna reach,further dilution of the suspended
sediment concentration will occur as the flow moves
downstream.In general,the suspended sediment
concentration in the Watana to Talkeetna reach will
be reduced by approximately 80 percent during the
summer months and slightly increased during the
winter months.
However,during periods of high tributary flow,
the-same amount of suspended sediment will be added
to the river by the tributaries as is presently
added.Talus slides along the mainstem will also
continue to contribute suspended sediment to the
fl ow .downstream from Watana as they have in the
past.
Downstream,summer turbidity levels will be reduced
to an estimated 20-50 NTU.Winter turbidity levels
w"l11 be increased to 10-20 NTU (Peratrovich,
Nottingham,and Drage 1982).Because of the re-
duced turbidity in summer,the vertical illumina-
tion will be enhanced.Winter vertical illumina-
tion will be reduced slightly.
-Talkeetna to Cook Inlet
In the Talkeetna to Cook Inlet reach,.al though the
tota 1 suspended sediment load will be dec rea sed,
the suspended sediment concentration and turbidity
levels during summer will remain high because of
the suspended sediment concentration of the
Chul itna Ri ver.The.Chul i tna Ri ver is the major
sedirnentcontri butor to the Sus itna with 28 percent
1t-2-92
".--
-
4.1 -Watana Development
of its drainage area covered by glacier.As dis-
cussed in Section 2.3.3(b),the preliminary 1982
summer data indicate that the suspended sediment
1oadwastwi ce that of tile Sus itna Ri ver above the
confluence.The average ChulHna River flow was
approximately 80 p'ercent of the 5us-itna flow.
The-relative change in suspended sediment concen-
tration downstream of the confluence can be esti-
mated by applyi ng the foHowing,mass balance rel a-
tionship.
Sc +\+5.r
I
Qc +Qs +QT
Sc +5s +Sr
Qc +Qs +Q'1
.....
-
....
Where:
Sc =
Ss =
ST =
Qc =
Qs =
QT =
S s
=
QI S =
Chul itna pre-project suspended sed iment
load in tons/day
Su sit'n'a'~fe:"f)iroject su spended sediment
load in tons/day
Ta 1keetna pre-project suspended sediment
load in tons/day
Chulitna pre-proje,et discharge inefs
Su sHna pre-project di scharge in cfs
Talkeetna pre-project disdlarge in cfs
Susitna post-project suspended sediment
load in tons/day
Susitna post-project discharge in cfs
-
The relationship can be approximated b~
~.[2'41~sQ:/:r/::2~]
if long term average flow relati01rsMps are usedrland
if it is assumed that the suspended sediment,tcculoen-
tration in the Susitna'River is reduced t602a~:p~rcent
of the pre-project concentration by the Watanareser-
voir,the Chulitna River h'ds twice the suspended load
of the Susitna;and the_Talkeetna has the same sus-
pended sed "iment concent rat i on as,the pre-proj ect
Susitna River.
E-2-93
4.1 -Watana Development
With the use of this relationship~for a Susitna
River pre-project discharge at Gold Creek of 30,000
cfs and a Gold Creek filling flow of 6000 cfs~the
suspended sediment concentration downstream of the
confl uence is estimated to increase by 8 percent.
This is because the Susitna River normally dilutes
the Chul itna Ri ver suspended sediment concentrat ion
and although the Susitna River suspended sediment
concentration is reduced by 80 percent~this is more
than offset by the reduction in flow.However,at a
filling flow of 12~000 cfs in the Susitna River~
there would be a decrease in suspended sediment con-
centrati on of about 3 percent.Si nce it was assumed
that there was a mass balance (i .e.~no sediment
deposition),it is possible that some accretion could
occur at the confluence because of the reduced velo-
city at the confl uence and because of the potential
increase in concentration over natural conditions at
Gold Creek filling flows of 6000 cfs.
Farther downstream,because of the varied tributary
suspended sediment concentrations,additional
changes in the suspended sediment concentration rela-
tive to the pre-project concentration will occur.
However,these will be minor.
The summer vertical illumination will remain near
zero.During winter,the low suspended sediment con-
centrations released from Watana dam will be diluted
by inflow from the Chulitna and Talkeetna Rivers.
Therefore,although suspended sediment concentrations
will be higher than natural conditions downstream of
the confluence~they should remain low.
(iv)Dissolved Oxygen
Initially,dur"ing the 3-year filling process,the
reservoir D.O.levels should approximate riverine
conditions.As fill ing progresses,some stratifica-
tion will begin to develop,but no substantial de-
creases in di.ssolved oxygen levels are immediately
anticipated.The volume of freshwater inflow,the
effects of wi nd and waves especi ally du ri ng spri ng
and fall turnovers,and the location of the outlet
structure at the bottom of the reservoir are expected
to keep the reservoir well mixed.
No significant biochemical oxygen demand is antici-
pated.The timber in the reservoir area will be
E-2-94
r
-
-
....
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4.1 -Watana Development
cleared,thereby e 1 imi nat i ng much of the associ ated
oxygen demand that would be created by the inundation
and decomposition of vegetation.Further,the chemi-
cal oxygen demand (COD)in the Susitna River is low.
COD levels measured upstream at Vee Canyon during
1980 and 1981 averged 16 mg/l.
No significant BOD loading is expected from the con-
struction camp and vill age,due to the wastewater
treatment facility currently proposed.
As a resul t of the above factors,di ssol ved oxygen is
expected to remain sufficiently high to support a
diverse aquatic habitat.
As previously noted,the low-level outlet will be
utilized for discharging water.During this time
period,the reservoir D.O.level should be equal to
the pre-project riverine conditions.Thus,the
"levels of oxygen immediately downstream from the
outlet are expected to be unchanged from pre-project
val ues.
(v)Total Dissolved Gas Concentration
As previously described,.supersaturated dissolved gas
conditions currently exist in the Susitna River below
the Devil Canyon rapids due to the entrainment of air
as the river flows through this violently turbulent
reach •
Supersaturated conditions are·also possible below
high head dams as a result of the passing of water
over a sp"illway into a deep plunge pool.The amount
of water being spilled,the height of the spillway,
and the depth of the plunge pool all influence the
amount of air that is dissolved in the water.If the
dissolved gases reach high levels (generally referred
to as greater than 116 percent),a fish kill due to
gas ernbol isms may resul t for many mi 1es downstream
(Turkheim 1975).
Since all water that is released during the filling
of the reservoir will pass through the low-level out-
let and thus,no spillage of water will occur at
Watana,this problem will not exist.Furthermore,
the reduced downstream flows during filling will
result in lower summer dissolved gas concentrations
below the Devil Canyon rapids.Based on observed
E-2-95
4.1 -Watana Development
pre-project conditions,August flows of 12,000 cfs at
Gold Creek should result in total dissolved gas
saturati on 1evel s of approximately 108 percent or
1ess.
(vi)Nutrients
Two opposing factors will affect nutrient concentra-
tions during the filling process.First,initial
inundation will likely cause *an increase in nutrient
concentrations due to leaching.Second,sedimenta-
tion will strip some nutrients from the water column.
The magnitude of net change in nutri ent concentra-
tions is unknown,but it is likely that nutrient con-
centrations will increase especially in close prox-
imity to the reservoi r floor for at 1 east a short
time during filling.
(vii)Total Dissolved Solids,Conductivity,Significant
Ions,Alkalinity,and Metals
Peterson and Nichols (1982)note that short-term
increases in dissolved solids,conductivity,and most
of the major ions could occur immediately after
filling begins.Bolke and Waddell (1975)found the
,h i ghestconcentrat ions of all major ions,except rnag-
Titesium,occurred immediately after dam closure.
'SymIDins et ale (1965),also identified similar
;'n;crea's,e'so f a lk ali n ity,iron,and manganese.Th ese
findings were all attributed to the initial inunda-
tion and leaching of rocks and soils in the reser-
voi r.
The products of leaching are expected to remain in a
narrow layer immediately adjacent to the impoundment
floor (Peterson and Nichols 1982).In addition,
inorganic glacial sediment will quickly blanket the
reservoir bottom thereby inhibiting the leaching pro-
cess.Hence,water quality within the balance of the
impoundment shoul d be unaffected.However,the dis-
charge during filling will be via a low-level outlet
and increased level s of the aforementioned parameters
could occur downstream from the dam although no
significant adverse impact are foreseen.
[E-2-96
.-
r
-
'"'"
i~
-
4.1 -Watana Development
Further discussions of the effects of the anticipated
leaching process are presented in Section 4.1.3(c)
(viii)and in Peterson and Nichols (1982).
(viii)Other
No additional water quality impacts of any signifi-
cance are anticipated.
(f)Ground Water Conditions
(i)Mainstem
Alluvial gravels in the river and tributary bottoms
upstream from the dam will be inundated.Other than
aquifers composed of the unconfined materials making
up the relict channel and in the valley bottoms,no
aquifers of significance are known to exist in the
reservoi r area.
Asa.result of the decreased summer flows (see
Section 4.1.2(b)[1]),water levels in the mainstem
of the ri ver will be reduced between Watana and
Talkeetna.This will in turn cause a reduction in
adjacent ground water 1evel s.However,the ground
water 1evel changes will be confi ned to the river
floodplain area.The ground water level will be
reduced by about 2 to 4 feet (0.6 to 1.2 m)during
the summer near the streambank with 1 ess change
occurring with distance away from the river.
A simil ar process will occur downstream from
Tal keetna,but the changes in ground water 1evel s
will be less because of the decreased effect on river
stages.
-
-
-
(i i )Sloughs
The reduced mai nstem flows and assoc i ated lower
Susitna River water levels will slightly modify the
ground water relat i onshi p between the mai nstern and
the sloughs.The mainstem water level s upstream and
downstream of a slough control.the ground water gra-
d ient in the slough and since both 1evel s change by
approximately the s arne amount for di fferent flows,
the gradient will rernai n the same.Because the gra-
dient is unchanged,the upwelling rate will likewise
remain the same.
E-2-97
4.1 -Watana Development
Because the sloughs are adjacent to the mainstem of
the river,the ground water level in the sloughs will
be lowered by the same amount·as the stage change
wi thi n the mai nstem.Thi s wi 11 have the effect of
dewatering the areas in the sloughs between where the
ground water table currently·intersects the slough
and where the lowered ground water table will inter-
sect the slough.
Data to confirm the areal extent of upwelling at
various flows are unavai 1 able at this time.However,
it is believed that slough upwelling extends from the
slough mouths well upstream t~the steeper reaches of
the sloughs near the upstream berms.Therefore,the
areas that wi 11 be dewatered wi 11 generally be the
steep upstream ends of the sloughs.If both mainstem
stage and ground water level change by approximately
2 feet (0.6 m),the potential loss in ground water
upwelling l~ngth will be the stage change (2 feet,or
0.6 m))multiplied by the slough gradient.Using the
18.6 foot per mile (3.5 m per km)gradient illustra-
ted in Figure E.2.21,thedewatered length would be
approximately 570 feet (l71m).This is 10 percent
of the slough length and,if a uniform upwelling rate
is assumed over the entire length of the slough,the
decrease in slough discharge at the mouth will also
be 10 percent.
(g)Lakes and St reams
Several tundra 1 akes will be inundated as the reservo"j r
approachs full pool.The mouths of the tributary streams
ente ri ng the reservoi r wi 11 be inundated for seve ral mi 1es
as discussed in Section 2.5.2 (see Table E.2.25).Bedload
and suspended sed i ment ca rri ed by these streams will be de-
posited at or near the new mouths of the streams.
No significant impacts to Tsusena or Deadman Creeks are
anticipated from their use as water supply and waste
recipient,respectively.
(h)Instream Flow Uses
(i)Fishery Resources,Riparian Vegetation,
and Wildlife Habitat
Impacts on fishery resources,riparian vegetation,
and wildlife habitat during the filling process are
discussed in Chapter 3.As summer flows are reduced,
E-2-98
4.1 -Watana Development
....
fi sh .access to slough hab itats will be decreased.
Since the temperature of the upwelling ground water
f"""in sl oughswill be essentially unchanged and upwell-
ingwill continue to occur,impacts on the incubation
ofsalmonid eggs are not expected to be significant •
.(it)Navigation and Transportation
Once impoundment of the reservoi r commences,the
character of the ri ver i mmed i ate ly upstream from the
dam will change from a fast-flowing river with numer-
ous rapids'to a still-water reservoir.The reservoir
will ultimately extend 54 river miles (87 km)up-
stream,terminating 8 mil es (13 kin)downstream from
the confl uence with the Tyone River,and wi 11 i nun-
date the major rapids at Vee Canyon.The reservoi r
will make possible increased boat traffic to this
reach of river by decreasing the navigational hazards
through Vee Canyon.
The reduced summer fl ows released from the reservoi r
during filling could reduce the navigation diffi-
culties between Watana and Devil Canyon during the
summer months.However,the 1owe r segment of this
reach from Devil Creek to Devi 1 Canyon will sti 11
consist of whitewater rapids suitable only for expert
kayakers.
.-
-
-
~I
Navigational difficulties between Devil Canyon and
the confluence with the Chulitna River will be in-
creased as the resul t of shallower water and a some-
what constricted channel.From an examination of the
navigation criterion established in Section 2.6.3 for
the Portage Creek to Talkeetna reach (i.e,a required
Gold Creek flow of 6500 cfs to maintain a 2.5-foot
(0.8-m)depth near Sherman)and the Gold Creek flows
for the three filling cases,it is apparent that
slight naVigational (Table E.2.38)problems could
develop near Sherman duri ng the second and thi rd
years of fi 11 ing during May,June,July,and 1ate
September when the Gold Creek flows are 6000 cfs.If
the fi rst year of fill ing is a dry year,some naviga-
tional difficuHy could a.lso occur at Shennan during
July of that year.However,to ensure that naviga-
tion is not impacted,the navigation depth near
Sherman will be monitored..If this reach is not
navigable,then~either the·channel bottom in the
problem reach near Shennan will be lowered to main-
tain a 1.5-foot (0.5-m)deep channel and the channel
will be marked with buoys;or the Gol d Creek dis-
charge will be increased to 6500 cfs.
E-2-99·
4.1 -Watana Development
There will be no impact on navigation below the con-
fluence of the Chulitna River except perhaps at
Alexander slough.Examination of Table E.2.39 indi-
cates that during filling,flows will be well in
excess of those needed to maintain navigational
depths at Kashwitna Landing or near Willow Creek (see
Section 2.6.3).The reduced summer flows from the
Susitna River will be somewhat compensated for by the
high flows from other tributaries.Minor restric-
tions on navigation may occur at the upstream access
to Alexander Slough,but this would occur only in low
streamflow years when the other tributaries also have
low flow.
Because of the delay in ice cover formation in the
Watana to Talkeetna reach,use of the river by snow-
mobile and dogsled will also be delayed (Section
4.1.2(e)[iii]).
(iii)Recreation
Since summer navigation will not be negatively im-
pacted and since fishery impacts will be mitigated
downstream of Watana,recreation impacts shoul d not
be significant.However,the kayaking recreational
potential of Vee Canyon will be lost due to reservoir
filling.
(iv)Waste Assimilative Capacity
The previ ous ly noted reduct ions to downstream summer
flows could result in a slight reduction in the waste
assimilative capacity of the river.However,no
adverse impacts will occur given the limited sources
of waste loading to the river (see Sections 2.6.6 and
4.1.1(g)[i 1])•
(v)Freshwater Recruitment to Cook Inlet Estuary
Given average hydrologic conditions,the annual
Susitna River flow contribution to Cook Inlet will be
reduced by its greatest proportion of approximately
11 percent,during the second year (WY 1992)of fill-
ing.Resource Management Associates (1983)used the
previously identified computer model (Section 2.6.7)
to estimate salinities during the entire filling
period.As expected,higher sal inities are present
throughout the scenario,however,these increases are
not substantial.
E-2-100
"'-
.....
I
-
-
-
4.1 -Watana Development
At Node 27,near the mouth of tht'!Susitna River (Figure
E.2.•12~},the maximum increase in salinity levels of
1400 mgjl.(increase from 9700 to 11,100 mgjl)was predicted
to occur during June when the greatest percentage reduction
inflow occurs (Figure E.2.127).Progressing southward down
.Cook Inlet away from the mouth of river,quantitive changes
are less and a slight time lag is evident.At the center of
Cook Inlet near East Forel~nd (Node 12)a maximum salinity
increase of 600 mgjl was predicted during July and August.
Salinity filling data (WY 1992)for five locations in Cook
Inlet are presented in Table £.2.31.
These higher Cook Inlet salinities will last only until
project operation,at which time a new equil ibrium will be
establishd as described in Section 4.1.3(f)(iii).
4.1.3 -Watana Operation
(a)Flows and Water levels
-
-
-
-I
(i)Project Operation
Watana will be operated in a storage-and-release
mode,so that summer flows will be stored for release
in winter.Generally,the Watana reservoir will be
at or near its normal maximum operating level of 2185
feet (666 m)each year at the end of September.
Gradually,the reservoir will be drawn down to meet
winter energy demand.The flow during this period
wi 11 be.governed by the wi nter energy demand,the
water level in the reservoi r,and the powerhouse
characteristics.The turbine characteristics will
allow a maximum powerhouse flow of approximately
21,000 cfs at full gate although it is unlikely that
thi s pm'lerhouse flow woul d occur duri ng the operat i on
of Watana prior to the construction of Devil Canyon.
In eary t4ay,the reservo;r wi 11 reach its mi nimum
annual leve't of approximately E1 2093 ft (638 m)and
tben begin to refill with the spring runoff.Flow in
.ex.cessof botfl the downstream flow requirements .and
1Jower needs wi 11 be stored d1Jri ng the summer unt;1
the reservoi r reaches the n{)rmal maximum operating
levelt)f 2185ft (666 m).If the reservoir reach€s
£12185 ft (666m),flow -gr€ater than that required
for power generat i onw~11 be released.However,
£-2-11n
4.1 -Watana Development
after the threat of significant flooding has passed
in late August,the reservoir will be allowed to sur-
charge to El 2190 ft (668 m)to mi nimize the volume
of water released in late August and September.
-Watana Turbine Operation
The six turbine units at Watana can be operated to
provide any flow above 1500 cfs up to the maximum
capability of the powerhouse (21,000 cfs)and still
maintain high efficiency.This is illustrated in
Figure E.2.148.
-Minimum Downstream Target Flows
During project operation,the minimum flows to be
provided at Gold Creek will be those presented as
Case C in Section 3.4.1.Target flows for May
through September were discussed in Section
4.1.2(a)(i),Reservoir Impoundment.Flows from
October through Apri 1 wi 11 be mai ntai ned at or
above 5000 cfs.It shoul d be noted that these
flows ar~minimum target flows.Project operation
fl ows will normally be greater than the targeted
minimum flows during the winter.During May,June,
July and October,operational flows will also nor-
mally be greater than the mi nimums.The 1 ate Jul y,
August,and September flows will normally coincide
closely with the minimum requirements.The minimum
target flows during operation are shown in Table
E.2.36 and Figure E.2.136.
If,during the summer,the natural flow falls below
the Gold Creek minimum values listed in Table
E.2.36,the now will be augmented to maintain the
downstream flow requi rement.
-Monthly Reservoir Simulations
As discussed in Section 3.2,a monthly energy simu-
lation program was run using the 32 years of syn-
thesized Watana floVi data given in Table E.2.6.
The simulation was initiated with the reservoir at
the normal maximum operating level and a full pool
was required at the end of the simulation.Energy
E-2-102
....
-
-
-
"""
4.1 -Watana Develo~nent
production \:las optimized by adjusting the monthly
o perat i ng rule curve and bymaximi zi ng the minimum
monthly energy production accordi ng to the monthly
energy demand p'attern,tak i ng into account the res-
ervoir characteristics and the downstream flow
requirements.The optimized rule curve is pre-
sented in Table L2.40.The mi nimum monthly ener-
gi es and the associ ated powerhouse di scharge are
presented in Tab1e E.2.41.
-Weekly Reservoir Simulations
The monthly reservoi r s irnul at ions are adequate for
determini ngenergy benefits and mean monthly flow,
but they do not provi de a good i nd icat i on of the
flow variability during a month in which the Watana
reservoi r is close to its normal maximum operati ng
1 evel.·Therefore,a weekl y reservoi r s imul at ion
program was developed.The weekly reservoir simu-
lation program is similar to the monthly reservoir
s imul at i on except that the input data is weekly
based rather than monthiy based and the program
uses a weekly time 'step instead of a monthly time
step..
The mean dai ly flows for each of the 32 years of
record at Gold Creek were divided into weekly peri-
ods starting at the beginning of the water year
(October 1)and averaged to provide mean weekly
flows.Flow on February 29 of leap years was not
considered significant and was disregarded.How-
ever,flow on September 30 of each year is signifi-
cant and was added to week 52 of each year.
Weekly flows at Watana and Devil Canyon were deter-
mined by taking the ratio of the discharge area of
the damsite to the Gol d Creek drainage area and
multiplying by the Gold Creek weekly flow.Since
the Cantwell weekly record was incomplete,it was
not used in the determination of the weekly flows
at Watana or Devil Canyon.
WY 1969 was modified as discussed "in Section 3.3.
The ratio of the long term weekly average flow to
the mean annual flow was multiplied by the 1:30
year low flow.
Weekly simulations were conducted for the 32 years
of record for the year 1995 and 2000 energy demand
E-2-103
4.1 -Watana Development
forecasts.Results from the two simulations are
very similar.This is because most of the energy
produced at Watana is usable!even in wet years,
with both energy forecasts.There is,however!one
important difference.Wi th the 1995 demand,there
is insufficient energy demand to provide a power-
house flow equal to the August downstream flow re-
qui rement.To provide the requi red discharge,a
flow release through the outlet facilities is
necessary.By 2000!the demand is 1 arge enough so
that a release of this kind is unnecessary.
-Daily Operation
In an effort to stabilize downstream flows,Watana
will be operated as a base-loaded plant until Devil
Canyon is completed.This will produce daily flows
that are vi rtually constant throughout a 24-hour
period for most of the year.There will be a grad-
ual change in daily flow to adjust to the changing
seasonal and weekend energy demands.During summer
it may be economically desirable to vary flow on a
daily basis to take advantage of the tributary flow
contribution downstream from Watana to meet the
flow requirements at Gold Creek.However,a daily
variation of not more than 2000 cfs is anticipated.
This would yield relatively stable flows from
Portage Creek to Gold Creek,but somewhat variable
river flows between Watana and Portage Creek.
(ii)Mean Monthly Flows!Annual Flows,and Water Levels
Monthly water levels and discharges at Watana for the
32-year period were computed using the monthly energy
simulation program.The monthly maximum!minimum,
and medi an Watana reservoi r 1evel s for the 32-year
simulation are illustrated in Figure E.2.149.
The maximum reservoir levels represent a simulation
of Wy 1956,one of the wettest years on record.The
maximum water levels coincide closely with the rule
curve because the powerhouse has sufficient genera-
tion capacity to utilize all flow above that required
to satisfy both the minimum energy production and the
rule curve.
The minimum reservoir levels represent a simulation
of WY 1970.This illustrates the effect of the
E-2-104
-
,....
.-
-
-
4.1 -Watana Development
modi fted WY 1969 drought and the 1ack of recovery
during the WY 1970 drought.In October~November~
and December of simulated WY 1971~the reservoir ele-
vationis a few feet lower.However~from the end of
Decembe r to the end of Apr il ~reservoi r e 1evat ions
during WY 1970 and WY 1971 are the same.In May of
WY 1971~·the·reservoir level drops to El 2068 ft
(627 m)but a strong recovery takes place in June~
July ~and August with water 1 evel s well above those
for WY 1970.
WY 1966 was selected as being representative of the
median year.The median year illustrates that during
the winter months~the reservoir water surface eleva-
tion follows the reservoi r rul e curve most of the
time.
The monthly Watana discharges for the simulation
period are presented in Table E.2.42.The maximum~
mean~and minimum flows for each month are summarized
in Table E.2.43.Pre-project flows are also pre-
sented for comparison.In general ~powerhouse flows
from October through April will be much greater than
natural flows.For example~in March the average
operational flows will be nine times greater than the
natural river flow.Average past-project flow for
May will be about 27 percent less than the natural
flow.Mean daily post-project flows during May will
show a slight change through the month in response to
the changing energy demand.In contrast~existing
basel ine flows vary considerably from the beginning
to the end of the month because of the timing of the
snow melt runoff.Flows during June~July~August
and September will be substantially reduced from pre-
project levels due to the annual reservoir filling
process.
Pre-and post-project monthly flows at Gold Creek are
listed in Tables E.2.8 and E.2.44.A summary is pre-
sented in Table E.2.45.The comparison is similar to
that ·for Watana although the pre-projectjpost-project
percentage changei s less due to tributary flow con-
tributions downstream from \4atana.Figure E.2.150
ill ustrates the Watana i nfl ow and outflow,the Watana
reservoir 1evel,and the Gol d Creek pre-project and
post-project flows for each month of the 32-year
simul ati on.
Farther downstream at Sunshine and Susitna Station,
p re-and post -project fl ow differences will be 1ess.
E-2-105
4.1 -Watana Development
During July,average monthly flows will be reduced by
11 percent at Susitna Station.However during the
winter,flows will be 100 percent greater than exist-
ing conditions.Monthly pre-and post-project flows
at the Sunsh"ine and Susitna Stations are tabulated
and summarized in Tables E.2.9,E.2.10,E.2.46,
E.2.47,E.2.48,and E.2.49.
Mean annual flow will remain the same at all sta-
tions.However,flow will be redistributed from the
summer months to the wi nter months to meet energy
demands.
Water surface elevations based on maximum,mean,and
minimum monthly f1 ows at Go1 d Creek for May through
September for selected mainstem locations between
Portage Creek and Talkeetna are illustrated in
Figures E.2.151 through E.2.153.The figures illus-
trate the water level change expected as a result of
operation of Watana.In general,there is a 2 to 4
foot (0.6 to 1.2 m)decrease in water level from
pre-project levels to post-project levels.However,
during low flow years,there is approximately a 1
foot (0.6 m)decrease in water level during August
and a half foot increase in September.Note that the
water levels are based on observed stage-discharge
measurements compiled by the Alaska Department of
Fish and Game (1982c).
(iii)Floods
-Spring Floods
For the 32 years of monthly simulations,Watana
reservoir had sufficient storage capacity to absorb
all floods.The largest flood of record,June 7,
1964,had a peak discharge of 90,700 cfs at Gold
Creek,corresponding to an annual flood recurrence
interval of better than 20 years.This flood pro-
vided the 1 argest mean monthly i nfl ow on record at
Gold Creek,50,580 cfs,and contained the largest
flood vol ume on record.However,even with this
large a flood,the simulated reservoir level in-
creased only 49 feet (15 m)from E1 2089 ft (637 m)
to E1 2138 ft (652 m).A further 47 feet (14 m)of
storage were avail ab1 e before a reservoi r re1 ease
would have been necessary.
The flood volume for the May-July 1:50-year flood
was determined to be 2.3 million acre-feet (R&M
E-2-106
4.1 -Watana Development
1981f).This is equivalent to the storage volume
contained between El 2117ft (645 m)and 2185 ft
(666 m),neglecting discharge.Since the maximum
elevation at the beginning of June was always
less than 2117 ft (645 m)during the simulation,
the 50-year flood vol ume can be stored without
necessitating a release,if it occurs in June.
If the flood event occurs in July,the 1:50-year
flood vol ume can also be accommodated wi thout
exceeding [1 2185 ft (666 m)if the powerhouse
discharge averages 10,000 cfs.Thus,for flows
up to the 1:50-year flood event,Watana reservoir
is capable of totally absorbing the floods with-
out requiring operation of the outlet facili-
ties.
Only for flood events greater than thel:50-year
year event and/or a fter the reservoi r reaches
E1 2185.5 ft (666.3 m),will the outlet faci1 i-
ties be operated.Discharge will be set equal to
i nf1 ow up to the full operati ng capacity of the
outlet faci·lities.During flood events of this
magni tude the powerhouse wi 11 a1 so operate at
maximum energy demand capacity,thereby reducing
the flood level in the reservoir.If inflow con-
tinues to be greater than outflow,the reservoir
will gradually rise to E1 2193 ft (669 m).At
that time,the main spillway gates will be opened
and operated so that the outflow matches the in-
flow.The main spillway will be able to handle
floods up to the 1:10,OOO-year event.Peak in-
flow for the 1:10,000-year flood wi'll exceed the
combined powerhouse,outlet facilities and main
spillway capacity resulting in a slight increase
in water level above E1 2193 feet (669 m).The
discharges and water levels associated with the
1:10,000-year flood are shown in Figure E.2.154.
If a flood greater than the 1:10,000-year flood
were to occur,the main spillway would be oper-
ated to match i nfl ow until the i nfl ow rate ex-
ceeds the capacity of the spillway.The reser-
voir elevation would rise until it reached E1
2200 ft (671 m).At this elevation,the erodible
dike )n the emergency spillway would be breached
and the emergency sp i 11way wou1 d operate.The
resulting total outflow through all the discharge
structure~would be 15,000 cfs less than the pro-
bable maximum flood (PMF)of 326,000 cfs.The
inflow and outflow hydrographs for the PMF are
illustrated in Figure E.2.154.
E-2-107
4.1 -Watana Beve10pment
Spri ng floods downstream wi 11 be reduced by the
discharge stored in Watana reservoir for up to the
50-year flood event.This will be true for Gold
Creek.However,further downstream,the timing of
the f1 ood peak at Watana wi 11 not necessari 1y be
coincident with the flood peaks at Sunshine or
Sus itna and wi 11 1ead to conservative est imates
(i.e.,reductions larger than would actually occur)
of the flood peak at these downstream locations.
Assuming the mean annual spring flood at Watana to
be equal to the maximum usab1 e powerhouse f1 ow,the
mean annual flood flow at Watana wi 11 be reduced
approximately 30,000 cfs.Hence Gold Creek,
Sunshine,and Susitna Station will have mean annual
floods reduced from 49,500 to 20,000;95,000 to
65,000;and 157,000 to 127,000 cfs,respectively.
For the 1:10-year spring flood,the flow reduction
at Watana will be 55,000 cfs.Hence the 1:10-year
floods at Gold Creek,Sunshine,and Susitna Station
wi 11 be reduced from 79,000 to 24,000;144,000 to
89,000;and 239,000 to 184,000 cfs,respectively.
It is important to note that these are spring
floods and the flow above Watana is adsorbed almost
in its entirety by the Watana reservoir.The
annual floods which have larger peak flow values
and the August summer floods which would occur when
the reservoi r is nearly full,coul d cause 1 arger
downstream floods than the spring floods.
For spring floods greater than the 1:50-year event,
it is possible that the Watana reservoir would fill
and inflow would be set equal to outflow.If this
occurred,floods downstream would be unaffected.
-Summer fl oods
During wet years,the Watana reservoir will reach
£1 2185 ft (666 m)sometime in August or September.
Desl{jn considerations were therefore established to
ensure that the powerhouse and outlet facil ities
woul-d have sufficient capacity to pass the 1:50-
year summer flood without operation of the main
spil1way~since this would result in nitrogen
-supersaturation which could be detrimental to down-
stream fisheries.A further decision criterion was
establ ished such that the reservoi r woul d be
allowed to sorcharge to £1 2193 ft (669 m)duf'ing
the 1:50 yea r flood.
£-2-108
,-
4.1 -Watana Development
The 1:50 year inflow and outnow hydrographs at
WataAa were deri ved as follows:
The mean annual flood peak at ~atana was multiplied
by the ratio of the mean annual summer flood peak
at Gold Creek to the mean annual flood peak at Gold
i:reek to obtain the meananAual summer flood peak
at Watana.This value was multiplied by the rati~
of the 1:50-year summer flood to the mean annual
summer n ood at Gold Creek,to obtai n the Watana
1 :50-year summer flood peak of 64,500 cfs.The
August to October dimensi.onless hydrograph (R&M
1981f)was next muHipl ied by the Watana flood peak
flow to obtain the inflow hydrograph.To obtain
the Otlt fl ow hydrograllh,the inflow was rOllted
through the reservoi r assumi og that the reservoi r
was at £1 2185 ft (666 m)at the commencement of
the flood.The flows and assoc i ated reservoi r
water levels are illustrated "in Figure E.2.154.
The outflow is the sum of the rel ease th-rough the
outlet facilities {24,OOO cfs)and the powerhouse
discharge.For the -dnalysis,the powerhouse di s-
charge was assumed to be 7000 c fs.
If summer floods of lesser magnitude than the 50-
year event occu r with the reservoi r full,i ofl ow
will match outflow up to the discharge capabil ity
of the outlet facilities and powerhouse.
To determine the magn itude of flood events duri ng
project operation,·weekly reservoir simul ations
were carried out (see Section 4.1.3{a)(i)).Dur-
ing the 32 years of reservoir simulations,the
Watana reservoir did not exceed El 2190 ft (66.8 m).
Flence,the spillway was not used.
-Annual Floods
The maximum weekly discharge at Bold Creek during
the 32-year simulation period was 36,100 cfs occur-
ring in WY 1~81.The simulation also included the
August 15,~1967 flood,which had an instantaneous
peak of 130,200 cfs at .Gold Creek and an equivalent
summer return peri odof 1 :65-years,thus demonstra-
ting the conservative nature of the above analysis.
Since the i'eservoi r was not full until after the
1967 flocOd pe-d ke d,the rna xi mump 0 s t--Ploj ec t wee 1<1y
flow at Go1d{;reek was 29,100 cfs ..
E-2-109
4.1 -Watana Development
The annual flood frequency curve for Gold Creek,
based on the weekly simulations is depicted in
Figure E.2.155.This curve represents both the
1995 and 2000 energy demand simulations,since
there is vi rtually no difference in the frequency
curves.The largest floods occur when the reser-
voi r is full in 1ate August or September when re-
leases are necessary.However,high spring dis-
charges during the snow melt runoff period from the
drainage area downstream from Watana also occur.
For example,Figure E.2.156 illustrates a post-
project spring flood of about 28,000 cfs at Gold
Creek during simulated year 1964.
The post-project mean annual flood at Gold Creek is
approximately 15,000 cfs.This flood represents
winter powerhouse discharges of up to 14,700 cfs
and occurs during years when neither the reservoir
outlet facilities operate or the contribution of
snow melt runoff between Watana and Gold Creek is
significant.
Post-project floods at Sunshine and Susitna Station
will be reduced by approximately the reduction at
Gold Creek,if it is asslftlled that flood peaks occur
at Gold Creek and other downstream locations at
approximately the same time.
(iv)Flow Variability
Under normal hydrologic conditions,flow from the
Watana development will be totally regulated.The
downstream flow will be controlled by one of the fol-
lowing criteria:downstream flow requirements,mini-
mum power demand,or reservoir operating rule curve.
There generally will not be significant changes in
mean daily f1 ow from one day to the next.However,
there can be significant variations in discharge from
one season to the next and for the same month from
one year to the next.
The flow variability at Watana and Gold Creek is
demonstrated by the weekly reservoir simulations for
1964,1967,and 1970 shown in Figures E.2.156,
E.2.157,and E.2.158.Average weekly flows for
Watana and mean daily flow~for Gold Creek are pre-
sented.
E-2-110
,...
4.1 -Watana Development
The Gol d Creek flows were determi ned by addi ng the
natural mean daily flow from the drainage area
between Watana and Gol d Creek to the weekly post-
project Watana di scharge.Note that because the
weekly s imul at i onswe,re based on average weekly
flows,.superimposing daily values causes some of
the daily Gold Creek flows to be slightly less than
the downstream flow requi rements.Natural Gold
Creek flows are included in the figures for
reference~
-
-
....
.....
(v)
The Watana flows show little variability because of
the high degree of reservoir regulation and the
relatively constant powerhouse flow.Gold Creek
exhibits considerably more daily variation because
of the variabil ity in local inflow.The year to
year variability is evidenced in the comparison of
flows between 1967 and 1970.
Monthly and annual flow duration curves based on
the monthly average flows for pre-project and post-
project operating conditions are illustrated in
Figures E.2.159 through E.2.162 for Watana,Gold
Creek,Sunshine,and Susitna Station.The flow
duration curves show a diminished pre-and post~
project difference with distance downstream from
Watana.The annual flow duration curve,based on
weekly average flows at Gold Creek,is presented in
Figure E.2.163.This figure is'similar to the
monthly value except that higher flows can b~
detected in the weekly based flow dura t ion cu rve.
Operation of Watana Fixed-Cone Valves
The six 78-inch (2 m)diameter fixed-cone valves,
each with a design capacity of 4000 cfs,will be
operated to rel ease excess water fran the Watana
reservoi r to avoid downstream gas supersaturati on.
The valves will draw water from the reservoir between
£1 ~025 ft (617mj and El 2085 ft (636 m).The water
will be discharged approximately 125 'feet (38 m)
above the normal :tailwater elevation as a·highly
diffused Jet tGacnieve significant energy dissipa-
tion without·the provision of a stilling basin or
pl uflge pool.
TableE.2.50 presents information on flow releases
from t~weekly reservoi r simulations for both the
1995 and 2000 energydemaRd forecasts.Included for
each year of the 32 years ofsimul ation are the week
of first release,the ~eek .of maximum release,the
E-2-111
4.1 -Watana Development
maximum Watana release,the powerhouse flow at the
time of maximum release,and the volume released.
As shown in Table E.2.50,these valves would operate
in the 1ate summer of al most every year when the
energy demand is equal to the,1995 demand.This
occurs because the powerhouse flow must be augmented
to provide the necessary 12,000 cfs downstream flow
in August and September.By the year 2000,the ener-
gy demand will have increased so that flow augmenta-
tion is no longer necessary.
In all but 7 years of the 32 years of simulation,the
maximum rel ease is 1 ess than 2500 cfs.Therefore,
there is an annual probabil ity of approximately 20
percent that a rel ease of more than 2500 cfs will
occ ur.
The week of fi rst release through the fixed-cone
valves in any year begins the week of July 29 or
later.Rel ease made necessary because the reservoi r
has reached the maximum operating level,occur the
week of August 19 or later.
Information ontt'le downstream temperature impacts
caused by the operation of the fixed-cone valves can
be f 0 undin se ct ion 4.1.3(c)(1).
(b)River Morphology
Impacts on river morphology occurring fr~n May through
September during Watana operation will be similar to those
occurring during reservor impoundment (Section 4.1.2[d]),
although flows will generally be increased during opera-
tions.
The reduction in streamflow peaks and the trapping of bed-
load and suspended sediments in the Watana reservoir will
continue to significantly reduce morphological changes of
the river above the Susitna-Chul itna confluence.The main-
stem river channel will continue to become tighter and more
clearly defined.Channel width reduction by vegetation en-
croachment will continue (R&M 1982d).
In winter,substantial di fferences may occur as the resul t
of ice processes as discussed in Section 4.1.3(c)(ii).
Above the Chulitna River,the effects of ice forces during
breakup on the river morphology will be effect i vely
E-2-112
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4.1 -Watana Development
eliminated (see Section 4.1.3(c)[ii]).Although an ice
cover could form as far upstream as Devil Canyon,the rapid
rise in streamflows which cause the initial ice movement at
breakup will·be el imi nated because of the Watana reservoi r
flow regulation and because warmer water temperatures re-
leased frOln Watana will tend to melt the ice in place
(Section 4.1.lee)[i])•..
In the sloughs,overtopping of the gravel berms at the up-
stream end duri ng summer will sel dam occur because of the
reduced flows.Movement of sand and gravel bars in the
sloughs wilT be minimized.Debris jams and beaver dams,
which previously were washed out by high flows,will remain
in place,with resultant ponding in those sloughs not main-
tained as part of the fisheries mitigation program (see
Chapter 3)..Vegetat i on encroachment i-n the s 1oug hs and side
channels may also occur as the high flows are reduced.
Impacts at the Chulitna River confluence and farther down-
stream will be similar to those occurring during reservoir
impoundment.
(c)Water Quality
(i)Water Temperature
-Watana Reservoir
After-impoundment,the Watana reservoi r wi 11 exhi-
bit the thermal characteristics of a deep 91 acial
1ake.Deep gl ac ial lakes commonly show temperature
stratificati on du ri ng both wi nter and summer
(Mathews 1956;Gilbert 1973;Pharo and Carmack
1979;Gustavson 1975).However,stratific'ation is
often relatively weak.Bradley Lake,Alaska,
(Figure E.2.164)demonstrated a distinct thermo-
cline in late July 1980,but was virtually isother-
mal by late September.A reverse thermocline was
observed duri ngthe wi nter months (U.S.Army Corps
of Engineers 1982)•
Similar thermal structures have been observed at
Eklutna Lake,Alaska during 1982 and 1983 (Figures
E.2.165 to E.2.167).
Reverse thermoclines during wi nter months-are typi-
cal of deep reservoirs and lakes with ice covers as
noted at Eklutna Lake and Williston Lake (Figure
E.2.168).However,the depth of the thermocline
under winter conditions is greatly influenced by
E-2-113
4.1 -Watana Development
time and mode of ice cover formation in addition to
water withdrawals from under the ice cover.
The seasonal variation in temperature within the
Watana reservoir and for a distance downstream will
change after impoundment.Bo1ke and Waddell (1975)
noted in an impoundment study that the reservoi r
not only reduced the range in temperature but a1 so
changed the timing of the high and low tempera-
tures.This will also occur in the Susitna River
where pre-project tempe ratures generally range from
DOC to 14°C (32°F to 5T°F)with the lows occurring
from October through April and the highs in July or
August.However,to mi nimize the pre-project to
post-project temperature differences downstream,
Watana will be operated to take advantage of the
temperature stratification within the reservoir.
During summer,warmer reservoir water will be with-
drawn from the surface through a multilevel intake
structure (Figure E.2.169).The intake nearest the
surface generally will be used.In this way warmer
waters will be passed down st ream.In wi nter,the
col der surface water wi 11 be withdrawn to provide
the coldest possible water downstream.
To provide quantitative predictions of the reser-
voir temperature behavior and outlet temperatures,
reservoi r thermal st udi es were undertaken in 1981
and 1982.
Results of the 1981 studies are presented in
Append ix A4 of the Susitna Hydroe1 ectrk Project
Feasibility Report (Acres 1982b).Review of these
studies resulted in the continuation of thermal
studies into 1982 and 1983 to further define the
1 ike1y reservoi r temperature structure and the
temperature and ice regime downstream of the Watana
and Devil Canyon d~ns.
Detailed analyses were performed for Watana and
Devil Canyon'Reservoirs using a one-dimensional
computer model,DYRESM.This model wa~verified,
using data collected at Ek1utna Lake during 1982.
A brief description of the DVRESMmode1 follows.
E-2-114
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4.1 -Watana Development
•rWRESM Mode 1
PredJctions of reservoir temperature stratifica-
tion and outflow temperatures have been made
using a one-dimensional numerical model developed
,by Imberger s et al.(1978).The dynamic reser-
voir simul~tion model,DYRESM,has been modified
to include ice cover formation and outflow
hydraulics associated with multiple intake struc-
t ures.
DYRESM approaches the problem of reservoi r temp-
erature modeling by parameterization of the phy-
sical process rather than numerical solution of
the appropriate differential equations.The
reservoir is model ed by a system of hori lontal
layers with uniform properties which move up and
down,in accordance with the volume-depth rela-
tiol1ship,as inflow and withdrawal increase and
decrease the reservoi r vol ume.Each layer has
dimensions suited to the function requi red of
them.For exampl e s the mixed layer may be
mode led by a reasonably coa rse layer st ructure in
the epilimnion thinning.down to a very narrow
layer in the transition lone.
The construction of the DYRESM model is that of a
main program with subroutines wtlich separately
model each ofthephysi cal processes of inflows
withdrawals mixed layer dynamics s and vertical
transport in the hypolimnion.Other subroutines
provide support for frequently required data such
as volumes and density.
The physi ca 1 processes i nvo 1ved in the model i ng
require definition of the time step over which
they act.II"lf1ow and outflow dynamics generally
ch-ange relatively slowly from day to day whereas
the mixed layer dynamics requi res a much fi ner
sub-daily time step.In DYRESM,the base time
step is set at one day for calls to subroutines
which deal with inflow and outflow.Calls to
other subroutines are based on the dynamics of
the situation and range between one quarter hour
and 12 h-ours./
Meteorological data are generally assumed to be
inputed as daily averages except for wi nd speed
which is given as six hour resultant wind speeds.
E-2-115
4.1 -Watana Dev~lopment
Allowance is bui 1t into the program for the
..difference in short wave radiation absorption
between day and night.DYRESM requires compre-
hensive data on wind speed,short and long wave
radiation,temperature,vapor pressure,and pre-
cipitation,in addition to physical characteris-
tics of the reservoir and inflow and outflow
quantities.
A detailed discussion of DYRESM is provided in
Imberger and Patterson (1980)•
•Eklutna Lake Modeling
The DYRESM program has been used extensively in
Australia and Canada to predict thermal profiles
within lakes and reservoirs.To assess the
accuracy of DYRESM in predicting the thermal
structure in gl aci ally fed reservoirs,a data
collection program w.as established in 1982 to
obtain data on the thermal structure of Eklutna
Lake located approximately 30 miles (50 km)north
of Anchorage,Al aska {Fi gure E.2.1).A weather
station was also established to provide the
necessary meteorological input to 0 YRESM.
Detailed daily simulations were made of Eklutna
Lake from June 1 to December 31,1982 to estab-
1 ish the adequacy of the n YRESM mo<1el.Si mul ated
and measured profiles at a station in the approx-
imate center of the lake are given in Figures
E.2.165 to £.2.167.In general most profiles are
modeled to within O.5°C (l°F).This is well
withi n the observed vari ati on of temperature at
the data collection stations througbout the lake
(R&M 1982i).Deviations in measured and simula-
ted profiles can be explained througn an assess-
ment of the meteorological variables used and the
rel i abil ity of the measurement of these vari-
ables.However,even with errors due toestima-
t ing weather data fran sources other than that of
the station at Eklutna Lake,the temperature pro-
files are reasonably modeled.
Outflow temperature.s from Eklutna lake for the
period June through December 1982 are presented
in Fi gures E.2.170 and E.2..171.In 1 ate June and
early July,significant deviations occur between
measu red ar:ld simul ated temperatures {fl gure
E.2.170).Thi.s devi.ation is believ.:ed t>Q be the
E-2-116
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4.1 -wata~a Developneot
combined result of the inability of OYRESM tn
model a three-dimensional system,possible under-
·estimatian ofa ir temperature and solar radia-
tioo,&lld possible overestimation of wind speed.
In ~eneral,simulated outflow temperature is lOC
(l.8°Flllelow the measured temperature from July
to mid-Septemf:>,er.From mi d-Se ptembe r to \)ecem-
ber,simulated and measured temperatures show
good agreement.
The configuration of Eklutna is such that the
portion of the lake near the intake structllres is
shallower than the rest of the lake,particularly
in early spri 09 when the lake is drawn down."01'i s
may result in a greater mixing influence from the
intake structure than is modeled by DYRESM.Kow-
ever,the major portion of the temperature devia-
tion is believed to be the result of uncertain-
ties associated with data collected during this
period.The model results for June 18 and July
14 .indicate reasonable agreement with measured
profiles (Figure L2'.165).This indicates that
although average meteorological conditions over
the entire period were suitably measured,condi-
t ions on a daily bas ismay be in error.Wi nd
speed in particular would have the major influ-
ence since an overestimatiofl of wind speed would
result in too much epilimnion mixing which would
result in cool er outflow temperatures.
The deviation in temperatures from July to mid-
September is believed to be mainly due to the
model approach of assumi ng an average 1 ake tem-
perature profile.Based 01'1 field measurements,
the intake port i on of Eklutna lake is generally
warmer than the mid-lake profile,and this would
explain the higher measured outflow tempera-
tures.
Ice cover formation an Eklutna lake began during
the latter part of November,1982 with a full ice
cover formed by mid-December.DYRESM,due-to a
Slight overestimation of daily cooling rates dur-
ing late October and November (Figure E.2.167)"
estimated ice cover formation to begin on Novem-
ber 17,with a full ice cover on November 19.
Measurements made on January 14,1983 indicates
an ice cover thickness of approximately 18 inches
(45 em)•This compares favorably with a predic-
ted ice thickness of 2J inch-es (52 em).
E-2-117
4.1 -Watana Development
Based on the 1982 study results,the abil ity of
DYRESM to predict the wi nter and summer thennal
stratification of a glacial lake under Alaskan
meteorlogical conditions is excellent.Thus,
the DYRESM program can be used to predict the
Watana average reservoi r tenperature profil e to
within O.5°C (I0F)and outflow temperature to
within 1°C (I.8°F).Ice cover formation and ice
thickness are believed to be predictable to with-
in 5 days and 5 inches (13 cm),respectively •
•Watana Reservoir Modeling
Detailed daily simulations were made of the temp-
erature structure of.Watana reservoi r operati ng
under Case C summer flows and maximum winter
energy productions based on reservoi r 1evel.
Meteorological data collected at Watana camp from
June through December 1981 was used as input to
DYRESM.Watana reservoi r inflow for the same
period was also input to the model.Reservoir
outflow requi rements for the temperature simul a-
tion period were obtained from the weekly reser-
voir s"imulation program described in Section
3.2.
Temperature profiles for the first day of each
month from June throllgh December a re ill ustrated
in Figures E.2.172 and E.2.173.A profile for
December 31,1981 is also shown in Figure
E.2.173.Th e temperature structure at Watana
follows the typical pattern for reservoi rs and
lakes of similar size and climatic conditions.
In general,stratification occurs during June,
July,and August.Maximum surface temperatures
occur in July and August.The maximum surface
temperature simulated was 11 °C (51-8°F)on JUly 3
and August 28.
Depths to the thermocline are variable with
strong dependence upon weather conditions,par-
ticularly wind speed.In June,typical mixed
1ayer depths are small and on the order of 5 to
15 feet (1.5 to 4.5 m).During July and August
the heat balance is positive into the reservoir
and strong stratification occurs.Mixed layer
depths during this period can be on the order of
130 feet (39.4 m),with a sharp temperature gra-
dient of approximately 5°C (41°F)in about 50
feet (15 m).
E-2-118
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4.1 -Watana Development
Multiple mixed 1 ayers are establ ished in Watana
by the model due to periods of warm calm weather
which provide surface warming with little mixing~
interspersed with windy periods which cause deep-
ening by mixing warm surface waters with cooler
wa-ter below.The duration and magnitude of the
wind dictates the effect on depth of mixing;
hence,the step appearance of some summer pro-
files (Figure E.2.172).
Cool i ng in September results in the gradual des-
truction of the summer stratification and the
deepeni ng of the epi 1 irnni on to depths greater
than 150 feet (45 m).This process continues
until an isothermal condition exists,which in
1981,was simulated to occur in mid-October.
Isothermal conditions conti nue unt n the reser-
voi r water reaches maximum density after which
reverse stratification occurs.
For the Watana reservoir sirnulation~a weak re-
verse stratifi cati on occur red in 1ate November
and remainea,relatively stable throughout Decem-
ber (Figure E.2.173).Under different meteorolo-
gical conditions~the simulated depth of about
180 feet (55 m)to the hypolimnion could be much
less due to less surface mixing or earlier ice
cover formation.
Ice cover formation on Watana reservoir was esti-
mated to occur on November 20 ~wi th a full ice
cover by November 22.Ice thickness on December
31 was estimated at 31 inches (77.5 cm).
The multilevel intake at Watana provides the
ability to select variable water temperatures
withi n a range dictated by the thennal structure
of the reservoir.The operating criterion for
this structure is to discharge water temperatures
as close to natural river temperatures as poss-
ibl e.This,in general ~results in the intake
.closest to the surface bei ng used~provided
hydraulic.submergence criteria are met.However~
upon occasion~dee~er intakes are used to provide
water temperatures closer to no rma 1.
The outflow temperature immediately downstream
from the Watana dam is given in Figures E.2.174
and E.2.175.A release,which occurs in August,
E-2-119
4.1 -~atana Development
has been included in the estimate of outflow tem-
peratures.This is further discussed below.
The comparison of natural temperatures and simu-
I ated outflow tempe ratures shows that duri ng sum-
mer months the outflow temperature follows
natural temperature trends but is cooler during
July and slightly warmer in August.On most
days,however~outflow temperatures in July and
August are within O.5°C (1°f)of natural tempera-
tures.In June,outflow temperatures lag signi-
ficantl y behi nd natural temperatures due to re-
servoir fill ing and the heat requi red to warm the
sizable Watana reservoir.The reverse is true in
September when cooling is insufficient to provide
near zero outflow temperatures (Figure E.2.174).
Duri ng September to mi d-November the s imul at ion
shows a gradual cool i ng of outflow temperatures
from 9.5°C (49.1°F)to 2°e (35.6°F)(Figures
E.2.174 and E.2.175).Stable outflow tempera-
tures of approximately.2°C (35.6°F)begin in
mid-November and continue throughout December.
In the weekly reservoir operation simulations for
WY 1981,a maximum release of 17,940 cfs occurs
during the week of August 19-25.This release is
the largest release in the 32-year simulation
with the year 2000 demand {see Table E.2.50).
Inspect i on of the Watana out fl ow tempe ratures in
Figure E.2.174 for the week of August 19-25 indi-
cates that maintaining water temperatures similar
to natural conditions wi 11 not be a problem.
Thi sis because most of the water discharged
through the fixed-cone valves will be drawn from
the epilimnion.This can be observed by examina-
tion of the August/Septenber temperature profiles
in Figures E.2.172 and L2.173.Since the intake
elevation of the fixed-cone valves is between £1
2025 ft (617 m)and 2085 ft {636 m)a nd the
epil imnion extends from the surface down to
approximately £12025 ft (617 m)during the time
period in which releases occur,it is apparent
that warmer epil imnion water will be discharged.
-Watana To Talkeetna
•Mainstem
The Watana operati on out flow temperatures,which
were simulated using DYRESM with 1981 met~orolog
ical data were used to determine the water
E-2-120
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4.1 -Watana Development
temperatures.in the reach between Watana and
Talkeetna..The discharge and outflow tempera-
tures from Watana were input to the program
HEATS 1M.'~Iatana discharges simulated for WY
1981,using the weekly reservoi I'model described
in $e<:tion3.2wereinput for June through
September.However,si'nce the October to
December 1981 pertod was not s imul ated with the
weekly reservoi r model,the long term average
weekly simulated di scharge was used for thi s
period.Meteorological data for 1981 was used
for June through December.
Results of the HEATSIM analysis are presented in
Figures E.2.176,£.2.177,and £.2.178 for the
period June to December.During June and Ju~y
warming of the Watana di scharge occurs between
the damsite andTa 1keetna.For the two August
temperature profiles illustrated in Figures
£.2.176~the heat balance between the water temp-
erature and atmosphere results in essentially no
heating or cooling.Temperatures at Ta"1 keetna
are equal to the Watana outflow temperatures.
In September the heat balance becomes negative
caus i ng cool i ng of the outlet temperatures.
Talkeetna temperatures are less than the Watana
outfl ow temperatures,but are much warmer than
natural temperatures.This cooling continues
throughout the wi nter months unt i 1 spri ng when
the heat balance aga in becomes posi ti vee [)ue to
the gradual reducti on in Watana outfl ow tempera-
tures and the climate conditions in October and
November,the downstream temperaturesexhi bi t a
trend of progressively cool ing through time which
is c lea 1'1 y demonstra ted by the upst ream movement
of the O°C (32°F)front with time on Fi gu re
£.2.178.
Coincident with stable ·outflow temperatures is
.the establishment of a stable ooe (32°F)water
temperature at River Mile 150 (Portage Creek).
Acompa ri son of 1981 observed water ternperatu res
f1ear Sherman and the DYRESM/HEATSIM temperature
simulation for the same location for June through
September withWatana operation is provided in
Figure E.2.L79.Although the absolute values do
not match,the simulated temperatures are in the
same range as the natural temperatures.In
£-2-121
4.1 -Watana Development
addition,both data sets show a similar response
to meteorological conditions.
Sensiti vity studi es we re undertaken to exami ne
the vari at ion in the.upstream 1ocat ion of O°C
(32°F)water and the ice cover formation.The
first assumed warm water discharge conditions
from Watana,as could be obtained with the use of
a low 1 evel intake,and t he second assumed a
linear reduction in Watana outlet temperature
from 4°C to 2°C (39.2°F to 35.6°F)between Novem-
ber 1 and mid-January.Long-term average mete-
orological conditions and mean monthly Watana
operat ion di scharges were used as input to both
downstream temperature simulations.
The simulation,assuming warm water withdrawal,
results in water temperatures being greater than
O°C (32°F)upstream of RM 131 (near Sherman)at
all times.The temperature profiles for the
October to April simulation are presented in
Figures E.2.180 and E.2.181.A comparison with
Figures E.2.141 and E.2.142 (Watana Impoundment)
shows the sensitivity of downstream temperatures
with discharge.That is,the higher operational
flows require a longer time to cool to DoC (32°F)
because of their larger heat content.
The second simulation illustrates a trend of up-
stream movement of the O°C (32°F)front during
the October to January period.The maximum
upstream 1ocati on of DoC (32°F)water is to RM
150 at Portage Creek.Figures E.2.182 and
E.2.183 illustrate this simulation.
The DYRESM and sensitivity runs place the up-
stream edge of O°C (32°F)water somewhere between
Sherman and Portage Creek by about the middle of
January •
•Sloughs
During project operation,the sloughs will seldom
be overtopped by the mai nstem flow du ri ng the
summer.Thus,the slough surface temperatures
will be the same as existing slough temperatures
for those times when,under pre-project condi-
tions,the sloughs are not overtopped.
E-2-122
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4.1 -Watana Development
Preliminary "investigations "indicate that ground
water upwelling temperatures in sloughs reflect
the long-term average water temperature of the
Susitna River which is approximately 3°C (37.4°F)
(Section 2.4.4).In the Devil Canyon to
Tal keetna reach,the long term average tempera-
ture will·not change significantly from pre-
project conditions as indicated by the tempera-
ture profiles discussed above.For example,
using the DYRESMfHEATSIM temperature res~ts for
June through December,and assuming O°C (32°F)
water through Apri 1 'and an average May tempera-
ture of 3°C (37.4°F),the average annual tempera-
ture at Sherman is calculated to be 3.5°C
(38.3°F).
-Talkeetna to Cook Inlet
During summer,temperatures downstream of the con-
fluence will reflect the temperatures of the
Talkeetna and Chulitna Rivers as discussed in
Section 4.1.2(e)(i).However,during fall,winter,
and early spring when natural flows are low,the
Sus itna Ri ver willexpe.rience increased flows and
the Susitna Ri ver water temperatures wi 11 have a
domi nant effect on the downstream temperatu reo For
example,using the October 15 simulation shown in
Figure E.2.178,the water temperature upstream of
Talkeetna is predicted to be 3.2°C (37.8°F).
Assuming the natural temperature of O°C (32°F)in
October,average monthly discharges of 5000 and
2700 cfs for the Chul i tna and Talkeetna Ri vers
(Table E.2.4)and a discharge of 6000 cfs for the
Susitnq.,the composite temperature downstream of
the confl uence would be 1.4°C (34.5°F).Hence,
thi s water temperature would be above the normal
temperature of O°C (32°F)for several miles down-
stream until it cooled to O°C (32°F).
Later in the fall and duri ng wi nter,the Su sitna
River water temperature near Talkeetna will be O°C
(32°F).Thus,in the reach downstream of the con-
fl uence there woul d be no change in temperature
from the existing O°C (32°F)temperatures.
(ii)Ice
-Watana Reservoir
As described in Section 4.1.3(c)(i),the OYRESM
temperature model,using 1981 data input,predicts
E-2-123
4.1 -Watana OeveTopnent
the lce cover to form on Watana reservoir on Novem-
ber 20 with a full ice cover on November 22.The
ice thickness is estimated at 31 inches (77.5 em)
on December 31.Although not modeled,the ice
cover thickness on the reservoir would continue to
grow through the winter until the heat balance
becomes positive.This is expected to occur in
late April or May.Open water conditions are
expected at the end of May.
-Watana to Talkeetna
To determine the extent,thickness and timing of
the ice cover information and the associated river
stagi ng,the results of the HEATSIM downstream tem-
perature modellng were input to an ice simulation
model,ICES 1M.A general descri pti on of the ICESIM
mode 1 f 011 ows •
The ICESIM s imul ates the format ion and mechani cal
progression of an ice cover and the water levels
associated with the process.
The ICESIM model includes a simple subroutine which
calculates backwater profiles in the river reach to
assess water 1evel s a-t different cross-sections.
The routine is similar to but less complex than the
HEC-2 model described in Section 2.2.4.This sim-
plicity is required so that the computer computa-
tional time remains reasonable while accounting for
the complexities of the ice processes.This re-
sults in less precise water level calculations com-
pared to HEC-2 model i ng accuracy,but it is consi-
dered adequate to provide representative results.
The ICESIM model was calibrated against the HEC-2
model results for a river discharge of 9700 cfs.A
compa ri son of the KEC-2 and ICES 1M cal cul at ions
indicates a reasonable agreement between the two
model results.
The model simulates the formation and progression
upstream from the ice cover given the starting lo-
cation of the ice cover and the time of its occur-
rence.The model checks the stability of the ice
cover and adjusts its thickness consistent with ice
supply,river geometry,and hydraulics of the
fl o-w.
An attempt was made to calibrate the ice process
simulation model with the field data collected
E-2-124
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4.1 -Watana Development
during the 1980 ri vel"freeLeup period.It became
apparent that the model could not simulate numerous
croSs sections wnerecritkal or near-critical velo-
cities.occur in the river,due to the relatively
'1 a.rge lellgthsof sub-reaches madeled.Nevertheless,
the model was used to:simulate-ice formation and pro-
gression'at average post-project winter flows,in
which case,many of the IIti nor riffles and rapids
apparent at low natural flows are well submerged.
Several qual itative checks were made to assess the
accuracy of this simulation.These include general
heat balance of the river waters,river hydraulic
characteristics as observed in the field,and com-
pa ri SOilS with sim 11 ar studies el sewherei n northern
climates.
During freezeup,because of the reI ease of warmer
water from Watana reservoir,.frazil ice will not be
generated for a considerable distance downstream
from Watana.Based on Ute results of the HEATSIM
temperature ana lyses,the reach betweeA Watana and
Devil Canyon will remain ice free.
Frazil ice should begi n to form upstream from
Talkeetna about the first week in N.ovember.However,
farther upstre,am,the water temperature would still
be above freezi ng.As with the natural ice cover
progressi on,the frazi 1 ice pans generated upstream
will agglomerate at natural lodgement points and the
cover wi 11 progress upstream from these.From the
temperature analysis,the reach of the river that
contributes ice to the system is limited due to
warmer upstream water tempe'I"attu'es.Depending on the
reservoir outflow temperatures,it could ta'ke from 30
to 90 days for the ice cover to progress to Devil
Canyon..Using the combined simulation from the
DYRESMand HEATSIM models for Watana operation as
input to ICESIM,the time of progression would be
about 30 days.The thickness of the ice cover as it
progresses through the reach varies from a few feet
to as much as 10 feet '(1 m),which is not unlike
existing conditions.The simulated ice cover thick-
ness and progress ion are illustrated in Fi gure
E.2.184.
With the formation of the ice cover,the river stage
necessary to pass the required di scharge wi 11 be
greater than that for open water conditions.A com-
parison of the simulated staging during cover forma-
tion relative to the ice-free water surface profile
E-2-125
4.1 -Watana Development
at a flow of approximately 10,000 cfs is shown on
Fi gu re E.2.185 •
A second ICESIM simulation was run assuming the
Watanaoutl et temperatures 1 i nearly decrease from 4°C
(39.2°F)on November 1 to 2°C (35.6°F)on January 15.
The simulated ice thickness and ice front location at
various times are illustrated in Figure E.2.184.
River staging due to the ice cover is presented in
Figure E.2.185.Figure E.2.184 shows a slower up-
stream progression with the 4°C (39.2°F)to 2°C
(35.6°F)outl et temperatures than with the simul ated
reservoi r outl et temperatures.Thi sis because the
simulated reservoir outlet temperatures are cooler in
late November and December.Figure E.2.185 shows
that although staging is similar in both examples,
there are differences.This is attroibutable to the
di fferences in di scharge.The DYRESM/HEATS 1M example
uses 1981 climatic data and weekly average discharges
whereas the 4°C (39.2°F)to 2°C (35.6°F)example
considers·the mean monthly discharges and the long
term daily average based meteorological data.
After the solid cover forms,there will still be open
leads due to high velocities and ground water upwell-
ing.The size of these 1 eads will be dependent on
the weather conditions and extremely cold air temper-
atures will be required for these leads to become ice
covered.The thickness of the stable cover will
range from about 5 to 10 feet (1.5 to 3 m).
In spring,the onset of wanner air temperatures in
the lower basin occurs several weeks before in the
middle and upper reaches.This will progressively
break up the cover starting from the downstream end.
However,the warmer upstream temperature of water
released from the reservoir will melt the cover
between Devil Canyon and Talkeetna.The influx of
warm water under the cover wi 11 tend to candl e the
ice and significantly weaken its structure.The
timing of the warmer water outflow will be similar
to the start of natural downstream breakup.However,
regulation of the spring flood will encourage melting
in place.With most of the cover melting in place
coupled with the weakness of the remaining ice,the
severity of ice jamming is expected to be signifi-
cant ly reduced.
E-2-126
-.
;@'lIIi,
(~
"""
4.1 -Watana Development
•Sloughs
With the staging that accompanies the pre-project
ice·formatfon proceSs many 6f the sloughs are over-
topped (Section 2.3.2[a]).With Watana operation,
the hi gher di scharge at freezeup wi 11 1ead to a
higher stage than under natural conditions.Conse-
quently,discharge wi 11 be i ncresed through those
sloughs currently overtopped if mitigation measures
are not taken.Discharge may also occur in sloughs
not currently overtopped.These higher discharges
may cause scou ri ng in the s 1oug hs.However,be-
cause of the increased backwater at the slough
mouths due to mainstem staging,velocities at the
downstream end of·the sloughs shoul d be reduced,
thereby reduci ng the chances of scouri ng in the
lower reaches of the sloughs.Velocities upstream
of the backwater effects may be as hi gh.as 3 fps
(0.9 m/sec)under the ice cover and may cause ero-
sion.However,the.bed material in the sloughs
becomes coarser (Figure [.2.21)with di.stance
upstream and is more resistant to the flow.
The important salmon spawning sloughs will be pro-
tected by the construction of elevated berms at the
upstream end of those slough~where ice effects are
anticipated.Thus,overtopping of sloughs during
the ice formation period will not occur.The
slough bed material will be maintained on a 5 year
rotating basis to provide suitable spawning habitat
(See Chapter 3).
-Talkeetna to Cook Inlet
Since the Susitna is currently the main source of ice
to the river system.below Tal keetna,the timing of
ice formation downstream from Talkeetna will be de-
layed about 4 weeks (currently October).The higher
post-project winter flows combined with the ice for-
mation will increase the water levels downstream.It
is not possible to quantatively analyze the impact on
the segment downstream of Talkeetna at thi s time.
However,it is noted that the increased staging in
thi s reach wi 11 be 1imited because of the numerous
alternative channels and subchannels available to
convey the discharge.
E-2-127
4.1 -Watana Development
(iii)Suspended Sediments
As the sediment-laden Susitna River enters the Watana
r~servoir,the river velocity will decrease and the
1arger diameter suspended sediments wi 11 settl e out
to form a delta at the upstream end of the reservoir.
The delta formation will be constantly adjusting to
the changing reservoir water level.Sediment will
pass through channels in the delta to be deposited
over the lip of the delta formation.Depending on
the relative densities of the reservoir water and the
river water,the river water containing the finer
unsettled suspended sediments will either enter the
reservoir as overflow (surface current),interflow,
or underflow (turbidity current).
Trap efficiency estimates using generalized trap
efficiency envelope curves developed by Brune (1953)
indicate 90-100 percent of the incoming sediment
would be trapped in a reservoir the size ofWatana
reservoir.However,sedimentation studies at glacial
lakes indicate that the Brune curve may not be appro-
priate for Watana.These studies have shown that the
fine glacial sediment (flour)may pass through the
reservoi r.Glacial 1 akes immediately below gl aciers
have been reported to have trap efficiencies of 70-75
percent.Kamloops Lake,British Columbia,a deep
glacial lake on the Thompson River,retains an esti-
mated 66 percent of the incoming sediment (Pharo and
Carmack 1979).
Particle diameters of 4 microns (0.16 mils)have been
estimated to be the approximate maximum size of the
sediment particles that will pass through the Watana
reservoir (Peratr{)vich,Nottingham &Drage,1982).
By examining the particle size distribution curve
(Figure £.2.80),it is estimated that about 80 per-
cent of the incoming sediment will be trapped.
In the Watana reservoir,it is expected that wind
mixing may be sufficient to retain particles less
than 12 micfons (0.5 mils)in suspension in the upper
50-foot (15 m)water layer (Peratrovich,Nottingham &
Drage 1982).Re-entrainment of sediment from the
shallow depths along the reservoi r boundary duri ng
high winds will result in short.,.term elevated turbid-
ity levels.This will be particularly important dur-
ing the summer refilling process when water levels
will rise,resubmerging sediment deposited along the
shoreline during the previous winter drawdown
period.
E-2-128
-
,""',
4.1 -Watana Development
For an engineering estimate of the time it would take
to fin the reservoll.wi1:h sediment,a conservative
assumption of a 100 percent trap efficiency was made.
Tflfs .resulted;n thedeposH ion of 472,500 acre-feet
ofsedimentaft.er 100 years (R&M 1982c),and is
equivalent·to 5.percent of the reservoir volume ..
Thus,sediment deposition will not affect the opera-
t ion.ofWatana reservoi l'over the 1i feof the proj-
ect.
During reservoir operation,the efect of bank insta-
bi 1ity on suspended sediments in the reservoi r wi 11
be the same as those that occur duri ng J'eservoi r
filling discussed in Section 4~1.2{e)..Suspended
sedi1l1ent concentrations downstream win be similar to
that discussed in Section 4.L2(e)(iii).
(iV).Turbidity
Turbidity patterns can have an impact on fisheries,
both in the reservoir arid downstream.The turbidity
pat.tern is a function of thermal structure,wind-
mixing,and reentrainment of fine sediments along the
reservoir boundaries.Turbidity patterns observed in
Ekl utna Lake provide the best available physical
model of anticipated turbi dity wi thi n Watana reser-
voir.Although it is only one tenth the size of the
Watana reservoi r,its morphometri c cha racteri st i cs
are similar to Watana.It is 7 miles (ll km)long,
200 feet (60 m)deep,has a surface area of 3420
acres (1368 hal ,and has a total storage of about
414,000 acre-feet.Bulk annual residence time is
1.77 years as compared toWatana's 1.65 years.It
also I'las 5..2 percent cif its basin covered by gla-
ciers,compared to 5.9 percent of Watana's drainage
area.It is bel ieved that turbidity patterns in the
two bodies ofw.ater will be somewhat similar,al-
though the di stance from the 91 acier to the lake wi 11
affect the temperature of the ri ver water as it
enters the lake~thus,affecting its equilibrium den-
sity and depth •.
Data collected at Ekl utriafrom·~.rch through October
1982 demonstrate the expected pattern at Watana (R&M
1982i).In March.turbid~ty beneath the ice cover
was uniformly less than 10 NTU in the downstream end
of the lake near the intake to the Eklutnahydroelec-
tric plant.Shortly after the i·cemelted in late May
E-2-129
4.1 -Watana Development
but before significant glacial melt had commenced,
turbidity remai ned at 7-10 NTU throughout the water
col umn.By mid-June,the turbidity had risen to
14-21 NTU,but no distinct turbidity p1u:ne was evi-
dent.In mid-June warming was evident only in the
upper 10 feet (3 m).Thus,it is assumed the 1ake
had completed its·spring overturn only sl ightly
before mid-June.By early July,a slight increase in
turbidity was noted at the lake bottom near the river
inlet.Distinct turbidity plumes were evident as
interf10ws in the upstream end of the lake from late
July through mid-September.Turbi dity val ues had
significantly decreased by the time the p1 ume had
traveled 5 miles (8 km)down the lake.In late
September,a turbid layer was noted at the bottom of
th.e lake as river water entered as underflow.By
mid-October,the lake was in its fall overturn
period,with near-uniform temperatures at approxi-
mate1y 7°C (44.6°F)and a turbidity of 30-35 NTU.
In Kam100ps Lake,B.C.,thermal stratification of the
lake tended to "short-circuit"the river plumes
especially during periods of high flow (St.John et
a1.1976).The turbid plume was confined to the sur-
face layers,resulting in a relatively short resi-
dence time of the incoming river water during summer.
St.John et al.(1976)noted.that high turbidity
values extended almost the entire length of Kam100ps
Lake duri ng the summer.He suggests that the effects
of dilution and particle settling were minimal
because the presence of the 10°_6°C (50 0 -42.8°F)
thermocline,effectively separated the high turbidity
water in the upper 1ayers of the 1ake from the hi gh1y
transparent hypo1 imnetic water.This phenomenon was
not apparent in Ek1 utna Lake where p1 urnes were evi-
dent up to 5 miles (8 km)down.the lake,but were
below the thermoc1in.e.In addition,Ek1utna Lake
particle settling and dilution were evident as tur-
bidity continually decreased down the length of the
1 ake.
The relatively cool,cloudy climate in south-central
Alaska would tend to prevent a sharp thermocline from
developing,so that the processes identical to those
observed in Kamloops Lake would not be expected eith-
er in Ek1utna L·ake,or the \~atana reservoir.
E-2-130
...-
4.1 -Watana Development
Turbidities based on the Eklutna Lake studies and
other sources were estimated for Watana (Peratrovich
Nottingham and Dta,ge1982)."The analysis indicates
that Watana reservoir turbidity levels will be in the
range of 10-50 NTU.'Thi s ral,1ge was de,termi ned from
the regression equation developed between turbidity
and suspended sediment ~oncentration using existing
USGS,data Jor,the Susitnii River.(Figure E.2.82).It
was est i mated that winter turbidity values at the
outlet after.formation of an ice cover on the reser-
voir will be in the 10-20 NTH range,summer values
wi 11 be in the 20-50 NTU range,ahd maximum expected
val ues at freezeup woul d be 40-50 NTU •
"""
-
.....
....
(v)Dissolved Oxygen
Susitna River inflow to the reservoir will continue
to have both high dissolved oxygen concentrations and
hi gh percentagesaturati ons.'The oxygen demand of
the water enteri ng the reservoi r wi 11 be low.No
man-made sources of oxygen demandi ng effl uent exi st
upstream from the impoundment.Chemi ca 1 oxygen
demand (COD )measurements at Vee Canyon duri ng 1980
and 1981 were low,.averaging 16mg/l.No biochemical
oxygen demand va]ues were recorded.
Wastewater from the permanent town and anticipated
recreationists will n6tcontribute an oxygen demand
of any significance to the reservoir.All wastewater
will be treated to avoid effluent~related problems.
The trees within the inundated area will be cleared,
removing the potential BOD theY'would have created.
A .1ayer'oforgani c.'matter 'at the reservoir bottom
will sti'll'remain and could create some localized
oxygen depletion along the reservoir floor.However,
the process of decomposition wi 11 be very slow be-
cause of the cold temperatures near the bottom.
The stratification that is anticipated in the reser-
voi r may 1 imi t .the oxygen repl'eni shment in the hypo-
limnion~The spring turnover,with its large inflow
of freshwater,will ~au~e mixing;however,the depth
to which this mixing will occur is unknown.However,
based on the reservoir temperature modeling,it is
anticipated that the upper 200 feet (60 m)of the
impoundment should maintain high D.O.
[-2-131
4.1 -Watana Development
Downstream from the dam.no dissolved oxygen changes
are anticipated.s fncewater will be drawn from the
upper layer of the reservei r.
{vi}Total Dissolved Gas Concentration
As previously noted.supersaturated dissolved gas
(nit'rogen)condit ions can result below high head dams
as a result of flow releases.Ouri 09 project opera-
tion.specially designed fixed-cone valves will be
used to discharge all releases with a recurrence
interval of less than 1:50 years.
As previously described in Section 4.1.3(a){v)opera-
tion of the fixed-cone valves will be linked to the
energy demand-.The forecasted energy demand for 1995
would necessitate releases for 30 of the 32 years of
simulated reservoir operation although in 23 of the
30 years the maximum annual release woul d be less
than 2500 cfs.Descriptions of the fi rst week of
release.week of maximum release.maximum release
(cfs).simultaneous powerhouse"flows (cfs)and total
release (acre-feet)are provided in Table E.2.50.In
contrast,the anticipated increase in energy demand
for the year 2000 would result in operation of the
fixed-cone valves in only 11 of the 32 years of sillll-
lated operati on.Detail ed information for the year
2000 simulation is also available in Table E.2.50.
In a 11 cases,the fi xed-cone val ves will be capab1 e
of discharging the released waters without increasing
the dissolved gas concentrations.
Detailed information on the effectiveness of the
valves for maintaining acceptable dissolved gas con-
centrations is available in Section 6.4.4.
Decreased downstream flows during summer operati on
wilT cause a reduction in the levels and variations
of dissolved gas concentrations below Devil Canyon.
Based upon pre-project data,mean post-project summer
flows (June to September)of 7900 to 12,100 cfs are
expected to produce concentrati ens,below the Devi 1
Canyon rapids,of less than 106 and 108 percent,res-
pectively.'
E-2-132
.....
....
....
-
-
4.1 -Wa tan a nev~l opment
MthQugnnopre-proJect H1easurements of dissolved gas
level se~jstfor the winter oped 09 ~it is anticipated
that pverJlgep-ost-project Hows;at Devi 1 Canyon (7570
to 10~550 cfs)will create elevated levels of di-s-
so~vedga~bel-Ow Devil CanYQn...Concentrations are
expected to vary ftoilfl ess than 106 percent to 108
,percent based,upon the avanable pre-project measure-
,ments ,tak~R at slightly Mgher,discharge conditions
and significantly higher -am1>ient air'temperatures.
Given thefrequentnatural'occurrence of levels
gre~terthan these concentrat ions ~no adverse impacts
are foreseen.•
(vii)Trophic Status (Nutrients)
A detailed .analysis of the antictpated trophic status
of the Watana reservoi r has been developed by Peter-
son and Nichols (1982).Information from their anal-
ysisfollows.
Reservo;r trop-hi c status is determined in part by the
relative amounts of carbon ~si 1 icon ~nitrogen ~and
phosphorus pr.esent in'asystem~as we 11 as the qua 1i-
tyand quantftyof light penetrati{)n.The average
1980-1981 C:Si:N::P June rati oaf 1080:340:28:1 i ndi-
cates that phosphorus will be the limiting nutrient
in the Susitna impoundments.Vo 11 enweider IS (1976)
model was considered to be the most reliable in
.determini ngphosphorus com::entrat ions at the Watana
impoul'ldment.However~because the val idity of this
model i sbased on phosphorus data from temperate ~
clear-water lakes~predicting trophic status of
silt-laden water bodies with reduced light conditions
and high inorganic phosphurus levels may over esti-
mate the actual'trophic status •
'The sprfng phosphorus concentration in phosphorus-
limited lakes is considered the best estimate of a
lake'ls trophi<:status.Bio-available phosphorus~or
orthophosphate~is the fr'actfonoftota 1 phosphorus
which controls algae growth·in a particular lake.
rhe measured dissolved orthoJ3hosphate concentration
at Yee;Canyoriwas considered to be the hi o-avail abl e
f-racti.on ill theSusitnaRiVer.Accordingly~the
average diss.Qlved orthophosphate concentration in
June was multipl i~d by the average annual flow to
cal'CcUlate the spring phosphorus supply.This value
4.1 -Watana Development
was in turn combined with phosphorus values from pre-
cipitation and divided by the surface area of the im-
poundment.The resultant spri ng phosphorus 1oadi ng
values for Watana reservoir were far below the mini-
mum loading levels that would result in anything
other than 01 igotrophi c conditi ons.Li kewi se,upon
incorporating spring loading values into
Vollenweider1s (1976)phosphorus model,the volume-
tric spring phosphorus concentration fell into the
same range as oligotrophic lakes with similar mean
depths,flushing rates,and phosphorus loading values
(Peterson and Nichols 1982).
The aforementioned trophic status predictions depend
upon several assumptions that cannot be quantified on
the basis of existing information.These assumptions
include:
-The C:Si:N:P ratio does not fluctuate to the extent
that a nutrient other than phosphorus becomes
limiting;
No appreciable amount of bio-avai1ab1e phosphorus
is released from the soil upon filling of the 'res-
ervoi rs;
-Phosphorus loading levels are constant throughout
the peak algal growth period;
-June phosphorus concentrations measured at Vee
Canyon correspond to the time of peak algal produc-
tivity;
-Phosphorus species other than dissolved orthophos-
phate are not converted to a bio-avai1ab1e form;
-Flushing rates and phosphorus sedimentation rates
are constant;
Phosphorus losses occur only through sedimentation
and the out1~t;and
-The.net loss of phosphorus to sediments is propor-
tional to the amount of phosphorus in each reser-
voi r.
Artifici a1 phosphorus loading of the reservoi r from
domestic sources was similarly investigated by
E-2-134
-
4.1 -Watana Development
Peterson and Nichols (1982).They concluded that the
maximum a110wa~le artificial loading is equivalent to
the waste from 115,800 permanent residents,if oli-
gotrophic conditions are to be maintained.However,
this estimate is conservative since the effects of
low light penetration and the use of wa ste treatment
have bee~neglected.
,....
i
i
-
-
-
-
(viii)Total Dissolved Soli(1s,Conductivity,
Signi,ficant Ions,A1 ka1 inity,and Metal s
The leaching process,as previously identified in
Section 4.1.2(e)(vii),is expected to result in
increased 1eve1.s of the above parameters within the
reservoi r inmed iate1y after impoundment.The magni-
tude of these changes cannot ,be quantified,but
should not be significant (Peterson and Nichols
1982).Furthermore,Baxter and Glaude (1980)have
found such effects are temporary and dimi ni sh with
time.,
The effects of leaching will diminish for two rea-
sons.First,the most solubl,e elements will dissolve
into the water rather quickly and the rate of leach-
ate producti on wi 11 correspond i ng1y decrease with
time.Second,much of the inorganic sediment carried
by the Susitna River will settle in the Watana reser-
voir.The format ion of an inorganic sed iment b1 anket
on the reservoi r bed will r~tard the 1eachi ng process
{Peterson and Nichols 1982).
Leachi ng byproducts shou1 d not be ref1 ect~d in the
river below the dam since the leachate is expected to
be confined to a small layer of water immediately
adjacent to the reservoir floor and the intake
structures will be near t he surface (Peterson and
Nichols 1982).
During periods of evaporatio,n,sl ightlyhigher con-
centrations of disso1 ved substances have been found
at the surface of impoundments (Love 1961;Symons
1969).,Because of the large surface area of the
,proposed impoundment,evaporation wi 11 be substan-
ti.a11y i.ncreased over existing conditions.The
annual ayerageev-aporatl on rate for May through
September atWatana is estimated at 10.0 inches or
0.3 percent of the reservoir vo1lJ11e(Peterson and
Nkhols 1982).{;hen the mixing ~ffects of wind
E-2-135
4.1 -Watana Development
and waves and the fact that direct precipitation
exceeds annual evaporation,no measurable increase in
dissolved solids is expected.
Dissolved solid concentrations are expected to in-
crease near the surface of the impoundment duri ng
winter.Mortimer (1941,1942)noted that the forma-
tion of ice at a reservoir surface forces dissolved
sol ids out of the freezing water,thereby increasing
concentrations of these solids at the top of the res-
ervoi r.No impacts shoul d result either in the
reservoir or downstream from the dam from this
process.
In contrast to the above discussions,precipitation
of metals such as iron,manganese and other trace
elements have been noticed in reservoirs,resulting
in reduced concentrati ons of these el ements (Neal
1967).Oligotrophic reservoirs with high pH and high
di ssol ved salt concentrat i onsgenerally precipitate
more metal than reservoirs with low pH and low dis-
solved salt concentrations.This is attributed to
the dissolved salts reacting with the metal ions and
subsequently settling out (Peterson and Nichols
1982).Average Susitna River TDS values for Vee Can-
yon and Gol d Creek duri ng wi nter are 141 and 150
mg/l,respectively.For summer they are somewhat
lower,approximately 98 and 91 I11g/1 respectively.
Average values for pH range between 6.9 and 7.6 for
the two stations.Although neither of the parameters
is excessively high,precipitation of metals may
reduce the quantities of metals in the reservoir.
(d)Ground Water Conditions
(i)Mainstem
As a result of the annual water level fluctuation in
the reservoi r,there wi 11 be 1oca 1i zed changes in
ground water in the immediate vicinity of the reser-
voi r.Ground water impacts downstream duri ng summer
will be similar to those described in Section
4.1.2(f)(i)and will be confined to the river area.
Since powerhouse flows will generally be greater than
filling flows during summer,the ground water level
change from natural condit ions wi 11 be sl ightly 1ess
than during filling.During winter,increased ice
E-2-136
4.1 -Watana ~evelopment
-
....
(i i)
staging will occur during freezeup (Section 4.1.3(c)
[iii])and hence ground water level will be increased
along ice covered sections of the matnstem.
Sloughs
Du ri ng wi nter in the Devi 1 Canyon to Talkeetna reach J
some of the sloughs (i.e.,those nearer Talkeetna)
will be adjacent to an ice-covered section of the
Susitna Ri ver.In ice-covered S.ect ions,the Sus itna
River will have staged to form an ice cover at
project operation flows of about 10,000 cfs.The
associated water level will be a few feet above nor-
mal w"inter water levels and will cause an increase in
the groundwater table.This will in turn cause an
increase in ground water flow adjacent to an ice cov-.
ered reach of the r1ver~
Sloughs upstream of Gold Creek,in the vicinity of
Portage Creek,may be adjacent to open water sections
of the Susitna'Ri ver.Because flows wi 11 average
approximately 10,000 cfs in winter,the associated
water level will be less than water levels occurring
under the natural freezeup process.Thi 5 is ill us-
trated by the higher stage shown during the normal
freezeup process than during an open water discharge
of 10,000 cfs in'Figure E.2.76.Hence,the ground
water table will be lower.Sloughs in this area may
experi ence a decrease in ground water fl ow in the
wi nter.
During summer,the mai nstem-51 ough ground water
-interaction will be similar to that discussed in Sec-
tion 4.1.2(f)(ii),with the exception that operation-
a1 flows wi 11 be greater than the downstream flows
during filling,and thus,the ground water table will
be closer to the natural elevation than during fill-
i ng •.
(e)lakes and Streams
The numerous small lakes identified in Section 2.5.1 will be
inundated by the Watana reservoi r duri ng the impoundment
phase.Most of them will remain below the reservoir surface
at all times but a few will become perched at low reservoir
levels.
The mouths of streams flowing into the reservoir will shift
upstream and downstream in response to the reservoi r water
level fluctuations.The position of the delta formation
E-2-137
4.1 -Watana Development
will likewise vary.Both bedload and suspended sediment
load will be deposited wherever the stream current enters
the still water of the impoundment.
The downstream tributaries described in Section 4.1.2(g)and
listed in Table E.2.27~will begin to modify their geomor-
phologic regimes and either downcut thei r beds or remai n
perched above the Susitna in response to the reduced river
levels during project operation.Anticipated stream impacts
are listed in Table E.2.27.
(f)Instream Flow Uses
(i)Fishery Resources~Riparian
Vegetation and Wildlife Habitat
Impacts of project operation on the fishery resour-
ces,riparian vegetation~and wildlife habitat are
discussed in Chapter 3.
(ii)Navigation and Transport~tion
Because the Watana reservoi r wi 11 decrease navi ga-
tiona1 difficulties between Watana and the Tyone
River~increased boat traffic in the reservoir area
wi 11 occur.Re servoi r water craft navi gati on wi 11
extend to November because of the delay in ice-cover
formation.Once an ice cover forms in late November
and December~the reservoi r wi 11 be ava il ab1 e for
surface travel by dogsled and snow machine through
April.
A1 though summer flows down stream of the dam wi 11 be
reduced from natural conditions during project opera-
tion~navigation and transportation in the Watana to
Tal keetna reach will not be si gn ifi cant 1y impacted.
However,because of the reduced water 1evel s ~ca ut ion
will be required in navigating various reaches.From
Figure E.2.160 there is a 10 percent chance that the
monthly Gold Creek fiow will be less than 6500 cfs in
May and a 3 percent chance that the flow will be less
than 6500 c fs in June.Ouri ng July ~August ~and
September Gold Creek flows during Watana operation
are greater than 6500 cfs.Thus~there is a minor
chance that navigat i on at Sherman will be impacted
during May and June.If this occurs~the mitigation
measures discussed in Secti on 4.1.2(h)(i;)will be
imp 1emented.
E-2-138
--
-
~,
I
-
-
,~
,....
'"""
4.1 -Watana Development
Downstream of Talkeetna,flows at Sunshine are great-
er than 17,ODO cfs,80 percent of the time in May and
100 percent of the time in June through September
(FigureE.2.161).Since this flow will maintain ade-
quate navigational water depths in this reach,no
.problems are anticipated from June through September.
The fact that 20 percent of the May val ues are 1ess
than 17,000 cfs is attributable to a later breakup in
some years.Since navigation cannot begin until
after breakup,there will be no navigation problems
in May ei ther:.'
At Susitna Station,flows drop below 43,000 cfs about
10 percent of the time in May and 15 percent of the
time in September.Figure E.2.162 indicates that at
these percent exceedence levels,the flows are simi-
1 ar to pre-project flows.Therefore,although the
flow necessary to maintain the navigability of the
upper end of Alexander Slough is not known,any navi-
gation problems at these flows would have occurred
under pre-project conditions and thus,the post-
project flows will not increase the navigational dif-
ficulties at Alexander slough.
During the fall and winter,a significant reach of
the ri ver between Watana·and Talkeetna wi 11 be ice
free for a few weeks longer than during existing con-
dit ions.The reach between Watana and Portage Creek
will not develop an ice cover.This will allow for a
longer boating season but wi 11 impede use of thi s
river reach as a transportation corridor by snow
machine or dogsled.
Down stream from Ta lkeetna,ice-cover formation wi 11
be delayed a few weeks and river stage during freeze-
up will be increased.This will delay winter trans-
portation across the ice.
,~
(iii)Waste Assimilative Capacity
No impacts to the summer waste assimilative capacity
of the river will occur during project operation.
The wastes generated by the approximate 130 staff
members and the;r fami 1i es at the permanent town wi 11
receive secondary treatment simil ar to the previously
described construction camp and village wastewater
treatment.The winter waste assimil ative capacity of
the river will be at least doubled due to the in-
creased winter flow.
E-2-139
4.1 -Watana Development
(i v)Freshwater Recruitment to Cook Inlet Estuary
Sal inity changes in Cook Inlet due to Watana opera-
tion were simulated using a computer model (Resource
Management Associates 1983).Results of the modeling
indicate that the sal inity in Cook Inlet will attain
a dynamic equilibrium within approximately one year
of reservoir operation.Winter salinities will be
greater and summer salinities will be reduc~d.
Nea r the mouth of the Su s itna Ri ver (Node 27)p re-
and post-proJect salinity differences will be great-
est during April.Watanaoperation sal inity concen-
trations are estimated to be approximately 19,600
mg/l,or a dec rease of 1400 mg/l from p re-proj ect
conditions.With the reduced flows during summer,a
maximum sal i nity increase of 700 mg/l above pre-
project salinity levels is predicted to occur in June
(Fi gure E.2.127)•
At the center of Cook Inl et near East Forel and (Node
12),salinity changes will be significantly less.
Concentration decreases of approximately 400 mg/l are
predicted in April.Ouring August a salinity
increase of about 100 mg/l is estimated to occur.
Additional comparisons are presente{\in Table
L 2.3L '
In general,sal inity variations wi 11 result in a
reduced post...,project salinity range.The maximum
reduction will be near the mouth of the Susitna River
where an annual maximum to annual minimum range
decrease of about 2000 mg/l can be expected.
4~2 -Devil Canyon Development
4.2.1 -Watana Operation/Devil Canyon Construction
Access tunnel construction at the Devil Canyon site is scheduled
to begin in 1995.The Devil Canyon development when completed in
2U02 will consist of a 646-foot {196 m)high,concrete arch dam,
outlet facilities capable of passing 38,500 cfs;a flipbucket
spillway with a caJ)acity o·f passing 125,000 cfs;an emergency
spillway with a capacity of 160,000 cfs;and a 600-MW capacity
underground powerhouse.Further infonnation on the physical
features of the Devil Canyon development can be foun{j in Section
7 of Exhi bit A.
£-2-140
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4.2 -Devil Canyon Development
The Devil Canyon diversion tunnel is designed to pass the
1 :25-year recurrence interval flood routed throug h Watana without
endangering the diversion dam.This lower level of flood protec-
tion than used for the Watana diversion is possible because of
the degree of regulation provided by the Watana reservoir.
During the Devil Canyon construction phase,most differences in
the quantity and quality of the water from the existing baseline
conditions will be the result of the presence and operation of
the Watana facil ity.Therefore,the conditions described in
Section 4.1.3 will,in many cases,be referred to when discussing
the impacts of Devil Canyon construction.
(a)Flows and Water Levels
(i)Watana Operation
Operation of Watana will be unchanged during the con-
struction of Devil Canyon.Hence,the discussion
presented in Section 4.1.3(a)remains appropriate.
During construction of the diversion tunnel,the flow
in the mainstem will be unaffected.Upon completion
of the diversion tunnels in 1996,the upstream cof-
ferdam will be closed and flow will be diverted
through the diversion tunnel without any interruption
in flow.This action will dewater approximately 1100
feet of the Susitna River between the upstream and
downstream cofferdams.
Because ice will not be generated in the Watana to
Devil Canyon reach,ponding during winter will be
unnecessary at Devil Canyon (see Section 4.1.3(c)
[iiJ).
Velocites through the 30-foot (9 m)diameter tunnel
at flows of 10,000 cfswill be 14 fps (4.2 mps).
(ii)Floods
The diversion tunnel is designed to pass flood flows
up to the 1:25-year summer flood,routed through
Watana (approximately 32,000 cfs).The flood fre-
quency curve for·Devil Canyon is illustrated in
Figure E.2.186 and is based on the weekly reservoir
simulations described in Section 4.1.3(a)(i).There
E-2-141
4.2 -Devil Canyon Development
is 1 ittl e change in di scharge for floods up to the
1:50 year flood because the Watana reservoir can
absorb the incoming flood,discharging a maximum of
31,000 cfs (24,000 cfs through the outlet facilities
and 7000 cfs through the powerhouse [assuming minimum
energy demand]).
(b)River Morphology
Si nce flows from Watana reservoi r ope rat i on wi 11 be
unchanged during constructi on of the Devil Canyon Dam,the
morphological processes described in Sections 4.1.2(b)and
4.1.3(b)for Watana operation will continue to occur.
The most significant impacts from construction will be at
the damsite,as the rapids at the upper end of Devil Canyon
wi 11 be blocked off and approximately 1100 feet (330 m)of
the Susitna River between the upstream and downstream
cofferdams will be dewatered.No impacts to the morphology
of the Susitna River are anticipated from borrow material
excavation since there are no borrow sites located within
the Susitna River.Although Borrow Site G (Figure E.2.187)
is located south of and adjacent to the Su sitna Ri ver,no
mining activities will be undertaken in the riverbed.
Cheechako Creek wi 11 be rerouted to faci 1i tate effici ent
borrow excavation.Consequently,it will be channeli zed to
the eastern boundary of the borrow site.
(c)Water Quality
(i)Water Temperature
There will be no difference in
Devil Canyon or at poi nts
construction site from those
4.1.3(c)(i).
(ii)Ice
water temperatures at
downstream from the
discussed in Section
Ice processes will be unchanged from those discussed
in Section 4.1.3(c)(ii),Watana operation.
(iii)Suspended Sediment/Turbidity/Vertical Illumination
Construction of the Devil Canyon facility is expected
to have siltation and turbidity impacts simi lar to
E-2-142
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4.2 -Devil Canyon Development
those anticipated at Watana,but of a much smaller
magnitude.
Tunnel excavation,placement of the cofferdams,exca-
vation of construction materials,dewatering,gravel
washing,and the clearing and disposal of vegetation
and overburden will all provide opportunities for the
introduction of sediment to the river.However,the
potential impacts from borrow site mining will be
greatly reduced since no instream work is currently
planned.
The material sources required for construction are
Borrow Site G and Quarry Site K (shown in Fi gure
E.2.188)and previously described in Borrow Site D
located near Watana (Fi gure E.2.133).Borrow Site G
is expected to provide approximately 2 million cubic
yards (cy)of aggregate with less than 5 percent
waste.Mining of this material will occur in the
dry.The Susitna River will form the north boundary
of the borrow area.The mouth of Cheechako Creek,
however,will be diverted to the eastern boundary of
the borrow site to facil itate access to all requi red
material.The area of disturbance,located entirely
within the confines of the Devil Canyon reservoir,is
likely to exceed 40 acres,but is not expected to
equal the approximate 80 acres shown in Figure
E.2.187.
Although washing will be required,the quantities of
fines should be limited since the borrow material is
predominantly composed of river washed sands and
gravels.All wash water will be directed to a series
of settling ponds.Prior to mining,all overburden
and vegetation will either be slashed and burned,
carefully stockpi 1 ed for futu re rec1 amat i on work or
buried.
Qua rry Site K is located in an upland site that is
estimated to contain total resources of 40 mill ion cy
of rock.However,only 1.5 million cy of this
q uant i ty wi 11 be needed for the sadd1 edam,ri prap
and other uses.Disposal of not more than 310,000
cy of oversized and undersized material will occur in
either the existing talus pile at the base of the
E-2-143
4.2 -Devil Canyon Development
cliff (see Figure E.3.189),near the site of the
saddl e dam,or along the reservoi r for beach
material.No washing of materials will be required;
and hence,no wastewater will be produced.
Overburden will be stri pped and carefully stockpil ed
for subsequent rehabilitation of the area.No silta-
tion problems will result from the development of
this site.It is expected that 10 to 15 acres of the
3D-acre primary quarry site will be disturbed.
Borrow Site D has been identified as the nearest
source of 300,000 cy of fine grained core material
requi red for the saddl e dam and emergency spi 11 way
fuseplug.Haul ing of this material will be via the
main access road between Watana and Devil Canyon.
Processing of the materi al will occur at Watana.No
adverse sedimentation problems will occur due to the
upland location of Borrow Site D and the use of
settling ponds for runoff treatment.
In summary,the improved summer water clarity,resul-
ting from the sediment trapping characteristics of
the Watana reservoir,is not expected to be adversely
affected during Devil Canyon construction activities.
During winter,the suspended sediment concentratons
and turbidity levels released from Watana,are
expected to pass downstream of the Devil Canyon
construction site without significant change.
Additional information on the proposed mitigation of
erosion problems is discussed in Section 6.2 and
Chapter 3.
(iv)Nutrients
Similar to Watana construction,increased concentra-
tions of nutrients and organics could result from
disturbances and subsequent erosion of organic soils.
However,since the overburden layer near the Devil
Canyon damsite is quite shallow and overburden and
vegetation will either be slashed and burned,safely
stockpiled for future rehabilitation or buried,
impacts should be insignificant.
E-2-144
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4.2 -Devil Canyon Development
(v)Metals
As discussed in Section 4.1.1(c)(v),Watana construc-
tion,disturbances to soils,and rock adjacent to the
river will increase dissolved and suspended materials
in the river.Although this may result in slightly
elevated metal levels within the construction area
and downstream,water quality should not be
significantly changed (Section 2.3.8 (k)).
(vi)Contamination by Petroleum Products
All state and federal regulations governing the
prevention and reclamation of accidental spills,
including the development and implementation of a
Spill Prevention Containment and Countermeasure Plan
(SPCC),wi 11 be adhered to.Addi t i anal i nformat i on
on proposed mitigative measures are provided in
Section 6.2 and Chapter 3.
(vii)Concrete Contamination
The potential for concrete contam i nat i on of the
Susitna River during the construction of the Devil
Canyon Dam will greatly exceed the potential for con-
tamination during Watana construction because of the
much larger volume of concrete required.It is esti-
mated that 1.7 million cubic yards of concrete will
be used in the construction of the dam.The waste-
water and waste concrete associated with the batching
of the concrete caul d,if di rectly di scharged into
the river,seriously degrade downstream water quality
-with subsequent fish mortal ity.To prevent these
problems,a modern efficient central batch plant will
be utilized.However,.approximately 20,000 cubic
yards of waste mat eri a 1 wi 11 be gene rated.Methods
similar to those discussed for Watana Construction,
Section 4.1.1(c)(v),will be used to minimize
potential contamination problems.-(viii)Other Parameters
No additional water quality impacts are expected.
E-2-145
4.2 -Devil Canyon Development
(d)Ground Water Conditions
Si nce the constructi on at Devil Canyon will not modify the
discharge,the ground water impacts di scussed under Watana
operation (Section 4.1.3(d))will remain relevant during
this period.Some local changes in ground water levels in
the immediate vicinity of the damsite may occur due to
dewatering of open and underground excavations.
(e)Lakes and Streams
The perched lake adjacent to the Devil Canyon damsite will
be.eliminated by construction of the saddle dam across the
low a rea on the south ban k between the emergency spi 11 way
and the main dam.The lake is just west of the downstream
toe of the saddle darn and will be drained and partially
filled during construction of the saddle darn.To facilitate
efficient borrow excavation,Cheechako Creek will be
rerouted to the eastern boundary of Borrow Site G.
(f)Instream Flow Uses
The diversion tunnel and cofferdams will block upstream fish
movement at the Devil Canyon constructi on site.However,
the Devil Canyon and Devil Creek rapids act as natural bar-
riers to most upstream fish movement.
Navigational impacts will be the same as during Watana oper-
ation (Section 4.1.3(f)(ii)),except that the whitewater
rapi ds at Devil Canyon will be e 1imi nated because of con-
struction activities.
(g)Support Facilities
The construction of the Devil Canyon hydropower project w"ill
require the construction,operation and maintenance of sup-
port facilities capable of providing the basic needs for a
maximum population of 1,900 people (Acres 1982a).The
facilities.including roads,buildings,utilities,stores
and recreation facilities will be essentially completed
during the first six years (1992-1997)of the proposed
eleven-year construction period.The Devil Canyon
construction camp and village will be built using components
f rom the Watana camp.The camp and vi 11 age wi 11 be located
approximately 2.5 miles (4 km)southwest of the Devil Canyon
dams ite.The 1ocat i on and 1ayout of the camp and vi 11 age
facilities are presented in Plates F.70,F.72,and F.73 of
Exhibit F.
E-2-146
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4.2 -Devil Canyon Development
(i)Water Supply and Wastewater Treatment
The Watana water supply and wastewater treatment
plants will be reduced ins i ze and reut il i zed at
Devil Canyon.As a result,processes identical to
those employed at Watana will be used to process the
domestic water supply and treat the wastewater.
The water intake has been desi gned to withdraw a
maximum of 775,000 gallons/day (less than 1 cfs)to
provide for the needs of the support communities
(Acres 1982a).Since the source of this supply is
the Sus itna Ri ver,no impacts on downstream flows
will occur throughout the duration of the camps'
existence.The water supply will be treated to con-
form to all state and federal regulations.
The wastewater treatment facility will be sized to
hand.1e 500,000 gallons daily.The effluent from this
secondary treatment facility will not affect the
waste assimilative capacity of the river and will be
discharged approx imate 1y 1000 feet downst ream from
the intake.
Prior to the completion of the wastewater treatment
facil ity,all wastewater will be chemically treated
and stored in 1agoons for future process i ng by the
facility.No raw sewage will be discharged to the
river.
Chemi cal toi 1ets wi 11 be p1 aced throughout the con-
structi on area and wi 11 be servi ced and di scharged
into the treatment facility.
The applicant will obtain all the necessary state and
federa 1 permits for the water supply and waste di s-
charge facilities.
Additional details pertaining to the proposed water
supply and wastewater discharge facilities are avail-
able in Acres 1982a.
E-2-147
4.2 -Devil Canyon Development
(ii)Construction,Operation,and Maintenance
Similar to vJatana,the construction,operation and
maintenance of the camp and village could cause
increases in turbidity and suspended sediments in the
local drainage basi ns (i.e.,Cheechacko Creek and
Jack Long Creek).In addition,there will be a
potential for accidental spillage and leakage of
petroleum products and concrete wastewater contamina-
ting ground water and local streams and lakes.
Through appropriate preventative techniques,these
potential impacts will be minimized.All required
permits for the construction and operation of the
proposed facilities will be obtained.
4.2.2 -Watana Operation/Devil Canyon Impoundment
(a)Reservoir Filling Criteria
Reservoir filling will be completed in two distinct stages.
Upon completion of the mai n dam to a height sufficient to
allow ponding above the outlet facilities (fixed-cone
val ves)which are located at El 930 ft and 1050 ft,the
iritake gates will be partially closed to raise the upstream
water level from its natural level of about El 850 ft.A
minimum flow of 5,000 cfs will be maintained at Gold Creek
if the fi rst stage of fill ing occurs between October and
April.From May through September,the minimum flows
described in Section 4.1.3(a)(i)will be released (See
Table E.2.30).
Once the level rises above the lower level discharge valves,
the diversion gates will be permanently closed and flow will
pass through the fixed cone valves.These valves will have
a discharge capacity of 38,500 cfs.They are described in
Se ct ion 4.2.3(a)(v)•
Since the storage volume required before operation of the
cone valves can commence is approximately 76,000 acre-feet,
the first phase of the filling process will require from one
to four weeks depending on time of year and Watana power-
house flows when filling is begun.The reservoir will not
be all owed to ri se above 1135 ft (344 m)for approximately
one year while the diversion tunnel is being plugged with
concrete.
When the dam is completed,an additional one million acre-
feet of water wi 11 be requi red to fi 11 the reservoi r to its
normal operating elevation of 1455 ft (441 m).Filling will
be accomplished as quickly as possible (currently estimated
to be between 5 and 8 weeks)utilizing maximum powerhouse
E-2-148
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4.2 -Devil Canyon Development
flows atWatana.During filling of Devil Canyon reservoir,
Gold Creek flows will be maintained at or above the minimum
flows 1 isted in Table E.2.36.
-
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(b)Flows and Water Levels
Because of the two distinct filling periods,the two-stage
impoundment sequence will take several years to complete,
even though the actual time for fi 11 i ng wi 11 only be two
months.As noted above,flows duri ng the fi rst stage of
fill ing will be impacted for only a few weeks.
Between the fi rst stage and second stage of fi 11 i ng,the
reservoir will not be allowed to exceed El 1135 ft (344 m).
Thus,the Devil Canyon reservoir will be held at a relative-
ly constant level.Flows in the Susitna River will be
unchanged from those during Watana operation (see Section
4.1.3(a)).
During the second stage of filling,1,014,000 acre-feet of
water will be added to the Devil Canyon reservoi r.The
Watana powerhouse will be operated to supply either the
total railbelt energy demand or maximum powerhouse capacity.
whichever is less.Assuming the medium load forecast for
2002,the peak demand is 1158 MW.This would require a
maximum Watana powerhouse flow of 22,000 cfs at normal
maximum operating head.Since this is greater than the
maximum possi bl e powerhouse flow of 21,300,the maximum flow
from Watana would be 21,300 cfs.However,it is anticipated
that powerhouse flows during filling would be more in the
range of 16,000 to 19,000 cfs.
The flow from the Watana reservoir that is in excess of the
downstream requirements (Table E.2.36)flow will be used to
fill the Devil Canyon reservoir.During this process,the
Watana reservoi r wi 11 be lowered about 25 feet.Al though
the flow from the Watana powerhouse will be up to twice the
normal flow,the impact of increased flow will be minimal in
the Devil Canyon reservoir.
Flow downstream from Devi 1 Canyon wi 11 be sl i ghtly reduced
during this filling 'process.However,
wi 11 be short and downstream flows wi 11
above the minimum target flows at
E.2.36).
the fill i n9 per i od
be maintained at or
Gold Creek (Table
,...
Since the filling time is short and will occur in the fall
or winter,floods are likely to be important only during the
time the reservoir is not allowed to increase above El 1135
ft.If a flood should occur during this time,the cone
E-2-149
4.2 -Devil Canyon Development
valves are designed to pass the routed 1:50-year design
flood of 38.500 cfs.
(c)River Morphology
No additional impacts on river morphology will be caused by
reservoi r fi 11 i ng other t han the obvi ous impact of trans-
forming the Susitna River between the Watana dam and the
Devil Canyon dam into a reservoir.Impacts described in
Section 4.1.3(b)will remain relevant.
(d)Water Quality
(i)Water Temperature
The outlet water temperatures from Watana will be un-
changed from those that occur when Watana is operated
alone.8ecause of the rapid filling of the Devil
Canyon reservoir.there will be minimal opportunity
for changes in the outlet temperatures at Devil
Canyon duri ng both stages of fi 11 ing.There will be
some damping of the temperature fluctuations caused
by varying meteorological conditions that occurred at
the Devil Canyon site when Watana operated alone.
Between the filling stages.the larger surface area
of the newly formed Devil Canyon reservoir will offer
more opportunity for atmospheric heat exchange.
However.since the retention time will only be about
4 days.it is expected that at the Devil Canyon
outlet and further downstream.little change in
water temperature will occur from that experienced
with Watana operating alone.
(ii)Ice
An extensive ice cover is not expected to form on the
Devil Canyon reservoi r duri ng the peri od when the
pool is maintained at El 1135 ft (344 m)beca'use of
the warm water inflow from the Watana reservoir.
Additional1y.since downstream winter temperatures
wi 11 not be signifi cantly affected by the pool.ice
processes downstream from Devil Canyon described in
Section 4.1.3(c)(ii)will remain relevant.
(iii)Suspended Sediments/Turbidity/Vertical Illumination
As previously discussed.the Watana reservoir will
act as a sediment trap.greatly reducing the quantity
E-2-150
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I
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4.2 -Devil Canyon Development
of suspended sediment entering the Devi 1 Canyon re-
servoi r.
Immediately prior to filling,the reservoir area will
be cleared of all vegetation.By delaying this
activity until filling is about to commence,erosion
and siltation problems prior to filling the reservoir
will be minimized.During filling,however.the lack
of soil stabilizing vegetative cover may cause in-
creased erosi on.These impacts are only expected to
create short-term increases in turbi di ty and sus-
pended sediment concentrations.In addition,suspen-
ded sediment concentration and turbidity increases
may also occur within the Devil Canyon impoundment as
a result of the slumping of the valley walls.How-
ever,since the Devil Canyon impoundment area is
characterized by a very shallow overburden layer with
numerous outcroppi ngs of bedrock,510pe i nstabi 1 ity
should not significantly affect turbidity and suspen-
ded sediment concentrations.A further discussion of
the slope stabil ity can be found in the Susitna
Hydroelectric Project Geotechnical Report (Acres
1981c)•
As reservoi r fill ing progresses,the Devil Canyon
reservoi r will provide additional settl i ng capabil-
ity.Thus,the net result will be a sl ight decrease
in suspended sediment and turbidity and a correspond-
ing increase in vertical illumination downstream from
Devil Canyon.
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(i v)Dissolved Oxygen
As previously discussed in Section 4.1.3(c)(v).water
discharged from Watana and entering Devil Canyon will
have a high dissolved oxygen concentration and low
BOD.
Because of the extremely short residence time,no
hypolimentic oxygen depletion is expected to develop
either during the one year that the reservoir is held
at El 1135 ft (344 m),or duri ng the fi nal six weeks
of reservoir filling.
Prior to filling,all standing vegetation in the
reservoir area will be cleared and burned,thereby
el im;nat ing much of the oxygen demand that woul d be
caused by i nundati on and subsequent long-term
decomposition of this vegetation.
E-2-151
4.2 -Devil Canyon Development
(v)Total Dissolved Gas Concentration
Di ssol ved gas supersaturat ion will not be a concern
during the filling of the Devil Canyon reservoir.As
the reservoir is filled,the rapids between the mouth
of Devil Creek and the Devil Canyon dam sHe w"il 1 be
inundated and the turbulence that presently causes
the supersaturation will thus be eliminated.
During the initial filling to El 1135 ft (344 m),the
diversion tunnel will be utilized.As such,there
will be no plunging discharge to entrain gas.After
elevation 1135 ft (344 m)is attained and for the
balance of the filling sequence,discharge will be
via the fixed-cone valves.No nitrogen supersatura-
tion is expected downstream from the dam.The opera-
tion of the fixed-cone valves is discussed in further
detail in the Mitigation Section 6.6.3.
(vi)Nutri ents
Similar to Watana,two opposing factors will affect
nutrient concentrations during the filling process.
First,initial inundation will likely cause an
increase in nutrient concentrations due to leaching.
Second,sed imentat i on will st ri p some nutrients from
the water column.The magnitude of the net change in
nutrient concentration is unknown,but it is likely
that nutrient concentrations will increase in close
proximity to the reservoir floor.
(vii)Total Dissolved Solids,Conductivity,
Significant Ions,Alkalinity,and Metals
Similar to the process occurring during Watana fill-
ing,increases in dissolved solids,conductivity and
most of the major ions \>iill likely result from leach-
ing of the reservoir soils and rocks during Devil
Canyon filling.For initial filling from El 850 ft
(283 m),no significant downstream impacts are fore-
seen,since it will take only about two weeks to
accumulate the 76,000 acre-feet of water required to
fill the Devil Canyon reservoir to EL 1135 ft
(344 m).In such a short time,insignificant leach-
ing would occur which could be detrimental to down-
stream water quality.
Subsequent to this initial phase of filling,and for
the remainder of the fi 11 ing proces,S",fixed-cone
valves will be utilized for reservoir discharge.
E-2-152
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4.2 -Devil Canyon Development
The valves will draw water from well above the bottom
of the impoundment {El 930 ft (282 m)and El 1050 ft
(318 m).Since the products of the leaching process
will be confined to a layer of water near the bottom
(Peterson and Nichols 1982),downstream water quality
should not be adversely impacted.
(e)
(f)
Ground Water Conditions
No major ground water impacts are anticipated during the
filling of the Devil Canyon reservoir.The increased water
level within the reservoir will be confined between bedrock
walls.Downstream there may be a slight decrease in the
ground water table caused by the reduced filling flows (see
Section 2.4.4).A decrease in the ground water level
in the same proportion as the decrease in mainstem stage
woul d be expected.The change in ground water level wi 11 be
confined to the alluvial deposits adjacent to the river.
Lakes and Streams
As the Devil Canyon
tributaries entering
Table E.2.26).As
transported by these
mouth of the stream.
pool level rises,the mouths of the
the reservoi rrlill be inundated (See
the reservoir is filled,sediment
streams will be deposited at the new
(g)Instream Flow Uses
(i )
(i i )
Fishery Resources,Wildlife Habitat,
and Riparian Vegetation
As Devil Canyon reservoi r is filled,new fishery
habitat will become available within the reservoir.
However,adverse impacts to fish habitat will occur
as tributary mouths become inundated.In addition,
terrestrial habitat will be pennanently lost as a
consequence of reservoir filling.Detailed informa-
tion on reservoir and downstream fisheries,wildlife,
and botanical impacts are presented in Chapter 3.
Navigation and Transportation
During filling,the rapids upstream from Devil Canyon
wi 11 be inundated and whitewater kayaki ng opportuni-
ties will be lost.Since the water surface level of
the reservoir w'ill be rising as much as 8 ft (2.4 m)
per day duri ng fi 11 ing,the reservoi r wi 11 be unsafe
E-2-153
4.2 -Devil Canyon Development
for boating.Downstream water levels may be slightly
less than normal Watana operation levels,but this
will not affect navi gat i on because the change will
be confined to the fall and early winter season.
(iii)Waste Assimilative Capacity
Although flows in the river will be reduced during
the two reservoir filling periods,the waste assimi-
lative capacity of the river will not be affected.
(iv)Freshwater Recruitment to Cook Inlet Estuary
Small temporary changes in the Cook Inlet sal inity
regime established during the operation of Watana
alone are expected only duri ng the second phase of
fill i ng Devil Canyon.Thi sis because of the brief
period of filling and the small volume required rela-
tive to the average annual Susitna River discharge to
Cook Inlet.
4.2.3 -Watana/Devil Canyon Operation
(a)Flows and Water Levels
(i)Project Operation
After Devi 1 Canyon comes on 1 i ne,Watana wi 11 be
operated as a peaki ng pl ant and Devi 1 Canyon wi 11 be
operated as a baseloaded pl ant.Advantage wi 11 be
taken of the two-reservoir system to optimize energy
production with the constraint that the downstream
flow requirements will be met.
Each September,the Watana reservoir will be filled
up to its maximum water level reaching 2190 ft
(664 m)during wet years.From October to I~ay the
reservoir will normally be drawn down to approximate-
ly El 2080 ft,although during dry years the reser-
voir will be drawn down to a minimum reservoir level
of 2065 ft (626 m).In May,the spring runoff will
begin to fi 11 the reservoi r.However,the reservoi r
will not be a 1J owed to fi 11 above El 2185 ft (626 m)
until 1 ate August when the threat of a significant
summer flood wi 11 have passed.If September is a wet
month,the reservoi r will be allowed to fill an
additional 5 ft (1.5 m)to El 2190 ft (664 m).
E-2-154
....
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4.2 -Devil Canyon Development
From November through the end of July,Devi 1 Canyon
will be operated at the normal maximum headpond
elevation of 1455 ft (441 m)to optimize power
product ion.
During August and early September,the Devil Canyon
reservoir level will be drawn down to a minimum level
of 1405 ft (426 m).Thus,most of the August down-
stream flow requirement at Gold Creek can be met by
withdrawing water from storage at Devil Canyon.This
will permit storage of additional water in the Watana
reservoi r which woul d otherwi se have to be rel eased
because the energy that would be produced to meet the
downstream flow requi rements woul d be greater than
the August 2010 energy demand.When the downstream
flow requirements decrease in mid-September,the
Devil Canyon reservoi r wi 11 be fi 11 ed to El 1455 ft
(441 m).
-Devil Canyon Turbine Operation
The four turbine units at Devil Canyon can be
operated to provide any flow above 1700 cfs up to
the maximum capacity of the powerhouse (15,000 cfs)
while maintaining a high efficiency.This is
illustrated in Figure E.2.190.
-Minimum Downstream Target Flows
The minimum downstream flow requirements at Gold
Creek will be unchanged when Devil Canyon comes on
line.Table E.2.36 illustrates these flows.A
further expl anation is provided in Sections
4.1.2(a)and 4.1.3(a).
-Monthly Reservoir Simulations
As described in Section 3.2,a multiple reservoir
simulation program was run using the 32 years of
synthesi zed Watana and [levi 1 Canyon flow data.The
development of the Watana and Devil Canyon fl ow
sequences used in the simulation is discussed in
Sections 2.2.1 and 3.3.
Similar to the simulation for Watana operating
alone,the simulation was initiated with both
reservoirs at normal maximum operating levels and a
full pool was required at the end of the simulation
peri ode Energy product i on was opt imi zed by
E-2-155
4.2 -Devil Canyon Development
adjusting the monthly reservoir operating rule
curves for each reservoir according to the monthly
energy demand pattern from mi d-September to
mid-May.The reservoir characteristics,salable
energy,and downstream now requirements were also
considered in developing the operating rule curves.
The optimized rule curve is i11ustrated in Table
E.2.40.The minimum monthly energies and the
associated powerhouse discharges are presented in
Table E.2.51.
-Weekly Reservoir Simulations
Weekly reservoir simulations for the 32 years of
record were condlJCted for both the 2002 and the
2010 energy demand forecasts.The weekly reservoir
simulation program is described in Section
4.1.3(a)(i).
In the 2002 simulation,there is insufficient
energy demand to uti1 i ze the energy potenti al of
the system.However,by 2010,the demand has
increased to where much of the previ ous ly excess
energy can be used.
-Daily Operation
With both Watana and Devil Canyon operating,Watana
can be operated as a peaking plant because it will
discharge directly into the Devil Canyon reservoir,
which wi11 be used to regulate the now.The
peaking of Watana will cause a daily fluctuation of
1ess than one foot in the Devi 1 Canyon reservoi r.
Devil Canyon will operate as a baseloaded plant for
the life of the project.
(ii)Mean Monthly Flows,Annual Flows,and Water Levels
The monthly maximum,minimum,and median Watana and
Devil Canyon reservoir levels for the 32-year
simulation are i1lustrated in Figures E.2.191 and
E.2.192.For the 2010 reservoir operation
simulations,water years 1956,1970,and 1966
represent a wet year,a drought year and an average
flow year respectively for both Watana and Devil
Canyon.From October through Ap ri1,the Watana
maximum and median reservoir levels correspond
closely to the reservoir operating rule curve (Table
E.2.40).During the fill ing months of May through
September,the water level is higher than the rule
curve in wet years because the rail belt system can
E-2-156
r~
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4.2 -Devil Canyon Development
not use additional energy.Hence,the excess water
goes into storage.In average yea rs,from May to
September,the reservoi r 1 evel is at or lower than
the rule curve.If the reservoir level matches the
rule curve,then the rail belt system can absorb all
available energy after the rule curves have been
satisified.If the reservoir level is below the rule
curve,then only the greater of the minimum energy
demand or the energy production from the minimum
downstream flow requirements is satisfied.
The Devil Canyon reservoir is maintained at El 1455
ft (441 m)most of the year.However,during August
and September,the reservoir is often drawn down to
meet the Gold Creek flow requi rement.In wet years,
there is an excess of flow and energy and hence no
need to draw the reservoi r down.In dry years,such
as occured in WY 1970,the Devil Canyon reservoir is
drawn down in April or early May to meet the minimum
energy demand and downstream flow requi rements if
Watana has a 1ready been drawn down to its mi ni mum
level.However,at no time during the 32-year simu-
lation are both reservoirs drawn down to their mini-
mum level.
Monthly Watana,Devil Canyon,and Gol d Creek flows
for the 32-year monthly energy simulation are pre-
sented in Tables E.2.52,E.2.53,and E.2.54.The
maximum,mean,and minimum flows for each month at
Watana,Devil Canyon and Gold Creek are summarized
and compared to pre-project flows and Watana opera-
tion flows in Tables E.2.43,E.2.55,and E.2.45.
From October through April,the post-project flows
are many times greater than the natural,unregulated
flows.Post-project flows during the months of June,
July,August,and September are 36,34,57,and 79
percent of the average mea n monthly pre-proj ect flow
at Gold Creek,respectively.The flow reductions
represent the volume of water used to fill the Watana
reservoi r.Vari ati ons in mean monthly post-project
flows occur,but the range is substantially reduced
from pre-project flows.Figures E.2.193 and E.2.194
illustrate the Watana i nfl ow and outflow,the Watana
reservoir level,the Devil Canyon reservoir inflow,
the Devil Canyon outflow,and the pre-project and
post-proj ect flows at Gol d Creek for each month of
the 32-year simulation.
E-2-157
4.2 -Devil Canyon Development
Fa rther down stream,percentage differences between
pre-and post-project flows are reduced by tributary
inflows.The pre-and post-project monthly flow sum-
maries for Sunshine and Susitna Station are compared
in Tables E.2.47 and E.2.49.Monthly post-project
flows are presented in Tables E.2.56 and E.2.57.Al-
though summer flows from May through October average
about 8 percent less at Susitna Station,winter flows
are about 100 percent greater than existing condi-
t ion s.
A compari son of post-project mean monthly fl ows with
Watana ope rat i ng alone and with Watana/Devil Canyon
operating shows that,although there are some differ-
ences,the differences are small.
Water surface elevations based on the maximum,mean,
and minimum flows at Gold Creek for r~ay through
September for selected mainstem locations between
Portage Creek and Talkeetna,are illustrated in
Fi gu res E.2.195 through E.2.197.Post-project water
levels are generally 3 to 4 feet (0.9 to 1.2 m)less
than natural water levels in June and July.In
August,the differences are 1 to 3 feet (0.3 to
0.9 m),and in September,the water levels are within
one foot (0.3 m).During low flow years,the
post-project September water levels are higher.
(iii)Flo od s
Spring Floods
Using the 2010 energy demand to drive the 32-year
monthly simul ation,no flow releases occurred
between May and July at either Watana or Devil
Canyon.All flow was either absorbed in the Watana
reservoi r or passed through the respective power-
houses.The June 7,1964,flood of record with an
annual flood recurrence interval of better than 20
years,resulted in a Watana reservoir elevation of
2151 ft (652 m)at the end of June,an elevation 34
ft (10.3 m)below the normal maximum operating
1eve 1.
The maximum mean monthly discharge at Devil Canyon
duri ng the 1964 spring flood period was approxi-
mat ely 10,50 a cf s•If pea kinflow i nt 0 De v i 1
Canyon reservoir,from the drainage area downstream
from Watana approached this discharge,flow at
Watana would be virtually shut off to ma"intain a
Devil Canyon reservoir level of 1455 feet (441 m).
Local inflow would supply most of the power needs.
E-2-158
-
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4.2 -Devil Canyon Development
However,the peak contribution downstream from
Watana is not likely to be as large as 10,500 cfs.
For example,the Gold Creek maximum historical one
day peak flow to mean monthly flow ratio for the
month of June is 2.05 (R&M 1982d).If this ratio
is used to compute the local inflow between Watana
and Devil Canyon,the peak one-day June inflow
during the simulation period would be approximately
9300 cfs,which is less than the maximum of 10,500
c fs.
For'the 1:50-year flood,the Devil Canyon outflow
with both Watana and Devil Canyon in operation will
be similar to but less than the flow with vJatana
operating alone because the Devil Canyon reservoir
is able to use the local runoff to help meet the
energy demand.This requires less flow from
Watana.Hence,less flow is passed into the Devil
Canyon reservoir and hence on downstream.
The Watana reservoi r wi 11 always be drawn down
sufficiently during the winter and spring to pro-
duce energy such that the 1 :50-year flood volume
can be stored within the reservoir if the flood
occurs in June.The flow contribution at Devil
Canyon for the drainage area between Watana and
Devil Canyon woul d approx imate 11 ,000 cfs.Hence,
the energy demands woul d be met by runni ng Devi 1
Canyon near capacity and reducing outflow from
Watana as much as possible to prevent flow
wastage.
For flood events greater than the 1:50 year event
and after Watana reservoir elevation reaches
2185.5 ft (662m),the powerhouse and outlet faci-
1 iti es at both Watana a nd Devil Canyon wi 11 be
operated to match inflow up to the full operating
capacity of the powerhouse and outlet facilities.
If i nfl ow to the Watana reservoi r conti nues to be
greater than out flow,the reservoi r wi 11 g radua lly
ri se to El 2.193 ft (664.5 m).When the reservoi r
level reaches 2193 ft (664.5 m),the main spillway
gates will be opened such that outflow matches
i nfl ow.Concurrent with openi ng the Watana mai n
spillway gates,the rnai n spillway gates at Devil
Canyon will be opened so that inflow matches
outflow.The main spillways at both Watana and
Devil Canyon will have sufficient capacity to pass
the 1:10,000-year event.Peak inflow for the
1:10 ,OOO-year flood wi 11 exceed outflow capacity at
E-2-159
4.2 -Devil Canyon Development
Watana resulting in a slight increase above 2193
ft (664.5 m).At Devi 1 Canyon there wi 11 be no
increase in water level.The discharges and water
levels associated with a 1:10,OOO-year flood for
both Watana and Devil Canyon are illustrated in
Figures E.2.154 and E.2.198.
If the probable maximum flood (PMF)were to occur,
the operation at Watana will be unchanged whether
Watana is operating alone or in series with Devil
Canyon.The main spillway will be operated to
match inflow until the capacity of the spillway is
exceeded.At this point,the reservoir elevation
will rise until it reaches El 2200 ft (667 m).If
the water level exceeds El 2200 ft (667 m),the
erodible dike in the emergency spillway will be
washed away and flow will be passed through the
emergency spillway.The resul t i ng total outflow
through all discharge structures will be 311,000
cfs.
At Devil Canyon a similar scenario would occur.
The main spillway will continue to operate,passing
the main spillway discharge from Watana.Once the
emergency spillway at Watana is overtopped,the
Devi 1 Canyon reservoi r wi 11 surcharge to El 1465
ft (444 m)and its emergency spillway will begin to
operate.Peak outflow will occur immediately after
the fuse plug erodes away.However,the peak is
slightly less than the peak inflow.The inflow and
outflow hydrographs for both the Watana and Devil
Canyon PMF are shown in Figures E.2.154 and
E.2.198,respectively.
For floods larger than the 1:100 year flood,the
Watana reservoir will fill to the normal maximum
operating level and inflow will be set equal to
outflow.Hence.for fl oods of magnitudes greater
than 1:100 years,the flood discharges at down-
stream locations will be decreased by only a small
amount from natural 1 eve 1s.The degree of reduc-
tion will depend on the volume of water the Watana
reservoir can absorb into storage.
The mean annual and l:lO-year spring flood dis-
charges at the Gold Creek.Sunshine,and Susitna
Station will essentially be the same as those
described in Section 4.1.3(a)(iii)less the local
contribution between Watana and Devil Canyon.The
loss of this local contribution will have the
greatest effect on the Gold Creek flows.
E-2-160
(~,
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I
4.2 -Devil Canyon Development
-Summer Floods
In wet years the combined,Watana and Devil Canyon
operat i on will produce more energy than can be
used,especially in the early years of the project.
If this occurs,the excess flow will have to be
released through the outlet facilities if the
reservoir elevation exceeds El 2185.5 ft (662 m).
Si nce Watana can pass the 1:50-yea r summer fl ood
without operating the main spillway,the summer
flood flows at Watana for up to the 1:50-year flood
will be the sum of the discharge through the outlet
facilities and the powerhouse.Since the capacity
of the outlet facilities is 24,000 cfs,the maximum
flood flow will be 31,000 cfs,if a powerhouse flow
of 7,000 cfs is assumed.
For the 1:50-year summer flood,if the Watana dis-
charge is maintained at approximately 31,000 cfs,
the reservoir will surcharge to 2193 ft (664.5).
At Devil Canyon,the Devi 1 Canyon powerhouse and
outlet facilities have sufficient capacity to pass
the 1:50 year summer flood of 38,500 cfs without
operati on of the mai n spillway.Th i s flood is
passed through the Oevil Canyon reservoir without
any change in water level.
-Annual Floods
The reservo"ir operation studies using weekly flow
values were used to determine the Gold Creek annual
flood frequency curves for the years 2002 and 2010.
The 2002 and 2010 flood frequency cu rves shown in
Figure E.2.199 are noticeably different for floods
with return periods between 1.4 years and 50 years.
This difference is particularly significant during
the weekly reservoir simulation of the August 1967
flood.Routing this flood through the Watana and
Devil Canyon reservoirs necessitates a discharge of
5,300 cfs over the main spillway in the 2002 demand
simulation.In the 2010 demand simulation,opera-
t i on of the rna in spi llway is unnecessary.It
should be noted that the August 1967 flood has a
recurrence interval of 1:65-years.For floods
above the 1:50 yea r flood,the Watana reservoi r
will be surcharged to El 2193 ft (664.5 m)and
inflow will be set equal to outflow up to the
capacity of the main spillway.
E-2-161
4.2 -Devil Canyon Development
Floods downstream of Gold Creek will be decreased
by approximately the same amount flows at Gol d
Creek are reduced.However~because flood peaks in
the lower basin do not occur at the same time as
floods at Watana and Dev il Ca nyon ~the error in
this approach will become increasingly larger with
distance downstream.
In low flow years~the Watana reservoir provides
total regulation of the flow at Gold Creek.Hence~
annual maximum flows are determined by the Gold
Creek flow requirement of 12~OOO cfs in August.
Maximum wi nter flows at Gol d Creek with both dams
producing energy will decrease to approximately
12~OOO cfs compared to maximum flows of 15~OOO cfs
with Watana operating alone.This is possible
because the 12 ~OOO cfs passes through both power-
houses where as the 15~OOO cfs only passed through
the Watana powerhouse.Additionally~the high
spring discharges at Gold Creek are reduced because
the local drai nage area is reduced to the area
between Devil Canyon and Gold Creek.
(iv)Flow Variability
Examples of the mean daily flow variability at Gold
Creek for 1964~1967~and 1970 for the 2002 and 2010
energy demand simulations are presented in Figures
E.2.200 through E.2.205.Because the drainage area
between Devil Canyon and Gold Creek is much less than.
the drainage area between Watana and Gold Creek~the
local inflow and hence daily flow variation at Gold
Creek is reduced with both dams operating compared to
Watana alone.
The monthly and annual flow duration curves for pre-
proj ect and post-project condit ions for the 32-yea r
simulation period are illustrated in Figures E.2.206
through E.2.210 for Watana,Devil Canyon,Gold Creek,
Sunshine,and Susitna Station.The flow duration
curves show less variability during post-project
operation and a diminished pre-and post-project dif-
ference with distance downstream from Watana.
The annual flow duration curve at Gold Creek based on
weekly flows is presented in Figure E.2.211.Figure
E.2.212 illustrates the flow at Gold Creek for vari-
ous probabilities of exceedance for each week of the
year assuming the 2010 demand.
E-2-162
4.2 -Devil Canyon Development
"""
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(v)Operation of Devil Canyon Fixed Cone Valves
The fixed-cone val ves at Devil Canyon will discharge
excess water from the reservoi r to mai ntai n the
nonnal maximum operating level at El 1455 ft (441 m).
Four 102-inch (2.6 m)diameter valves,each with a
capacity of 5800 cfs,wi 11 be located approximately
170ft (51.5 m)above the normal tailwater elevation
and three 90-inch (2.3 m)diameter valves,each with
a capacity of 5100 cfs,will be located approximately
50 ft (15 m)above the normal tailwater elevation.
Total discharge capacity will be 38,500 cfs.
Th~valves will draw water from El 930 ft (282 m)and
El 1050 ft (318 m)and discharge it as highly diffus-
ed jets to achieve energy dissi pation and avoid gas
supersaturation.
Table E.2.58 provides data on flow releases based on
the weekly reservoir simulations for the 2002 and
2010 forecasts.Included for each year are the first
week of release,the week of maximum release,the
maximum Devil Canyon release,the powerhouse flow at
the time of maximum rel ease,and the vol ume rel eased
for both the 2002 and 2010 simulations.
In the 2002 simulation,large releases occur at Devil
Canyon in 22 of the 32 years even though most of the
system energy is being generated bY the Devil Canyon
powerhouse.That is,there is an annual probability
of 66 percent that significant releases will occur at
Devil Canyon in the early years of the project.To
minimize the Devil Canyon releases,when a release is
necessary,the release is at Watana,thus,allowing
the Devil Canyon powerhouse to be used up to its
maximum capacity to provide the system energy needs.
However,because the capacity of the outlet facil i-
ties at Watana is much less than at Devil Canyon
(24,000 cfs versus 38,500 cfs),during high flow
years when Watana outflow is greater than approxi-
mately 24,000 cfs,Watana will be used to generate
the system energy needs to prevent theWatana reser-
voir from surcharging.This is evident in the simu-
lations of WY 1959 and WY 1967.In WY 1967,Watana
reservoi r is full at the time of the 1 ate August
flood.This not only results in operation of the
Devil Canyon outlet facilities at their maximum capa-
city,but also requires operation of the Devil Canyon
spillway.
E-2-163
4.2 -Devil Canyon Development
In the 2002 simulation,reservoir releases occur as
early as the week of July 8.
By the yea r 2010,the rel ease pattern is vastly
different.There is an annual probabil ity of 30
percent that a sizeable release (over 2500 cfs)will
occur.In WY 1967,for example,the release is
reduced from 43,800 cfs in 2002 to 15,100 cfs in
2010.In addition,there a re no occas ions when
either the Watana or Devil Canyon spillways operate.
Because the val ves are located at the base of the
Devil Canyon dam,there is a potential for downstream
adverse temperature effects duri ng peri ods of high
release.This is discussed in Section 4.2.3 (c)(i).
(b)River Morphology
Average monthly flows during Watana/Devil Canyon operation
will be similar to those of Watana operation,although minor
redistribution of the flow does occur.The change in Watana
reservoir operation during the fi rst few years after Devil
Canyon comes on line decreases the ability of the reservoir
system to absorb high flows.Consequently,the occurrences
of high flows capable of initiating gravel bed movement in
the Susitna River above Talkeetna will be increased.Pro-
ject impacts previously described in Sections 4.1.2(b)and
4.1.3(b)for Watana impoundment and operation will remain
relevant except that river bed stabil ity will tend to de-
crease since the larger return period flood flows have been
increased.
(c)Water Quality
(i)Water Temperature
-Watana and Devil Canyon Reservoirs
The program DYRESM,described in Section 4.1.3(c)
(i)was used to predict reservoir temperature pro-
files and outflow temperatures from both the Watana
and Devil Canyon reservoi rs.The Watana i nfl ow,
the inflow temperature,and the meteorology for the
period June through December 1981 were used.These
data are the same as for Watana operating alone
(Section 4.1.3(c)(i)),however,Watana outflow is
changed due to the different mode of operating the
Watana reservoi r when both projects are opera-
tional.The simulated flows for June through
September of WY 1981 from the Case C weekly reser-
voir simulation for the 2010 demand were used as
E-2-164
,--
,-
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r
.~
I
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4.2 -Devil Canyon Development
the source of i nfl ow data for the two reservoi rs.
Since the available simulation data ended at the
end of WY 1981 (September 30,1981),mean weekly
flows from the Case C,2010 demand simulation were
used for the October to December period.
Watana out flow,outflow temperature,and the flow
contribution from the area between the damsites are
inputs to the Devil Canyon reservoir.The tempera-
ture of the out flo\'1 from the Watana reservoi r is
more stable than the natural thennal regime.Thus,
a stabl e temperature regime is input to Devi 1
Canyon.However,the Devil Canyon inflow tempera-
tures are cooler in June and warmer in September
than occur naturally.Devil Canyon reservoi r
exhibits the general pattern of early summer warm-
ing,summer stratification,and fall to winter
cool ing through an isothermal condition to reverse
strat ifi cat;on.
St rat ificat i on and outflow temperatures at Watana
under the assumed operati on scenari 0 are essen-
tially the same as for Watana operating alone.
Typ;'cal reservoi r temperature profiles at Devil
Canyon are given in Figures E.2.213 and E.2.214 for
June to September and October to December,respec-
tively.Oevil Canyon reservoir,because of its
smaller size than Watana,exhibits responses to
meteorological conditions in a manner more similar
to Eklutna Lake.This is particularly true for
strong wind storms which result in stepped tempera-
ture profiles (see Figures E.2.166 and E.2.213).
Generally,reservoir stratification is weak in June
but builds during July and August.Typical mixed
1 ayer depths are in the order of 50 to 70 ft (15 to
21 m)during the summer months.For 1981 weather
data,cooling at Devil Canyon is delayed to late
September and early October.This is partly due to
warmer Watana i nfl ows to the Devil Canyon reser-
voi r.
Isothermal conditions occur in late November •
Cool ing conti nues throughout the reservoi r depth
until maximum density is reached.Reverse strati-
fication begins in mid-December.By the end of
December,the reservoir is weakly stratified.The
mixed layer depth in December is about 30 ft (9 m).
However,it would be greatly influenced by severe,
cold weather,mixing events,and Watana outfiow and
tempe rature.
E-2-165
4.2 -Devil Canyon Development
The maximum Devil Canyon reservoir surface tempera-
ture of S.8°C (4JOF)occurs on August 28.The
minimum surface temperature occurs at the end of
the simulation period (December 31,1981)and
equals 2.4°C (36°F).
The DYRESM model attempts to have the Devil Canyon
outflow temperatures,1 ike Watana,follow the
inflow temperatures.The two-level intake struc-
ture at Devil Canyon provides some flexibility but
not as much as at Watana.However,the stable
water surface at Devil Canyon negates the need for
additional intakes.
Figures E.2.215 and E.2.216 illustrate the Devil
Canyon reservoir inflow and outflow temperature for
June through December.Maximum outflow tempera-
tures occur in late July to mid-August and are
about 8°C (46°F).Temperatures in June fluctuate
due to the tendency for mixing and deepening of the
thermocline during this weak stratification period
(Figure E.2.215).
For this simulation period,high summer runoff
resul ted in power operation at maximum reservoi r
operating levels with releases occurring at both
reservoirs.This resulted in a depression of the
temperatures to about 5°C (41°F)during the maximum
release period of August 19-25 (Figure E.2.215).
Thi s coldest temperature only occurs for one day,
with temperatures rising to about 6°C (43°F)in
three days.As the release is reduced,outflow
temperatures increase and eventually return to
about 7°C (45°F)by early September.
Devi 1 Ca nyon out flow temperatures from mi d-
September to December 31,exhibit a much more grad-
ual reduction in temperatures than observed at
Watana.Temperatures during this period fall from
a hi gh of 8°C (46°F)on September 14 to a low of
3.5°C (38°F)on December 31.
To test the effectiveness of the two-level intake
structure at Devil Canyon in providing the desired
temperatures,a temperature s imu 1at i on was made
using Ohly the lower intake.All other input data
were identical to the DYRESM simulation described
above.The results of the simulation indicate that
outlet temperatures of 1 to 2°C cooler would occur
duril1g June and July if only the lower intake was
E-2-166
-
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4.2 -Devil Canyon Development
used.Because of the large flow release in August
which dominated the outflow temperatures,there is
1 ittle difference during August.Thus,based on
thi s analysi s,the two-l eve 1 intake structure does
provide increased flexibility in outlet temperature
selection.
Because the Devil Canyon outlet facilities are
located at El 930 ft (282 m)and El 1050 ft
(318 m),any water released through them will be
near 4°C (39.2°F).5i nce this coul d have an
adverse impact on the downstream fishery,the
Watana/Devil Canyon two reservoir system will be
operated whenever possible so that the maximum
power generat i on will occur at Devil Canyon and
releases will be discharged at Watana.In this
way,flows of 12,000 to 15,000 cfs from the Devil
Canyon powerhouse at a temperature of approximately
8°C (46°F)(Figure E.2.215),will aid in maintain-
ing acceptable downstream temperatures.
Examination of TableE.2.58 illustrates the fre-
quency of releases and the discharge through the
Devil Canyon powerhouse and outlet facilities.The
data i ndi cate that the worst case is WY 1981.The
temperature simulation predicts a minimum tempera-
ture of 5°C at the dam during this release.Since
the powerhouse flows are approximately equal to or
greater than all other releases for the 2010 demand
and will be about 8°C,the composite outlet temper-
ature during all other releases should be greater
than 6°C.
-Devil Canyon to Talkeetna
Mai ns tern
The temperature regime downstream of Devi 1 Canyon
darn will di ffer from both the natural regime and
the predicted Watana operati on regime.There-
fore,studies using the HEATSIM model described
in Section 4.1.2(e)(i)were undertaken to esti-
mate the temperatures in the reach between Devil
Canyon and Talkeetna.Three outflow temperature
scenarios were considered.
The downstream temperatures were simulated using
the DYRESM resul ts from the reservoi r ope rat ion
simulation and 1981 meteorological data as input.
The results of the HEATSIM program are shown in
Figures E.2.217 and E.2.218 for June to September
E-2-167
4.2 -Devil Canyon Development
and October to December,respectively.Gener-
ally,outflow temperatures are warmed with dis-
tance downstream during June and July,and this
warming is on the order of 2°C (3.5°F)between
Devi 1 Canyon and Ta 1keetna.In August there is
no significant temperature change due to the 1981
climatic conditions and high flows used in the
simulation.
Cooling begins slowly in September with a gradual
O.5°C (l0F)reduction between Devil Canyon dam-
site and Talkeetna on September 15.This accel-
erates as cooler air temperatures occur,reaching
a maximum cooling in January.On December 21,
outflow temperatures of 3.5°C (38°F)are cooled
to approximately O.5°C (33°F)by Talkeetna.
During the release period in August and early
September in WY 1981,the minimum outflow temper-
ature of 4.6°C (40°F)observed on August 21 has
warmed to 4.7°C (40.5°F)by Sherman and to 4.9°C
(41°F)by Talkeetna.
To assess the impact of wi nter outflow tempera-
tures on downstream temperatures,scenarios
assuming a constant outflow tanperature of 4°C
(39.2°F)and an outflow temperature decreasing
linearily from 4°C (39.2°F)on November 1 to 2°C
(35.6°F)on January 15 were simulated.The
long-term average meteorological data for the
Devil Canyon to Tal keetna reach were used for
both simul ati ons.The temperature profil es for
the constant 4°C (39.2°F)outflow are illustrated
in Figure E.2.219 and E.2.220.Temperatures are
above O°C (32°F)for the entire reach between
Devil Canyon dam and Talkeetna until January 15.
On January 15,O°C (32°F)water is estimated to
occur at river mile 99 just upstream from
Talkeetna.In late January,less cooling occurs
and water temperatures for the Devi 1 Canyon to
Talkeetna reach remains above O°C (32°F)(Figure
3.2.220).
Figures E.2.221 and E.2.222 illustrate the tem-
perature profil es with a reduction in outflow
temperatures to 2°C (35.5°F)by January 15 and
remaining constant thereafter.Water is pre-
dicted to cool to O°C (32°F)at about river mile
119 on January 15 (Figure E.2.221).This is the
maximum upstream location for O°C (32°F)water
during the Winter.In February,the location of
O°C water moves downstream to about river mi 1e
104 and moves to below Talkeetna in March (Figure
E.2.222)•
E-2-168
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4.2 -Devil Canyon Development
•Sloughs
Us i ng the results of the downstream temperature
program,the average annual temperature at
Sherman is calculated to be approximately 4°C.
This is an increase of about 1°C above the natu-
ral long-term average temperature.Therefore,
based on the ground water studies described in
Section 2.4.4 and the above preliminary analysis,
the slough upwelling temperatures in the vicinity
of Sherman may increase approximately 1°C.
-Talkeetna to Cook Inlet
As discussed in Section 4.1.2(e)(i),summer temper-
atures downstream of the Chulitna confluence will
cont i nue to refl ect the temperatures of the
Talkeetna and Chulitna Rivers.Temperature effects
from October to April will be similar to those des-
cribed in Section 4.1.3(c)(i),except that because
the Susitna Ri ver water temperatures are warmer
than during Watana operating alone,the influence
will be felt farther downstream.
-
(i i )Ice
-Reservoir
Ice formation on the Watana reservoir will be Slml-
lar to that described in Section 4.1.3(c)(ii).The
.DYRESM model i ng of Devil Canyon reservoi r for the
ca se con si dered i nd i cates that no ice cover will
form on the Devil Canyon reservoir through December
31.Si nce the water surface temperature is 2.4°C
at that time,an ice cover may not form on the
Devil Canyon reservoi r.If an ice cover does form,
it will be 1imited.
-Devil Canyon to Talkeetna
The downstream temperature modeling indicates that
the furthest upstream movement of O°C (32°F)water
in the three cases considered is RM 119.Thus,it
is unlikely that there will be significant ice
formation in this reach.Open water will likely
exist from Devil Canyon to Tao,keetna.Hence,no
ice modeling was performed for this reach.
E-2-169
4.2 -Devil Canyon Development
-Talkeetna to Cook Inlet
Because of the warmer water temperatures and the
greater flows in the Susitna River,ice formation
downstream of Talkeetna will be delayed.Increased
staging further downstream will continue to occur
because of the increased flow.
The warm water discharged from the Devil Canyon
reservoir will begin to melt the downstream ice
cover in the spring.This coupled with flow regu-
lation by the Watana reservoir will tend to reduce
the severity of ice jams.
(iii)Suspended Sediments/Turbidity/Vertical Illumination
Of the suspended sediments passing through the Watana
reservoi r,only a small percentage is expected to
settle in the Devil Canyon reservoir;This is attri-
butable to the small sizes of the particles (less
than 4 mi crons in di ameter)enteri ng the reservoi r
from Watana and the relatively short retention time
of the Devil Canyon reservoir (2 months)in compari-
son to the Watana reservoi r (1.67 yea rs).The su s-
pended sediment and turbidity levels that occur
within the Devil Canyon impoundment and downstream
wi 11 be only sl i ghtly reduced from those that exi st
at the outflow from Watana.Vertical illumination
will increase sl ightly.
Some slumping of the reservoir walls and resuspension
of shoreline sediment will occur,especially during
August and September when the reservoir may be drawn
down as much as 50 feet (15 m).These processes will
produce short-term,localized increases in suspended
sediments.However,as noted in Acres (1982c),since
the overburden layer is shallow,no significant
slumping or sediment entrainment problems should
a ri se.
(iv)Dissolved Oxygen
As discussed in Section 4.1.3(c)(v),
dissolved oxygen concentrations can
lower levels of deep reservoirs.
reduction of
occur in the
Stratification and the slow biochemical decomposition
of organic matter will promote lower oxygen levels
near the Devil Canyon reservoir bottom over time.
However,all vegetation will have been cleared and
[-2-170
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4.2 -Devil Canyon Developmc
burned prior to inundation thereby reducing the
potent i a 1 oxgen demanding decomposit i on process.No
estimates of the extent of oxygen depletion are
available.
Within the upper layers (epil imnion)of the reser-
voir,dissolved oxygen concentrations will remain
high.Inflow water to the impoundment will continue
to have a high dissolved oxygen content and low BOD.
Ice cover formation,if it occurs,will be limited.
Thus,there will be year round turbulence near the
surface to maintain high dissolved oxygen levels.
Si nce water for energy generat ion is drawn from the
upper 1ayers of the reservoi r,no adverse effects to
downstream dissolved oxygen levels will occur.
During periods of release through the Devil Canyon
outlet facilities,water with somewhat reduced oxygen
levels will be discharged.Given the dynamic nature
of the ri ver,these reduced concentrat ions shoul d
quickly return to saturation levels.No quantitative
estimates of these reduced oxygen levels are avail-
abl e.
(v)Total Dissolved Gas Concentration
No supersaturated gas conditions will occur down-
stream from the Devil Canyon Dam.The fixed-cone
valves described in Section 4.2.3(a)(v)will elimi-
nate potential nitrogen supersaturation problems for
all flow releases and floods with a recurrence
interval less than 1:50-years.The frequency of
fixed-cone valve operation is discussed in Section
4.2.3(a)(v)and presented in Table E.2.58.Further
information is provided in Section 6.4.
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(vi)Trophic Status (Nutrients)
Peterson and Nichols (1982)assessed the anticipated
trophic status of Devil Canyon reservoir,similar to
the discussion in Section 4.1.3(c)(vii).Vollen-
weider's (1976)model was utilized for their predic-
tions.
The analysis indicates that under natural conditions,
Devil Canyon reservoir will be oligotrophic.Esti-
mates of permissible artificial phosphorus loading
reveal that the reservoir is capable of maintaining
oligotrophic status while receiving the untreated
E-2-171
4.2 -Devil Canyon Development
effluent of 48,300 pennanent residents.This esti-
mate is based upon Devi 1 Canyon alone.With both
reservoirs,pennissible artificial phosphorus loading
will be predicted on the artificial loading factor at
Watana.
(vii)Total Dissolved Solids,Conductivity,
Alkalinity,Significant Ions and Metals
Similar to the Watana reservoir,the leaching process
in the Devi 1 Canyon reservoi r is expected to resul t
in increased levels of the aforementioned water qual-
ity properties near the reservoir floor.Although
leaching of the more soluble soils and minerals will
diminish with time,other sources will continue to
dis sol ve•Th es e e ff e ct s wi 11 not dim i nish as rap i d1Y
as is anticipated for Watana.The blanketing of the
Devil Canyon reservoir floor with quantities of inor-
ganic sediment will not occur.It is anticipated,
however,that the 1 eachate wi 11 be confi ned to a
1ayer of water near the impoundment floor and al-
though the magnitude of the increase cannot be quan-
tified with available data,detrimental effects to
aquatic organisms are not anticipated (Peterson and
Nichols 1982).
During operation of the fixed-cone valves,no leach-
ing products should be passed downstream.The lower
set of valves at El 950 ft (288m)w"ill be located
approximately 50 ft (15 m)above the reservoir floor.
The lone of degredation is expected to be signifi-
cantly closer to the floor (Peterson,personal commu-
ni cat i on 1983)and out of the range of the intake
lone.
The presence and extent of the ice cover dictates the
increase in dissolved solids near the reservoir sur-
face duri ng the wi nter.Reservoi r temperature model-
ing (Section 4.2.3[iJ)indicates that surface temper-
atures ivill only be reduced to 2.4°C (36°F)by the
end of December.Consequently,1 ittl e if any ice
cover is anticipated,and no increases in dissolved
solids are expected near the reservoir surface during
the winter.
Similar to Watana,concentrations of metals will be
reduced by reactions with dissolved salts and subse-
quent precipitation.No quantitative estimates of
these changes are available.
E-2-172
4.2 -Devil Canyon Development
(d)Ground Water Conditions
Effects on ground water conditions will be confined to the
Devil Canyon reservoi r i tsel f.Downstream flows and hence
impacts will be simil ar to those occurring wi th Watana
operating alone.
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(e)Lakes and Streams
A maximum drawdown of 50 feet will occur during the August
and September with subsequent refilling in late September or
October.As a result,the streams fl owi ng into the Devil
Canyon reservoir listed in Table E.2.26 will be affected
simi 1ar to those streams enteri ng Watana reservoi r,des-
cribed in Section 4.1.3(e).However,with the decreased
drawdown,the impacts will be less.
No 1akes in the Devil Canyon impoundment wi 11 be impacted
other than the previously described small lake at the Devil
Canyon dams He.
The impacts to tributaries downstream from Devil Canyon will
not change from the conditions estab1 ished duri ng Watana
_operation as discussed in Section 4.1.3(e).
(f)Instream Flow Uses
The effects on the fishery resource,wildlife habitat,and
riparian vegetation are described in Chapter 3.
""'"(i)Navigation and Transporation
The Devil Canyon reservoi r will transform the Devil
Creek rapids and most of the Devil Canyon rapids into
calm water.This will affor~recreational opportuni-
ties for leisure boaters but totally eliminate the
world-class whitewater kayaking opportunities.
Since the Devil Canyon facility will be operated as a
baseloaded pl ant,downstream impacts wi 11 be simi 1ar
to ,those resulting from Watana operation (Section
4.1.3(f)(ii)).
Examination of Figure E.2.208 reveals that flows drop
below 6500 cfs at Gold Creek about 10 percent of the
time in May and June.During July,August,and
September,flow is always greater than 6500 cfs.
Therefore,since a prel imi nary analys is showed the
Sherman area to be navigab1~at that flow,impacts to
navigation will be minimal (see Section 2.6.3).How-
ever,if navigation problems develop,the mitigation
measures described in Section 6.3 will be imple-
mented.
E-2-173
4.3 -Access Plan
Downstream from Talkeetna,flows are greater than the
minimum navigation discharges established in Section
2.6.3,100 percent of the time from June through
September.Therefore,no navigation impacts will
occur below Talkeetna.
(ii)Freshwater Recruitment to Cook Inlet Estuary
Numerical modeling of the Cook Inlet salinity varia-
tions indicate that concentrations will be essen-
tially the same for either Watana operating alone or
both Watana and Devil Canyon operating (RMA 1983).
Table E.2.31 compares the expected salinities at five
select locations identified in Figure £.2.126,
assuming average hydrologic and operational condi-
tions.
4.3 -Access Plan
The Watana access road wi 11 begi n with the constructi on of a 2.O-mil e
(3.2 km)road from the Alaska Railroad at Cantwell,to the junction of
the George Parks and Denali Highways.Access will then follow the
existing Denali Highway for 21.3 miles (34.4 km).Portions of this
road segment wi 11 be upgraded to meet standards necessary for the
anticipated construction traffic.From the Denali Highway,a 41.6-mile
(67.1 km)gravel road will be constructed in a southerly direction to
the Watana campsite.An additional 2.6 miles (4.2 km)of road will
allow access to the south side of the damsite after completion of
construction of the main dam.
Access to the Devil Canyon site will be via a 37.0-mile (59.7 km)road
from Watana,north of the Susitna River,and a 12.2-mile (19.7 km)
railroad extension from Gold Creek to Devil Canyon,on the south side
of the Susitna River.
Access roads will consist of unpaved 24-feet (7.3 m)wide running
surfaces with shoulder widths of 5 feet (1.5 m).Design speed will be
55 mph (89 kmph)where acceptable,and 40 mph (65 kmph)in areas of
steep grades and sharp turns to avoid the need for excessively deep
cuts and extensive fills.
Side borrow techniques will be the primary construction method used to
develop the access roads.This will minimize disturbance to areas away
from the access road by confining construction-related activities to a
narrow strip on each side of the road.Careful stripping of the vege-
tation and organic soils,excavation,construction,backfilling and
vegetative rehabilitation should be confined to an area with a maximum
wi dth of between 100 and 140 feet (30 and 42 m).
£-2-174
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4.3 -Access Plan
A few borrow sites of 10-20 acres (5-10 ha)will be needed along the
road alignment for construction materials.These borrow sites will be
located in well-drained upland areas.
Additional detail on the proposed access corridors and their construc-
t i on can be found in Chapter 10 and in Exhi bit A,Sections 1.12 and
7.12.The methodology behind the-selection of these corridors is
explained in Chapter 10,Section 2.4.
4.3.1 -Flows
Flow rates on streams crossed by the access road wi 11 not be
chan'ged.However,localized impacts on water levels and flow
vel ociti es coul d occur if crossi ngs are improperly desi gned.
Because they do not restrict streamflow,bridge crossings will be
p referred to cul verts or low-water cross i ngs.Bri dge supports
will be located outside active channels,if possible.
Improperly desi gned cul verts can restri ct upstream fi sh movement
because of high velocities or perching of the culvert above the
streambed.However,maintenance of adequate fish passage will be
ensured as per AS-16.05-840.Culverts are more susceptible to
ice blockage problems which can cause restricted drainage and
road flooding,especially during winter snowmelt periods.All
culverts will be designed to handle flood flows and icing
problems.
Low-water cross i ngs wi 11 on ly be used in areas of infrequent,
light traffic (for example,for construction of the transmission
line).They will conform to the local streambed slope and will
be constructed of materi al s that wi 11 allow water to flow over
them instead of percolating through them.
4.3.2 -Water Quality
Most water qual ity impacts associated with the proposed access
routes will occur duri ng constructi on.The pri nci pa 1 impacts
associated with construction will be increased suspended sediment
and turbidity levels and accidental leakage and spillage of
petroleum products.Given proper design,construction,and moni-
toring,few water quality impacts are anticipated from the subse-
quent use and maintenance of these facilities.
(a)Turbidity and Sedimentation
Some of the more apparent potential sources of turbidity and
sedirnentati on probl ems duri ng access road construction
include:
E-2-175
4.4 -Transmission Corridor
-Instream operation of heavy equipment;
-Location and type of permanent stream crossings (culverts
vs.bridges);
-Location of borrow sites;
-Lateral stream transits;
-Vegetation clearing;
-Side hill cuts;
-Disturbances to permafrost;and
-Construction timing and schedules.
These potential sources of turbidity and sedimentation are
addressed in Chapter 3,Sections 2.3 and 2.4.3.
(b)Contamination by Petroleum Products
Contamination of water courses from accidental spill s of
hazardous materials,namely fuels and oils,is a major con-
cern.During construction of the trans-Alaska oil pipeline,
oil spills were a greater problem than anticipated.Most
spills occurred as a result of improperly maintained
machines,equipment repair,refueling,and vehicle acci-
dents.
Water pumping for dust control,gravel processing,dewater-
ing,and other purposes can also lead to petroleum contamin-
ation since water pumps are usually placed on the river or
lake bank.
A Spill Prevention Containment and Countermeasure Plan
(SPCC)will be developed and implemented prior to the start
of construction to minimize petroleum contamination prob-
lems,as required by law.
A more detailed discussion of petroleum contamination prob-
1ems as they relate to fi shery impacts are provi ded in
Chapter 3,Sections 2.3 and 2.4.3.
4.4 -Transmission Corridor
The transmission line consists of four segments:the Anchorage-Willow
line,the Fairbanks-Healy line,the Willow-Healy Intertie,and the Gold
Creek-Watana line.All Susitna transmission lines will be 345 kV.A
description of the segments is contained in Section 2.8.Route selec-
tion is discussed in detail in Chapter 10.
The Gold Creek-Watana segment is composed of two sections:Watana to
Devil Canyon and Devil Canyon to Gold Creek.Construction of the por-
t i on from the Watana dams ite to Devil Canyon will foll ow the same
centra 1 corri dor as the access road between Watana and Devil Canyon.
Hence,impacts to stream flows and water quality will be confined to
those streams discussed in Section 4.3.From Devil Canyon to the
E-2-176
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4.4 -Transmission Corridor
intertie at Gold Creek,the transmission corridor will parallel the
railroad extension from Gold Creek to Devil Canyon.This will help to
minimize impacts associated with vehicular construction access.
The Willow-Healy intertie is being built as a separate project and will
be completed in 1984 (Commonwealth Associates 1982).When Watana is
completed a second parallel line will be added to the Intertie.Also,
the existing 1 ine will be increased in voltage from 138 kV to 345 kV.
In 2002,when Devil Canyon comes online,a third parallel line will be
constructed from Gold Creek to Willow.The existing access points and
construction trails will be utilized to construct the additional lines.
Thus,the impacts of new const ruct i on wi 11 be mi nimi zed as a resu lt of
the previous construction.The Environmental Assessment Report for the
intertie (Commonwealth Associates 1982)discusses the expected environ-
mental impacts of transmission line construction in this segment.
For construction of the north (Fai rbanks-Healy)and south (Anchorage-
Willow)stubs,stream crossings will be required.The potential
effects wi 11 be of the same type as those previ ously di scussed in
Section 4.3 and in Chapter 2,Section 2.3.However,impacts should be
1ess than those caused by access road constructi on because of the
1 imited access necessary to construct a transmission 1 ine.Short-term
erosion related problems can be caused by stream crossings,vegetative
clearing,siting of transmission towers,locations and methods of
access and disturbances to the permafrost.With proper design and
construction practices,few erosion-related problems are anticipated.
Contamination of local waters from accidental spills of fuels and oils
is a second potential water quality impact.The Spill Containment and
Countermeasure Pl an (SPCC)to be developed and impl emented wi 11 mi ni-
mize the potential contamination of the watershed.
Once the transmission line has been built,there should be few impacts
associated with routine inspection and maintenance of towers and lines.
Some localized temporary sedimentation and turbidity problems could
occur when maintenance vehicles are required to cross streams to repair
damaged lines or towers.A thorough description of all transmission
corridors,their development and maintenance is presented in Exhibit A,
Sections 4 and 10.
E-2-177
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5 -AGENCY CONCERNS AND RECOMMENDATIONS
Throughout the past three years,all the appropriate State and Federal
resource agencies have been consulted.Numerous water quantity and
quality concerns were raised.The issues identified have been empha-
sized in this report.Some of the major topics include:
-Flow regimes during filling and operation;
-Mo rphol og ical stream chang es expected;
-Reservoir and downstream thermal regime;
-Winter ice regime;
Sediment and turbidity increases during construction;
-Sedimentation process and turbidity in the reservoirs and downstream;
-Dissolved oxygen levels in the reservoirs and downstream;
-Nitrogen supersaturation downstream from the dams;
-Trophic status of the reservoirs;
-Potenti al contaminati on from acc idental petrol eum spill sand 1eak-
age;
-Potential contamination from concrete wastewater;
-Wastewater discharge from the construction camps and villages;
-Downstream ground water impacts;and
-The effects on instream flow uses including navigation,transporta-
tion,and recreation.
A complete complement of the correspondence with the various agencies
is presented in Chapter 11.Incl uded are the comments received from
the agencies on the Draft Exhibit E submitted to them on November 15,
1982 for review and comment.
E-2-179
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6 -MITIGATION,ENHANCEMENT,AND PROTECTIVE MEASURES
6.1 -Introduction
Mitigation measures were developed to protect,maintain,and/or enhance
the water qual ity and quantity of the Susitna Ri ver.These measures
were developed primarily to avoid or minimize impacts to aquatic habi-
tats,although all instream flow needs were given consideration.
The first phase of the mitigation process identified water quality and
quantity impacts from construction,filling,and operation,and incor-
porated mitigative measures in the preconstruction planning,design,
and scheduling where feasible.Three key mitigation measures were
incorporated into the engineering design:(1)minimum flow require-
ments were selected to provide the fishery resources with adequate
flows and water levels for upstream migration,spawning,rearing,over-
wintering and out-migration while maintaining the economic viability of
the project;(2)multilevel intakes were added to improve downstream
temperature control;and (3)fixed-cone val ves were incorporated to
prevent excessive total dissolved gas supersaturation from occurring
more frequently than once in fifty years.
The second phase of the mitigation process will involve the implementa-
tion of environmentally sound construction practices during construc-
tion.This will involve the education of project personnel in the
proper techniques needed to minimize impacts to aquatic habitats.Mon-
itoring of construction practices will be required to identify and
correct problems.
Upon completion of construction,the third phase of mitigation will
consist of operational monitoring and surveillance to identify problems
and employ corrective measures as quickly and effectively as possible.
Mitigation planning,development,and refinement will continue through-
out the detail design,permitting and licensing,construction,and
operation and mai ntenance phases of the project.A design criteri a
manual and a construction procedures manual are currently being pre-
pared.In addition,a detailed erosion control plan and a Spill Pre-
vention Containment and Countermeasure Plan (SPCC)will be developed.
The mitigative,enhancement and protective measures presently proposed,
are highlighted in the following sections.In some cases,the reader
has been referred to other chapters,especially Chapter 3,for a thor-
ough discussion of proposed mitigation.
6.2 -Mitigation -Construction
Mitigation measures during construction will be necessary to mlnlmlZe
the potential of significant impacts occuring to the qual ity of the
adjacent water resources.
6.2 -Mitigation -Construction
Prior to construction,all permits and certificates required for dam
construction and instream work will be obtained including:
-COE Section 404 Permit;
-FAA 14 CFR 77.13;
ADNR 18AAC93.150.200;and
-ADF&G AS 16.05.870.
A 401 Water Quality Certification,pursuant to Section 401 of the
Federal Water Pollution Control Act,was filed with ADEC on December 9,
1982.A copy of the letter requesting this certification is attached
at the end of this section.
Compliance with the terms and conditions of the various permits,cer-
tifications and licenses will mitigate many of the project-related
impacts on water resources.
The more likely water quality impacts of Watana construction are:
siltation related problems associated with development of Borrow Areas
E and I,contami nat i on caused by concrete production waste products,
contamination by petroleum products,and construction,operation,and
maintenance of Support Facilities.Detailed discussion of additional
fishery oriented mitigative measures is contained in Chapter 3.
6.2.1 -Borrow Areas
Prior to develorxnent of the borrow areas,all necessary permits
for materi al removal wi 11 be obtai ned from the Bureau of Land
Management (BLM),Co rps of Engi neers,ADEC,ADNR,and the Cook
Inlet Region Incorporated (CIR!).The development of Borrow
Sites E and I has been identified as a major concern because of
their potential contributions to increased siltation and turbi-
dity in the immediate area and downstream.Mitigation of these
impacts primarily involves the methodology and scheduling of min-
ing activities and the construction and operation of settling
ponds.
Instream mlnlng of Borrow Sites E and I will be scheduled for the
summer (May -September)when high sediment and turbidity 1 evel s
in the Susitna River already exist.Mining will begin in Site I,
just upstream of the natural rock weir as shown in Figure
£.2.135.By developing this section first and the continuing
upstream into E,it is believed that the pool created behind the
wei r wi 11 serve as a settl ing pond for future upri ver i nstream
work,Additional geotechnical investigations will be completed
to confirm the stability of the rock formation for this purpose.
No instream activities will occur between October and May.
Stockpiling of borrow material and dry excavation "in bermed areas
will eliminate the need for winter instream gravel mining
activities.
E-2-182
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6.2 -Mitigation -Construction
The waste products from the gravel processing operation will be
redeposited into the excavated site in areas of low velocities to
avoid their entrainment in the river flow.Washwater resulting
from these operations will be discharged into bermed settl ing
ponds where suspended particles will be allowed to settle.
The processing plant for concrete aggregates and filters will
produce a limited amount of spoil.Potential impacts will be
controlled by running the wash water into a series of settling
ponds.Fi nes will be removed from the wash water by gravity or
as it filters through the existing granular soil berms before
reentering the river.It is estimated that 200-300,000 cy of
fine sand,and silt will be produced by this operation.These
fines will be disposed of within the excavation area to preclude
their entrainment in the river flow.
All waste water will be di scharged into recelVl ng waters in
accordance with ADEC permit requirements (AS46.03.100).
Upon completion of mining activities,most of the borrow sites
will be below the natural river level.Additional areas will be
inundated by the future Devil Canyon reservoi r.Selective spoil
disposal wi 11 provide a di versi fi edshorel i nee All upl and areas
will be rehabitated using the stockpiled organic layer and re-
quired erosion prevention activities will be employed.
Tsusena Creek and Bear Creek,if required,will be reconstructed
to allow natural fish movements to and from the river.Further
information on material removal and erosion control is discussed
in Chapter 3,Section 2.4.3.
6.2.2 -Contamination by Petroleum Products
A SPCC wi 11 be developed in accordance with 40 CFR 112.7 as re-
qui red by EPA.
All oil spills will be reported to the ADEC regardless of their
size as mandated in 18 AAC 70-080.
Section 2.4.3 (e)of Chapter 3 describes specific measures that
will be employed to minimize the potential contamination of sur-
face water and ground water from petroleum products.
6.2.3 -Concrete Contamination
The use of an effic ient central batch pl ant wi 11 reduce the po-
tential problems that could be caused by waste concrete and con-
crete wash water.Rejected concrete will be disposed of by haul-
age di rectly to an upl and disposal area or dumped,all owed to
harden and disposed fn an excavated area.
E-2-183
6.2 -Mitigation -Construction
Waste water from the washing of mlxlng and hauling equipment will
be processed and stored in a lined pond until its specific gravi-
ty drops to a point which allows its reuse as mixing water for
concrete batchi ng.Thi s system wi 11 mi nimi ze t he wastewater
effluent to be returned to the river systems.
At concrete placement areas,the wash water resulting from clean-
up of placing equipment,curing and green cutting will be col-
lected in sumps and pumped to settling ponds to remove the sus-
pended materials before the effluent is discharged into the
ri ver.Ponds will generally be unl ined with sand fi lters to
ensure removal of most waste products.Wastewater will be
neutralized to avoid elevated pH discharges.Control of toxic
chemicals in the effluent will be accomplished through careful
selection of concrete additives,the provision of filters for
the effluent,and the close monitoring of operations by the
Construct i on Manager.
All effluents will comply with ADEC and EPA effluent standards
(AS 46.03.100;18 AAC 70.020 and 18 AAC 72.010).
Airborne particulates win also be controlled with the use of a
modern central batchi ng pl ant.The pl ant will be fully enclosed
to facilitate winter operation requirements and the transfer of
materials will be via enclosed pipes.
6.2.4 -Support Facilities
(a)Water Supply
All required permits will be obtained and complied with.
Withdrawal of water for the construction camp and vill age
will meet ADF&G criteria for the protection of fisheries
resources.A water appropriation permit (AS 46.15;llAAC93)
will be obtaind from ADNR.
An application will be filed with ADEC for approval of the
proposed water supply system pl an as mandated by 18 AAC
80.100.
(b)Wastewater Treatment
As noted in Section 4.1.1 all the necessary wastewater and
waste disposal permits will be obtained,and compl ied with.
These include ADEC permits 18 AAC 72.060 and 18 AAC 72 and a
E-2-184
r-:--
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6.3 -Mitigation -Watana Impoundment Impacts
401 Water Qual ity Certification pursuant to Section 401 of
the Federal Water Pollution Control Act.
It is anticipated that compliance with all the necessary
permits and certificate(s)will include the mitigation of
any water quality impacts associated with the support
facilities.
6.2.5 -Others
Additional mitigation measures are contained in Chapter 3.
These measures include:stream crossings and encroachments
guidelines,erosion control plans,blasting guidelines,and
guidelines for clearing of vegetation.
6.3 -Mitigation -Watana Impoundment
The primary concerns during filling and operation of the reservoir,as
discussed in Section 4,include:
-Maintenance of minimum downstream flows for fishery resources and
other instream now needs.
Morphological changes to the river and adjoining tributary mouths;
-Changes in downstream sediment concentrations;
-Mai ntenance of an acceptable downstream thermal regime throughout the
year;
-Ice processes;
-Downstream gas supersaturation;
-Eutrophi cat ion processes and trophi c status;and
-Effects on ground water levels and ground water upwelling rates.
Downstream flows will be provided to minimize the impact f-Jl ling the
reservoir could have on downstream fishery resources and other instream
flow uses.Flow selection is discussed in Sections 3.4,3.6,and
4.1.2.Reducti on in salmon access to the sloughs has been i dent i fi ed
as a key impact to be mitigated.A flow of 12,000 cfs from August
through mid-September incom'bination with the fishery mitigation
measures discussed in Chapter 3,will provide access to the important
salmon spawning sloughs.
Mi nimum flows of 6000 cfs at Gol d Creek are proposed for May,June,
July,and late September.Navtgation problems are n,at anticipated
[-2-18:&
6.4 -Mitigation -Watana Operation
with these flows (see Section 2.6.3),however,there is a potential for
a slight increase in navigational difficulty in the vicinity of
Sherman.If this occurs,either the channel near Sherman will be
dredged to provide the minimum 1.5 foot depth required and the channel
will be marked,or the minimum flow will be increased to 6500 cfs.
Changes in mainstem river morphology between Devil Canyon and Talkeetna
will occur (see Section 4.1.2),but are not expected to be significant
enough to warrant mitigation except for the mouths of some tributaries
where selective reshaping and grading may be required to insure salmon
access.
During the first winter of filling the reservoir will cool to 4°C
(39.2°F).From then until the following August when the outlet facil-
ity will begin operating,the water temperature at the Watana low-level
outlet will be approximately 4°C to 5°C (39.2 to 41.0°F).Although
these temperatures will be moderated somewhat downstream,downstream
thermal impacts may occur.Although,no mitigation measures have been
incorporated to offset these below normal downstream temperatures,the
filling sequence is designed to fill the reservoir to an elevation
which will allow operation of the outlet facilities sometime during the
salmon spawning season.Thus,the impact of the reduced temperatures
can be minimized.
Eutrophication was determined not to be a problem and therefore no
mitigation is required.
6.4 -Mitigation -Watana Operation
The primary concerns during Watana operation are identical to those
identified for Watana fill ing.
6.4.1 -Flows
The operational flow selection process is discussed in Section
3.
From May through September,the mlnlmum downstream flows at Gold
Creek will be the same as those provided during reservoir f"ill-
ing.However,from October through April the flow at Gold Creek
will be increased from pre-::project natural f10ws to a m"inimum of
5000 cfs.The minimum flows were selected to provide a balance
between power generat i on and i nstream flow requi rements,parti-
cularly in the Devil Canyon to Talkeetna reach of the river.
To provide stable downstream flows Watana will be operated pri-
marily as a base-loaded plant until Devil Canyon is constructed.
Further discussion is presented in Section 4.1.3.
E-2-186
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6.4 -Mitigation -Watana Operation
6.4.2 -River Morphology
The mainstem Susitna River will remain stable between Watana and
Tal keetna.However,three streams crossed by the Al aska Ra il-
road,Skull Creek and two unnamed creeks at RM 127.3 and 110.1
could degrade from 3.6 to 7.0 feet (R&M 1982f).If this occurs
and bridge abutments are threatened,mitigation measures will be
taken to limit the scouring.
Because of the increased discharge during freezeup,the river
stage will be higher.Without mitigation,this will result in
increased flow through some of the sloughs which are currently
overtopped duri ng the freezeup process.The higher stage may
also cause flow through some sloughs which are presently not
overtopped in winter.To minimize the impact on important salmon
spawning sloughs,berms will be constructed at the heads of these
sloughs to prevent the sloughs from being overtopped during post-
project river freezeup.The spawning gravels in these sloughs
will be maintained ona 5-year rotating schedule.Further infor-
mation on this mitigation measure is contained in Chapter 3.
6.4.3 -Temperature
As noted in Section 4,the impoundment of the Watana reservoi r
will change the downstream temperature regime of the Susitna
River.To minimize the potential change,multilevel intakes have
been incorporated in the power pl ant intake structures so that
water can be drawn from various depths.By selectively withdraw-
ing water,an acceptable temperature for the downstream fishery
can be maintained at the powerhouse outlet and downstream
throughout the year.Using a reservoir temperature model,it was
possible to closely match existing Susitna River water tempera-
tures for most of the year.
6.4.4 -\Total Dissolved Gas Concentration
The avoidance of gas supersaturation will be achieved by the
inclusion of fixed-cone valves as the "normal"outlet facili-
ties.
By using the reservoir storage capacity coupled with the mlnlnlUm
summer powerhouse flow and the fixed-cone valve discharge,all
flow releases with a recurrence interval of up to 1:50 years will
be discharged with minimum potential for nitrogen supersatura-
tion.As previously described in Section 4.1.3,six 78-inch
(2 m)diameter valves with a design capacity of 4000 cfs each,
will be located approximately 125 feet (38 m)above normal tai 1-
water 1evel s.These val ves wi 11 discharge the fl ow as hi ghly
diffused jets to achieve significant energy dissipation without a
stilling basin or plunge pool.
E-2-187
6.6 -Mitigation -Devil Canyon Impoundment
Little literature and no precedent data were available regarding
the performance of fixed-cone valves in reducing or preventing
supersaturated discharges.As such,a theoretical assessment of
their anticipated performance was conducted based upon available
studies of the aeration efficiency of simil ar Howell-Bunger
valves (fixed-cone)and the physical and geometric characteris-
tics of diffused jets discharging freely into the atmosphere.
The results of the assessment indicated that no serious super-
saturation of nitrogen is likely to occur with flow releases
through the val ves.Estimated gas concentrations that would
occur as a result of a flow release are 101 percent at Watana and
102 percent at Devil Canyon.For releases of greater frequency
at less discharge,the concentrations are expected to be slightly
lower.
To support these conclusions,a field test of similar valves was
undertaken at the Lake Comanche Dam on the Mokelumne River in
California (Ecological Analysts 1982).The results of the tests
i ndi cate that the val ves prevented supersaturati on and,to a
1imited extent,may have reduced ex i st i ng nitrogen concentra-
tions.Flows of 4000 cfs with a dissolved nitrogen concentration
of 101 percent at the intake structure were passed through four
Howell-Bunger valves.Gas concentrations in the discharge were
97 percent.At 330 feet and 660 feet (l00 and 200 m)downstream,
concentrations were 95 and 97 percent,respectively.
6.5 -Mitigation -Devil Canyon Construction
Mitigation of the impacts of Devil Canyon construction activities w"il 1
be achieved using the same measures described for Watana.All the
appropriate permits and certi fications will be obta-j ned and adhered
to.
Borrow site development at Devil Canyon is not expected to cause signi-
ficant increases in suspended sediment loads and turbidities.Excava-
tion of Site G will be outside the river.Subsequently,it will be
completely inundated during Devil Canyon reservoir filling.Petroleum
product contamination will be minimized through the development and
implementation of a SPCC.Concrete wastes and wash water will be
handl ed in simi 1ar manners to those descri bed for Watana.All the
applicable water supply and wastewater treatment criteria will be main-
tained as specified in the appropriate permits.Fish and wildlife
mitigation measures are described in Chapter 3.
6.6 -Mitigation -Devil Canyon Impoundment
Other than the continuance of the downstream flows at Gold Creek
established during the operation of Watana,no additional mitigation
measures are planned during the Devil Canyon impoundment period.
E-2-188
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6.8 -Mitigation -Access Road and Transmission Line
6.7 -Mitigation -Devil Canyon/Watana Operation
6.7.1 -Flows
The downstream flow requirements at Gold Creek will be the same
as those used to govern Watana operating by itself.After Devil
Canyon is on line,Watana will be operated as a peaking plant.
The Watana tailrace will discharge directly into the Devil Canyon
reservoir thus,peaking at Watana w"ill have no downstream im-
pacts.The Devil Canyon reservoir will provide the flow regula-
tion required to stabilize the downstream flows.
The Devil Canyon power facilities will always be operated as a
base loaded plant.
6.7.2 -Temperature
Multilevel intakes similar to those at Watana have been incor-
porated into the Devil Canyon design.Only two intake levels
will be needed because of the limited drawdown at Devil Canyon.
6.7.3 -Total Dissolved Gas Concentration
Similar to Watana (Section 6.5.3),fixed-cone valves will be
utilized to minimize dissolved gas (nitrogen)supersaturation
downstream of the dam.
As discussed in Section 4.2.3(c),the Devil Canyon dam will
include seven valves at two levels with a total design capacity
of 38,500.cfs.Four 102-inch (2.6 m)diameter valves,each with
a capacity of 5800 cfs,will be located approximately 170 feet
(52 m)above normal tail water.Three more val ves,with diameters
of 90 inches (2.3 m)and respective capacities of 5100 cfs,will
be located approximately 50 feet (15 m)above normal tailwater
elevations.Operation of these valves is expected to result in a
maximum dissolved gas concentration of 102 percent for the 1:50
year flood event.
6.8 -Mitigation -Access Road and Transmission Lines
The mitigation plan to be used to minimize the impacts of construction,
operation,and maintenance of the access roads and transmission lines
is described in Chapter 3.
E-2-189
AlASKA POWER
AUTHORITY
SUSITNA
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FILE
Phone:(
(
DEC 10 1982
ALASKA POWER AUTHORITY
December 9,1982
Mr.Robert Martin
Regional Environmental Supervisor
Alaska Department of Environmental
Conservation
437 IIE II Street
Anchorage,Alaska'99501
Re:Section 401 Water Quality Certification
Susitna Hydroelectric Project
Dear Mr.Martin:
Federal Energy Regulatory Commission (FERC)regulations
(December,1982)pertaining to preparation of License Exhibit E fo
major unconstructed projects require that as an appendix,either:
/I{A)A copy of the water quality certificate (or agency statement
that such certification is waived)as described in Section 401 of the
Federal Water Pollution Control Act (Clean Water Act)[see U.S.C.134];
or
'34 WEST 5th AVENUE·ANCHORAGE,ALASKA 99501
r-,
!
(8)A copy of a dated letter from the applicant to the appropriate
agency requesting such certification./I
Please consider this letter as a request bi the Alaska Power
Authority to the Alaska Department of Environmental Conservation for a
Section 401 water quality certification.
Please keep us informed regarding any other requirements pursuant
to Section 401 certification.
.-
~CerelY·O
L-:---'\.d JJ
Eric P.Yould 'J\
Executive Director
cc:T.Arminski
,"J.Hayden'--Acres
J.Marx -Harza-Ebasco
..,..E-2-191
.~.I
-
.....~~&~[@~&~&~~&
·~EPT.OF ENVIRONMENTAL CONSERVATION
SOUTHCENTRAL REGIONAL OFFICE
r-
0
0
0
December 21,1982
"...
BILL SHEFFIELD,GOVERNOR
437 E.Street
SECOND FLOOR
ANCHORAGE,ALASKA 99501
(907)274-2533
P.D.BOX 515
KODIAK,ALASKA 99615
(907)486-3350
P.D.BOX 1207
SOLDOTNA.ALASKA 99669
(907)262-5210
P.O.BOX 1709
VALDEZ.ALASKA 99686
(907)835-4698
P.O.BOX 1064
WASILLA.ALASKA 99687
(907)376-5038
-
.....
I""';
18~LH
Mr.Eric Yould
Executive Director
Alaska Power Authority
334 West 5th Avenue
Anchorage,Alaska 99501
Subject:Susitna Hydroelectric Project
401 Water Quality Certificate
Dear Mr.Yould:
This letter is to confirm that our office has received your December 9,
1982 request for Section 401 certification of the Federal Energy Regula-
tory Commission (FERC)license f9r the subject project.
As you are aware,studies are still under way to evaluate the project's
potenti ali mpacts upon the envi ronment.These studi es and concl us ions
from others must be completed when your agency applies for the necessary
Corps of Engi neers constructi on permit (s).As thi s Department must a 1so
issue a 401 certificate for the Corps permit(s)and the above data,
necessary for project evaluation,will then be available,we will honor
your December 9,1982 request for 401 certification at that time.Thus,a
401 certificate will be issued of the Corps of Engineer permit(s)and
the FERC license at the same time.
If you have any questions concerning the above,please advise.
SinCerelY>~
~£~/0'h~»--;d:f--
Tim Rumfelt
Environmental eld Officer
TR/mr
B.EC~IVEQ
U~C 2 71982
E-2 -19 bu fjlYlEB AUlliORJJY
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....
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....
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and Water Level Data for the Susitna River at Devil Canyon.
Prepared for Acres American Incorporated •
Harrison,W.D.1981b.Susitna Hydroelectric Project,
Gl ac i er Studi es.Prepared for Acres Amer ican Incor porated.
•1981c.Susitna Hydroelectric Project t Hydrographic Surveys
---C'loseout Report:Surveys and Site Facilities.Final Draft.
Prepared for Acres American Incorporated.
1981d.Susitna Hydroelectric Project t Hydrology:Lower
Susitna Studies:Open Water Calculations.Preliminary Draft.
Prepared for Acres American Incorporated.
1981e.
1980-81.
Susitna Hydroelectric Project t Ice Observations
Prepared for Acres American Incorporated.
,~
I
1981f.Susitna Hydroelectric Project t Regional Flood Studies.
Prepared for Acres American Incorporated.
•1981g.Susitna Hydroelectric Project,River Mile Index.
---;::-Prepared for Acres Amer ican Incor porated.
1981h.Susitna Hydroelectric Project t Water Quality.
Annual Report 1980.Prepared for Acres American Incorporated.
E-2-199
1981i.Susitna Hydroelectric Project,Water Quality Annual
Report,1981.Prepared for Acres American Incorporated.
Harrison,W.D.1982a.Susitna Hydroelectric Project,1982
Susitna Basin Glacier Studies.Prepared for Acres American
Incorporated.
1982b.Susitna Hydroelectric Project,Hydraulic and Ice
Studies.Prepared for Acres American Incorporated.
•1982c.Susitna Hydroelectric Project,Reservoir------~Sedimentation.Prepared for Acres American Incorporated.
1982d.Susitna Hydroelectric Project,River Morphology.
Prepared for Acres American Incorporated.
1982e.Susitna Hydroelectric Project,Slough Hydrology
Interim Report.Prepared for Acres American Incorporated.
1982f.
Analysis.
Susitna Hydroelectric Project,Tributary Stability
Prepared for Acres American Incorporated.
1982g.Susitna Hydroelectric Project,Water Quality
Interpretation 1981.Prepared for Acres American Incorporated.
1982h.Susitna Hydroelectric Project,Winter 1981-1982 Ice
Observations Report.Prepared for Acres American Incorporated.
1982i.Eklutna Lake Data.Unpublished.
1982j.Susitna River Hydroelectric Project Data.
Un pub 1 i shed.
Raphael,J.M.1962.Prediction of Temperature in Rivers and
Reservoirs.Journal Power Division,Proc.American Society of
Civil Engineers,88 (P02).157-181.
Resource Management Associates.1983.Susitna Hydroelectric Project,
Sal inity Model.Prepared for Acres Jliiier;can Incorporated.
St.John et al.1976.The Limnology of Kamloops Lake.B.C.Depart-
ment of Env ironment.Vancouver,B.C.
Schmidt,D.1981.Summary of Key Findings of 1981 Dissolved Gas
Investigation of the Sus;tna River in the Dev;l Canyon Vicinity.
Unpublished report.
Schmidt,D.,ADF&G.October 1982.Personal communication.
Sittig,M.1981.Handbook of Toxic and Hazardous Chemicals.Noyes
Publications.Park Ridge,New Jersey.
E-2-200
Simons,D.B.and F.Senturk.1977.Sediment Transport Technology.
Water Resources Publ ications.Fort Coll ins,Colorado.465.
Stevens,M.A.and D.B.Simons.
Granular Material on Slopes.
(editor).River Hydraul ics.
1971.Stabil ity An alyses for Coarse
Chapter A.In:H.W.Shen
Volume 1.Fort Collins,Colorado.
-
.-
I
-
~
I
-
Symons,J.M.,S.R.Weibel and G.G.Robeck.1965.Impoundment
Influences on Water Quality.JAWWA.Volume 57.No.1.
1969.Water Qual ity Behavior in Reservoirs.U.S.Publ ic
Health Service,Bureau of Water Hygiene.Cincinnati,Ohio.
Terrestrial Environmental Specialists,Inc.1982.Susitna
Hydroelectric Project,Environmental Studies Land Use Analysis:
Navigational Use.Prepared for Acres American Incorporated.
Tetra Tech,Inc.1977.User1s Guide for the Estuary Hydrodynamic and
Water Quality Models.Donald T.Smith,Tetra Tech,Inc.Prepared
for U.S.Department of the Army Co rps of Eng in eers,Al aska
Di strict.
Texas Water Dev el opmen t Board.1970.A Compl et i on Report on
Stochastic Optimization and Simulation Techniques for Management
of Regional Water Resource Systems -Volume lIB -FILLIN - 1
Prog ram Desc ri pt ion.
Trihey,E.W.1981.Susitna Hydroelectric Project,Instream Flow
Assessment for the Proposed Susitna Hydroelectric Project:Issue
Identification and Baseline Data Analysis 1981 Study Plan.
Prepared for Acres American Incorporated.
•1982a.Preliminary Assessment of Access by Spawning Salmon to
--""'Side Slough Habitat Above Ta1keetna.Draft.Prepared for Acres
American Incorporated.
1982b.Susitna Hydroelectric Project,Instream Flow
Assessment for the Proposed Susitna Hydroelectric Project:Issue
Identification and Baseline Data Analysis 1981 Summary Report.
Prepared for Acres American Incorporated.
1982c.Susitna Intergravel Temperature Report.Draft.
AE I DC.
ADF&G.september 15,1982.Personal communication.
ADF&G.October 1982.Personal communication.
Turkheim,R.A.1975.Biophysical Impacts of Arctic Hydroelectric
Development.In:J.C.Day (editor).Impacts of Hydroelectric
Projects and Associated Developments on Arctic Renewable Resources
and the Inuit.UnlVersity of western O1tario,Ontario,Canada.
E-2-201
u.s.Army Corps of Engineers.1975.Program Description and User
Manual for Streamflow Synthesis and Reservoir Regulation SSARR).
U.S.Army Corps of Engineers,Nort Paclflc Dlvislon.Port and,
Oregon.
1979.Volume 3:Water Quality Knik Arm -Upper Cook Inlet.
U.S.Army Corps of Engineers,Alaska District.
1982.Bradley Lake Hydroelectric Project -Design Memorandum
No.2,Appendix E.
USFWS.1982.A Guide to Stream Habitat Analysis Using the Instream
Flow Incremental Methodology:Instream Flow Information Paper
No.12.Ken Bovee,Instream Flow and Aquatic Systems Group,
Western Energy and Land Use Team,USFWS.Fort Collins,Colorado.
U.S.Forest Service.1979.Roadway Drainage Guide for Install ing
Culverts to Accommodate Fish.Alaska Region Report No.42.U.S.
Department of Ag ricul ture,Al aska.
U.S.Geological Survey (USGS).1949-1964.Surface Water Records for
Alaska.
1965-1982.Water Resources Data for Alaska.
Vollenweider,R.A.1976.Advances in Defining Critical Loading
Level s for Phosphorous in Lake Eutroph"ication.Mem.1st.Ital,
Idrobio.No.33.
E-2-202
""iIICbo,
TABLE E.2.1:SUSITNA RIVER REACH DEFINITIONS
.....
-
~
I
-
-
.-
River Mi fe
RM 149 to 144
RM 144 to 139
RM 139 to 129.5
RM 129.5 to 119
RM 119 to 104
RM 104 to 95
RM 95 to 61
RM 61 to 42
RM 42 to 0
Source:R&M 1982d
Average
Slope
0.00195
0.00260
0.00210
0.00173
0.00153
0.00147
0.00105
0.00073
0.00030
Predomlnent Channel Pattern
Single channel confined by valley
walls.Frequent bedrock control
poInts.
Split channel confIned by val ley wall
and terraces.
Split channel confined occasionally by
terraces and val ley wal Is.Main chan-
nels,side channels and sloughs occupy
va IIey bottom.
Spilt channel with occasional tendency
to braid.Main channel frequently flows
against west valley wal I.Subchannels
and sloughs occupy east floodplain.
Single channel frequently Incised and
occasional Islands.
Transition from split channel to
bra i ded.Occas Iona'Iy bounded by
terraces.Braided through the con-
fluence with Chulitna and Talkeetna
Rivers.
BraIded with occasional confinement by
terraces.
Combined patterns;western floodplain
braided,eastern floodplain spl It
channe I.
Spl It channel with occasional tendency
to braid.Deltaic dIstributary channels
begin forming at about RM 20.
TABLE E.2.2:PERIODS OF RECORD FOR GAGING STATIONS
Station Name
USGS Gage
Number
Susltna
River Mi Ie
Drainage
2Area(ml )
Periods .of Record
Streamf low (Continuous)~-W~ter -Quallty2 Aqency
Susltna River nr.Denali I 15291000
Susltna River nr.Cantwel I
(Vee Canyon)I 15291560
Susltna River nr.Cantwell -
(Vee Canyon)
Susltna River nr.Watana Damslte'-
Susltna River at Gold Creek I 15292000
290.8
223.1
223.1
182.23
136.6
950
4,140
4,140
5,180
6,160
5/57-9/66,11/68-Present
5/61-9/72,5/80-Present
6/80-Present
8/49-Present
1957-66, 1968-69,1974-Present I USGS
(6/30/82)
1962-72,1980-Presentl7/27/82)I USGS
1980-81 I R&M
Consult.
I R&M10/80-12/81 Consult.
1949-58,1962,1967-68,1974-Present I USGS
(9/16/82)
Susltna River at Gold Creek . -
Susltna River at Sunshine 15292780
136.6
83.9
6,160
11,100 5/81-Present
1980-Present(10/14/82)I R&M
1971,1975,1977,1981-Present
(10/13/82)
Susltna River at Susltna Station
Maclaren River nr.Paxson
Chul itna River nr.Talkeetna
Talkeetna River nr.Talkeetna
Skwentna RIver nr.Skwentna
Yentna River nr.Susltna Station
Notes:
15294350
15291200
15292400
15291500
15294300
15294345
25.8
259.84
498.0
497.0
528.0
428.0
19,400
280
2,570
2,006
2,250
6,180
10/7 4-Present
6/58-Present
2/58-9/72,5/80-Present
6/64-Present
10/59-Present
10/80-Present
1955,1970,1975-Present(10/5/82)
1958-61, 1967-68,1975
1958-59,1967-72,1980-Present
(6/3/82)
1954,1966-Present(10/14/82)
1959, 1961,1967-68, 1974-75,
1980-81
1981-Present (8/11/82)
USGS
USGS
USGS
USGS
USGS
USGS
1.AI I streamflow gage stations are currently active,however,flow data Included in this document Is through September 1981.
2."Present"In periods of record Indicates station Is active as of January 1983.A dClte after "Present"Indicates the
most recent data available.
3.Watana continuous water quality monitor was Instal led at river mi Ie 183.0.
4.River ml Ie at tributary's confluence with Susltna River.
5.River ml Ie at Yentna-Susttna confluence.
Source:USGS and R&M
j l
TABLE E.2.3:USGS STREAMFLOW SUMMARY <cfsl
-
-
-
.....
Station Denali Cantwell Gold Creek Susitna Maclaren Ghu Iltna Talkeetna Skwentna
Yrs.of Record 22+12+32 7 23+16+17+22
Oct Max 2,165 5,472 8,212 58,640 734 8,062 4,438 7,254
Mean 1,187 3,236 5,757 35,694 421 4,916 2,562 4,492
Min 528 1 638 3.124 19,520 249 2.898 1 450 1.929
Nov Max 878 2,487 4,192 31,590 370 3,213 1,718 4,195
Mean 528 1,514 2,568 16,289 189 2,075 1,180 1,930
Min 290 780 1,215 9,933 95 1,480 765 678
Dec Max 575 1,658 3,264 14,690 246 2,100 1,103 2,871
Mean 344 1,053 1,793 9,794 127 1,494 836 1,320
Min 169 543 866 6.000 49 1 000 556 624
Jan Max 444 1,694 2,452 10,120 162 1,623 851 2,829
Mean 257 896 1,463 8,417 100 1,299 680 1,117
MIn 119 437 724 6,529 44 974 459 600
Feb Max 330 1,200 2,028 9,017 140 1,414 777 1,821
Mean 215 761 1,243 7,665 87 I,115 573 952
Min 81 426 723 5,614 42 820 401 600
Mar Max 290 1,200 1,900 8,906 121 1,300 743 1,352
Mean 195 711 1,123 6,842 78 988 512 839
MIn 42 429 713 5,368 41 738 380 600
Apr Max 415 1,223 2,650 12,030 145 1,600 1,038 2,138
Mean 232 883 1,377 8,350 87 1,176 603 1,110
Min 43 465 745 6,233 50 700 422 607
May Max 3,468 12,150 21,890 83,580 2,131 13,890 8,840 22,370
Mean 2,092 8,044 13,277 64,896 823 8,634 4,336 8,755
MIn 629 1 915 3,745 48,670 208 2,355 2,145 1,635
June Max 12,210 34,630 50,580 165,900 4,297 40,330 19,040 36,670
Mean 7,261 18,808 27,658 123,447 2,886 22,527 11,619 19,137
Min 4,647 9 909 15.500 90.930 1.751 17.390 5,207 10,650
July Max 12,110 22,790 34,400 181,400 4,649 35,570 15,410 28,620
Mean 9,600 17,431 24,383 141,300 3,216 27,047 10,974 17,811
Min 6,756 12,220 16,100 115,200 2,441 20 820 7,080 11,670
Aug Max 12,010 22,760 38,538 159,600 4,122 33,670 16,770 20,160
Mean 8,246 15,252 21,996 118,973 2,633 22,749 9,459 13,535
Min 3,919 6,597 8,879 91,360 974 11,300 3,787 7 471
Sept Max 5,452 12,910 21,240 91,200 2,439 22,260 10,610 13,090
Mean 3,300 7,971 13,175 71,239 1,138 11,544 5,369 8,156
Min 1,822 3,376 5 093 48,910 470 6 704 2,070 3,783
Note:Sunshine streamflow data were not Included due to the brief period of record
<approximately 1 yrl.
-Source:USGS
i~
-
-
TABLE E.2.4:FILLED STREAMFLOW SUMMARY (cfs)
station Denali Cantwell Watana Dev I I Canyon Gold Creek -S-unsh I ne Susltna Maclaren Chu Iltna Talkeetna Skwentna
Oct Max 2,165 5,472 6,458 7,518 8,212 18,555 58,640 734 9,314 4,438 7,254
Mean 1,165 3,149 4,513 5,312 5,757 13,906 31,102 418 5,040 2,720 4,329
Min 528 1.638 2.403 2.867 3,124 18,593 15,940 249 2.898 1,450 1.929
Nov Max 878 2,487 3,525 3,955 4,192 9,400 31,590 370 3,277 1,786 4,195
Mean 500 1,460 2,052 2,383 2,568 6,104 13,361 182 2,083 1,209 1,867
Min 192 780 1.021 1 146 1.215 3.978 6 606 95 1,236 765 678
Dec Max 575 1,658 2,259 2,905 3,264 6,137 15,081 246 2,143 1,239 2,871
Mean 315 951 1,405 1,652 1,793 4,249 8.426 117 1,487 846 1,295
Min 146 543 709 810 866 2.650 4,279 49 891 515 624
Jan Max 651 1,694 1,780 2,212 2,452 4,739 12,669 162 1,673 1,001 2,829
Mean 248 850 1,157 1,352 1,463 3,550 7,971 99 1,288 682 1,068
Min 85 437 619 687 724 2.218 5 032 44 974 459 600
Feb Max 422 1,200 1,560 1,836 2,028 4,057 11,532 140 1,414 805 1,821
Mean 206 706 979 1,147 1,243 3,009 7,117 81 1,092 568 911
Min 64 426 602 682 723 2.082 4,993 42 820 401 490
Mar Max 290 1,273 1,560 1,779 1,900 3,898 9,193 121 1,300 743 1,352
Mean 192 659 898 1,042 1,123 2,683 6,397 74 979 491 826
Min 42 408 569 664 713 2.013 4.910 36 738 379 522
Apr Max 415 1,702 1,965 2,405 2,650 5,109 12,030 145 1,600 1,038 2,138
Mean 231 835 1,113 1,282 1,377 3,257 7,242 86 1,194 573 1,088
Min 43 465 609 697 745 2,205 5,531 50 700 371 607
May Max 4,259 13,751 15,973 19,777 21,890 50,302 94,143 2,131 20,025 8,840 22,370
Mean 2,306 7,473 10,398 12,230 13,277 27,955 61,376 832 9,519 4,150 8,555
Min 629 1.915 2.857 3,428 3.745 8 645 29,809 208 2,355 1,694 1.635
June Max 12,210 34,630 42,842 47,816 50,580 110,073 176,219 4,297 40,330 19,045 40,356
Mean 7,532 17,567 22,913 25,938 27,658 63,810 123,830 2,888 22,892 11,416 18,462
Min 4.647 9.909 13.233 14.710 15.500 39 311 67,838 1,751 15,587 5,207 10,650
JUly Max 12,110 22,790 28,767 32,388 34,450 85,600 181,400 4,649 35,570 15,410 28,620
Mean 9,688 16,873 20,778 23,101 24,383 64,538 134,130 3,241 27,044 11,118 16,997
Min 6,756 12,220 14,844 15,651 16,100 45 267 102,121 2,441 20.820 7.080 11,670
-\l
1 1 J J ]1 )I -)-))1 J J
TABLE E.2.4 (Page 2)
Station Dena II Cantwell Watana Devil Canvon Gold Creek Sunshine Susitna Maclaren Chulitna Talkeetna Skwentna
Yrs.of Record
Aug Max 12,010 22,760 31,435 35,270 38,538 84,940 159,600 4,122 33,670 18,033 20,590
Mean 8,431 14,614 18,431 20,709 21,996 56,642 112,851 2,644 22,732 10,459 13,335
Min 3,919 6,597 7,772 8.484 8,879 24,656 62,368 974 11,300 3.787 7,471
Sep Max 6,955 12,910 17,206 19,799 21,240 53,703 104,218 2,439 23,260 10,610 13,371
Mean 3,334 7,969 10,670 12,276 13,175 32,169 66,790 1,167 11,956 6,084 8,371
Min 1,194 3,376 4,260 4.796 5.093 14.268 34 085 470 6.424 2.070 3,783
Ann Max 3,651 7,962 9,833 10,947 11,565 28,226 63,159 1,276 12,114 5,276 10,024
Mean 2,885 6,184 7,986 9,084 9,703 23,611 48,873 998 9,045 4,226 6,622
Min 2 127 4,159 4,712 .5,352 5,596 14 355 31,428 693 6,078 2,233 4.939
Notes:1.Based on 32 years of record.
2.Gold Creek data are not tilled since 32 years of record are avaIlable.
3.Sunshine discharge tor WY1980 and Oct-Apr WY1981 were computed from
Gold Creek,Talkeetna,and Chulitna discharges tor the same period.
TABLE Ee 2.5:MODIFIED STREAMFLOW SUMMARY
:station Watana Dev I I Canyon r.:;old Creek Sunshine Suslnta Station
Oct Max 6.458 7.518 8.212 18.555 58.640
Mean 4.523 5.324 5.770 13.966 31,426
MIn 2.403 2 867 3.124 9.416 18.026
Nov Max 3.525 3.955 4.192 9.400 31.590
Mean 2.059 2.391 2.577 6.028 13.501
MIn 1.021 1.146 1.215 3.978 6.799
Dec Max 2.259 2.905 3.264 6.139 15.081
Mean 1.415 1.665 1.807 4.267 8.518
Min 709 810 866 2,734 4.763
Jan Max 1.780 2.212 2.452 4.739 12.669
Mean 1.166 1.362 1.474 3.565 8.030
Min 636 757 824 2.507 6.071
Feb Max 1.560 1.836 2.028 4.057 11.532
Mean 983 1.153 1.249 2.999 7.149
Min 602 709 768 1.731 4.993
Mar Max 1.560 1.779 1.900 3.898 9.193
Mean 898 1.042 1.124 2.681 6.408
MIn 569 664 713 2.013 4.910
Apr Max 1.965 2.405 2.650 5.109 12.030
Mean 1.100 1.267 1.362 3.226 7,231
Min 609 697 745 2.205 5.531
May Max 15.973 19.777 21,890 50.302 94.143
Mean 10.355 12.190 13.240 27.949 61.646
Min 2.857 3.428 3.745 8.645 29 809
June Max 42.842 47.816 50.580 111.073 176.219
Mean 23.024 26.078 27.815 64.089 124.614
Min 13.233 14 710 15.530 39.311 67.838
July Max 28.767 32,388 34.400 85.600 181.400
Mean 20.810 23.152 24.445 64.641 134.550
Min 15.871 17.291 18.093 48.565 102.184
Aug Max 31.435 35.270 38.538 84.940 159.600
Mean 18.629 20.928 22.228 57.215 113.935
Min 13.412 15.257 16.220 42.118 80.252
Sep Max 17.206 19.799 21.240 53.703 104.218
Mean 10.792 12.414 13,321 32.499 67.530
Min 5.712 6.463 6.881 18 502 39.331
Annual Max 9.833 10.947 11.565 28.226 63.159
Mean 8.023 9.130 9.753 23.732 49.004
Min 6.100 6.800 7.200 17.951 36.285
Note:Based on 32 years of record.
OJ )-)J 1 t )1 --1 J -J J
TABLE E.2.6:WATANA PRE-PROJECT MONTHLY FLOW (CFS)MODIFIED HYDROLOGY
YEAR OCT NOV [IEC JAN FEB MAR APR MAY JUN JUL AUG SEP ANNUAL
1 4720.2084.1169.815.642.569.680.8656.16432.19193.16914.7320.6648.1
2 3299.1107.906.808.673.620.1302.11650.18518.19787.16478.17206.7733.7
3 4593.2170.1501.1275.841.735.804.4217.25773.22111.17356.11571.7776.7
4 6286.2757.1281.819.612.671.1382.15037.21470.17355.16682.11514.8035.2
5 4219.1600.1184.1088.803.638.943.11697.19477.16984.20421.9166.7400.4
6 3859.2051.1550.1388.1051.886.941.6718.24881.23788.23537.13448.8719.3
7 4102.1588.1039.817.755. 694.718.12953.27172.25831.19153.13194.9051.0
8 4208.2277 •1707.1373.1189.935.945.10176.25275.19949.17318.14841.8381.0
9 6035.2936.2259.1481.1042.974.1265.9958.22098.19753.18843.5979.7769.4
10 3668.1730.1115.1081.949.694.886.10141.18330.20493.23940.12467.8011.0
11 5166.2214.1672.1400.1139.961.1070.13044.13233.19506.19323.16086.7954.0
12 6049.2328.1973 •1780.1305.1331.1965.13638.22784.19840.19480.10146.8602.9
13 4638.2263.1760 •1609.1257.1177 •1457.11334.36017.23444.19887.12746.9832.9
14 5560.2509.1709.1309.1185.884.777.15299.20663.28767.21011.10800.9277.7
15 5187.1789.1195.852.782.575.609.3579.42842.20083.14048.7524.8262.7
16 4759.2368.1070.863.773.807.1232.10966.21213.23236.17394.16226.8451.5
17 5221.1565.1204.1060 •985.985.1338.7094.25940.16154. 17391.
9214.7374.4
18 3270.1202.1122.1102.1031.890.850.12556.24712.21987.26105.13673.9095.7
19 4019.1934.1704.1618.1560.1560 •1577 •12827.25704.22083.14148.7164.8032.2
20 3447.1567.1073.884.748.686.850.7942.17509.15871.14078.8150.6100.4
21 2403.1021.709.636.602.624.986.9536.14399.18410.16264.7224.6114.6
22 3768.2496.1687.1097.777.717.814.2857.27613.21126.27447.12189.8588.5
23 4979.2587.1957.1671. 1491.1366.1305.15973.27429.19820.17510.10956.8963.4
24 4301.1978.1247.1032.1000.874.914.7287.23859.16351.18017.8100.7112.0
25 3057.1355.932.786.690. 627.872.12889.14781.15972 •13524.9786.6313.7
26 3089.1474.1277 •1216.1110.1041.1211.11672.26689.23430.15127.13075.8402.7
27 5679.1601.876.758.743.691.1060.8939.19994.17015.18394.5712.6834.8
28 2974.1927.1688.1349.1203.1111.1203.8569.31353.19707.16807.10613.8232.6
29 5794.2645.1980.1578.1268.1257.1408.11232.17277 •18385.13412.7133.6992.2
30 3774.1945.1313.1137.1055.1101.1318.12369.22905.24912.16671.9097.8183.7
31 6150.3525.2032.1470.1233.1177 •1404.10140.23400.26740.18000.11 000.8907.9
32 6458.3297.1385.1147.971.889.1103.10406.17017.27840.31435.12026.9580.4
MAX 6458.3525.2259.1780.1560.1560.1965.15973.42842.28767.31435.17206.9832.9
MIN 2403.1021.709.636. 602.569.609.2857.13233.15871.13412.5712.6100.4
MEAN 4523.2059.1415.1166.983.898.1100.10355.23024.20810.18629.10792.8023.0
TABLE E.2.7:DEVIL CANYON PRE-PROJECT MONTHLY FLOW (CFS)MODIFIED HYDROLOGY
YEAR OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP ANNUAL
1 5758.2405.1343.951.736.670.802.10491.18469.21383.18821.7951.7537.8
2 3652.1231.1031.906.768.697.1505.13219.19979.21576.18530.19799.8615.9
3 5222.2539.1758.1484.943.828.879.4990.30014.24862.19647.13441.8918.0
4 7518.3233.1550. 1000.746.767.1532.17758.25231.19184.19207.13928.9356.4
5 5109.1921.1387.1224.930.729.1131.15286.23188.19154.24072 •11579.8866.9
6 4830.2507.1868.1649.1275.1024.1107.8390.28082. 26213.24960.13989.9707.4
7 4648.1789.1207.922.893.852.867.15979.31137.29212.22610.16496.10608.2
8 5235.2774.1987.1583. 1389. 1105.1109.12474.28415. 22110.19389.18029.9668.7
9 7435.3590.2905.1792. 1212.1086.1437.11849.24414.21763.21220.6989.8866.8
10 4403.2000.1371.1317.1179.878.1120.13901.21538.23390.28594.15330.9649.6
11 6061.2623.2012.1686.1340.1113.1218.14803.14710.21739.22066.18930.9084.4
12 7171.2760.2437.2212.1594.1639.2405.16031.27069. 22881.21164.12219.10021.3
13 5459.2544.1979.1796. 1413.1320.1613 •12141.40680.24991.22242.14767.10946.5
14 6308.2696.1896.1496.1387.958.811.17698.24094.32388.22721.11777 •10431.8
15 5998.2085.1387.978.900.664.697.4047.47816.21926.15586.8840.9250.7
16 5744.2645.1161.925.829.867.1314.12267.24110.26196.19789.18234.9555.5
17 6497.1908.1478. 1279. 1187.1187.1619.8734.30446.18536.20245.10844.8697.0
18 3844.1458.1365.1358.1268.1089.1054.14436.27796.25081.30293.15728.10460.4
19 4585.2204.1930.1851.1779.1779.1791.14982.29462.24871.16091.8226.9175.4
20 3976.1783.1237.1012.859.780.959.9154.19421.17291 •15500.9188.6800.1
21 2867.1146.810.757.709.722.1047.10722. 17119.21142.18653.8444.7063.9
22 4745.3082.2075.1319.944.867.986.3428.31031.22942.30316.13636.9657.2
23 5537.2912.2313.2036.1836.1660.1566.19777 •31930.21717.18654.11884.10199.0
24 4639.2155.1387.1140.1129.955.987.7896.26393.17572.19478.8726.7738.3
'}I:"3491.1463.997.843.746.690.949.15005.16767. 17790.15257.11370.7160.5<.,J
26 3507.1619.1487.1409. 1342.1272 •1457.14037.30303.26188.17032.15155.9606.6
27 7003.1853.1008.897.876.825.1261.11305.22814.18253.19298.6463.7705.5
28 3552.2392.2148.1657.1470.1361.1510.11212.35607.21741.18371.11916.9438.8
29 6936.3211.2371.1868.1525.1481.1597.11693.18417.20079.15327.8080.7765.1
30 4502.2324.1549.1304.1204.1165.1403.13334.24052.27463.19107.10172.9023.0
31 6900.3955.2279.1649.1383.1321.1575.11377.26255.30002.20196.12342.9994.5
32 7246.3699.1554.1287.1089.997.1238.11676.17741.31236.35270.12762.10577.9
MAX 7518.3955.2905.2212.1836.1779.2405.19777.47816.32388.35270.19799.10946.5
MIN 2867.1146.810.757.709.664.697.3428.14710.17291 •15257.6463.6800.1
MEAN 5324.2391.1664.1362.1152.1042.1267.12190.26078.23152.20928.12414.9129.7
1 ]e
I 1 -))1 1 )J I --1 ]1
TABLE E.2.8:GOLD CREEK PRE-PROJECT MONTHLY fLOW (CfS)MODIfIED HYDROLOGY
YEAR OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEF'ANNUAL
1 6335.2583.1439.1027.788.726.870.11510.19600.22600.19880.8301.8032.1
2 3848.
,
1300.1100.960.820.740.1617.14090.20790.22570.19670.21240.9106.0
3 5571.2744.1900.1600.1000.880.920.5419.32370.26390. 20920.14480.9552.1
4 8202.3497.1700.1100.820.820.1615.19270.27320.20200.20610.15270.10090.4
5 5604.2100.1500.1300.1000.780.1235.17280.25250.20360 •26100.12920.9681.6
6 5370.2760. 2045.1794.1400. 1100.1200.9319.29860.27560 •25750.14290.10256.4
7 4951.1900.1300.980.970.940.950.17660.33340.31090.24530.18330.11473.3
8 5806.3050.2142.1700.1500. 1200.1200.13750.30160 •23310.20540.19800.10384.1
9 8212.3954.3264.1965.1307.1148.1533.12900.25700.22880.22540.7550.9476.4
10 4811.2150.1513.1448.1307.980.1250.15990.23320.25000.31180.16920.10559.9
11 6558.2850.2200.1845.1452.1197.1300.15780.15530.22980.23590.20510.9712.3
12 7794.3000.2694.2452.1754. 1810.2650.17360.29450.24570.22100.13370.10809.3
13 5916.2700.2100.1900.1500.1400.1700.12590.43270.25850.23550.15890.11565.2
14 6723.2800.2000.1600.1500.1000.830.19030.26000.34400.23670.12320.11072.9
15 6449.2250.1494.1048.966.713.745.4307.50580.22950.16440.9571.9799.6
16 6291.2799.1211.960.860.900.1360.12990.25720.27840.21120.19350.10168.8
17 7205.2098.1631.1400.1300.1300. 1775.9645.32950.19860.21830.11750.9431.8
18 4163.1600.1500.1500.1400.1200. 1167.15480.29510.26800.32620.16870.11218.5
19 4900.2353.2055.1981.1900.1900.1910.16180.31550.26420.17170.8816.9810.6
20 4272 •1906.1330.1086.922.833.1022.9852.20523.18093.16322.9776.7200.1
21 3124.1215.866. 824.768.776.1080.11380.18630.22660.19980.9121.7591.2
22 5288.3407.2290.1442.1036.950.1082.3745.32930.23950.31910.14440.10251.0
23 5847.3093.2510.2239.2028.1823.1710.21890.34430.22770.19290.12400.10885.5
24 4826.2253.1465.1200.1200. 1000.1027.8235.27800.18250.20290.9074.8086.2
"}I:"3733.1523.1034.874.777.724.992.16180.17870.18800. 16220.12250.7631.0L.J
26 3739.1700. 1603.1516.1471.1400.1593.15350.32310.27720.18090.16310.10275.4
27 7739.1993.1081.974.950.900.1373.12620.24380.18940.19800.6881.8189.3
28 3874.2650.2403.1829.1618.1500. 1680.12680.37970.22870.19240.12640.10109.0
29 7571.3525.2589.2029.1668. 1605.1702.11950.19050.21020.16390.8607.8194.5
30 4907.2535.1681.1397.1286. 1200.1450.13870.24690.28880.20460 •10770.9489.3
31 7311.4192.2416.1748.1466 •1400.1670.12060 •29080.32660.20960 •13280.10747.7
32 7725.3986.1773. 1454.1236.1114. 1368.13317. 18143.32000.38538.13171.11255.3
MAX 8212.4192 •3264.2452.2028.1900.2650.21890.50580.34400.38538.21240.11565.2
MIN 3124.1215.866.824.768. 713.745."3"745.15530.18093.16220.6881.7200.1
MEAN 5771.2577 •1807.1474.1249.1124.1362.13240.27815.24445.22228.13321.9753.3
TABLE E.2.9:SUNSHINE PRE-PROJECT MONTHLY FLOW (CFS)MODIFIED HYDROLOGY
YEAR OCT NOV [IEC JAN FEB MAR APR MAY JUN JUL AUG SEP ANNUAL
1 14003.5639.3611.2748.2276.2033.2311.22418.45613.59179.54849.27734.20347.1
'I 12226.4712.3804.2930.2435.2144.3563.42196.58872 •69474.58356.51069.26136.1""3 13713.5702.3782.3470.2511.2282.2357.11258.68738.64937.53363.32057.22117.5
4 17394.7199.4080.2818.2343.2317.4292.50302.64075.54231.49954.33737.24544.3
5 13227.5092.3977 •3667.2889.2423.3204.32595.54805.53386.57701.28376.21921.8
6 12188.6340.4313.3927.3189.2577 •2658.21758.69686.70894.77692.35385.26041.6
7 11011.4367.3161.2612.2286.2209.2244.33157.73941.80569.69034.44495.27588.4
8 15252.7029.4907.4006.3471.2844.2907.34140.79153.62302.53243.48121.26550.7
9 18399.9032.6139.4067.2996.2643.3399.27759.60752.59850.56902.20098.22824.2
10 11578.5331.3592.3387.3059.2280.2895.29460 •64286.67521.71948.36915.25345.8
11 15131.6415.4823.4059.3201.2675.2928.34802.39311.58224.55315.43086.22651.3
12 16996.6109.5504.4739.3478.3480.5109.32438.60886.63640.60616.36071.25075.2
13 14579.6657.4820.4222.3342.2975.3581.24520.87537.67756.61181.38711.26766.6
14 13956.6052.4690.4074.3621.2399.2025.35245.56629.78219.52938.29182.24260.8
15 18555.5907.3533.2797.2447. 2013.2381.8645.111 073.58836.46374.23267.23864.9
16 15473.7472 •4536.3373.2962.2818.3435.24597.58488.65042.56375.53703.24971.3
17 18208.5321.3965.3404.3009.2875.3598.16479.69569.55243.62007.30156.22934.7
18 11551.4295.3856.3698.3294.2793.2639.32912.66162.77125.82747.37379.27566 .1
19 10706.5413.4563.4181.3986.3898.4359.36961.76770.69735.46730.20885.24149.1
20 10524.4481.3228.2689.1731.2022.2442.21306.49349.48565.42970.24832.17950.7
21 9416.3978.2848.2600.2448.2382.3150.25687.47602.60771.54926.27191.20393.7
'1'1 12264.7467.4930.3325.2514.2351.2640.10652.76208.64787.74519.32402.24629.0""""23 14313.6745.4922.4257.3801.3335.3210.36180.66856.62292.51254.34156.24407.1
24 13588.6018.4030.3312.2984.2646.2821.18215.59933.51711.51085.25238.20235.8
25 11284.4699.3524.2882.2519.2220.2916.31486.43713.51267.43222.29114.19195.1
26 12302.4938.3777.3546.2990.2810.3160.29380.72836.75692 •51678.35567.25023.2
27 15565.4238.2734. 2507.2355.2281.3294.22875.56366.55506.52155.18502.20000.7
28 10620.•5888.5285.4231.3640.3171.3537.27292 •87773.62194.55157.32719.25221.6
'10 17399.7130.5313.4213.3227.3002.3542.22707.48044.57930.42118.22742.19910.2'-I
30 11223.5648.4308.3674.3206.2963.3704.33876.59849.71774.48897.26790.23144.3
31 17688.9400.5189.4218.3699.3519.4627.26907.65084.84273.50624.27835.25416.2
32 16580.8195.4805.4433.4057.3412.4292.36160.50890.85600.84940.32460.28226.1
MAX 18555.9400.6139.4739.4057.3898.5109.50302.111 073.85600.84940.53703.28226.1
MIN 9416.3978.2734.2507.1731.2013.2025.8645.39311.48565.42118.18502.17950.7
MEAN 13966.6028.4267.3565.2999.2681.3226.27949.64089.64641.57215.32499.23731.6
J J }1 )}1 1 1 J 1 )J 1 J J J
TABLE E.2.10:SUSITNA PRE-PROJECT MONTHLY FLOW (CFS)MODIFIED HYDROLOGY
YEAR OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP ANNUAL
1 26869.11367.6197.6072.5256.5377.5657.66294.101616. 124890.106432.39331.42444.7
')18026.6933.5981.7074.7295.6382.7354.59273.82255.123164.100947.73471.41783.1
L
3 31053.16364.6989.8274.7036.5853.5985.45294.132547.137322.116186.82076.49825.4
4 44952.16289.9746.8069.6775.6350.7993.88840.130561.125949.97610.44168.49279.5
5 20169.11829.5272.7202.4993.4980.6306.58516.108881. 116732.128587.66275.45270.4
6 23896.9168.6183.7255.5845.5316.6412.58164.169045.148877.120120.53504.51429.1
7 19923.10522.7295.6179.6831.6324.7182.82486.161346.168815.131620. 104218.
59701.9
8 41822.21548.14146.10600.8356.7353.7705.63204.176219.140318.124813.87825.58911.9
9 52636.19887.10635.7553.6387.6679.8099.70321.112897. 122280.
99609.53053.47830.1
10 30543.9528.4763.7795.6564.5666.6468.56601.110602.146217.138334.67904.49606.5
11 25754.10165.7005.6716.6310.5651.5830.50062.84134.129403.113972.81565.44172.5
12 33782.12914.13768.12669. 10034.
9193.9803.85457.151715.138969.116697.62504.55111.2
13 29029.13043.8977 •9050.6183.5951.6635.54554.163049.143441.121221.74806.53254.8
14 27716.10755.8865.8671.7854.6058.5565.53903.85648.146420.106707.70782.45235.4
15 37846.11702.5626.6351.5762.4910.5531.35536.153126.124806.92280.46110.44338.1
16 28747.10458.6127.6952.6196.6170.7120.49485.110075.138407.111846.89944.47893.5
17 36553.12313.9159.8031.7489.7091.8048.52311.125183.117607.118729.63887.47470.1
18 26396.12963.8322.8029.7726.6683.7281.58107.134881.136306.137318.89527.53073.6
19 37725.15873 •15081.11604.11532.8772.8763.94143.137867. 130514.
86875.42385.50399.0
20 26323.11086.7195.6924.6164.5535.6112.52954.108336.115548.97076.57772.41999.8
21 22683..6799.5016.6074.5581.5732 •5769.53036.94612.132985.117728.80585.45014.0
22 32817.16607.8633.6509.6254.5883.5788.29809.122258.139183.133310.69021.48289.9
23 32763.14922 •8791.9380.8458.6646. 6895.
74062.176024.142787.107597.60220.54305.3
24 26782.14853.8147.7609. 7477.6313.7688.64534.122797.123362.107261.45227.45453.5
25 20976.10113.6081.7402.6747.6294.6963.61458.67838.102184.80252.56124.36285.1
26 19520.10400.9419.8597.7804.7048.6867.47540.128800.135700.91360.77740.46102.6
27 31550.9933.6000.6529.5614.5368.7253.70460.107000. 115200.
99650.48910.43089.2
28 30140.18270.13100.10100.8911.6774.6233.56180.165900.143900.125500.83810.55979.3
29 38230.12630.7529.6974.6771.6590.7033.48670.90930.117600.·102100.55500.42002.4
30 36810.15000.9306.8823.7946.7032.8683.81260.119900.142500.128200.74340.53676.8
31 58640.31590.14690.10120.9017.8906.12030.66580.142900.181400.126400.91200.63158.6
32 34970.16200.8516.7774.7589.6177 •10350.83580.108700.152800.159600.67170.55728.8
MAX 58640.31590.15081.12669.11532.9193.12030.94143.176219.181400.159600.104218.63158.6
MIN 18026.6799.4763.6072.4993.4910.5531.29809.67838.102184.80252.39331.36285.1
MEAN 31426.13501.8517.8030.7149.6408.7231.61646.124614. 134550.113935.67530.49003.6
TABLE E.2.11:INSTANTANEOUS PEAK FLOWS OF RECORD
Dena It Cantwell Gold Creek Maclaren
Date Flows Ccfs)Date Flow Ccfs)Date Flow (cfs)Date Flow (cfs)
8/10/71 38,200 8/10/71 55,0002 6/7/64 90,700 8/11/71 9,260
8/14-15/67 28,200 6/8/64 51,200 8/10/71 87,400 9/13/60 8,920
7/28/80 24,300 6/15/623 46,800 6/17/72 82,600 8/14/67 7,460
8/4/76 22,100 6/17/72 44,700 6/15/62 80,600 7/18/63 7,300
8/9-10/81 22,000 1 8/14/67 38,800 8/15/67 80,200 6/16/72 7,070
7/12/75 21,700 7/18/63 32,0004 6/6/66 63,600 6/14/62 6,540
7/27/68 19,000 8/14/81 30.5001 8/25/59 62.300 8/5/61 6 540
Notes:~MaxImum dalty flow from prelIminary USGS data.
3 Estimated maximum dally flow based on discharge records at Denali and Gold Creek.
4 ApproxImate date.
Maximum dally flow.
Source:USGS
TABLE E.2.12:DISTRIBUTION STATISl
L NG b I 1ume 00 orma
Sum of Mean Sum of Mean
Gaoe Station River N CS CK Deviations Deviation CSL CKL Deviations Deviation
Dena Ii Susitna 20 2.4985 10.3480 -49.50 12.95 1.8453 7.0725 -33.19*11.21
Cantwe I I Susitna 11 0.3325 3.1348 -0.90*6.46 -0.1474 3.2888 1.15 5.85*
Gold Creek Susitna 25 0.6830 2.9269 -22.90 5.16 0.0664*2.8362 -10.28 4.23
Maclaren Maclaren
22 0.9062 3.4430 -15.76 7.16 0.5539 2.6682*-8.75 6.14
Chu I itna Chulitna 18 2.9054 13.7449 -33.82 10.15 2.0599 10.0328 -23.88*10.58
Talkeetna Talkeetna 15 1.8140 6.6111 -1.99 8.16 1.0398 4.7599 5.88 8.80
Notes:N
CS
CK
CSL
CKL
CSLA
CKLA
record length in years
coefficient of skewness of
coefficient of kurtosis of
coefficIent of skewness of
coefficient of kurtosis of=coefficient of skewness of
=coefficient of kurtosis of
natural data
natural data
the natura I logs of
the natura I logs of
the natura I logs of
the natura I logs of
the data
the data
the transformed
the transformed
data
data
Avg.CV =average coetfi
Sum of Deviations =<Q
Mean Deviation =~I Q-
Q =measured flow90=mean flow
*=Distribution best fi
Theoretical Values -
Gumbel 1 Loq Norma
CS 1.14
CK =5.4
CSL =0.0
CKL =3.0
Source:R&M 1981f
-
"ICS FOR ANNUAL INSTANTEOUS PEAK FLOWS
Log Pearson Type III
3 Parameter Loq Normal Loq Person Type III (Moments)(Maximum Likelihood)
Avg.Sum of Mean Avg.Sum of Mean Avg.Sum of Mean
CSLA CKLA CV Deviations Deviation CV Oeviations Deviation CV Deviations DevIation
0.0633*4.2263*23.59*38.16 8.39*35.46 -38.81 8.39*No Solution
-0.1172*3.2667*18.79*1.32 6.01 19.01 1.92 6.21 Upper Boundary is Too Low
-0.0805 2.9658*15.01*-18.09*4.11*15.39 -19.01 3.97 15.51 -20.67 5.38
-0.3915*2.6563 25.66 8.93 3.99*15.93*-8.18*4.90 No So I ut,i on
0.3512*6.8509*14.05 -27.36 9.21*Lower Boundary is Too High 12.85*-29.93 9.45
;"0.0921*4.0752*30.54*-0.74*5.27 40.08 -3.38 5.65 32.65 -5.43 1.92*
cient of variation for al I return periods estimated
-qo/Oo for 1.25,2,5,10,and 20 year return periods00I15for1.25,2,5,10 and 20 year return periods
tting a given parameter
3 Parameter Log Normal
CSLA 0.0
CKLA =3.0
-.
TABLE E.2.13:COMPARISON OF SUSITNA REGIONAL FLOOD PEAK ESTIMATES
WITH USGS METHODS FOR GOLD CREEK
-
Single 1 USGS 2
Susftna Area II
Return Station Regional Regional
Station Location Period Estimate Estimate EstImate
(Yrs.)(cfs)(cfs) (cfs)
Susitna River at Gold Creek 1.25 37,100 37,700 48,700
2 49,500 49,000 59,200
5 67,000 64,200 73,000
10 79,000 74,500 83,400
50 106,000 100,000 104,000
100 118,000 110,000 115,000
Notes:
3USGS
Cook Inlet
Regional
Estimate
(cfs)
43,800
53,400
55,300
71,600
-
-
I~-
-
1 Based on three parameter log normal distribution and shown to three significant
figures.
2 Lamke,R.D.,1970.Flood Characteristics of Alaskan Streams,USGS,Water
Resources Investigation,78-129.
3 Freethey,G.W.,and D.R.Scully,1980.Water Resources of the Cook Inlet BasIn,
Alaska,USGS,Hydrological Investigations Atlas HA-620.
Source:R&M 1981f
TABLE E.2.14:HEC 2 WATER SURFACE ELEVATIONS (feet)
Deadman Creek to Devi I Creek for Select Watana Flows
River Mi Ie 8100 cfs 17200 cfs 26700 cfs 30700 cfs 42200 cfs 46400 cfs
162.1 1211.2 1213.5 1215.7 1216.5 1218.4 1219.3
167.0 1276.3 1278.7 1279.9 1280.6 1281.4 1281.3
173.1 1330.8 1333.0 1334.9 1335.7 1337.3 1337.9
174.0 1340.0 1342.8 1344.2 1345.0 1346.0 1346.2
176.0 1363.9 1366.5 1367.9 1368.5 1369.5 1369.8
176.7 1370.8 1373.5 1375.1 1375.9 1377.3 1377.6
178.8 1391.6 1394.3 1396.3 1397.2 1398.8 1399.2
180.1 1410.6 1412.1 1412.9 1413.4 1414.2 1414.6
181.0 1414.4 1416.5 1417 .8 1418.3 1419.2 1419.4
181.8 1428.8 1432.0 1434.2 1435.1 1436.6 1436.8
182.1 1435.3 1437.9 1439.8 1440.7 1442.4 1442.8
182.5 1440.7 1442.4 1443.8 1444.5 1445.7 1446.0
182.8 1443.7 1445.6 1446.8 1447.4 1448.3 1448.5
183.5 1449.8 1452.2 1453.8 1454.5 1455.7 1456.0
183.8 1451.6 1454.1 1455.8 1456.5 1457.8 1458.0
184.0 1453.5 1456.3 1458.1 1458.9 1460.3 1460.6
184.2 1454.6 1457.5 1459.4 1460.2 1461.6 1461.8
184.4 1456.2 1459.3 1461.3 1462.3 1464.0 1464.4
184.8 1462.9 1465.9 1467.4 1468.1 1469.1 1469.2
185.4 1473.0 1475.8 1477.4 1478.1 1479.4 1479.7
185.9 1497.3 1497.9 1498.3 1498.5 1498.3 1499.0
186.5 1505.3 1509.0 1510.9 1511.6 1513.5 1513.1
186.8 1510.1 1513.0 1515.0 1515.9 1517.8 1518.2
Source:R&M 1982b
TABLE E.2.15:HEC 2 WATER SURFACE ELEVATIONS (feet)
Devil Canyon to Talkeetna for Select Gold Creek Flows
....
River Mi Ie 9700 cfs 13400 cfs 17000 cfs 23400 cfs 34500 cfs 52000 cfs
98.6 344.0 344.5 345.5 346.5 348.0 348.5
99.6 348.6 350.1 350.8 352.3 353.1 355.1
100.4 359.2 359.4 359.7 359.9 360.7 362.0
101.0 362.7 363.4 363.8 364.5 365.3 366.8
101.5 366.6 367.2 367.6 368.4 369.2 370.8
102.4 373.0 373.9 374.5 375.6 376.7 378.4-103.2 378.1 379.4 380.3 381.8 383.4 386.2
104.8 391.5 392.5 393.2 394.2 395.5 397.8
106.7 409.9 410.6 411.2 412.0 413.1 415.1
108.4 421.6 422.8 423.6 424.8 426.4 429.2-110.4 437.6 438.8 439.6 440.8 442.6 445.9
110.9 443.8 444.7 445.4 446.3 447.8 450.6
111.8 452.5 453.2 453.8 454.8 455.7 458.0
112.3 455.7 456.6 457.2 458.3 459.4 461.6
112.7 459.4 460.1 460.5 461.4 462.3 464.0
~113.0 461.3 462.1 462.7 463.8 464.9 466.6
116.4 485.6 486.6 487.4 489.0 490.7 493.5
117.2 495.5 496.2 496.7 497.8 499.0 501.1
119.2 510.0 511.2 512.0 513.4 514.9 516.5
~119.3 511.6 512.5 513.3 514.5 515.9 517.5
120.3 520.0 520.4 520.8 521.8 522.6 524.5
120.7 521.7 522.6 523.3 524.3 525.4 527.2
121.6 530.6 530.9 531.1 532.7 533.4 534.8
122.6 538.5 539.4 539.9 541.5 542.8 544.6-123.3 542.9 543.7 544.4 545.7 547.1 549.4
124.4 555.2 555.8 556.3 557.1 558.2 560.1
126.1 571.0 571.7 572.3 573.3 574.2 575.8
127.5 585.3 585.9 586.4 587.3 588.1 589.4....128.7 595.0 595.9 596.5 597.6 598.4 599.7
129.7 605.2 606.0 606.7 607.8 608.9 610.8
130.1 612.9 613.7 614.1 614.2 615.0 616.1
130.5 616.0 616.9 617 .4 618.0 619.0 620.4
130.9 617.7 618.7 619.4 620.3 621.6 623.3
~131.2 619.5 620.5 621.3 622.7 624.2 626.6
131.8 627.1 627.6 628.0 628.9 629.4 630.4
132.9 639.0 639.9 640.6 641.8 643.4 645.6
133.3 645.8 646.3 646.6 647.5 648.2 649.7
134.3 655.1 655.9 656.5 657.5 658.6 660.4
134.7 659.9 660.6 661.2 662.3 663.6 665.7
135.4 668.9 669.4 669.8 670.4 671.1 672.4
135.7 671.2 672.1 672.7 674.1 675.4 677 •.1
136.4 681.2 682.2 683.0 684.1 685.3 687.3
136.7 684.0 685.1 685.8 687.0 688.1 689.9
137.0 687.1 688.2 688.9 690.5 692.0 694.9
137.2 690.6 691.6 692.3 693.2 694.6 697.0
137.4 693.1 694.1 694.9 ·695.7 697.2 699.5
138.2 702.0 702.9 703.6 704.5 705.4 706.9
138.5 703.7 704.7 705.5 706.7 707.8 709.7
138.9 707.2 708.1 708.9 710.3 711.7 714.3
139.4 716.8 717.4 717 .8 718.3 719.1 720.7
140.2 723.6 724.5 725.2 726.3 727.3 728.9
140.8 733.2 734.1 734.8 736.0 737.4 739.9
141.5 744.0 744.8 745.4 746.2 747.2 749.0
142.1 752.2 753.2 753.9 755.4 756.7 758.7
142.3 754.4 755.3 756.1 757.6 759.0 761.3
143.2 763.9 764.7 765.2 766.2 767.5 769.9
144.8 786.0 787.1 788.0 789.4 790.9 793.3
147.6 818.8 819.9 820.7 822.1 823.8 827.0
148.7 832.9 834.3 835.3 836.6 838.6 841.7
148.9 835.1 836.4 837.5 838.8 840.9 844.2
149.2 837.5 838.8 839.8 841.1 843.1 846.5
149.3 839.6 840.9 841.9 843.3 845.3 848.9
149.4 841.5 842.6 843.5 844.7 846.9 850.5
149.5 844.3 845.1 845.8 846.8 848.4 851.3-149.8 848.4 849.4 850.1 851.1 852.4 854.6
150.2 850.6 851.9 852.8 854.0 855.8 858.7
Source:R&M 1982b
TABLE E.2.16:DETECTION LIMITS AND CRITERIA FOR WATER QUALITY PARAMETERS
Parameters(1)
Temperature,°C
Total Suspended Sediments(2)
Turbidity (NTU)
Dissolved Oxygen
D.O.Percent SaturatIon
Nitrate Nitrogen
Total Phosphorus
Ortho-Phosphate
Total Dissolved Sol Ids(3)
Conductivity,umhos/cm @ 25°C
SignifIcant Ions
Sulfate
Chloride
Ca,Calcium
Mg,Magnesium
Na,Sodium
K,PotassIum
Tota I Hardness
pH,pH Un Its
Total Alkalinity,as CaC03
Free Carbon Dioxide
Chemical Oxygen Demand
Total OrganIc Carbon
True Color,Platlnum Cobalt Units
Metals
Ag,SII ver
AI,AI um I n um
As,Arsenic
Au,Gold
B,Boron
Ba,Barium
8 i,81 smuth
Cd,Cadmi um
Co,Coba It
Cr,Chromium
Cu,Copper
Fe,Iron
Hg,Mercury
Mn,Manganese
Mo,Molybdenum
Ni,Nickel
Pb,Lead
pt,PIat In um
Sb,Antimony
Se,Selenium
S i,Si I icon
Sn,TIn
Sr,Stront i urn
TI,Titanium
W,Tungsten
V,Vanadium
Zn,Zinc
Zr,Zirconium
Organic Chemicals (ug/l)
-Endrln
-lindane
-Methoxych lor
-Toxaphene
-2,4-0
-2,4,5-TP Si Ivex
Gross Alpha (Picocurle/I iter)
R&M
Detection
limIt
0.1
1
0.05
0.1
1
0.1
0.01
0.01
1
1
1
0.2
0.05
0.05
0.05
0.05
1
+0.01
-2
1
1
1.0
1
0.05
0.05
0.10
0.05
G.05
0.05
0.05
0.01
0.05
0.05
0.05
0.05
O.1
0.05
0.05
0.05
0.05
0.05
0.10
0.10
0.05
0.10
0.05
0.05
1.0
0.05
0.05
0.05
0.0002
0.004
O.1
0.005
O.1
0.01
3
USGS
Detection
Llmlt(4)
0.01
0.01
0.01
1
0.05
0.01
0.01
0.1
O.1
0.1
0.001
0.01
0.001
0.01
0.1
0.001
0.001
0.001
0.001
0.01
0.0001
0.001
0.001
0.001
0.001
0.001
0.001
0.1
0.01
0.01
0.00001
0.00001
0.00001
0.001
0.00001
0.00001
Criteria
Levels
20,15(M),13(Sp)
no measurable
Increase
25 NTU Increase
7 and 17
110
10
0.01
1,500
200
200
6.5 -9.0
20
3.0 (S)
50
0.05
0.073 (S)
0.440
0.043
1.0
0.0035 (S)
0.0012,0.0004
o.1
0.01
1.0
0.00005
0.05
0.07
0.025
0.03
9
0.01
0.007 (S)
0.03
0.004
0.01
0.03
0.013
100
10
15
-
-.
I~
-
I"""
I
TABLE E.2.16 (Cont'd)
Rlllo1 USGS
DetectIon Detection Criteria
Parameters ( 1)limit Limlt(4)Levels
Others
Settleable Solids,mIll 0.1
Ammonia Nitrogen 0.05 0.01 0.02
Organic Nitrogen 0.1
Kheldahl Nitrogen 0.1 0.1
Nitrite Nitrogen 0.01 0.01
Total Nitrogen 0.1 0.01
Total I norgan Ic Carbon 1.0
(I)AI I parameters and values are expressed in mg/l unless otherwise noted.
(2)
TSS -(nonfi Iterable)material on a standard fiber f liter after filtration of a
well-mlxed sample.
(3)
TDS -(filterable)material that passes through a standard glass fiber filter
and remains after evaporation.
(4)
USGS detection limits are taken from "1982 Water Quality Laboratory Services Catalog"
USGS Open-Fi Ie Report 81-1016.The limits used are the limits for the most precise
test available.
(M)-Migration Routes
(Sp)-Spawning Areas
(S)-Suggested Criteria
Source:USGS and RM
TABLE E.2.17:PARAMETERS EXCEEDING CRITERIA BY STATION AND SEASON
Parameter Station Season Criteria
D.O.%Saturation G S L
Phosphorus,Total (d)V,G,T,S,SS S,101,B E
pH T S L
V,S 101
G,T B
Total Organic Carbon G,SS S S
V,G,SS W
SS B
True Color V,G,T,S S L
AI uml num (d)V,G S,101 S
Aluminum (t)G,T,S 5 S
Bismuth (d)V,G 5 S
G W
Cadm1 um (d)G,T,SS S E
Cadmi um (t)G,T,S,SS S E
T,SS 1'1
Copper (d)SS S A
T W
T,SS B
Copper (t)G,T,S,SS S A
T,SS 1'1,B
Iron (tl G,T,S.SS S E
T,SS B
Lead (tl G,T,S,SS S A
SS B
Manganese (d)G,S E
Manganese (tl G,T,S,SS S E
T,SS B
Mercury (d)G,T,S,SS S E
T,S W
Mercury ttl G,T,S,SS S E
T,5,SS W
T,SS B
NIckel (t)G,S,SS S A
Zinc (dl S W A
T B
Zinc tt)G,T,S,SS S A
T.SS 101,B
Notes:
Parameter Stations Seasons Criteria
S -Summer
W -WInter
B -Breakup
(d)dIssolved D
(t)total V
recoverable G
C
T
S
SS
-DenalI
-Vee Canyon
-Gold Creek
-Chu I itna
-Talkeetna
-SunshIne
-Susltna Station
L -Established by law as per Alaska
Water Quality Standards,1979.
E -Established by law as per EPA
Quality CrIteria for Water,1976.
S -Criteria that have been suggested
but are not law,or levels which
natural waters usually do not
exceed.
Source:USGS AND R&M
A -Alternate level to 0.01 of the
96-hour LCSO determined through
bioassay (EPA 1976).
TABLE E.2.18:LOCATION OF OPEN LEADS OBSERVED BETWEEN
PORTAGE CREEK AND TALKEETNA DURING MID-WINTER 1982
LocatIon River Mile
1.Slough 21
2.Slough 19
3.East Bank
4.West Bank
5.Mouth of Indian River
6.Side Channel on East Side
7.Side Channel
8.Slough 11
9.Side Channel on East Side
10.Mouth of Slough 10
II.Braided Segment on West Side
12.Side Channel on East Side
13.Slough 9A
14.Slough 9
15.Slough SA
16.SIde Channel through Islands
17.Slough as
18.Curry Slough
19.Side Channel on West Bank
20.Island Complex
21.Side Channel between Islands
22.Lane Creek Slough
23.Side Channel (near Gash Creek outflow)
Source:Trlhey personal communication 1983
142.0
139.8
139.5
138.8
138.6
137.2
136.3
135.7
135.0
133.8
131.3
130.2
129.4
128.7
125.5
125.0
122.5
119.7
119.4
117.2
115.0
113.8
111.3
TABLE E.2.19:1981 BEDLOAD TRANSPORT DATA SUSITNA RIVER BASIN
Water Total Bedload
Discharge Transport Rate
Station Date Ccfs)(tons/day>
Susitna River at Gold Creek 7/22/81 37,200 2,180
Chul itna River 1 7/22/81 31,900 3,450
Talkeetna River 7/21/81 16,800 1,940
Susitna River at Sunshine 7/22/81 89,000 3,520
Susitna River at Gold Creek 8/26/81 25,900 380
Chulitna River 8/25/81 22,500 5,000
Talkeetna River 8/25/81 9,900 800
Sus itna River at Sunshine 8/26/81 61,900 4,520
Susrtna River at Gold Creek 9/28/81 8,540
Chul itna River 9/29/81 6,000 3,820
Talkeetna River 9/29/81 2,910 30
Susitna River at Sunshine 9/30/81 19,100 400
Note:1.Bedload data gathered approximately 4 miles below Chulitna River
gaging site on 7/22/81.Data gathered at Chulitna gaging sIte on
other dates.
Source:R&M 1982d
TABLE E.2.20:SUSPENDED S
MAY TO SEPT
May June Ju Iv
SusDended SE diment Suspended Sediment Sus
Mean Mean Tons Mean Mean Tons Mean Mean
Discharge Concentration Per Discharge Concentratior Per Discharge Conce
Dav (cfs)(mal I)DaY (cfs)(m~/l)Day (cfs)(mq/I
1 1,100 9 27 25,000 1,730 117 ,000 33,000 1,3
2 1,200 13 a42 23,500 2,030 129,000 31,100 1,2
3 1,300 17 60 27,500 2,200 a163,000 29,500 5
4 1,400 18 a68 29,000 1,800 a 141,000 27,800 5
5 1,500 19 a77 26,500 1,300 a93,000 25,900 6
6 1,600 19 82 22,500 940 a57,100 23,600 6
7 1,600 20 a86 24,400 1,000 a65,900 22,500 5
8 1,600 21 a91 22,300 950 a57,200 21,100 6
9 1,500 22 a89 21,500 730 a42,400 19,700 5
10 1,400 23 87 26,800 495 35,800 18,900 4
11 1,400 20 a76 37,300 249 25,100 17,700 61
12 1,500 18 a73 36,700 189 18,700 17,200 1,0
13 1,600 18 78 34,000 290 26,600 19,500 1,1
14 1,700 15 69 31,400 464 39,300 23,300 1,1
15 1,900 12 62 37,400 493 49,800 25,000 1,1
16 2,100 12 a68 42,400 562 64,300 25,400 9
17 2,200 15 a89 43,300 936 109,000 25,700 7
18 2,400 17 allO 41,300 885 98,700 25,400 8,
19 2,600 19 133 40,200 256 27,800 25,200 9'
20 2,800 30 a227 36,300 241 23,600 24,700 1,1
21 3,000 50 a405 35,400 232 22,200 24,200 1,0
22 3,400 80 734 35,600 212 20,400 23,700 8
23 3,700 270 a2,700 34,700 203 19,000 24,700 9
24 4,500 549 6,670 34,300 213 19,700 25,900 8
25 6,000 828 13,400 34,100 184 16,900 27,400 9
26 8,000 1,120 24,200 33,600 278 25,200 28,900 9
27 10,000 1,270 34,300 34,300 1,040 96,300 28,400 8
28 15,000 747 30,300 33,000 1,220 109,000 31,300 9
29 65,,000 450 30,400 33,400 1,220 110,000 38,300 1,1
30 28,000 540 40,800 33,400 1,2-70 115,000 41,300 1,3
31 27,000 1.670 122,000 ------41,700 1,3
IVIAL ••Ibti,UUU --:JUt .bU:J ':HI,lUU --I,~:Jti,UUU tilti,UUU
Total discharge for period (cfs-days)•••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••
Total load for perrod (tons)••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••
Note:
a Computed from estimated concentration graph.
Source:USGS
EDIMENT AT GOLD CREEK
EMBER 1952
Auaust September
Dended Se diment Suspended SE dlment Suspended Sediment
Tons Mean Mean Tons Mean Mean Tons
ntration Per Discharge Concentration Per OJ schargE Concentration Per
)Day (cfs)(rna/I)Day (cfs)(rna/I)Day
,00 116,000 41,900 1,390 157,000 30,000 870 a70,500
20 102,000 38,300 981 101,000 28,700 772 59,800
,62 44,800 32,100 826 71,600 24,500 682 45,100
,44 40,880 27,100 900 65,900 21,400 602 34,800
95 48,600 24,500 900 59,500 18,000 560 a27,200
70 42,700 23,500 909 57,700 14,800 520 20,800
,60 34,000 23,.600 860 54,800 12,900 420 a14,600
87 39,100 24,700 828 55,200 11,900 270 a8,680
,95 31,600 25,600 824 57,000 12,400 130 4,350
29 21,900 26,200 873 61,800 12,700 70 a2,400
,62 31,600 27,400 836 61,800 13,500 54 1,970
130 47,800 24,400 1,150 75,800 14,200 50 al,920
90 62,700 22,400 2,190 132,000 13,500 50 a 1,820
40 71,700 20,400 2,100 a116,000 12,300 50 al,660
50 77 ,600 19,800 1,580 a84,500 10,800 50 al,460
109 62,300 18,700 1,200 a60,600 10,200 58 1,600
'56 52,500 16,500 960 a42,800 10,500 65 1,840
,60 a59,000 15,600 650 27,400 10,000 70 al,890
'90 a67,400 14,800 531 21,200 9,500 70 al,800
30 75,400 14,400 639 24,800 10,000 70 al,890
180 70,600 14,800 554 22,100 11,300 70 a2,140
137 53,600 15,100 414 16,900 15,700 73 3,090
118 61,200 15,300 435 18,000 15,400 76 3,160
173 61,000 15,200 531 21,800 14,800 90 3,600
172 71,900 15,000 377 15,300 13,800 90 3,350
172 75,800 15,000 275 11,100 12,900 99 3,450
188 68,100 14,200 293 11,200 12,300
110 3,650
127 78,300 13,500 410 a14,900 12,000 89 2,880
20 ,116,000 13,6.QQ.568 20,900 12,000 81 2,620
il0 ".146,000 15,000 720 a29,200 12,400 68 2,280.
i60 153.000 20.000 860 a46,400 --------Z.U85.UUU 648,6UU --1,616,200 434,4UU --jj6,jUU
•••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••e ••••••••••••••••••.••••'3,067,700.••..•.•..•..•.......•..••.•••••.•..•.•.••.•..••.........•.•..••.••.•....•.••...•..•..•6,284,363
-
TABLE E.2.21:1982 TURBIDITY AND SUSPENDED SEDIMENT ANALYSIS
-
3Suspended
2 Sediment
Date Date Turbidity Concentration 01 scharge
Location Sampled Analyzed (NTU)(mg/I)(cts)
Susltna River at 6/4/82 6/11/82 82
Vee Canyon 6/30/82 8/3/82 384
(RM 223)7/27/82 8/18/82 720
8/26/82 9/14/82 320r-
Susitn~River near 6/3/82 6/11/82 140 769 35,800
Chase 6/8/82 6/24/82 130 547 44,400
CRM 103)6/15/82 6/24/82 94 170 24,200
6/22/82 8/3/82 74 426 37,000
6/30/82 8/18/82 376 392 30,200
7/8/82 8/18/82 132 156 20,700
7/14/82 8/3/82 728 729 30,800
7/21/82 8/18/82 316 232 24,900
7/28/82 8/18/82 300 464 30,800
8/4/82 8/18/82 352 377 22,700
8/10/82 8/26/82 364 282 20,000
8/18/82 8/26/82 304 275 17,700
8/25/82 9/14/82 244 221 16,800
8/31/82 9/14/82 188 252 19,300
9/19/82 10/12/82 328 439 28,700
~Susitna River at 5/26/82 5/29/82 81
Cross Section LRX-4 1,4
(RM 99)
Susitna Riv~r below 5/26/82 5/29/82 98
Talkeetna'5/28/82 6/2/82 256 43,600
(approximately RM '91)5/29/82 6/2/82 140 42,900
5/30/82 6/2/82 65 38,400
5/31/82 6/2/82 130 39,200
6/1/82 6/2/82 130 47,000
Susltna River at SunShlne-6/3/82 6/11/82 164 847 71,000
Parks Highway Bridge 6/10/82 6/24/82 200 414 64,500
(RM83)6/17 /82 6/24/82 136 322 50,800~6/21/82 8/3/82 360 755 78,300
6/28/82 8/18/82 1,056 668 75,700
7/6/82 8/3/82 352 507 46,600
7/12/82 8/3/82 912 867 59,800
7/19/82 8/18/82 552 576 60,800
7/26/82 8/18/82 696 1180 96,800
8/2/82 8/18/82 544 704 62,400
8/9/82 8/26/82 720 746 54,000
8/16/82 8/26/82 784 728 47,800
8/23/82 9/14/82 552 496 38,600
8/30/82 9/14/82 292 439 39,800
9/17/82 10/12/82 784 1290 86,500
Chul itna Rlver l 5/26/82 5/29/82 194
(approximately I mi Ie 5/28/82 6/2/82 272
above Chul itna-Susltna 5/29/82 6/2/82 308
Con f I uence)5/30/82 6/2/82 120
5/31/82 6/2/82 360
6/1/82 6/2/82 324
TABLE E.2.21 (Page 2)
Location
ChulItna River (Canyon)6
(18 miles above the
Chulltna-Susltna
Confluence)
Talkeetna River l aj
Railroad BrIdge'
(0.5 miles above Susitna-
Talkeetna Confluence)
Talkeetna ~iver at
USGS Cable
(6 miles above Susltna-
Talkeetna Confluence)
r
3Suspended
2 Sediment
Date 4DateTurbidityConcentrationDischarge
Sampled Analyzed (NTU)(mg/I)(cfs)
6/4/82 6/11/82 272 424 11,500
6/22/82 8/3/82 680 813 19,500
6/29/82 8/18/82 1,424 1600 29,000
7/7/82 8/3/82 976 1030 20,700
7/13/82 8/18/82 1,136 1200 22,700
7/20/82 8/18/82 1,392 1250 23,100
7/27/82 8/18/82 664 1010 31,900
8/3/82 8/18/82 704 960 23,300
8/11/82 8/26/82 592 753 21,300
8/17/82 8/26/82 1,296 1250 21,900
8/24/82 .9/14/82 632 843 18,200
9/1/82 9/14/82 316 523 17,300
9/18/82 10/12/82 1,920 1550 29,200
5/26/82 5/29/82 17 5,680
5/28/82 6/2/82 39 6,250
5/29/82 6/2/82 21 5,860
5/30/82 6/2/82 20 5,660
5/31/82 6/2/82 44 7,400
6/1/82 6/2/82 55 9,560
6/2/82 6/11/82 146 340 17,900
6/9/82 6/24/82 49 311 14,700
6/17/82 6/24/82 28 216 11,400
6/23/82 8/3/82 26 164 12,400
6/29/82 8/18/82 41 321 10,700
7/7/82 8/3/82 20 100 6,750
7/13/82 8/3/82 132 226 8,880
7/20/82 8/18/82 148 226 8,400
7/28/82 8/18/82 272 14,200
8/3/82 8/18/82 49 180 8,980
8/10/82 8/26/82 53 212 6,980
8/17/82 8/26/82 82 198 6,230
8/24/82 9/14/82 68 263 5,920
8/31/82 9/14/82 37 276 9,120
9/20/82 10/12/82 34 301 14,800
Notes:1 Samples collected by R&M Consultants.All other samples were collected by USGS.
2 R&M Consultants conducted all turbidity analysis.
3 Suspended sediment concentrations are prelimInary unpublished data provided by the
U.S.Geological Survey (USGS).
4 Discharges for "Susitna near Chase"and "Susitna at LRX-4"are from provisional USGS
stream gage data at the Alaska Railroad Bridge at Gold Creek.
5 Discharges for "Susitna Below Talkeetna"and "Susltna at SunshIne"are from
provisional USGS stream gage data at the Parks Highway BrIdge at Sunshine.
6 Discharges for "Chulitna River (Canyon)"are from provisIonal USGS stream gage data
at the Parks Highway Bridge at Chulitna.
7 Discharges for 'tTalkeetna at R.R.Bridge"and "Talkeetna at USGS Cable"are from
provisIonal USGS stream gage data near Talkeetna.
....
r
....
TABLE E.2.22:SUSITNA RIVER AT GOLD CREEK -MONTHLY SUMMARY
OF SUSPENDED SEDIMENT,WY 1953
TABLE E.2.23:SIGNIFICANT ION CONCENTRATIONS
Ranges of Concentrations (mg/I)
1 2UstreamofPro'ect Downstream of Pro"ect
Summer Winter Summer Winter
8 I car bonate (a I ka IInIty )39 -81 57 -161 23 -87 46 -88
Ch lorlde 1.5 -11 16 -30 1.2 -15 5.7 -35 ~
Su I fate 2 -
31 11 -39 -31 10 -38
Calcium (dissolved)13 -29 25 -51 10 -37 18 -39
Magnesium (dissolved)1.1 -6.4 3.8 -16.0 1.2 -7.8 3.2 -10.0
Sodium (dissolved)2.1 -10.0 6.3 -23.0 1.8 -10 4.9 -21.1
Potassium (dissolved)1.3 -7.3 2.0 -9.0 0.9 -4.4 1.2 -5
Notes:=Denal I and Vee Canyon
2 =Gold Creek,Sunshine and Susitna Station
Source:USGS &RBM
TABLE E.2.24:LAKES POTENTIALLY IMPACTED BY ACCESS
ROADS AND/OR TRANSMISSION LINES
-
Lake
Deadman Lake
BIg Lake
Unnamed Lake,
NW of Deadman Creek
Unnamed Lake east
of Tsusena Butte
La ke comp Iex near
Watana camp at MP 41
Fog Lakes
SwImming Bear Lake
High Lake
Merma id La ke
Un named La ke
complex
Location
Sec.13 &14,T225,R4W,
Fairbanks,MeridIan
Sec.19 &20,T22S,R4W;
Sec.25,T22S,R4W;
Fal rbanksMer Id Jan
Sec.25,T22S,R5W
Fairbanks,Meridian
Sec.21,T33N,R5E,
Seward Meridian
Sec.15,16,&21,
T32N,R5E,Seward Meridian
T31N,R5E &R6E,
Seward Meridian
Sec.4,T32N,R3E,
Seward Meridian
Sec.20,T32N,R2E,
Seward Mer IdIan
Sec.25,T32N,R1E,
Seward MerIdian
Sec.15, 16,21,22 &28,
T32N,R1E,Seward Meridian
Impacts
Increased access from Watana access
road near MP 27
Increased access from Watana access
road near MP 28;Location of proposed
campground"(see Chapter 7 of Exhibit E)
Increased access from Watana access
road near MP 27
Increased access from Watana access
road near MP 32
Impact from location of camp;
water qua Iity
Increased access by road across to
Watana Dam;potential development by
Native Corporation
Increased access from Devil Canyon
access road near MP 18
Increased access from Devil Canyon
access road near MP 28
Increased access from Devil Canyon
access road near MP 29;Location of
proposed campground (see Chapter 7 of
Exhibit E)
Increased access from Devil Canyon
access road near MP 31
TABLE E.2.25:STREAMS AND SLOUGHS TO BE PARTIALLY OR COMPLETELY
INUNDATED BY WATANA RESERVOIR (EI 2,190)
Approximate 1 Approximate Length
Stream Gradient of Stream
Susitna ElevatIon of Reach to be to be
River Mi Ie at Mouth Inundated Inundated
Stream at Mouth (ft.ms I)(ft/ml Ie)(miles)
1•unnamed 236.0 2,140 500 0.12.unnamed 233.8 2,055 450 0.3
3.Oshetna River 233.5 2,050 70 2.04.unnamed 232.7 2,040 750 0.25.Goose Creek 231.2 2,030 133 1.26.unnamed 230.8 2,025 825 0.2
7.unnamed 229.8 2,015 575 0.3
8.unnamed 229.7 2,015 875 0.2
9.unnamed 229.1 2,010 1,800 O.110.unnamed 228.5 2,000 1,900 0.1
1 1•unnamed 228.4 2,000 950 0.212.unnamed 227.4 1,980 2,100 O.1
13.unnamed 226.8 1,970 350 0.614.unnamed 225.0 1,930 650 0.4
15.unnamed 224.4 1,920 1,350 0.216.unnamed 221.5 1,875 300 1.0
17.unnamed 220.9 1,865 1,625 0.218.unnamed 219.2 1,845 350 1.0
19.unnamed 217.6 1,830 725 0.5
20.unnamed 215.1 1,785 1,350 0.321.unnamed 213.2 1,760 1,075 0.4
22.unnamed 213.0 1,755 725 0.6
23.unnamed slough 212.2 1,750 13 0.3 (entire
length24.unnamed 212.1 1,750 1,475 0.325.unnamed slough 212.0 1,750 13 0.5 (entire
length)26.unnamed 211.7 1,745 1,475 0.327.unnamed 210.2 1,720 670 0.728.unnamed slough 208.7 1,705 13 0.3 (entire
length)29.Jay Creek 208.6 1,700 150 3.230.unnamed slough 208.0 1,695 9 0.4 (entire
length)
31.unnamed 207.3 1,690 300 0.9 (entire
length)32.unnamed 207.0 1,685 500 1.033.Koslna Creek 206.9 1,685 120 4.2
34.unnamed slough 205.7 1,670 18 0.5 (entire
length35.unnamed 205.0 1,665 1,050 0.5 (entIre
length)
36.unnamed 204.9 1,665 750 0.4 (entire
length)37.unnamed 203.9 1,655 775 0.738.unnamed 203.4 1,650 350 0.5 (entire
length)39.unnamed 201.8 1,635 700 0.840.unnamed slough 200.9 1,630 9 0.2 (entire
length)41.unnamed 200.7 1,625 575 1.042.unnamed 198.7 1,610 825 0.743.unnamed 198.6 1,605 975 0.644.unnamed 197.9 1,600 975 0.645.unnamed 197.1 1,595 850 0.746.unnamed 19 9.7 1,590 850 0.747.unnamed 196.2 1,585 600 1.048.unnamed 195.8 1,580 550 1.1
.....
-
""'"
-
TABLE E.2.25 (Page 2)
Approximate
'
Length
Approximate of Stream
Susitna Elevation Stream Gradient to be
RI ver Mile at Mouth at Mouth Inundated
Stream Name at Mouth (ft.ms I)(ft/mlle)(mi les)
49.unnamed 195.2 1,575 200 1.3 (enti re
length)
50.unnamed 194.9 1,560 375 1.7
51.Watana Creek 194.1 1,560 50 10.0 (longest
fork)
51A.Delusion Creek --1,700 250 1.9
(tributary to
Watana Creek)
52.unnamed slough 193.6 1,565 9 0.4 (entire
length)
53.unnamed 192.7 1,550 400 1.5 (entire
length)
54.unnamed 192.0 1,545 175 3.9 (longest
fork)
55.unnamed 190.0 1,530 1,300 0.5
56.unnamed 187.0 1,505 975 0.7
57.unnamed 186.9 1,505 400 1.7
58.Deadman Creek 186.7 1,500 300 2.3
The elevations at the mouths were approximated from USGS 1:63,360 topographic
quadrangle maps.A control survey,conducted by R&M Consultants,identified several
Inaccuracies In the USGS contours along the length of the reservoir.Most notable of
those Is an elevation "reduction"of approximately 30 feet at the upstream end of the
reservoir.Thus,there are four unnamed streams on the USGS maps which would appear to
be inundated at their mouths but are actually above the upper end of the reservoir as
surveyed.
TABLE E.2.26:STREAMS AND SLOUGHS TO BE PARTIALLY OR COMPLETELY
INUNDATED BY DEVil CANYON RESERVOIR (El 1.455)
Approximate length
Approximate Stream Gradient of Stream
Susltna Elevation of Reach to be to be
River Mi Ie at Mouth Inundated InundatedStreamNameatMouth(ft.msl)(ft/mi Ie)(mi les)
1•Tsusena Creek 181.9 1,450 25 0.22.unnamed (Bear Creek 181.2 1.440 75 0.23.unnamed slough 180.1 1.430 10 0.6 (entire
length)4.unnamed 179.3 1,420 350 0.15.unnamed slough 179.1 1,420 175 0.26.unnamed slough 177.0 1,385 700 0.17.Fog Creek 176.7 1,380 75 1.08.unnamed 175.3 1,370 150 0.6
9.unnamed 175.1 1,365 900 0.110.unnamed 174.9 1,360 950 O.1
11.unnamed 174.3 1,350 350 0.312.unnamed slough 173.9 1,345 13 O.1 (entire
length)13.unnamed 173.9 1,345 275 0.414.unnamed 173.0 1,335 1,200 O.115.unnamed 173.0 1.335 600 0.216.unnamed 172.9 1,330 625 0.2
17.unnamed slough 172.2 1,350 15 2.0 (entire
length)17A.unnamed (tributary
to slough)--1,350 550 0.217B.unnamed (tributary
to slough)--1,350 1,050 0.118.unnamed slough 172.0 1,320 13 0.5 (entire
length)19.unnamed slough 171.5 1,315 13 0.8 (entire
length)19A.unnamed (tributary
to slough)--1,320 1,350 0.1
19B.'unnamed (tributary
to slough)--1,320 1,350 0.120.unnamed slough 171.5 1,315 13 0.2 (entire
length)21.unnamed 171.4 1,315 1,400 0.122.unnamed 171.0 1,310 250 0.623.unnamed s,Jough 169.5 1,290 15 0.7 (entire
length)
24.unnamed 168.8 1,280 875 0.225.unnamed slough 168.0 1,265 16 0.2 (entire
26.length)unnamed 166.5 1,235 350 0.627.unnamed 166.0 1,230 1,125 0.228.unnamed 164.0 1,200 1,275 0.229.unnamed 163.7 1,180 1,350 0.230.Dev!I Creek 161.4 1,120 250 1.431.unnamed 157.0 1,030 350 1.332.unnamed 154.5 985 1,175 0.433.unnamed
(Cheechako Creek)152.4 950 325 1.6
~j -)1 1 -1 J 1 'J J )]}
TABLE E.2.27:DOWNSTREAM TRIBUTARIES POTENTIALLY IMPACTED BY PROJECT OPERATION
Anticipated
River Bank of Reason Post-Project Potential
1
No.Name Mi Ie Susitna for Concern Response Impacts Foreseen
PortaQe Creek 148.9 RB fish access degrade
2 Jack Long Creek 144.8 LB fish access perch possible restriction of fish access
3 Indian River 138.5 RB fish access degrade
4 Gold Creek 136.7 LB fish access degrade
5 unnamed 132.0 La Ra II road (RR)perch
6 Fourth of July Creek 131.1 RB fish access degrade
7 Sherman Creek 130.9 LB RR/flsh access perch possible restriction of fIsh access
8 unnamed 128.5 LB Railroad perch
9 unnamed 127.3 LB Ra i I road degrade possible limited scour at RR bridge
10 Sku II Creek 124.7 LB Ra i I road degrade possible limited scour at RR brIdge
11 unnamed 123.9 RB fish access perch
12 Deadhorse Creek 121.0 LB RR/fish access perch possible restriction of fish access
13 unnamed 121.0 RB fish access degrade
14 Little Portage Creek 117.8 LB Ra I Iroad perch
15 McKenzie Creek 116.7 LB fish access degrade
16 Lane Creek 113.6 LB fish access degrade
17 Gash Creek 111.7 LB fish access degrade possible limited scour at RR bridge
18 unnamed 110.1 LB Ra Ilroad degrade
19 Whiskers Creek 101.2 RB fish access perch (but
backwater)
lReferenced by facing downstream (LB =left bank,RB =right bank).
Source:R&M 1982f
TABLE E.2.28:SUMMARY OF SURFACE WATER AND GROUND WATER APPROPRIATIONS
Townshio Grid Surface Water Appropriation Ground Water Appropriation
Equivalent Flow Rates Equivalent Flow Rates
cfs ac-ft/yr cfs ac-ft/yr
Susrtna 0.153 50.0 0.0498 16.3
Fish Creek 0.000116 0.02100 0.00300 2.24
Wi I low Creek 18.3 5,660 0.153 128
Little Wi Ilow Creek 0.00613 1.42 0.00190 1.37
Montana Creek 0.0196 7.85 0.366 264
Chunilna 0.00322 0.797 0.000831 0.601
Susitna Reservoir 0.00465 3.36 -- --
Chulina (Chunilna)----0.00329 2.38
Kroto-Trapper Creek 0.0564 10.7 -- --
Kah i Itna 125 37,000 ----
Yentna 0.00155 0.565 ----
Skwentna 0.00551 1.90 0.000775 0.560
Source:DWight 1981
r
TABLE E.2.29:WATER RIGHT APPROPRIATIONS ADJACENT TO THE SUSITNA RIVER
Days Of
ADL Number Type Source <Depth)Amount Use
Cert if I cate
45156 single family dwell ing well (unknown)650 gpd 365.....general crops II "0.5 ac-ft/yr 91
Certificate-43981 single family dwelling weI f (90 ft)500 gpd 365
Certificate
78895 single family dwelling well (20 ft)500 gpd 365-200540 grade school well (27 ft)990 gpd 334
209233 fire station well (34 ft)500 gpd 365
Certificate
200180 single family dwelling unnamed stream 200 gpd 365
lawn &garden Irrigation II 11 100 gpd 153
200515 single fami Iy dwellIng unnamed stream 500 gpd 365
206633 single family dwell ing unnamed lake 75 gpd 365
206930 single family dwell ing unnamed lake 250 gpd 365
206931 single family dwelling unnamed lake 250 gpd 365
Permit
206929 general crops unnamed creek 1 ac-ft/yr 153
Permit
206735 single fami Iy dwell ing unnamed stream 250 gpd 365
Pending
209866 single family dwelling Sherman Creek 75 gpd 365
I"'"'lawn and garden Irrigation II "50 gpd 183
Source:Dwight 1981
r-
I
I
12/16/82
TABLE E.2.30:SUSITNA RIVER -LIMITATIONS TO NAVIGATION
River Mil e Locat ion 1
19
49
61
127-128
151
160-161
225
291-295
Oeser i pt ion
Alexander Slough Head
Mouth of Wi Ilow Creek
Sutitna Landing-Mouth
of Kashwltna River
River Cross-Over near
Sherman and Cross-
Section 32
Dev i I Canyon
Dev i I Creek Rap Ids
Vee Canyon
Denal i Highway Bridge
Severity
Access to slough limited
at low water due to
shallow channel
Access from creek limited
at low water
Access from launching site
I imited at low water
Shal low In riffle at low
water
Severe rapids at all flow
levels
Severe rapids at al I flow
levels
Hazardous but navigable
rapids at most flows
Sha Ilow water and frequent
sand bars at low water
Note:lLocatlons obtained from River Mile Index
(R&M Consultants 1982)
1 )J 1 1•]J 1 •1 )
TABLE E.2.31:TEMPORAL SALINITY ESTIMATES FOR SELECT COOK INLET LOCATIONS
Location Conditions Oct Nov Dec Jan Feb Mar Aor Mav Jun Jul Au!:!Seot
Cook Inlet Pre-ProJect 9,949 12,856 15,153 16,937 18,543 19,942 20,976 15,699 9,729 6,592 5,792 7,231
near the Watana Filling
Susltna River (WY 1992)10,330 13,151 15,411 17,159 18,734 20,107 21,133 16,439 11,071 7,588 6,508 7,836
Mouth Watana Operation 10,080 12,539 14,374 15,930 17,355 18,617 19,612 15,475 10,393 7,206 6,252 ·7,616
(Node #27)(WY 1995)
Watana/Dev II 10,093 12,498 14,313 15,825 17,188 18,451 19,500 15,570 10,484 7,248 6,290 7,609
Canyon Ooeration
Center of Pre-ProJect 21,868 22,911 23,921 24,813 25,591 26,263 26,824 26,788 25,388 22,912 21,174 21,072
Cook Inlet Watana Filling 22,100 23,102 24,077 24,942 25,698 26,352 26,900 26,910 25,742 23,476 21,738 21,545
near East (WY 1992)
Foreland Watana Operation 22,048 22,995 23,900 24,704 25,411 26,028 26,548 26,537 25,345 23,107 21,442 21,315
(Node #12)(WY 1995>
Watana/Dev t I 22,050 22,992 23,891 24,688 25,385 25,995 26,514 26,519 25,354 23,128 21,465 21,326
Canyon Ooeratlon
Mouth of Pre-Project 29,109 29,496 29,727 29,893 30,037 30,158 30,239 29,816 29,000 28,270 28,112 28,567
Cook Inlet Watana Filling 29,160 29,529 29,754 29,916 30,056 30,173 30,253 29,878 29,164 28,435 28,254 28,676
(Node #1)(WY 1992)
Watana Operation 29,127 29,472 29,673 29,828 29,965 30,080 30,161 29,798 29,076 28,359 28,190 28,625
(WY 1995)
Watana/Dev II 29,128 29,468 29,667 29,821 29,954 30,070 30,155 29,806 29,085 28,364 28,196 28,624
Canyon Ooeratlon
Center of Pre-Project 8,916 10,616 12,659 14,681 16,522 18,158 19,551 19,442 16,083 12,100 9,263 8,301
Turnagain Arm Watana Filling 9,262 10,951 12,963 14,951 16,760 18,365 19,732 19,677 16,541 12,752 9,931 8,928
(Node #55)(WY 1992)
Watana Operation 9,212 10,810 12,665 14,466 16,108 17,573 18,834 18,772 15,782 12,171 9,508 8,601
(WY 1995)
Watana/Dev II 9,216 10,809 12,652 14,436 16,054 17,495 16,745 18,712 15,776 12,192 9,534 8,623
Canyon Ooeratlon
Center of Pre-Project 3,675 6,538 9,252 11,610 13,657 15,446 16,550 11,970 1,923 325 400 1,248
Kn Ik Arm Watana Filling 3,834 6,754 9,482 11,832 13,862 15,630 16,710 12,119 2,008 350 437 1,355
(Node #46)(WY 1992)
Watana Operation 3,807 6,658 9,260 11,445 13,318 14,950 15,939 11,540 1,913 335 421 1,312
(WY 1995)
Watana/Dev II 3,809 6,658 9,249 11,422 13,276 14,885 15,862 11,502 1,916 337 422 1,315
Canyon Ooeratlon
Notes:1.All concentrations are reported in mg/I and represent end of the month salinity estimates.
2.Nodes correspond to computer simulation locations.
Source:RMA 1983
TABLE E.2.32:ESTIMATED LOW AND HIGH FLOWS AT ACCESS ROUTE STREAM CROSSINGS
Road A
(cfs)1MiIeAr2a30-Day Minimum Flow Peak Flows (cfs)2
DralnaQe Basin Location (mi )Recurrence Interval (yrs)Recurrence Interval (yrs)
2 10 20 2 10 25 50----------- --
Denali Hi~hW~~toWatanaCa!p lQmen
Li Iy Creek 3 3.7 0.8 0.6 0.5 25 54 78 96
Seattle Creek 6 11.1 2.4 1.8 1.5 74 147 205 248
Seattle Creek
Tr i butary 8 1.5 0.3 0.2 0.2 10 24 35 44
Seattle Creek
Tr i butary 9 2.7 0.8 0.5 0.4 13 29 42 51
Brushkana Creek 12 22.0 5.5 3.8 3.4 115 217 299 354
Brushkana Creek
Site 14 21.0 4.9 3.5 3.1 121 228 315 374
Up per Deadman
Creek 20 12.1 3.0 2.1 1.9 64 127 177 211
Deadman Creek
Tr I butary 28 54.5 13.2 9.3 8.2 276 488 661 767
Watana to Dev i I
Canyon Segment
Tsusena Creek 2.5 126.6 26 19 17 780 1309 1744 2000
Devil Creek 22 31.0 6.7 4.8 4.2 199 369 506 597
Dev II Canyon to
Go I d Creek Ra I I roac
Segment
3
Gold Creek 0.2 25.0 5.4 3.9 3.4 162 304 418 497
NOTES:
Minimum flows estimated from the following USGS regression equation (Freethey and Scully
1980)•
M =aA b (LP +l)c (J +10)dd,rt
where:M
d
rt
A
LP
J
a,b,c
minimum flow (cfs)=number of days
=recurrence interv~1 (yrs)=drainage area (mi )
=area of lakes and ponds (percent)
=mean minimum January air temperature (OF)
=coefficIents
2 Peak flows estimated from the following USGS regression equation (Freethey and
Scu Ily 1980).
where:Q
t
A
LP
P
a,b,c,d
=annual peak discharge (cfs)
=recurrence interv~1 (yrs)
=drainage area (ml )
=areas of lakes and ponds (percent)=mean annual precipItation (in)=coefficients
3 Ra llroad mile location.
1 I ]1 1 ----~J -~J --'I -~-I ----J J J 1
Stream Name
TABLE E.2.33:AVAILABLE STREAMFLOW RECORDS FOR MAJOR STREAMS
CROSSED BY TRANSMISSION'CORRIDOR
Transmission Line
Per iod of Crossing from
USGS Gage Continuous Drainag~Areal Gage
Description ~§G!il!l!I1l~~Record (mi )(approx.)
Mean Annua~
Streamflow
(cfs)
Anchorage-Willow Segment
Little Susitna
River Near Palmer 15290000 1948-present 61.9 35 mi.dis
Willow Creek Near Willow 15294005 1978-present 166 7 mi.dis
Fairbanks-Healy Segment
Nenana River /Jl Near Healy 15518000 1950-1979 1,910 2 mi.dis
Nenana Ri ver /J2 Near Healy 15518000 1950-1979 1,910 20 mi.dis
Tanana River At Nenana 15515500 1962-present 15,600 5 mi.u/s
Willow-Healy Intertie
Talkeetna River Near Tal keetna 15292700 1964-present 2,006 5 mi.dis
Susitna Ri ver At Gold Creek 15292000 1949-present 6,160 5 mi.u/s
Indian River ------82 15 mi.u/s
E.F.Chulitna Chulitna River 15292400 1958-72,1980-2,570 40 mi.u/s
River near Tal keetn a present
M.F.Chulitna Chulitna River 15292400 1958-72,1980-2,570 50 mi.u/s
River near Talkeetna present
Nenana River Near Windy 15516000 1950-56,1958-73 710 5 mi.u/s
Yanert Fork ------N/A 1 mi.u/s
Healy Creek ------N/A 1 mi.u/s
Watana-Gold Creek Segment
Tsusena Creek ------149 3 mi.u/s
Devil Creek ------71 9 mi.u/s
Sus itna River At Gold Creek 15292000 1949-present 6,160 13 mi.u/s
lAreas for ungaged streams are at the mouth.
2d/s =downstream,u/s =upstream.Distances for ungaged streams are from the mouth.
3Averages determined through the 1980 water year at gage sites.
206
472
3,506
3,506
23,460
4,050
9,647
8,748
8,748
9,647
TABLE E.2.34:MONTHLY FLOW REQUIREMENTS AT GOLD CREEK
MONTH A Al A2 C Cl C2 J!
OCT 5000 5000 5000 5000 5000 5000 5000
NOV 5000 5000 5000 5000 5000 5000 5000
DEC 5000 5000 5000 5000 5000 5000 5000
JAN 5000 5000 5000 5000 5000 5000 5000
FEB 5000 5000 5000 5000 5000 5000 5000
MAR 5000 5000 5000 5000 5000 5000 5000
APR 5000 5000 5000 5000 5000 5000 5000
MAY 4000 5000 5000 6000 6000 6000 6000
JUN 4000 5000 5000 6000 6000 6000 6000
JU LI 4000 5100 5320 6480 6530 6920 7260
AUG 6000 8000 10000 12000 14000 16000 19000
SEPI 5000 6500 7670 9300 10450 11620 13170
1'"",'""'
Nates :
Derivation of transitional flaws.
1 DATE CASE
JUL SEP A Al A2 C Cl C2 D
25 21 4000 5000 5000 6000 6000 6000 6000
26 20 4000 5000 5000 6000 7000 7000 7500
19 19 4000 5000 5000 7000 8000 8500 9000
18 18 4000 5000 6000 BOOO 9000 10000 10500
17 17 4000 5000 7000 9000 10000 11500 12000
16 16 4000 6000 8000 10000 llOOO 13000 14000
15 15 5000 7000 9000 llOOO 12500 14500 16000
lIThree additional flaw regimes were investigated with respect to project
economics •These regimes are discussed in Exhibit B,pp.B-2-123 through
B-2-128 and are identified as Cases E,F,and G.
TABLE E.2.35:NET BENEFITS FOR SUSITNA HYDROELECTRIC
PROJECT OPERATING SCENARIOS
LTPWcl!NET BENEFITS PERCENT
CHANGE
x 10 6 )(1982 dollars x 10 6 )
RELATIVE
(1982 dollars TO CASE A
....Thermal Option Y 8238
Case A 7004 1234
Case Al 6998 1240 +0.5....
Case A2 7012 1226 -0.6
Case C 7097 1141 -7.5
Case C1 7189 1049 -15.0
Case C2 7357 881 -29.0
Case D 7569 669 -46.0
Note:
1/-Long-Term Present Worth Costs
Y Three additional Flow regimes were investigated with respect to project
economics.These regimes are discussed in Exhibit S,pp.B-2-123 through
B-2-128 and are identified as Cases E,F,and G•
....
12/16/82
TABLE E.2.36:MINIMUM DOWNSTREAM FLOW REQUIREMENTS AT GOLD CREEK
Flow (cfs)
Month During Filling Operation
Oct 2,000 5,000
Nov Natural 5,000
Dec Natural 5,000
Jan Natural 5,000
Feb Natural 5,000
Mar Natural 5,000
Apr Natural 5,000
May 5,680(1)6,000
Jun 6,000 6,000
Jul 6,480(2)6 480(2),
Aug 12,000 12,000
Sep 9 100 0 )9,300(4),
Notes :
(1)May 1 2,000*(2)Jul 1-26 6,000
2 3,000*27 7,000
3 4,000*28 8,000
4 5,000*29 9,000
5-31 6,000 30 10,000
31 11,000
0)Sep 1-14 12,000 (4)Sep 1-14 12,000
15 11,000 15 11,000
16 10,000 16 10,000
17 9,000 17 9,000
18 8,000 18 8,000
19 7,000 19 7,000
20-27 6,000 20-30 6,000
28 5,000
29 4,000
30 3,000
*Natural flows up to 6000 cfs will be discharged when they are greater than
stated flows.
TABLE E.2.37:WATANA FLO~
Fi II inq Case With 10:tProbabi I itv of Exceedance Fi II inQ Case With 50~Probabi I itv of
Pre-WY 1991 WY 1992 WY 1993 Pre-WY 1991 WY 1992
Project Project
Month Flow Outflow %ChanQe Outflow %ChanQe Outf low %ChanQE Flow Outflow %ChanQe Outflow %Chane
Oct 5,272 5,272 -5,272 0.0 819 84.5 4,713 4,713 -3,454 26.7
Nov 2,352 2,352 -2,352 0.0 2,352 0.0 2,102 2,102 -2,102 0.0
Dec 1,642 1,642 -1,642 0.0 1,642 0.0 1,468 1,468 -1,468 0.0
Jan 1,340 1,340 -1,340 0.0 1,340 0.0 1,198 1,198 -1,198 0.0
Feb 1,138 1,138 -1,138 0.0 1,138 0.0 1,018 1,018 -1,018 0.0
Mar 1,028 1,028 -1,028 0.0 1,028 0.0 919 919 -919 0.0
Apr 1,261 1,261 -1,261 0.0 1,261 0.0 1,127 1,127 -1,127 0.0
1 3 1
May 12,158 8,690 28.5 2,956 75.7 2,956 75.7 10,870 7,402 31.9 3,329 69.4
Jun 25,326 20,005 21.0 1,000 96.1 8,989 64.5 22,644 17,323 23.5 1,103 95.1
Jul 22,327 5,309 76.2 9,076 59.3 1,477 93.4 19,963 2,945 85.2 2,378 88.1
2 4 2
Aug 20,142 14,993 25.6 8,649 57.1 15,382 23.6 18,008 12,859 29.6 8,105 55.0
Sep 12,064 6,743 44.1 6,397 47.1 10,787 6,767 37.3 6,767 37.3
Notes:1• F i I ling beg i ns.
2.Commissioning of units possible.
3.Operation possible.
4.Fi I ling complete.-
S FOR THREE FILLING CASES (CFS)
E ceedance F i I t I nq Ca!e With 90l Probabi I it of Exceedance
WY 1993 Pre-WY 19~1 W 19~z WY 19~5 WY 1~~4
Project
e Outflow %ChanQE Flow Dutf low %Chanqe Dutf low %Chanqe Outflow %ChanQe Outflow %ChanQ6
4
981 79.2 4,213 4,213 -1,493 64.6 1,140 72.9 1,140 73.0
2,102 0.0 1,879 1,879 -1,879 0.0 1,879 0.0
1,468 0.0 1,312 1,312 -1,312 0.0 1,312 0.0
1,198 0.0 1,071 1,071 -1,071 0.0 1,071 0.0
1,018 0.0 910 910 -910 0.0 910 0.0
919 0.0 822 822 -822 0.0 822 0.0
1,127 0.0 1,008 1,008 -1,008 0.0 1,008 0.0
3 1 2
3,329 69.4 9,715 6,247 36.0 3,696 62.0 3,696 62.0
1,103 95.1 20,238 14,917 26.3 1,867 90.8 1,867 90.8
2,163 89.2 17 ,842 2,836 84.1 2,836 84.1 2,836 84.0
4
9,668 46.3 16,095 8,934 44.5 8,713 45.9 8,713 45.9
3
9,641 7,131 26.0 7,131 26.0 7,131 26.0
TABLE E.2.3B:GOLD CREEK FU
~1111nq Lase W1th urn t'robab111t y ot l:.xceedance ~lll1nq lase WHh U~i"'robab1 l1ty ot I
t're-Wy ~':1':11 Wy 19':1Z W 199}t're-W 1 ':191 WY J ';I':1Z
Project Project
Monti-Flows Flows %Chanqe Flows %Chanqe Flows %Chanqe Flows Flows %Chanqe Flows %ChanqE
Oct 6,453 6,453 -6,453 0.0 2,000 69.0 5,732 5,732 -4,473 22.0
Nov 2,879 2,879 -2,879 0.0 2,879 0.0 2,557 2,557 -2,557 0.0
Dec 2,010 2,010 -2,010 0.0 2,010 0.0 1,785 1,785 -1,785 0.0
Jan 1,640 1,640 -1,640 0.0 1,640 0.0 1,457 1,457 -1,457 0.0
Feb 1,393 1,393 -1,393 0.0 1,393 0.0 1,238 1,238 -1,238 0.0
Mar 1,258 1,258 -1,258 0.0 1,258 0.0 1,118 1,118 -1,118 0.0
Apr 1,544 1,544 -1,544 0.0 1,544 0.0 1,371 1,371 -1,371 0.0
1 3 1
May 14,882 11,414 23.3 5,680 61.8 5,680 61.8 13,221 9,753 26.2 5,680 57.0
Jun 31,001 25,680 17.2 6,675 78.5 14,664 52.7 27,541 22,220 19.3 6,000 78.2
Jul 27,330 10,312 62.3 14,079 48.5 6,480 76.3 24,280 7,262 70.1 6,694 72.4
4 2
Aug 24,655 19,506 20.8 13,162 46.0 19,895 19.3 21,903 16,754 23.5 12,000 45.2
Sep 14,767 9,446 36.0 9,100 38.4 13,120 9,100 30.6 9,100 30.6
Notes:1.Filling begins.
2.Commissioning of units possible.
3.Operation possible.
4.Filling complete.-
-..""
lWS FOR THREE FILLING CASES (CFS)
cl<ceeaance t 11l1nQ Las e Wltn ';IU~t'robal:llllt ot t.xceedance
W 1993 t're-WY 1';1';1"W 19n WY.19':13 W 1994
Project
l Flows %ChanQE Flows Flows %ChanQe Flows ~~ChanQe Flows %ChanQe Flows ~~ChanQe
4
2,000 65.1 5,073 5,073 -2,353 53.6 2,000 60.6 2,000 60.6
2,557 0.0 2,263 2,263 -2,263 0.0 2,263 0.0
1,785 0.0 1,580 1,580 -1,580 0.0 1,580 0.0
1,457 0.0 1,290 1,290 -1,290 0.0 1,290 0.0
1,238 0.0 1,096 1,096 -1,096 0.0 1,096 0.0
1,118 0.0 990 990 -990 0.0 990 0.0
1,371 0.0 1,214 1,214 -1,214 0.0 1,214 0.0
3 1 2
5,680 57.0 11,699 8,231 29.6 5,680 57.4 5,680 51.4
6,000 78.2 24,371 19,050 21.8 6,000 75.4 6,000 75.4
6,480 73.3 21,486 6,480 69.8 6,480 69.8 6,480 69.8
4
13,563 19,382 12,221 36.9 12,000 38.1 12,000 38.1
3
11,610 9,100 21.6 9,100 21.6 9,100 21.6
-
....._-.
TABLE E.2.39:MONTHLY PRE-PRO,/ECT AND WATANA FILLING FLOWS
AT GOLD CREEK,SUNSHINE AND SUSITNA STATION
-
.-
Gold Creek :sunshine Sus itna Station
Pre-Pre-
Fi IIlng3 Pre
Fi IIlng3Project
'
Fi IIIng3 Percen Project2 Percen Project2 Percent
Month Flows Flows Chanoe Flows Flows Change Flows Flows Change
Oct 5,732 4,473 22.0 13,874 12,615 9.1 31,219 29,960 4.0
Nov 2,557 2,557 0.0 5,981 5,981 0.0 13,396 13,396 0.0
Dec 1,785 1,785 0.0 4,215 4,215 0.0 8,414 8,414 0.0
Jan 1,457 1,457 0.0 3,524 3,524 0.0 7,937 7,937 0.0
Feb 1,238 1,238 0.0 2,973 2,973 0.0 7,086 7,086 0.0
Mar 1,118 1,118 0.0 2,667 2,667 0.0 6,374 6,374 0.0
Apr 1,371 1,371 0.0 3,247 3,247 0.0 7,279 '7,279 0.,0
May 13,221 5,680 57.0 27,909 20,368 27.0 61,558 54,017 12.3
Jun 27,541 6,000 78.2 63,458 41,917 33.9 123,387 101,846 17.4
Jul 24,280 6,694 72.4 64,205 46,619 27.4 133,642 116,056 13.2
Aug 21,903 12,000 45.2 56,378 46,475 17.6 112,269 102,366 8.8
Sep 13,120 9,100 30.6 32,009 27,989 12.6 66,511 62,491 6.0
Annual 9,599 4,479 53.3 23,418 18,216 22.2 48.194 43,079 10.6
Notes:1.Based on the median three-year moving average annual flow.
~2.Sunshine and Susitna Station pre-project flows are based on the long-term ratio of
the mean at Gold Creek.
3.Fi II ing flows based on the second year (WY 1992)of fi Iling scenario.-
I~
TABLE E.2.40:MONTHLY OPERATING RULE CURVES AT
WATANA AND DEVIL CANYON
Elevation (ttl 1 ,-
Watana Operation Watana/Dev i I Canyon Operation
Month Watana Watana Dev II Canyon
Oct 2184 2185 1455
Nov 2171 2170 1455
Dec 2154 2150 1455
Jan 2137 2130 1455
Feb 2122 2112 1455
Mar 2107 2095 1455
Apr 2093 2080 1455
May 2100 2092 1455
Jun 2135 2125 1455
Jul 2165 2160 1455
Aug 2180 2180 1455
Sept 2190 2190 1455
Notes:1 Target elevation at end ot month.
TABLE E.2.41:WATANA OPERATION -MONTHLY
MINIMUM ENERGY DEMANDS
~
Demand Pattern Associated
Percent of Minimum Powerhouse
Month Annual Demand Energy GWh(l)Discharge (cfs)
I~'
Oct 8.70 220.7 5910
Nov 9.06 243.1 6810
Dec 11.17 284.5 7860
Jan 10.21 260.0 7330
Feb 8.78 202.0 6420
Mar 8.88 226.2 6620
Apr 7.66 188.9 5830
May 7.14 181.7 5430
Jun 6.70 165.3 4980
Ju I 6.62 168.8 4750
i~Aug 6.96 304.2 8280
Sept 7.32 266.0 7400
(1)Taken from year 21 of energy sImulation.
TABLE E.2.42:WATANA POST-PROJECT MONTHLY FLOW (CFS)WATANA OPERATION
YEAR OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEf'ANNUAL
1 5665.9716.11285.9706.8958.8081.7384.5633.4854.4617.9034.8301.7761.CjI
"5841.6641.7716.7190.6290.6468.5674.7874.4836. 4778.8808.5266.6459.0"-
3 7083.10164.11617.10165.9158.8247.7508.5327.5002.4797.8436.6391.7819.7
4 8269.10751.11398.9709.8928. 8182.8086.11376.4960.4561.8072.5544.8325.3
5 5691.6592.11300.9978.9120.8150.7646.8369.4962.4591.6321.5546.7353.8
6 5684.7246.11666.10279.9367.8398.7644.5259.5175.6850.14063.8458.8345.5
7 7620.9582.11155.9707.9071.8206.7422.9500.9089.8819.10055.8275.9046.5
8 7779.10271.11823.10264.9506.8447.7649.7001.7123 •4748.8778.7254.8381.0
9 9605.10930.12375.10371.9358.8485.7969.6804.4964.4756.8303.7550.8455.1
10 5732.6513.7773.9972 •9266.8206.7589.6969.4838.4781.8969.7390.7325.4
11 8736.10207,.11789.10291.9455.8473.7774.9582.4870.4813.7733.4876.8220.4
12 6483.10322.12090.10670.9621.8843.8669.10116.5203.4747.9380.6076.8519.7
13 6050.10257.11877.10499.9574.8689. 8161.8042.16899.7579.11004.7286.9649.7
14 9131.10503.11825.10199.9501.8395.7480.11611.4959.9516.12488.7780.9468.1
15 6516.9783.11311.9743. 9098.8087.7313.5333.18354.5020.9608.7253.8931.5
16 5759.6536.7538.9561.9089.8319.7936.7712.4963.5167.8274.10382.7592.4
17 8792.9559.11320.9951.9301.8496.8042.5259.6476.4555.7561.6764.7999.0
18 5722.6505.7606.9993.9348.8401.7553.9142.6838.5550.16189.8754.8471.0
19 7590.9928.11821.10508.9877 •9072 •'8280.9386.7756.5706.8978.7648~8876.0
20 5757.6543.7573.7637.9065.8198.7554.5259.4852.4630.9756.7674.7028.9
21 5908.6809.7856.7330.6420.6619.5826.5428.4983.4747.8284.7403.6470.6
22 5971.6790.7879. 7336. 6419.6615.5823.5502.5167.4939.8686.7049.6518.8
23 7860.10581.12074.10561.9808.8878.8009.12218.9601.4742.10220.7856.9367.6
24 5697.6590.11363.9922 •9317.8386.7618.5259.4974.4585.9727.8326.7641.5
25 5781.6573.7622 •7092.6638.8139.7576.9442.4860. 4655.9304.6836.7052.8
26 5901.6783.7811.7274.6359.6537.5739.5347.7870.6791.9037.6065.6798.3
27 7756.9595.10993.9648.9060.8202.7763.5887.4964. 4588.10594.6881.7993.1
28 5828.6628.7677 •7136.6231.7593.7907.5555.12444.4745.9567.7273.7378.6
29 5692.9188.12096. 10468.9584.8768.8112.7951.4844.4608.9022.7826.8176.0
30 5882.6684.7751.7216.6307.6478.5679.8310.5123.7742.8211.7627.6929.3
31 5681.11305.12148.10361.9550.8689.8108.6968.5433.9232.9070.7020.8630.1
32 9053.11291.11501. 10038.9288.8401.7807.7208.4874.5632.19391.9316.9497.5
MAX 9605.11305.12375. 10670.9877 •9072 •8669.12218.18354.9516.19391.10382.9649.7
MIN 5665.6505.7538.7092.6231.6468.5674.5259.4836. 4555.6321.4876.6459.0
MEAN 6766.8668.10301.9399.8685.8098.7478.7520.6628.5550.9779.7311.8015.1
j 'j ))j j 1 J J j J ])J })J
TABLE [,2.43:MJNTHLY MAX Ht..IM ,MINIHJM,AND MEAN FLOWS AT WATANA (CFS)
MONTH PRE-PROJECT POST-PROJECT
WATANA OPERATION WIDC OPERATION
MAX MIN MEAN MAX MIN MEAN MAX MIN MEAN
OCT 6458.0 2403.1 4522.8 9605.4 5664.6 6766.1 11900.7 5564.1 9764.4
NOV 3525.0 1020.9 2059.1 11305.1 6504.8 8667.7 11048.4 6683.3 9112.6
DEC 2258.5 709.3 1414.8 12374.9 7538.2 10300.9 12386.3 7775.9 10881.2
JAN 1779.9 636.2 1165.5 10670.4 7091.7 9399.2 11497.6 7227.3 10287.5
FEB 1560.4 602.1 983.3 9876.9 6231.4 8685.3 11021.6 6272.0 9924.6
MAR 1560.4 569.1 898.3 9072.1 6468.3 8098.3 10315.6 6459.8 9059.2
APR 1965.0 609.2 1099.7 8668.6 5674.3 7478.1 9199.9 5100.4 7793.9
MAY 15973.1 2857.2 10354.7 12218.0 5258.9 7519.6 7501.6 4072.9 5826.6
JUN 42841.9 13233.4 23023.7 18353.5 4835.5 6628.3 6626.9 3198.6 5123.6
JUL 28767.4 15871.0 20810.1 9515.9 4555.1 5549.6 6625.6 3442.5 4736.1
AUG 31435.0 13412.1 18628.5 19391.0 6320.6 9778.8 14043.2 3263.4 5947.5
SEP 17205.5 5711.5 10792.0 10381.7 4875.6 7310.7 13672.9 4009.2 7838.4
ANNUAL 9832.9 6100.4 8023.0 9649.7 6459.0 8015.1 9832.9 6343.8 8015.1
TABLE E.2.44:GOLD CREEK POST-PROJECT MONTHLY FLOW eCFS)WATANA OPERATION
YEAR OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP ANNUAL
1 7280.10216.11555.9918.9105.8238.7574.8487.8022.8024.12000.9282.9145.8
')6390.6833.7910. 7342.6437.6589.5989.10314.7108.7562.12000.9300.7831.3L
3 8061.10738.12016.10491.9317.8392.7624.6529.11599.9076.12000.9300.9595.1
4 10186.11491.11816.9991.9137.8332.8319.15608.10810.7406.12000.9300.10380.5
5 7076.7092.11616.10191.9317.8292.7939.13953.10736.7967.12000.9300.9635.0
6 7195.7955.12161.10685.9717.8612.7904.7860.10153.10622.16276.9300.9882.5
7 8469.9894.11416.9871.9287.8452.7654.14207.15257.14078.15432.13411 •11468.8
8 9377 •11044.12258.10591.9817.8712.7904.10575.12008.8110.12000. 12213.10384.1
9 11783.11948.13380.10856.9624.8660 •8237.9746.8566.7883.12000.9121.10162.0
10 6875.6933.8170.10339.9624.8492.7954.12818.9829. 9288.16209.11843.9874.3
11 10129. 10844.12316.10736.9769.8709.8004.12318.7167.8287.12000.9300.9978.8
12 8227.10994.12810.11343.10071.9322.9354.13838.11869.9478.12000.9300.10726.1
13 7329.10694.12216.10791.9817.8912.8404.9299.24152.9986.14667.10430.11381.9
14 10294.10794.12116.10491.9817.8512.7534.15342.10296. 15149.15147.9300.11263.3
15 7778.10244.11610.9939.9283.8225.7449.6061.26092.7887.12000.9300.10468.3
16 7291.6967.7679.9658.9177 •8412.8064.9736. 9470. 9772.12000.13506.9309.7
17 10776.10092.11747. 10291.9617.8812.8479.7810.13487.8262.12000.9300.10056.4
18 6616.6903.7985.10391.9717.8712.7871.12067.11636.10363.22704.11951.10593.9
19 8471.10347.12171.10872.10217.9412.8614.12740.13602.10043.12000.9300.10654.4
20 6582.6882.7830.7839.9239.8345.7726.7169.7866.6852.12000.9300.8128.7
21 6629.7004.8013.7518.6586.6771.5920.7272.9214.8997.12000.9300.7947.1
')')7491.7701.8482.7681.6678.6848. 6091. 6390.10484.7762.13149.9300.8181.2L"-
23 8728.11087.12626.11130.10345.9335.8414.18135.16602.7692.12000.9300.11289.7
24 6222.6865.11581.10091.9517.8512.7731.6207.8914.6484.12000.9300.8615.7
')1:"6457.6742.7725.7179.6725.8236.7696.12733.7949.7483.12000.9300.8370.1<..,J
26 6551.7008.8138.7574.6719.6896. 6121.9025.13491.11081.12000.9300.8671.0
27 9816.9987.11197.9865.9267.8412.8077 •9568.9350.6513.12000.8051.9347.6
28 6728.7351.8393.7616.6647.7982.8384.9665.19061.7908.12000.9300.9255.0
')0 7469.10068.12705.10920.9985.9117.8406.8669.6617.7243.12000.9300.9378.3"-I
30 7015.7274.8119.7476.6537.6577 •5811.9811.6908.11710.12000.9300.8235.0
31 6842.11972.12532.10639.9783.8912. 8374.8888.11113.15152.12030.9300.10469.9
32 10320.11980.11890.10344.9552.8626.8071.10118.6000.9792.26494.10461.11172.4
MAX 11783. 11980.13380. 11343.10345.9412.9354.18135.26092.15152.26494.13506.11468.8
MIN 6222.6742.7679.7179.6437.6577 •5811.6061.6000.6484.12000.8051.7831.3
MEAN 8014.9186.10693.9708.8951.8324.7740.10405.11420.9185.13378.9840.9745.4
~1 C~-]1 J 1 J 1 j J 1 )
TABLE E.2.45:MONTHLY MAXIMUM,MINIMUM,AND MEAN FLOWS AT GOLD CREEK (CFS)
'MONTH PRE-PROJECT POST-PROJECT
WATANA OPERATION WI DC OPERATION
MAX MIN MEAN MAX MIN MEAN MAX MIN MEAN
OCT 8212.0 3124.0 5770.8 11782.5 6221.8 8014.0 10983.0 6453.2 7764.9
NOV 4192.0 1215.0 2577 .1 11979.9 6741.5 9185.7 11848.8 7103.9 9630.8
DEC 3264.0 866.0 1807.2 13380.4 7678.9 10693.3 13134.1 8040.5 11270.9
JAN 2452.0 824.0 1474.1 11342.5 7179.3 9707.8 12045.8 7423.9 10596.7
FEB 2028.0 768.0 1249.1 10344.5 6437.0 8951.1 11452.8 6457.3 10190.9
MAR 1900.0 713.0 1123.7 9411.7 6576.7 8323.7 10604.2 6618.1 9285.6
APR 2650.0 745.0 1361.7 9353.6 5811.1 7740.1 9759.4 5950.4 8100.4
MAY 21890.0 3745.0 13240.0 18134.9 6061.3 10404.9 12380.0 6000.0 8706.3
JUN 50580.0 15530.0 27814.9 26091.6 6000.0 11419.5 13305.2 6000.0 9882.9
JUL 34400.0 18093.0 24445.1 15151.9 6484.0 9184.6 11846.2 6484.0 8387.3
AUG 38538.0 16220.0 22228.1 26494.0 12000.0 13378.4 21146.2 12000.0 12633.5
SEP 21240.0 6881.0 13320.9 13506.1 8050.5 9839.6 18330.0 9300.0 10510.3
ANNUAL 11565.2 7200.1 9753.3 11468.8 7831.3 9745.4 11473.3 7776.4 9745.4
TABLE E.2.46:SUNSHINE POST-PROJECT MONTHLY FLOW (CFS)WATANA OPERATION
YEAR OCT NOV nEC JAN FEB MAR APR MAY JUN JUl AUG SEP ANNUAL
1 14948.13272.13727.11639.10593.9545.9015.19395.34035.44603.46969.28715.21460.9
'}14768.10245.10614.9312.8052.7993 •7935.38420.45190.54466.50686.39129.24861.4...
3 16203.13696.13898.12361.10828.9794.9061.12368.47967.47623.44443.26877 •22160.5
4 19378.15193.14196.11709.10660.9829.10996.46640.47565.41437. 41344.27767.24834.4
r:14699.10084.14093.12558.11206.9935.9908.29268.40291.40993.43601.24756.21875.2,.J
6 14013.11535.14429.12818.11506.10089.9362.20299.49979.53956.68218.30395.25667.8
7 14529.12361.13277.11503. 10603.9721.8948.29704.55858.63556.59936.39576.27583.9I
8 18823.15023. 15023.12897.11788. 10356.9611.30965.61001.47102. 44703.40534.26550.7
9 21970.17026.16255.12958.11313.10155.10103.24605.43618.44853.46362.21669.23509.9
10 13642.10114.10249.12278.11376.9792.9599.26288.50795.51809.56977 •31838.24660.1
11 18702.14409.14939.12950.11518.10187.9632.31340.30948.43531.43725.31876.22917.7
12 17429.14103.15620.13630. 11795.10992.11813.28916.43305. 48548.50516.32001.24992.0
13 15992.14651.14936.13113.11659.10487.10285.21229.68419.51892.52298.33251.26583.3
14 17527.14046.14806.12965.11938.9911.8729.31557.40925.58968.44415.26162.24451.1
15 19884.13901.1364.9.11688.10764.9525.9085.10399.86585.43773.41934.22996.24533.6
16 16473 •11640.11 004.12071.11279.10330.10139.21343.42238. 46974.47255.47859.24112.2
17 21779.13315.14081.12295.11326. 10387.10302.14644.50106.43645.52177 •27706.23559.4
18 14004.9598.10341.12589.11611 •10305.9343.29499.48288.60688.72831.32460 •26941.5
19 14277 •13407. 14679.13072 •12303. 11410.11063.33521.58822.53358.41560.21369.24992.9
20 12834.9457.9728.9442.10048.9534.9146.18623.36692 •37324.38648.24356.18879.2
21 12921.9767.9995.9294.8266 •8377 •7990.21579.38186.47108.46946.27370.20749.6
22 14467.11761.11122.9564.8156.8249.7649.13297.53762.48599.55758.27262.22559.2
23 17194.14739.15038.13148. 12118. 10847.9914.32425.49028.47214.43964.31056.24811.2
24 14984.10630.14146.12203.11301. 10158.9525.16187.41047.39945.42795.25464 •20765.2
25 14008.9918.10215.9187.8467.9732.9620.28039.33792.39950. 39002.26164.19934.2
26 15114.10246.10312.9604.8238.8306.7688.23055.54017.59053.45588.28557.23418.8
27 17642.12232.12850.11398. 10672.9793.9998.19823.41336.43079.44355.19672.21159.0
28 13474.10589.11275.10018.8669.9653.10241.24277 •68864.47232.47917.29379.24367.6
29 17297.13673.15429.13104.11544.10514.10246.19426.35611.44153.37728.23435.21094.0
30 13331.10387.10746.9753.8457.8340.8065.29817.42067.54604.40437.25320.21889.9
31 17219.17180.15305.13109.12016.11031.11331.23735.47117.66765.41694.23855.25138.4
32 19175.16189.14921.13324.12374.10924.10996.32962.38747.63392.72896.29750.28143.3
MAX 21970.17180.16255.13630.12374.11410.11813.46640.86585.66765.72896.47859.28143.3
MIN 12834.9457. 9728.9187.8052.7993.7649.10399.30948.37324.37728.19672 •18879.2
MEAN 16209. 12637.13153.11798.10701.9881.9604.25114.47694.49381. 48365.29018.23723.7
J 1 1 1 ]1 1 1 J ---J 1 J J J
TABLE E.2.47:MJNTHLY MAXIM.1M,MINIM.1M,AND />EAN FLO~AT SUNSHINL(CFS)
MONTH PRE-PROJECT PaS"T -PROJECT
WATANA OPERATION I,J/DC OPERA II ON
MAX MIN MEriN MAX MIN MEAN·MAX MIN MEAN
OCT 18555.0 9416.0 13966.0 21969.5 12833.8 16209.3 21536.9 13141.6 15960 .1
NOV 9400.0 3978.0 6028.4 17180.1 9457.1 12637.0 16926.8 9753.6 13082.2
DEC 6139.0 2734.0 4267.2 16255.4 9728.0 13153.3 16009.1 9989.0 13730.9
JAN 4739.0 2507.0 3564.6 13629.5 9187.3 11798.2 14738.9 9383.1 12687.1
FEB 4057.0 1731.0 2998.9 12373.5 8052.0 10701.0 14089.6 8133.9 11940.7
MAR 3898.0 2013.0 2681.0 11409.7 7992.5 9881.0 12746.1 8035.9 10842.9
APR 5109.0 2025.0 3225.6 11812.6 7649.4 9604.0 12314.5 7508.4 9964.3
MAY 50302.0 8645.0 27948.9 46640.4 10399.3 25113.8 42287.3 10338.0 23415.2
JUN 111073.0 39311.0 64089.0 86584.6 30948.0 47693.7 73798.2 30357.5 46157.0
JUL ij5600.0 48565.0 64641.4 66764.9 37323.7 49380.9 63459.2 36956.0 48583.6
AUG 84940.0 42118.0 57214.7 72896.0 37728.0 48364.9 67548.2 37728.0 47620.1
SEP 53703.0 18502.0 32499.2 47859.1 19671.5 29018.0 44997.5 20921.0 29688.6
ANNUAL 28226.1 17950.7 23731.6 28143.3 18879.2 23723.7 28024.6 19068.6 23723.7
TABLE E.2.48:SUSITNA POST-PROJECT MONTHLY FLOW (CFS)WATANA OPERATION
YEAR OCT NOV DEC JAN FEF MAR APR MAY JUN JUL AUG SEF ANNUAL
1 27814.19000.16313.14962.13572 •12888.12361.63270.90038.110314.98552.40312.43558.5
"')20568 •12466.12791.13456.12912.12230.11726.55497.68572.108156.93277.61531.40508.4.:.
3 33543.24358.17105.17165.15353.13365.12689.46405.111776.120008.107266.76896.49868.4
4 46936.24283.19862.16959.15091.13862.14696.85178.114051.113155.89000.38198.49569.6
5 21641.16821.15388.16093.13310.12491.13009.55189.94367.104339.114487.62655.45223.8
6 25721.14363.16299.16145.14162.12827.13116.56705.149338.131938.110646.48514.51055.3
7 23441.18516.17411.15070.15147.13836.13886.79033.143263. 151802. 122522.
99299.59697.5,
8 45392.29542.24263.19491.16673.14865.14409.60029.158067.125118.116273.80238.58911.8
9 56207.27881.20752.16443.14703.14191.14802.67167.95763.107283.89069.54625.48515.7
10 32607.14312.11421.16686.14881.13177.13171.53430.97111.130505.123363.62827.48920.8
11 29325.18158.17121.15607.14627.13163.12533.46599.75771.114710.102382.70355.44438.9
12 34216.20908.23885.21560.18351.16704.16506.81935.134134.123876. 106597.
58434.55028.0
13 30441.21037.19093 •17941.14499.13462.13339.51263.143931.127577. 112337.
69346.53071.5
14 31287.18749.18981.17561.16170,13570.12268.50215.69944.127169.98183.67762.45425.8
15 39175.19696.15742.15242.14078.12422.12234.37291.128638.109743.87840.45839.45006.8
16 29747.14626.12595.15649.14512.13682.13824.46231.93824.120338.102726.84100.47034.4
17 40124.20307.19276.16921 •15806.14602.14752.50476.105720.106009. 108899.
61437.48094.7
18 28849.18265.14807.16919.16043. 14195.
13984.54693.117007.119869.127402.84608.52448.9
19 41295.23867.25197.20495.19849.16284.15466 •90703.119919.114136.81705.42869.51242.8
20 28632.16063.13695.13677 •14480.13047.12816.50271.95679.104307.92754.57296.42928.4
21 26188.12588.12163.12768.11399.11727.10609.48928.85196.119322. 109748.
80764.45370.0
22 35021.20901.14825.12748.11896 •11780.10797.32454.99812.122996.114549.63881.46220.2
23 35644.22916.18907.18270.16775.14158.13599.70307.158196.127709. 100307.
57120.54709.5
24 28178.19465.18264.16500.15793.13824.14392.62506.103911.111596.98971.45453.45983.0
"'),;:-23700.15332.12772.13707.12696.13805.13666.58011.57917.90867.76032.53174.37024.2.:.OJ
26 22332.15708.15954.14655.13052.12544.11395.41215.109981.119061.85270.70730.44498.1
27 33627.17927.16116.15420.13931.12880.13957.67408.91970.102773.91850.50080.44247.5
28 32994.22971.19090. 15887.
13940.13256.12937.53165.146992.128938.118260.80470.55125.2
29 38128.19173.17645.15865.15088.14102.13737.45389.78497.103823.97710.56193.43186.2
30 38918.19739.15744.14902.13197.12409.13044.77201.102118. 125330. 119740.
72870.52422.5
31 58171.39370.24806.19011.17334.16418.18734.63408.124933.163892.117470.87220.62880.8
32 37565.24194.18632.16665.15906.13689.17054.80382.96557.130592. 147556.
64460.55646.0
MAX 58171.39370.25197.21560.19849.16704.18734.90703.158196.163892.147556.99299.62880.8
MIN 20568.12466. 11421.12748.11399.11727.10609.32454.57917.90867.76032.38198.37024.2
MEAN 33670.20109.17404.16264.14851.13608.13610.58811.108218.119289.105086.64049.48995.7
1
1 J J 1---]~-J 1 I 1 J J J
TABLE E.2.49:MONTHLY MAXIMUM,MINIMUM,AND MEAN flOWS AT SUSITNA (CfS)
MONTH PRE-PROJECT POST-PROJECT
WATANA OPERATION WIDC OPERATION
MAX MIN MEAN MAX MIN MEAN MAX MIN MEAN
OCT 58640.0 18026.1 31426.3 58171.2 20567.9 33669.5 58425.2 20926.6 33420.4
NOV 31590.0 6799.3 13500.7 39370.1 .12466.2 20109 {3 36526.8 12773.9 20554.5
{lEe 15081.0 4763.4 8517.5 25197.4 11420.8 17403.6 25763.1 11432.2 17981.2
JAN 12669.1 6071.9 8030.0 21559.6 12747.9 16263.6 22262.9 12763.8 17152.6
FEF 11532.2 4993 t1 7148.6 19848.7 11399.4 14850.7 20933.1 11427.2 16090.4
MAR 9192.6 4910.4 6407.9 16704.3 11726.5 13607.9 17986.8 11699.0 14569.8
APR 12030.0 5530.8 7231.2 18733.6 10608.9 13609.6 19717.5 10655.9 13969.9
MAY 94143.2 29809.3 61646.1 90702.7 32453.9 58811.0 88615.3 32626.2 57112.4
JUN 176218.8 67838.0 124613.8 158195.6 57916.9 108218.5 157474.1 57089.1 106681.9
JUL 181400.0 102184.3 134549.5 163891.9 90867.2 119289.1 160586.2 90191.2 118491.8
AUG 159600.0 80251.5 113935.4 147556.0 76031.5 105085.6 142208.2 76031.5 104340.8
SEP 104218.4 39331.2 67529.9 99299.0 38197.7 64048.6 104218.4 38197.7 64719.3
ANNUAL 63158.6 36285.1 49003.6 62880.8 37024.2 48995.7 62736.3 36786.6 48995.7
TABLE E.2.50:WATANA FIXED
1995 Simulation
Simulated Week of Week of Maximum Powerhouse Total
Water First Maximum Release Flow Relet
Year Release Release cfs cfs Acre-
1950 Aug 26-Sept Sep 2-8 1,011 9,514 30,€
1951 Aug 5-11 Aug 5-11 167 9,030 2,::
1952 Aug 19-25 Aug 19-25 724 8,898 20,~
1953 Aug 12-18 Aug 12-18 266 8,946 5,1
1954 Sept 2-8 Sept 9-15 347 9,424 6,~
1955 Sept 9-15 Sept 9-15 343 9,265 4,~
1956 Aug 19-25 Sept 9-15 9,615 9,245 545,~
1957
1958 Aug 19-25 Sept 2-8 1,309 9,337 53,1
1959 Aug 5-11 Sept 2-8 4,925 9,089 119,~
1960
1961 Aug 26-Sept Sept 2-8 828 9,194 23,f
1962 Aug 26-Sept Sept 2-8 10,755 9,066 298,~
1963 Aug 19-25 Aug 26-Sept 7,546 8,887 189,f
1964 Ju Iy 29-Aug 4 Sept 9-15 1,113 9,414 66,1
1965 Aug 26-Sept 1 Aug 26-Sept 1,112 9,082 15,~
1966 Oct 1-6 Oct 1-6 2,379 10,140 48,1
1967 Aug 19-25 Sept 2-8 15,380 9,066 47,1
1968 Aug 12-18 Sept 2-8 921 9,285 49,~
1969 Sept 2-8 Sept 2-8 302 9,776 8,::
1970 Aug 26-Sept Sept 9-15 692 9,801 22,(
1971 Sept 2-8 Sept 2-8 5,597 9,076 119,f
1972 July 29-Aug 4 Aug 26-Sept 795 9,011 22,2
1973 July 29-Aug 4 Sept 9-15 917 9,659 25,~
1974 Aug 12-18 Sept 9-15 677 9,840 21,S
1975 Aug 5-11 Sept 2-8 898 9,233 34,~
1976 Aug 19-25 Sept 9-15 1,286 9,706 53,f
1977 Aug 26-Sept Sept 2-8 1,083 9,267 30,S
1978 Aug 19-25 Aug 26-Sept 859 9,440 33,(
1979 Aug 19-25 Sept 2-8 1,208 9,288 42,€
1980 Aug 26-Sept Sept 2-8 1,187 9,130 39,1
1981 Aug 19-25 Aug 19-25 21,526 8,710 602,~
-
CONE VALVE OPERATION
000 Simulation
Week of Week of Maximum Powerhouse Total
3se First Maximum Release Flow Release
-feet Release Release cfs cfs Acre-feet
500
500
300
100
~OO
300
500 Aug 26-Sept Sept 9-15 8,587 10,272 356,400
100 Sept 2-8 Sept 2-8 272 10,375 3,800
500 Sept 2-8 Sept 9-15 2,196 10,272 42,300
500
WO Aug 26-Sept Sept 2-8 9,747 10,073 182,700
500 Aug 26-Sept Sept 2-8 2,660 10,073 57,600
100
WO
100
100 Aug 19-25 Sept 2-8 14,372 10,073 371,900
WO
500
)00
iOO Sept 2-8 Sept 2-8 2,614 10,090 64,000
100
500
~OO
500
,00 Sept 2-8 Sept 2-8 204 10,566 5,500
~OO
)00
300 Sept 2-8 Sept 2-8 176 10,320 2,400
100 Sept 2-8 Sept 2-8 167 10,150 2,300
500 Aug 19-25 Aug 19-25 17,943 9,684 500,300
-
-
-TABLE E.2.51:WATANA!DEVIL CANYON OPERATION
MONTHLY MINIMUM ENERGY DEMANDS
WATANA DEVIL CANYON
Assoc~atea AssoClated
Demand Pattern Minimum Powerhouse MinimlUll Powerhouse
~Percent of Energy Discharge Energy Discharge
Month Annual Demand GWh (cfs)GWh (cfs)
Oct 8.70 442.9 11,900 207.2 6,660
Nov 9.86 247.5 7,020 224.2 7,140
Dec 11.17 287.3 8,040 264.0 8,140
Jan 10.21 259.5 7,420 244.6 7,540
Feb 8.78 199.7 6,450 192.0 6,550
~Mar 8.88 221.3 6,590 217.0 6,690
Apr 7.66 162.7 5,100 203.6 6,540-May 7.14 205.4 6,240 195.7 6,090
Jun 6.70 121.9 3,730 202.4 6,450
Jul 6.62 126.5 3,590 205.1 6,320
Aug 6.96 143.6 3,910 335.3 10,670
Sept 7.32 218.1 6,030 251.0 8,620
Note:Monthly minimum energy demands taken from year 21 of energy simulation.
-I
-
TABLE E.2.52:WATANA POST-PROJECT MONTHLY FLOW (CFS)WATANA/DEVIL CANYON OPERATION
YEAR OCT NOV ItEC JAN FEB MAR APR MAY JUN JUL AUG SEP ANNUAL
1 5564 •10435.12315.11438.10786.8708.7283.4470.4011.3800.4081.7547.7512.1
'1 11900.694B.7941.7346.6377 •6512.6824. 6344.4283.3925.3994.6939.6617.0L
3 9062.9851.12276.11401.11 022.9708.7407.'4993.3199.3629.5170. 5760.7776.7
4 9261.10917.12249.11409.11003.9827.7985.7029.6219.3931.3768.4193.8134.8
5 114 7B.6741.11580.11103.10783.8778.7545.6287.3312.3780.3263.4124.7391.6
6 10209.6683.12250.11377.10962.10316.7544.4550.5182.5129.7016.12466.8628.5
7 7078.10812. 12317.11456.10735.8834.7321.6881.6114.5830.8243.13194.9051.0
8 7183.10907.12248.11395. 10967.10194.8572.4982.6537.3771.5122.8992.8381.0
9 8806.10831. 12129.11313.10943.10208.9198.6060.5625.3855.4418.5853.8252.1
10 11674.6810.7784.9626.10929.8833.7489.4878.3432.3443.5550.10150.7528.3
11 8141.10947.12222.11360.10967.10203.8619.7502.4273.3791.3700.4009.7964.5
12 10337.10068.12172.11374.11004.10125.9074.7178.5969.4107.6899.4895.8592.4
13 9420.9620.12348.11410.10992 •10210.8946.6097.5752.6626.13869.12746.9832.9
14 8536.11048. 12290.11405.10966.10240.8273.7187.6378.5757.8597.10BOO.9277.7
15 8163.11013.12306.11443.11000.8715.7212.5143.5707.6499.6927.5164.8262.7
16 10477.8758.12353.11498.10753.8947.7835.5742.4737.4587.5402.1048B.8451.5
17 8197.10789.12268.11399.10978.9626.7941.4566.5896.3674.3624.4935.7803.3
18 11738.6815.7793.9300.11011.9029.7453.7144.6563.5029.8676.13673.8666.8
19 6994.11011.12386. 11388. 10961.10170.9185.7299.6230.6135.4013.6880.8537.2
20 11765.6840.7834.8576.10728.8825.7453.4777.4080.4168.4335.7482.7218.3
21 11901.7018.8039.7419.6448.6592.5100.6242.3729.3593.3914.6029.6343.8
22 11696.6814.7898.7352.6397.6537.5682.4624.4463.3927.6384.9000.6736.5
23 7955.10985.12210.11300.10870.10124.9154.6463.5819.6512.7118.9214.8963.4
24 7715.10748.12330.11451.11014.9397.7517.5073.4338.4230.4381.8326.8022.4
25 11844.6936.7938.7336.6370.8005.7475.7327.4025.3979.4185.6235.6815.1
26 11900.6975.7942.7335.6337.6460.5608.5810.6308.6148.5613.7337.6990.9
27 8655.10825.12334.11217.10723.8830.7663.4209.3625.4226.5226.8131.7953.8
28 11801.6792.7776.7227.6272.8B25.7806.4073 •5982.6466.6986.5189.7113.6
29 10179.10413.12205.11360.10940.10167.9200.6261.4440.4028.4075.7047.8344.7
30 11758.6849.7904.7322. 6356.6519.7233.7022.6458.6041.5073 •4972 •6970.3
31 11642.8455.12272 •11412.10993 •10208.9085.5002.6627.5933.6653.7035.8768.7
32 9433.10951.12289.11453.11004.10223.8723.5240.4643.5011 •14043. 12026.9580.4
MAX 11901.11048.12386.11498.11022.10316.9200.7502.6627.6626.14043.13673.9832.9
MIN 5564.6683.7776.7227.6272.6460.5100.4073.3199.3443. 3263.4009.6343.8
MEAN 9764.9113.10881.10288.9925.9059.7794.5827.5124.4736.5947.7838.8015.1
1 )j ]j )J J "J J -I 1 1 J
TABLE E.2.53:DEVIL CANYON POST-PROJECT MONTHLY FLOW (CFS)WATANA!bEVIL CANYON OPERATION
YEAR OCT NOV I1EC JAN FEB MAR APR MAY JUN JUL AUG SEF'ANNUAL
1 6602.10756.12482.11575.10887.8809.7405.6305.6048.5990.10941.8950.8886.0
2 6553.7072.8066.7443'.6472.6589.7026.7913.5744.5714.10860 •7859.7286.3
3 6490.10226.12526.11611'.11124.9808.7481.5766.7439.6373.10727.8261.8975.4
4 6623.11386.12518.11589.11137.9930.8135.9744. 9980.5760.10597.7958.9603.3
5 6757.7069.11783.11240.10910.8869.7733.9876.7024.5951.9972.7959.8758.6
6 6747.7139.12562.11638.11186.10460 •7710.6222.8383.7547.11210.10144.9239.5
7 7630.11012.12479.11567.10873.8992.7470.9901.10079.'9211.'11700.16496.10608.2
8 8217.11398.12528.11605.11167.10364 •8743.7280.9671.5932.10849.8402.9668.7
9 10206.11485.12775.11624.11113. 10320.9370.7957.7941.5865.10680.8739.9834.1
10 6708.7080.8040.9862.11159.9017.7723.8639.6640.6340.10198.13013.8682.2
11 9043.11350.12561.11646.11168.10355.8774.9254.'5756.6024.10476.7720.9509.1
12 6581.105,07.12629.11806.11292.10433.9515.9571.10255.7147.11064.8149.9904.4
13 6617.9907.12560.11597.11148.10353.9108.6905.10408.8173 •16223.14767.10638.6
14 9290.11229.12477 •11593.11169. 10315.8314.9579.9808.9378.11051.11008.10431.8
15 8980.11309.12492 •11569.11126.8803.7299.5740.10542.8342 •.11146 •.8569.9650.2
16 6759.9042.12437.11566.10809.9006.7917.7043.7634.7540.10669.9529.9156.0
17 9478.11132.12536.11618.11181.9835.8222.6206.10396.6057.10415.8394.9610.5
18 6612.7071.8036.9556.11248.9228.7657.9024.·9641.8123.12865.15728.9546.8
19 7567.11274.12612.1i622.11180.i0389.9400.9455.9988.8923.10921.8710.10165.1
20 6594.7056.7998.8704.'10839.'8919.7562.5989.5992. 5682.11178.8712.7918.0
21 6664. 7143.8140.7540.6555.6689.6544.6088.6449. 6325.10673 •8623.7293.0
22 6972.7400.8285.7574.6564.6687.5855.6245.6796.5742.10406.9249.7320.5
23 8519.11304.12565.11665.11215.10418.9414.10267.10320.8409.11364.8784.10350.8
24 6266.10932.12464 •11559.11143.9484.7590.5682.6871.5806.11188.8952.'8981.6
'11:"6579.7044.8004.7393.6426.8067.7552.9436 •.6018.5797.11037.8420.7662.0L.J
26 6618. 7120.8152.7528.6569.6690.5853.8174..9915.,8906.10942.8145.7896.4
27 7792.11077.12459.11363.10856.8965.7864.6575.6445.5797.11498.8882.9123.0
28 6680.7257.8236.7536.6539.9076.8113 •6715.10229.8499.11131.8576.8225.7
29 '6722.10985.12591.11650.11197.10391.'9389.6730.5580.5721.10937.8773.9211.8
30 6786. 7228.8141.7489.6504 •.6583..7318.7986.7606.8586 •10647.'8702.'7809.6
31 6685.8892.12513.11591.11143.10352.9263.6239.9482.9188.11236.8362.9572 .1
32 7855.11346.12458.11593.11122.10331.8865.6510.5598.8177 •17878.12762.10376.4
MAX 10206.11485.12775. 11806.11292.10460.9515.10267.10542.9378.17878.16496.10638.6
MIN 6266.7044.7998.7393.6426.6583.5853~5682.5580.5682.9972.7720.7286.3
MEAN 7318.9445.11128.10485.10094.9204.8006.7657.8146.7094.11334.9603.9121.7
TABLE E.2.54:GOLD CREEK POST-PROJECT MONTHLY FLOW (CFS)WATANA/DEVIL CANYON OPERATION
YEAR OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP ANNUAL
1 7179.10934.12578. 11650.10939.8865.7473 •7324. 7179. 7206.12000.9300.9380.2
2 6749.7141.8135.7498.6524.6632.7139.8785.6555.6708.12000.9300.7776.4
3 6839.10431.12669. 11727.11181.9860.7523.6195.9795.7902.12000.9300.9609.5
4 7307.11650.12668.11690.11212.9983.8218.11255. 12070.6776.12000.9300.10337.3
5 7252.7248.11896. 11316.10980.8919.7838.11870.9085.7156.12000.9300.9573.3
6 7287.7392.12739.11782. 11311.10536.7803.7151.10161.8894.12000.10444.9788.5
'7 7933.11124.12572 •11625.10950.9079.7553.11582.12282.11089.13620.18330.11473.3,
8 8788.11674.12683.11722. 11278.10459.8834.8556.11415.7132.12000.10173.10384.1
9 10983.11849.13134.11797.11208.10383.9465.9008.9227.6982.12000.9300.10443.8
10 7116.7230.8182.9993.11287.9119.7853.10728.8423.7949.12783.14603.9592.6
11 9540.11577.12750.11805.11280.10439.8856.10231.6577 •7265.12000.9300.10137.1
12 7204.10747.12887.12046.11453.10604.9759.10900. 12635.8837.12000.9300.10692.4
13 7074.10063.12681.11701.11234.10433.9195.7354.12998.9032.17532.15890.11257.3
14 9705.11333.12581.11697. 11282.10356.8333.10911.11714.11390.12000.11551.11072.9
15 9431.11474.12599.11639.11191.8852.7348.6000.13305.9366.12000.9300.10199.1
16 7306.9196.12487.11601.10840.9039.7963. 7766.9244.9185.12000. 10645.9769.4
17 10187.11322 •12689.11739.11293.9948.8378.7117.12900.7381.12000.9300.10345.3
18 6931.7213.8172.969B.11380.9339.7770.10069.11354.9841.15192.16870.10305.0
19 7882.11423.12737.11752.11301. 10510.9519.10652. 12076.10472 •12000.9300.10800.3
20 6890.7179.8091.8778.10902.8972.7625.6687.7094.6484.12000.9300.8318.1
21 6921.7212.8196.7607.6614 •6743.6578.6746.7960.7842.12000.9300.7820.4...,...,7515.7725.8500.7697.6656.6770 •5950.6562.8695.6750.12000.10053.7914.2.:.....:..
23 8829.11485.12762.11868.11406.10581.9559.12380.12820.9462.12000.9300.11037.3
24 6453.11030.12542.11620.11214.9529.7630.6021.8279.6484.12000.9300.9329.5
25 6820.7104.8041.7424.6457.8102.7595.10612.7121.6807.12000.9300.8132.5
26 6850.7200.8269.7635.6698.6818.5990.9487.11922 •10438.12000.9300.8565.2
27 8528.11217.12532.11440.10930.9039.7976.7890.8011.6484.12000.9300.9606.7
28 7001.7516.8491.770B.6687.9215.8283.8184.12592.9629.12000.9300.8895.9
29 7357.11299.12808.11811.11340.10516.9494.6986.6213.6662.12000.9300.9641.2
30 7191.7439.8272.7582.6587.6618.7366.8522. 8244.10003.12000.9300.8275.9
31 7096.9129.12650.11690.11226. 10431.9358.6922.12307.11846.12000.9300.10325.4
32 8334.11633.12677.11760.11268.10448.8994.8150.6000.8941.21146.13171.11053.7
MAX 10983.11849.13134. 12046.11453.10604.9759.12380.13305.11846.21146.18330.11473.3
MIN 6453.7104.8041.7424.6457.6618.5950.6000.6000.6484.12000.9300.7776.4
MEAN 7765.9631.11271.10597.10191.9286.8100.8706.9883.8387.12634.10510.9745.4
1
J 1 1 1 ))1 })J )
TABLE E.2.55:iMJNTHLYMAXIM.JM,MINIKlM.AND t-£AN FLOWS AT DEVILC:ANYON
MONTH PRE,,;'PROJECT POST-PROJECT
WATANA OPERATION WIDC OPERATION
MAX MIN MEAN MAX MIN MEAN MAX MIN MEAN
OCT 7517..6 2866.5 5324.3 11005.0 6034.4 7567.6 10205.5 6265.8 731804
NOV 3955.0 1145.7 2390.8 11735.1 6681.4 8999.4 11485.2 '7043.8 9444.5
DEC 2904.9 810.0 1664.5 13021.3 7628.7 10550.6 12775.0 7998.0 11128.2
JAN 2212.0 756.9 1362.1 11102.5 7148.0 9595.7 11805.8 7392.6 10484.6
FEB 1836.4 708.7 1152.5 10152.9 6384.5 8854.5 11292.4 6426.2 10094.3
MAR 1778.7 663.8 1042.1 9290.4 6541.4 8242.1 10459.6 6582.8 9203.9
AP~:2405.4 696.5 1267.0 9109.0 5763.9 7645.4 9514.8 5853.2 8005.7
MAY 19776.8 3427.9 12190.3 16021.7 5801.2 9355.2 10266.8 5682.3 7656.6
JUN 47816.4 14709.8 26078.1 23328.0 5598.0 9682.7 10541.6 5579.5 8146.1
JUL 32388.4 17291.0 23152.2 13136.9 5805.8 7891.7 9378.0 5682.0 7094.4
AUG 35270.0 15257.0 20928.2 23226.0 9971.6 12078.5 17878.2 9971.6 11333.6
SEF'19799.1 6463.3 12413.6 12390.3 7632.8 8932.3 16495.8 7719.9 9603.0
ANNUAL 10946.5 6800.1 9129.7 10763.2 7341.2 9121.8 10638.6 7286.3 9121.7
TABLE E.2.56:SUNSHINE POST-PROJECT MONTHLY FLOW (CFS)WATANA!DEVIL CANYON OPERATION
YEAR OCT NOV nEC JAN FEB MAR APR MAY JUN JUl AUG SEP ANNUAL
1 14847.13990.14750.13371.12427.10172.8914.18232.33192.43785.46969.28733.21695.3
2 15127.10553.10839.9468.8139.8036.9085.36891.44637.53612.50686.39129.24806.6
3 14981.13389.14551. 13597.12692.11262.8960.12034.46163.46449.44443.26877 •22174.9
4 16499.15352.15048.13408.12735. 11480.10895.42287.48825.40807.41344.27767.24791.3
5 14875.10240.14373.13683.12869.10562.9807.27185.38640.40182.43601.24756.21813.5
6 14105.10972 •15007.13915.13100.12013.9261.19590.49987.52228.63942.31539.25573.7
7 13993.13591.14433.13257. 12266.10348.8847.27079.52883.60568.58124.44495.27588.4
8 18234.15653.15448.14028.13249.12103. 10541.28946.60408.46124.44703.38494.26550.7
9 21170.16927 •16009.13899.12897.11878. 11331.23867.44279.43952.46362.21848.23791.6
10 13883.10411.10261.11932.13039.10419.9498.24198.49389.50470.53551.34598.24378.4
11 18113.15142.15373.14019.13029.11917. 10484.29253.30358.42509.43725.31876.23076.1
12 16406.13856.15697.14333.13177.12274.12218.25978.44071.47907.50516.32001.24958.3
13 15737.14020.15401. 14023.13076.12008.11076.19284.57265.50938.55163.38711.26458.7
14 16938.14585.15271.14171. 13403.11755.9528.27126.42343.55209.41268.28413.24260.8
15 21537.15131.14638.13388.12672 •10152.8984.10338.73798.45252.41934.22996.24264.4
16 16488.13869.15812.14014.12942.10957.10038.19373.42012.46387.47255.44998.24571.8
17 21190.14545.15023.13743.13002.11523.10201.13951.49519.42764.52177 •27706.23848.3
18 14319.9908.10528.11896. 13274.10932.9242.27501.48006.60166.65319.37379.26652.5
19 13688.14483.15245.13952.13387.12508. 11968.31433.57296.53787.41560.21369.25138.8
20 13142.9754.9989.10381.11711.10161.9045.18141.35920.36956.38648.24356.19068.6
21 13213.9975.10178.9383.8294.8349.8648.21053.36932.45953.46946.27370.20622.9
22 14491.11785.11140.9580.8134.8171.7508.13469.51973 •47587.54609.28015.22292.2
23 17295.15137.15174.13886.13179.12093.11059.26670.45246.48984.43964.31056.24558.8
24 15215.14795.15107.13732.12998.11175.9424.16001.40412.39945.42795.25464 •21479.0
25 14371.10280.10531.9432.8199.9596. 9519.25918.32964.39274.39002.26164.19696.6
26 15413.10438.10443.9665.8217. 8228.7557.23517.52448.58410.45588.28557.23313.0
27 16354.13462.14185.12973.12335.10420.9897.18145.39997.43050.44355.20921.21418.1
28 13747.10754.11373.10110.8709.10886.10140.22796.62395.48953.47917.29379.24008.5
29 17185.14904.15532.13995.12899.11913.11334.17743.35207.43572 •37728.23435.21356.9
30 13507.10552.10899.9859.8507.8381.9620.28528.43403.52897.40437.25320.21930.9
31 17473. 14337.15423.14160.13459.12550.12315.21769.48311.63459.41664.23855.24993.9
32 17189.15842.15709.14739.14090.12746. 11919.30994.38747.62541.67548.32460.28024.6
MAX 21537.16927.16009.14739.14090.12746. 12315.42287.73798.63459.67548.44998.28024.6
MIN 13142.9754.9989.9383.8134.8036.7508.10338.30358.36956.37728.20921.19068.6
MEAN 15960 •13082.13731.12687.11941.10843.9964.23415.46157.48584.47620.29689.23723.7
'1
))]-_..)]1 1 )1 1 J
TABLE E.2.57:SUSITNA POST-PROJECT MONTHLY FLOW (CFS)WATANA/DEVIL CANYON OPERATION
YEAR OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP ANNUAL
1 27714.19719.17336.16695.15407.13516.12260 •62108.89195.109496.98552.40330.43792.9..,20927.12774.13016.13611.12999.12273 •12876.53967.68020.107303.93277 •61531.40453.6L
3 32321.24051.17757. 18401.17217.14833.12588.46070.109972.118833.107266.76896.49882.8
4 44058.24442.20714.18658.17166.15513.14595.80825.115311.112525.89000.38198.49526.4
I:'21816.16977 •15668.17218.14973.13119.12908.53107.92716.103528.114487.62655.45162.1.J
6 25812.13800.16877. 17243.15756.14752.13015.55996.149346.130211.106370.49659.50961.3
7 22905.19746.18567. 16824.16811.14464.13785.76407.140288.148813.120709. 104218.59701.9
8 44804.30171.24687. 20622.18134.16612.15339.58010.157474.124140.116273.78198.58911.9
9 55407.·27781.20505.17385.16288.15913.16031.66429.96424.106382.89069.54803.48797.4
10 32848.14609.11432.16340.16544.13805.13071.51339.95705.129166.119938.65587.48639.1
11 28736.18892.17554.16676.16138.14894.13386.44513.75181.113688.102382.70355.44597.2
12 33192 •20662.23961. 22263.19733. 17987.16912.78997.134900.123235.106597.58434.54994.3
13 30187.20406.19558.18852.15917.14983.14130.49317.132777.126623.115202.74806.52946.9
14 30698.19287.19445. 18767.17635.15414.13067.45784.71362.123410.95037.70013.45235.4
15 40828.20925.16731. 16942.15987.13050.12134.37229.115852.111222.87840.45839.44737.5
16 29762.16855.17403.17593.16176.14309.13723.44261.93599.119751.102726.81239.47494.0
17 39535.21536.20217.18370.17483.15738.14651.49783.105132.105128.108899.61437.48383.6
18 29164.18575.14993. 16226.17706.14823.13883.52695.116725.119348.119890.89527.52160.0
19 40706.24943.25763.21375.20933.17382.16371.88615.118393.114565.81705.42869.51388.7
20 28940.16359.13956.14616.16143.13675.12715.49789.94907.103939.92754.57296.43117.8
21 26481.12797.12347.12857.11427.11699.11267.48402.83942.118167.109748.80764 •45243.2..,..,35044.20925 •14843.12764 •11874.11703.10656.32626.98023.121984.113400.64634.45953.2LL
23 35745.23314.19043.19009.17836.15404.14744.64552.154414.129479.100307.57120.54457.1
24 28409.23630.19224.18029.17491. 14842.14291.62320.103276.111596.98971.45453.46696.8
"'1:'24063.15694.13088.13952.12428.13672 •13566.55889. 57089.90191.76032.53174.36786.6...J
26 22631.15900.16085.14716.13031.12466.11264.41677.108413.118418.85270.70730.44392.3
27 32339.19157.17451.16995.15594.13507.13856.65730.90631.102744.91850.51329.44506.6
28 33267.23136.19188.15979.13980. 14489.12836.51684.140522.130659.118260.80470.54766.1
29 38016.20404.17748.16756.16443.15501.14825.43706.78093.103242.97710.56193.43449.0
30 39094.19904.15897.15008.13247.12450.14599.75912.103454.123623.119740.72870.52463.4
31 58425.36527.24924.20062.18777.17937.19718.61442.126127.160586.117440.87220.62736.3
32 35579.23847.19420.18080.17622.15511.17977 •78414.96557.129741.142208.67170.55527.3
MAX 58425.36527.25763.22263.20933.17987.19718.88615.157474.160586.142208. 104218.62736.3
MIN 20927.12774.11432.12764 •11427.11699.10656.32626.57089.90191.76032.38198.36786.6
MEAN 33420.20554.17981. 17153.16090.14570.13970.57112.106682.118492.104341.64719.48995.7
TABLE E.2.58:DEVIL CANYON F
2002 Simulation
Simulated Week of Week of Maximum Powerhouse Total
Water First Maximum Release Flow Release
Year Release Release cfs cfs Acre-fel
1950
1951
1952 Aug 5-11 Aug 5-11 7,533 12,315 331,51
1953 Ju Iy 29-Aug 4 Ju Iy 29-Aug 4 9,399 12,127 570,71
1954 Aug 5-11 Aug 12-18 10,207 12,428 456,01
1955 Ju Iy 29-Aug 4 Aug 26-Sept 1 22,289 12,838 801,81
1956 July 15-21 Ju Iy 29-Aug 4 17,516 12,127 1,385,71
1957 Ju IY 29-Aug 4 July 29-Aug 4 7,639 12,127 806,11
1958 July 29-Aug 4 July 29-Aug 4 14,748 12,127 532,31
1959 Aug 12-18 Aug 26-Se pt 1 38,979 0 1,427,91
1960 Aug 26-Sept Sept 9-15 13,943 13,355 463,71
1961 July 15-21 July 22-28 12,452 11,976 897,61
1962 July 9-14 July 22-28 13,665 11,976 1,326,31
1963 July 15-21 July 22-28 18,744 11,976 1,200,21
1964 July 15-21 July 15-21 11,173 12,097 437,01
1965 Aug 5-11 Aug 12-18 16,231 12,428 691,81
1966 Oct 1-6 Aug 19-25 8,952 12,579 244,41
1967 Ju Iy 29-Aug 4 Aug 12-18 43,844 (1 )0 1,707,01
1968 JUly 15-21 July 22-28 11,590 11,976 535,81
1969
1970
1971
1972 July 9-14 JUly 9-14 8,237 12,217 764,61
1973
1974
1975 Sept 9-15 Sept 16-22 3,957 13,613 113,81
1976
1977 Ju Iy 29-Aug 4 Ju IY 29-Aug 4 8,892 12,127 399,01
1978
1979 Aug 5-11 Aug 12-18 6,462 12,428 167,31
1980 July 15-21 Ju Iy 29-Aug 4 19,011 12,127 935,31
1981 JUly 22-26 Aug 12-18 31,645 12,428 1,849,41
-.
(1)Includes discharge 0 f 5344 cfs over spi I Iway.
c
-'.:
IXED CONE VALVE OPERATION
201 Simulation
Week of
First
Release
Week of
Maximum
Release
Maximum
Release
cfs
Powerhouse
Flow
cfs
Total
Release
Acre-feet
)0
)0
)0
)0 Sept 2-8 Sept 2-8 4,790 13,763 72,200
)0 Aug 5-11 Aug 12-18 10,760 13,763 567,500
)0 Sept 23-30 Sept 23-30 1,353 13,763 18,800
)0
)0 Aug 26-Sept Sept 2-8 13,306 13,763 256,400
)0
)0 Sept 23-30 Sept 23-30 815 13,763 11,300
)0 Aug 12-18 Sept 2-8 8,469 13,763 387,800
)0 Aug 12-18 Aug 19-25 7,997 13,763 258,100
)0
)0 Sept 23-30 Sept 23-30 7,486 13,763 103,900
)0 Oct 1-6 Octo 1-6 465 13,763 6,500
10 Aug 12-18 Aug 19-25 15,098 13,763 582,800
10
10 Sept 9-15 Sept 9-15 3,241 13,763 45,000
10 Sept 23-30 Sept 23-30 3,160 13,763 43,900
10
10
10 Sept 16-22 Sept.16-22 445 13,763 6,200
JO Aug 12-18 Aug 19-25 26,856 8,069 822,600-.
-,
GLOSSARY
Accretion -the gradual addition of material by the deposition of
sediment carried by the water of a stream.
Alluviu.- a general term for all detrital deposits resulting from
the operations of modern rivers,thus including the sediments laid
down in riverbeds,floodplains,lak~s,fans at the foot of
mountain slopes and estuaries.
Aquiclude - a formation that will not transmit water fast enough to
furnish an appreciable supply for a well or spring.
Aquifer -stratum or zone below the surface of the earth capable of
producing water as from a well.
Aufeis - a sheet of ice on a river fl oodpl ain
Bankfull stage -the water surface elevation attained by the stream
when flowi ng at capac ity;i.e.,stage above which banks are
overflowed.
Bifurcate -forked as in a Y-shape.
Candle -elongate prismatic crystals of ice arranged perpendicular to
the surface and in a weakened state.
Colluvial -consisting of alluvium in part and also containing
angul ar fragments of the original rocks.
Diel - a chronological day (24 hours)or distinct from the dayl ight
portion of varying duration.
Epilimnion -the upper layer of a body of water,usually with a small
but variable temperature gradient.
Eutrophication -the process by whi ch a body of water becomes overly
rich in nutrients and deficient in dissolved oxygen.
Floodplain -that portion of a river valley,adjacent to the river
channel,which is built of sediments during the ~resent regimen of
the stream and which is covered with water when the river
overflows its banks at flood stages.
Fluvial -of or pertaining to riyers;produced by river action.
Frazil ice -ice of small plate-like crystals suspended in the flow.
Glacial flour -rock finely ground by a glacier.
Hypolimnion -that part of a lake below the thermocline.
Ice pan - a large,flat piece of ice.
lacustrine -pertaining to,produced by,or formed in a lake or
lakes.
lithology -the physical character of a rock.
Meltstream -water resulting from the melting of snow or of glacier
ice.
Outwash -drift deposited by meltwater streams beyond active glacier
ice.
Periglaclal -refers to areas,conditions,processes,and deposits
adjacent to the margin of a glacier.
Stratigraphic unit -unit consisting of stratified mainly sedimentary
rocks grouped for description.
Thalweg -the line joining the deepest points of a stream channel.
Thermocline -the horizontal plane in a thermal stratified lake
located at the depth where temperature decreases most rapidly with
depth.
Till -nonsorted,nonstratified sediment carried or deposited by a
glacier.
Water year - a one year period extending from October 1 to September
30.