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Home My WebLink AboutAPA1800ALASKA RESOURCES LIBRARY U...OF INTERIOR ... :.:·t·W. 1"1'1S ,5 F \ 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: iiJ ARLIS Alaska Resources .Inft ation Services chorage,Alaska L.....--__ALASKA POWER AUTHORITY __--I - , 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 """ """ ,.... """ - ,.... """ 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 - - r- ) - ..... 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 ; 1 GENERAL DESCRIPTION OF THE LOCALE .... - - - ,- I ,.,.. 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. E-1-1 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 E-1-2 - ...... - ~\ - - --. - 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. E-1-3 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. £-1-4 - - ~, - - -, I""" I ,.... - - ".,. ,.... - 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. E-1-5 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. E-1-6 ~I _. - - - ,.... ...... .... I - - - 1.2 -Susitna Basin 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 E-1-7 '1 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. E-1-8 ,.,.. '"'" ~, - - - - - ..... - 1.2 -Susitna Basin 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 • E-1-9 - ..... -. - - - - 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 E-l -11 )c )1 1 J )lJ 1 )J J )1 ]»1 ~/J YUr<ON~.~"· ..r--..""..... / / \. ~~~-........., \\, 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.!.! ( LOWER DRAINAGE BASIN UPPER DRAINAGE BASIN 10 ..-.---- ,/-...... ,/--/-------...- /-......,/...... ",, /, \ \ \ I I I / /e&/ / / / o 20 MILES SCALE ~i~~~5iiiiiiiiiiiiiiiiiiiiiiiiiiiil ",.--........ /<, /....... /"-,,- /0 <,/4" /(I <, /"- / / / / / / ,/ / SUSITNA RIVER ,/ DRAINAGE BASIN ~"" / ,/ ,/ ,///,.., -'" ..,.".,.........".".,.,-,....- //'" /'"LOWER DRAINAGE BASIN ",,// ,/ ,/ / / / I I I I / / / / / / / I / / / / / / I I f, \ \ \/--, \"'",/,,/",/, ,,//,'--'",<, <,-,-, \ \ \ j SUSITNA RIVER 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 - ".... - 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. .... 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. - (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. """' - - (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 .-. ..... r ..... - - 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 ..... r"""'I ! - -- -- .... - - .... 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 - 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. - - (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 r---- - - -, - - .- 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 ~~_.._-_._--- - - - 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. - - - ,- -. - (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 - ,... - - - (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 - -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 - ..... - (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 - - - - 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 f5A, - - - 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 ~, - 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 ~ , 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 - - .... - 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-. ! - """ .- """ 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 - - .... - 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 r--:-:-", ..... - .... ..... ..... F"" I i 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 -I I ..... 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 .... - 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 - - - .... I 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 ""'" - - - - - - -I ! - 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 - - ..... - - - ,..,. 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 .- I I 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 ,~ - - - - - 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 -- ,.... - .... - 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 r:...-, 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 r-, -- .... - 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 -. 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. - - - (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 """' """ ,- I""" I - - - 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. - - (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 r' ,.,.. 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 .... - 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~ ,~ - -i - "'" 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 - - 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 (~, .- r i - I""'" 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 """ .... I .- - - (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 ,-- ,- .... r .~ I - 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 - - - 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 - - 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 .- - 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. .- ""'" - (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. - - (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 - - 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 - - I""" I - 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 - - - ,- ..... - 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 - ,...,. - - ,PM 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 - - - - - - - .- -- - 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-:-- - - 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 - - - 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 - - - - - 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 FILE P5700 Q m ')77.·II 9 ~l{ft)(jf:NO. -/cSl-D {.,1 . Z ~ai ~0 <Y Ci 5 c 0-I-U.~~. 4 ~a -:rJD~I--- f---r-- VTS f---YiJ1;\IH I--..<f 1--.'--.....,~,..-f---.,- _.J f---- I''''J r--.!.-."'- '-----r:c f----,-DF ~-'-.DC--.--APA r BUFF. 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 - .....~~&~[@~&~&~~& ·~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 REFERENCES .... - Acres American Incorporated.1982a.Susitna Hydroelectric Project, Feasibility Report.Design Development Studies.Final Draft. Vol ume 5.Appendix B.Prepared for the Al aska Power Authority. •1982b.Susitna Hydroelectric Project,Feasibility Report. --....Hydrological Studies.Final Draft.Volume 4.Appendix A. Prepared for the Alaska Power Authority. 1982c.Susitna Hydroelectric Project,1980-81 Geotechnical Report.Final Draft.Vol ume 1.Prepared for the Al aska Power Authori ty. 1982d.Susitna Hydroelectric Project.Scour Hole Development Downstream from High Head Dams. 1983.Susitna Hydroelectric Project,Slough Geohydrology Report.Unpubl i shed. Acres Consul ting Services Limited.1980.Dunvegan Power Project Peace River Ice Study.Prepared for the Energy Resources Conservation Board. 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Gustavson,T.C.1975.Bathymetry and Sediment Distribution in Proglacial Malaspina Lake,Alaska.Journal of Sedimentary Petro logy.450:461. Harrison,W.D.University of Alaska,Geophysical Institute.February 1983.Per son a1 Commun i cat ion. Hydro-North.1972.Contingency Plan Study Paxson -Summit-Lakes Area Trans-Alaska Pipeline.Prepared for Alyeska Pipeline Service Company. Imberger,J.and J.C.Patterson.1980.A Dynamic Reservoir Simula- tion Model -DYRESM:5.Proc.Symposium on Predictive Ability of Surface Water Flow and Transport Models.Berkeley,California. Imberger,J.et ale 1978.Dynamics of Reservoir of Medium Size.Jour Hydraulic Div.,Proc.American Society of Civil Engineers,104-,--- No.HY5.725-743. E-2-197 Joyce,M.R.,L.A.Rundqui st and L. L.Moul ton.1980.Gravel Removal Guidelines Manual for Arctic and Subarctic Floodplains.U.S. Fish and Wildlife Service,Biological Services Program FS/OBS- 80/09. Kavanagh,N.and A.Townsend.1977.Construction-Related Oil Spills Along Tran s-Al aska Pi pel ine.JFWAT Spec;al Report,15.Joint State/Federal Fish and Wildlife Advisory Team,Alaska. Lamke,R.D.1970.Flood Characteristics of Alaskan Streams.USGS, Water Resources Investigation.78-129. Lantz,R.L.1977.Guidelines for Stream Protection in Logging Operations.Research Division,Oregon State Game Commission. Oregon. Lauman,T.E.1976.Salmonid Passage at Stream-Road Crossings. Oregon Department of Fi sh and Wil dl i fee Oregon. LeBeau,J.ADEC.October 1982.Personal communication. Lindstedt,S.J.1979.Oil Spill Response Planning for Biologically Sensitive Areas.1977 Oil S ill Conference Prevention,Behavior, Control,Cleanup.American Petro eum Instltute,Environmenta Protectlon gency,U.S.Coast Guard.New Orleans,Louisiana. Love,K.S.1961.Relationship of Impoundment to Water Quality. JAWWA •Vo 1urn e 53. Mathews,W.H.1956.Physical Limnology and Sedimentation in a Glacial Lake.Bulletin of the Geological Society of America. Vol ume 67. McNeely,R.N.V.P.Neimanism and K.Dwyer.1979.Water Quality Sourcebook A Guide to Water Quality Parameters.Environment Canada,Inl and Water Directorate,Water Qual ity Branch.Ottawa, Canada. Meier,M.F.1966.Some Glaciological Interpretations of Remapping Programs on South Cascade,Nisqually and Klawatti Glaciers, Washington.Canadian Journal of Earth Sciences.Volume 3. 811 -818. Michel,B.1971.Winter Regime of Rivers and Lakes.Cold Regions Science and Engineering Monograph I11-B1A.U.S.Army Corps of Engineers. Mortimer,C.H.1941.The Exchange of Di ssolved Substances Between Mud and Water in Lakes,Parts 1 and 2.Journal of Ecology. Vol ume 29. Mortimer,C.H.1942.The Exchange of Di ssolved Substances Between Mud and Water in Lakes,Parts 3 and 4.Journal of Ecology. Vol ume 30. Neal,J.K.1967.Reservoir Eutrophication and Dystrophication Following Impoundment.Reservoir Fish Resources Symposium. Georgia University.Athens,Georgia. E-2-198 - -Neill,C.R.1967. Bed Materi ale Mean Velocity Criteria for Scour of Coarse Uniform IAHR,12th Congress.Fort Coll ins t Colorado. 1968.A Re-examination of Beginning of Movement for Coarse Granul ar Bed Materi al s.Internal Report.Hydrologic Research Station.Wallingford t England. Parker t G.1980. 1m Ov erv i ew • 792-801. Do...."stream Response of Gravel-Bed Streams to Dams; Surface Water Impoundments.ASCE.New York. .... Peratrovich t Nottingham and Drage,Inc.1982.Susitna Reservoi r Sedime~tation and Water Clarity Study.Prepared for Acres American-Incorporated. 1983.Susitna Hydroelectric Project Nitrogen Supersaturation Study.Prepared for Acres American Incorporated. Peterson,L.A.February 1983.Personal communication. Peterson,L.A.and G.Nichols.1982.Water Quality Effects Resulting from Impoundment of the Susitna River.Prepared for Acres American Incorporated. Pharo,C.H.and E.D.Carmack.1979.Sedimentation Processes in a Short Residence -Time Intermontane Lake,Kamloops Lake t Briti sh Columbia.Sedimentology.26. R &M Consultants t Inc.1981a.Preliminary Channel GeometrYt Velocity 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. 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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 STATISTICS FOR ANNUAL INSTANTEOUS PEAK FLOWS Log Pearson Type III (M I LIk IIh d)t )III (MTL PtL N3 PL NG b I 1ume oq orma arame er oq orma oq erson ype omen s ax mum e 00 Sum of Mean Sum of Mean Avg.Sum of Mean Avg.Sum of Mean Avg.Sum of Mean Gaqe Station River N CS CK Deviations Deviation CSL CKL Deviations Deviation CSLA CKLA CV Deviations Deviation CV Oevlatlons Deviation CV Deviations Deviation DenaII Susitna 20 2.4985 10.3480 -49.50 12.95 1.8453 7.0725 -33.19*11.21 0.0633*4.2263*23.59*38.16 8.39*35.46 -38.81 8.39*No Sol utlon Cantwell Sus Itna 11 0.3325 3.1348 .,..0.90*6.46 -0.1474 3.2888 1.15 5.85*-0.1172*3.2667*18.79*1.32 6.01 19.01 1.92 6.21 Upper Boundary is Too Low Gold Creek Susltna 25 0.6830 2.9269 -22.90 5.16 0.0664*2.8362 -10.28 4.23 -0.0805 2.9658*15.01*-18.09*4.11*15.39 -19.01 3.97 15.51 -20.67 5.38 Maclaren Maclaren 22 0.9062 3.4430 -15.76 7.16 0.5539 2.6682*-8.75 6.14 -0.3915*2.6563 25.66 8.93 3.99*15.93*-8.18*4.90 No So I ut.lon ChuI Itna Chu Iitna 18 2.9054 13.7449 -33.82 10.15 2.0599 10.0328 -23.88*10.58 0.3512*6.8509*14.05 -27.36 9.21*Lower Boundary Is Too High 12.85*-29.93 9.45 Talkeetna Talkeetna 15 1.8140 6.6111 -1.99 8.16 1.0398 4.7599 5.88 8.80 -0.0921*4.0752*30.54*-0.74*5.27 40.08 -3.38 5.65 32.65 -5.43 1.92* 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 natural logs of the natural logs of the natural logs of the natural logs of the data the data the transformed the transformed data data Avg.CV =average coefficient of variation for all return periods estimated Sum of Deviations =15...Q -~/QD for 1.25,2, 5, 10, and 20 year return periods Mean Deviation =5...Q -00 I 15 for 1.25,2, 5, 10 and 20 year return periods Q =measured flow %=mean flow *=Distribution best fitting a given parameter Theoretical Values - Gumbel 1 Loq Normal 3 Parameter Log Normal CS 1.14 CK =5.4 CSL 0.0 CKL =3.0 CSLA 0.0 CKLA =3.0 Source:R&M 1981f I J I ) 1 J 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 SEDIMENT AT GOLD CREEK MAY TO SEPTEMBER 1952 6,284,363 y ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••......................................................................................................................................................................g p Total load for period (tons) May June Julv Auoust September Suspended SEdiment Suspended Sediment Suspended SEdiment Suspended SEdiment Suspended Sediment Mean Mean Tons Mean Mean Tons Mean Mean Tons Mean Mean Tons Mean Mean Tons Discharge Concentration Per Discharge Concentrat lor Per Discharge Concentration Per Discharge Concentration Per DischargE Concentration Per Day (cf s )(mo/I)Day (cfs )(mo/I)Day (cf s )(mo/I)Day (cf s )(mo/I)Day (cfs)(mo/I)Dav 1 1,100 9 27 25,000 1,730 117,000 33,000 1,300 116,000 41,900 1,390 157,000 30,000 870 a70,500 2 1,200 13 a42 23,500 2,030 129,000 31,100 1,220 102,000 38,300 981 101,000 28,700 772 59,800 3 1,300 17 60 27,500 2,200 a163,000 29,500 562 44,800 32,100 826 71,600 24,500 682 45,100 4 1,400 18 a68 29,000 1,800 a141,000 27,800 544 40,880 27,100 900 65,900 21,400 602 34,800 5 1,500 19 a77 26,500 1,300 a93,000 25,900 695 48,600 24,500 900 59,500 18,000 560 a27,200 6 1,600 19 82 22,500 940 a57,100 23,600 670 42,700 23,500 909 57,700 14,800 520 20,800 7 1,600 20 a86 24,400 1,000 a65,900 22,500 560 34,000 23,600 860 54,800 12,900 420 a14,600 8 1,600 21 a91 22,300 950 a57,200 21,100 687 39,100 24,700 828 55,200 11,900 270 a8,680 9 1,500 22 a89 21,500 730 a42,400 19,700 595 31,600 25,600 824 57,000 12,400 130 4,350 10 1,400 23 87 26,800 495 35,800 18,900 429 21,900 26,200 873 61,800 !12,700 70 a2,400 11 1,400 20 a76 37,300 249 25,100 17,700 662 31,600 27,400 836 61,800 13,500 54 1,970 12 1,500 18 a73 36,700 189 18,700 17,200 1,030 47,800 24,400 1,150 75,800 14,200 50 al,920 13 1,600 18 78 34,000 290 26,600 19,500 1,190 62,700 22,400 2,190 132,000 13,500 50 al,820 14 1,700 15 69 31,400 464 39,300 23,300 1,140 71,700 20,400 2,100 a 116,000 12,300 50 al,660 15 1,900 12 62 37,400 493 49,800 25,000 1,150 77,600 19,800 1,580 a84,500 10,800 50 al,460 16 2,100 12 a68 42,400 562 64,300 25,400 909 62,300 18,700 1,200 a60,600 10,200 58 1,600 17 2,200 15 a89 43,300 936 109,000 25,700 756 52,500 16,500 960 a42,800 10,500 65 1,840 18 2,400 17 all0 41,300 885 98,700 25,400 860 a59,000 15,600 650 27,400 10,000 70 al,890 19 2,600 19 133 40,200 256 27,800 25,200 990 a67,400 14,800 531 21,200 9,500 70 al,800 20 2,800 30 a227 36,300 241 23,600 24,700 1,130 75,400 14,400 639 24,800 10,000 70 al,890 21 3,000 50 a405 35,400 232 22,200 24,200 1,080 70,600 14,800 554 22,100 11,300 70 a2,140 22 3,400 80 734 35,600 212 20,400 23,700 837 53,600 15,100 414 16,900 15,700 73 3,090 23 3,700 270 a2,700 34,700 203 19,000 24,700 918 61,200 15,300 435 18,000 15,400 76 3,160 24 4,500 549 6,670 34,300 213 19,700 25,900 873 61,000 15,200 531 21,800 I 14,800 90 3,600 25 6,000 828 13,400 34,100 184 16,900 27,400 972 71,900 15,000 377 15,300 13,800 90 3,350 26 8,000 1,120 24,200 33,600 278 25,200 28,900 972 75,800 15,000 275 11,100 12,900 99 3,450 27 10,000 1,270 34,300 34,300 1,040 96,300 28,400 888 68,100 14,200 293 11,200 12,300 110 3,650 28 15,000 747 30,300 33,000 1,220 109,000 31,300 927 78,300 13,500 410 a14,900 12,000 89 2,880 29 25,000 450 30,400 33,400 1,220 110,000 38,300 1,120 116,000 13,600 568 20,900 12,000 81 2,620 30 28,000 540 40,800 33,400 1,270 115,000 41,300 1,310 146,000 15,000 720 a29,200 12,400 68 2,280 31 27,000 1.670 122,000 ------41,700 1,360 153,000 20.000 860 a46,400 -- -- -- TOTAL ••108,000 --3U/,003 971,100 --1,95l:l,UUU l:lll:l,UUU --:l.u8,,,uuu b48,bUU --1.616,200 434,400 --55b,50U Total dlschar e for erlod (cfs-da s).......•••••.....•....•••••....•••..•••••.•••3,067,700 l I Note: a Computed from estimated concentration graph. Source:USGS I - 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 FLOWS FOR THREE FILLING CASES (CFS) Fi II lnq Case With 10"·Probabi I ity of Exceedance Fill i no Case With 50"Probabi I ity of E,ceedance Fill ina Case With 90';Probabi I it of Exceedance Pre-WY 1991 WY 1992 WY 1993 Pre-WY 1991 WY 1992 WY 1993 Pre-W 19~1 :WY 19Y£WY 19~5 WY 1994 Project Project Project Month F.low Outflow %Chanqe Outflow %Chan~e Outflow %Chenqe Flow Outflow %Chan~e Outf low %Chenoe Outflow %Chance Flow Outflow %Chanqe Outf low %Chanqe Outflow %Chanqe Outflow %Chenqe 4 Oct 5,272 5,272 -5,272 0.0 819 84.5 4,713 4,713 -3,454 26.7 981 79.2 4,213 4,213 -1,493 64.6 1,140 72.9 1,140 73.0 Nov 2,352 2,352 -2,352 0.0 2,352 0.0 2,102 2,102 -2,102 0.0 2,102 0.0 1,879 ",879 -1,879 0.0 1,879 0.0 Dec 1,642 1,642 -1,642 0.0 1,642 0.0 1,468 1,468 -1,468 0.0 1,468 0.0 1,312 1,312 -1,312 0.0 1,312 0.0 Jan 1,340 1,340 -1,340 0.0 1,340 0.0 1,198 1,198 -1,198 0.0 1,198 0.0 1,071 1,071 -1,071 0.0 1,071 0.0 Feb 1,138 1,138 -1,138 0.0 1,138 0.0 1,018 1,018 -1,018 0.0 1,018 0.0 910 910 -910 0.0 910 0.0 Mar 1,028 1,028 -1,028 0.0 1,028 0.0 919 919 -919 0.0 919 0.0 822 822 -822 0.0 822 0.0 Apr 1,261 1,261 -1,261 0.0 1,261 0.0 1,127 1,127 -1,127 0.0 1,127 0.0 1,008 1,008 -1,008 0.0 1,008 0.0 1 3 1 3 1 2 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 3,329 69.4 9,715 6,247 36.0 3,696 62.0 3,696 62.0 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 1,103 95.1 20,238 14,917 26.3 1,867 90.8 1,867 90.8 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 2,163 89.2 17,842 2,836 84.1 2,836 84.1 2,836 84.0 2 4 2 4 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 9,668 46.3 16,095 8,934 44.5 8,713 45.9 8,713 45.9 3 Sep 12,064 6,743 44.1 6,397 47.1 10,787 6,767 37.3 6,767 37.3 9,641 7,131 26.0 7,131 26.0 7,131 26.0 Notes:1• Fi IIIng begIns, 2.Commissioning of units possible. 3.Operation possible. 4.Filling complete. l TABLE E.2.38:GOLD CREEK FLOWS FOR THREE FILLING CASES (CFS) t ll11nq Case With U%Probabllit y or ~xceeaance Flows %Chanqe Flows %Chanqe Flows 60.6 %Chanqe W 1994 2,000 4 Flows 0.0 0.0 0.0 0.0 38.1 21.6 69.8 0.0 0.0 51.4 75.4 60.6 %Chanqe W 1993 990 Flows 2,000 2,263 1,580 1,290 1,096 1,214 2 5,680 6,000 6,480 12,000 3 9,100 or I:.xceedance 38.1 53.6 0.0 0.0 0.0 0.0 0.0 21.6 0.0 57.4 75.4 69.8 %ChanqeFlows 2,353 2,263 1,580 1,290' 1,096 990 1,214 5,680 6,000 6,480' 12,0001 9,100 36.9 21.6 29.6 21.8 69.8 t .i t t rnq cas e Wltn ,u;"r-rODaDlllt 5,073 - 2,263 1,580 1,290 1,096 990 1,214 1 8,231 19,050 6,480 12,221 9,100 Flows %Chanqe 5,073 2,263 1,580 1,290 1,096 990 Pre- Project Flows 1,214 11,699 24, 371 21,486 19,382 11,610 73.3 57.0 78.2 65.1 0.0 0.0 0.0 0.0 0.0 0.0 %Chanqe 2,557 1,785 1,457 1,238 1,118 1,371 3 5,680 6,000 6,480 4 13,563 0.0 0.0 22.0 2,000 0.0 0.0 0.0 0.0 57.0 78.2 72.4 45.2 30.6 %Chanqe Flows 2,557 1,785 1,457 1,238 1,118 1,371 5,680 6,000 6,694 2 12,000 9,100 -4,473 26.2 19.3 70.1 23.5 30.6 %Chanqe Flows W 1991 WY 1992 WY.1993 5,732 Flows t a.i t mq Lase Wltn U;o r ro all:y or t.>ceeaance 5,732 2,557 2,557 1,785 1,785 1,457 1,457 1,238 1,238 1,118 1,118 1,371 1,371 1 13,221 9,753 27,541 22,220 24,280 7,262 21,903 16,754 13,120 9,1 00 Pre- Project Flows 69.0 0.0 0.0 0.0 0.0 0.0 0.0 61.8 52.7 76.3 19.3 %Chanqs 2,879 2,010 1,640 1,393 1,258 1,544 3 5,680 14,664 6,480 4 19,895 38.4 0.0 0.0 0.0 0.0 0.0 0.0 61.8 78.5 48.5 46.0 2,879 2,010 1,640 1,393 1,258 1,544 5,680 6,675 14,079 ~ 13,162 9,100 6,453 -6,453 0.0 2,000 2,879 - 2,010 - 1,640 - 1,393 - 1,258 - 1,544 - 1 11,414 23.3 25,680 17.2 10,312 62.3 19,506 20.8 9,446 36.0 6,453 2,879 2,010 1,640 1,393 1,258 1,544 14,882 31,001 27,330 24,655 14,767 Pre- Project FlowsManU Feb Jan Jun Apr Oct Mar Jul May Aug Sep 1 Nov I) Dec Notes:1.Filling begins. 2.Commissioning of units possible. 3.Operation possible. 4.Filling complete. 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.2.50:WATANA FIXED CONE VALVE OPERATION 1995 Simulation LOOO Simulation Simulated Week of Week of Maximum Powerhouse Total Week of Week of Maximum Powerhouse Total Water First Maximum Release Flow Release First Maximum Release Flow Release Year Release Release cfs cfs Acre-feet Release Release cfs cfs Acre-feet 1950 Aug 26-Sept Sep 2-8 1,011 9,514 30,600 1951 Aug 5-11 Aug 5-11 167 9,030 2,300 1952 Aug 19-25 Aug 19-25 724 8,898 20,800 1953 Aug 12-18 Aug 12-18 266 8,946 5,100 1954 Sept 2-8 Sept 9-15 347 9,424 6,900 1955 Sept 9-15 Sept 9-15 343 9,265 4,800 1956 Aug 19-25 Sept 9-.15 9,615 9,245 545,500 Aug 26-Sept Sept 9-15 8,587 10,272 356,400 1957 1958 Aug 19-25 Sept 2-8 1,309 9,337 53,100 Sept 2-8 Sept 2-8 272 10,375 3,800 1959 Aug 5-11 Sept 2-8 4,925 9,089 119,500 Sept 2-8 Sept 9-15 2,196 10,272 42,300 1960 1961 Aug 26-Sept Sept 2-8 828 9,194 23,600 1962 Aug 26-Sept Sept 2-8 10,755 9,066 298,900 Aug 26-Sept Sept 2-8 9,747 10,073 182,700 1963 Aug 19-25 Aug 26-Sept 7,546 8,887 189,600 Aug 26-Sept Sept 2-8 2,660 10,073 57..600 1964 Ju IV 29-Aug 4 Sept 9-15 1,113 9,414 66,100 1965 Aug 26-Sept 1 Aug 26-Sept 1,112 9,082 15,400 1966 Oct 1-6 Oct 1-6 2,379 10,140 48,100 1967 Aug 19-25 Sept 2-8 15,380 9,066 47,100 Aug 19-25 Sept 2-8 14,372 10,073 371,900 1968 Aug 12-18 Sept 2-8 921 9,285 49,400 1969 Sept 2-8 Sept 2-8 302 9,776 8,300 1970 Aug 26-Sept Sept 9-15 692 9,801 22,000 1971 Sept 2-8 Sept 2-8 5,597 9,076 119,600 Sept 2-8 Sept 2-8 2,614 10,090 64,000 1972 Ju IV 29-Aug 4 Aug 26-Sept 795 9,011 22,200 1973 Ju IV 29-Aug 4 Sept 9-15 917 9,659 25,500 1974 Aug 12-18 Sept 9-15 677 9,840 21,900 1975 Aug 5-11 Sept 2-8 898 9,233 34,500 1976 Aug 19-25 Sept 9-15 1,286 9,706 53,600 Sept 2-8 Sept 2-8 204 10,566 5,500 1977 Aug 26-Sept Sept 2-8 1,083 9,267 30,900 1978 Aug 19-25 Aug 26-Sept 859 9,440 33,000 --- 1979 Aug 19-25 Sept 2-8 1,208 9,288 42,800 Sept 2-8 Sept 2-8 176 10,320 2,400 1980 Aug 26-Sept Sept 2-8 1,187 9,130 39,100 Sept 2-8 Sept 2-8 167 10,150 2,300 1981 Aug 19-25 Aug 19"';25 21,526 8,710 602,500 Aug 19-25 Aug 19-25 17,943 9,684 500,300 -, 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.