HomeMy WebLinkAboutAPA2923dSUSITNA HYDROELECTRIC PROJECT
AQUATIC MITIGATION REPORT SERIES
MIDDLE RIVER FISH
MITIGATION PLAN
Draft Mitigation Report No. 3
June 1985
Prepared By:
Woojward-Clyde Consultants
701 Sesame Street
Anchorage, Alaska 99503
In Association With :
Entrix, Inc .
4794 Business Park Boulevard
Anchorage, Alaska 99503
Submitted To :
Harza-Ebasco Susitna Joint Venture
711 H Street
Anchorage, Alaska 99501
For :
The Alaska Power Authority
327 W. 5th Avenue, 2nd Floo;
Anchorage, Alaska 99501
The authors of this report are S. C. Crumley, L. L. Moulton, and L. A.
Rundquist. The draft version of this report was prepared while they were
employees of Woodward-Clyde Consultants. The final version was prepared while
employees of Entrix, Inc., under contract to Woodward-Clyde Consultants.
11
Preface
This report represents one volume of a three volume report series on aquatic
mitigation planning for the proposed Susitna Hydroelectric Project. These volumes
are:
1. Access, Construction and Transmission Aquatic Mitigation Plan
2. Impoundment Area Fish Mitigation Plan
3. Middle River Fish Mitigation Plan
A primary goal of the Alaska Power Authority's mitigation policy is to maintain
the productivity of natural reproducing populations, where possible. The planning
process follows procedures set forth in the Alaska Power Authority Mitigation
Policy for the Susitna Hydroelectric Project (APA 1982), which is based on the
U .S. Fish and Wildlife Service and Alaska Department of Fish and Game mitigation
policies. Mitigation planning is a continuing process, which evolves with
advances in the design of the project, increased understanding of fish populations
and habitats in the basin and analysis of potential impacts. An important element
of this evolution is frequent consultation with the public and regulatory agencies
to evaluate the adequacy of the planning process. Aquatic mitigation planning
began during preparation of the Susitna Hydroelectric Project Feasibility Report
( 1981) and was further developed in the FERC License Application ( 1983). A
detailed presentation of potential mitigation measures to mitigate impacts to chum
salmon that spawn in the side sloughs was prepared in November 1984. It is
expected that the three reports in the present report series will also continue to
evolve as the understanding of project effects is refined.
iii
Title Page •
Preface.
Table of CCntents.
List of Figures.
TABIE OF a:m.nns
Page
i
iii
iv
vi
1. 0 :nliR)[l]Cl'IQ{. 1
1.1 Bac:kgrairxi • 1
1. 2 Approach to Mitigati~ • 1
1.3 soepe. 5
2. 0 ~ IMPACl' ASSESSHENl' • 6
2.1 utilizati~ Within Habitat Types • 6
2 .1.1 Ma.instem an::l Side Cl1annal Habitats. 7
2 .1. 2 Side Slcu;;h an::l Uplan::l Slcu;;h Habitats. 8
2 .1. 3 Trib.rt:aiy an::l Trib.rt:aiy M::IUth Habitats. 9
2 .2 Relatia1Ship between Rlysical Olarges and Habitat utilizaticrl. 11
2 • 2 .1 Ma.instem and Side Olannel. Habitat Types • 12
2. 2. 2 Side Slcu;;h an::l Uplan::1 Slcu;hs. 12
2. 2. 3 Trib.rt:aiy and Trib.rt:aiy M::IUth Habitats. 14
2 •. 3 Selecti~ of Evaluati~ Species. 14
3 • 0 MITIGATICN OPriCNS . 18
3 .1 Flc:M Release • 18
3 . 2 Habitat z.t:x:lificati~ • l.9
3 • 2 .1 Slcu;;h Excavati~ . 19
3 • 2. 2 Olannel Barriers. 20
3. 2. 3 Olannel Width z.t:x:lificaticn:J • 22
3. 2. 4 Preventim ot Slcu;;h ~~. 25
3.2.5 Gated water SUWJ.y System • 2s
3. 3 .Artificial Prqagatim . 27
iv
4.0
TABIE OF a:tmNl'S (continued)
~ FOR MIIDIE SUSI'INA RIVER FISH MITIGATICN PIAN •
Stage 1-(1996-2001). 4.1
4.2
4.3
4.4
4 .1.1 Impact Analysis •
Mitigaticn.
2-(2002-2008).
4.1.2
stage
4.2.1 Ilip!ct Analysis •
4. 2. 2 Mitigaticn.
stage 3-(2008-2020).
4. 3 .1 Illpact Analysis •
4.3.2 Mitiqaticn.
SChedul.in; of Mitigatioo •
4. 4.1 Flow Release.
4.4.2 St:ructural Mcdificatioo of Habitats •
4.5 Mbnitorin; •
4. 5.1 Mclnitorin; of Sal:mc:n lqul.ations.
4.5.2 Mitigatiat Mc:nitorin; •
REFERENCES •
APmiDIX •
APmiDIX FIGURES •
APPENDIX TABUS.
v
Page
29
29
29
62
66
66
75
75
75
8 7
87
87
87
88
89
90
93
96
97
118
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure U.
LISl' OF FIGURES
Mitigaticm Plan Davel.cpaent and !Dplementaticm.
~ Arml.ys.is • • • • • • • • • • • • • • 4
21
23
~-• • • • • • • • • • • • • • • • • . . . • • • • 26
SUsit:na River nowa at Gold creek under Natural (1994)
and FUlin;J of Reservoir (1995) Rsqimea with case E-VI
Fl.CM ~ • • • • • • • • • • • • • • • • • • • 30
Q::llpri.sa18 of SUsit:na River Natural and stage 1 1996
st:reamfl.owa Excw!ded 97' of the time at Gold creek. • • 38
Q::llpri.sa18 of SUsit:na River Natural and stage 1 1996
st:reamfl.owa ExoeMed sot of the time at Gold creek. • • 39
Q::llpri.sa18 of SUsit:na River Natural and stage 1 1996
st:reamfl.cwa Excw!ded 6% of the time at Gold creek •
Silllll.ated Natural and stage 1 2001 SUSitna River
Teuperatures at River Mile 150 ••••••••••
Silllll.ated Natural and stage 1 2001 SUsi tna River
'l'ellperatures at River Mile 130. • • • • • • • • •
Simlated Natural and staga 1 2001 SUSit:na River
'l'eap!ratures at River Mile 100.
vi
40
41
42
43
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
LISl' OF FI~ (Ccrltinued)
Page
Carparisa1 of flow duraticn curves for natural an:l si:m.llated
stage 1 1996 Energy Oeman:i streamfl.ows for weeks 45 to 4 9
based en mean weekly flows for 34 years of record • • • 45
Percent of Time Sl YX'PFStul Passage 0cx:urs tJn:ier Natural
an:l stage 1 Flows at S1c:u;h SA. • • • • • • • • • • • •
Percent of Time SIJOOPSstul Passage Ocx:urs tJrCer Natural
an:l stage 1 Flowa at S1c:u;h 9 • • • • • • • • • • • • •
Pel:oent of Time SIXX"P"stul Passage Ocx:urs t.J'n:3er Natural
an:l stage 1 Flows at S1c:u;h 9A. • • • • • • • • • • • •
Pel:ceut of Time SIXX"P"Stul Passage 0cx:urs t1rxSer Natural
an:l stage 1 Flows at S1c:u;h ll. • • • • • • • • • • • •
Percent of Time SllOOeSStul Passage 0cx:urs t.l'n:3er Natural
48
50
52
55
an:l stage 1 Flows at~ Side Olannel ll. • • • • • • 56
Percent of Time SU<X'eSSful Passage 0cx:urs tJn:ier Natural
an:l stage 1 Flows at S1c:u;h 21. • • • • • • • • • • • •
Percent of Time SUccessful Passage Occurs tJn:ier Natural
an:i stage 1 Flows at Side Olannel. 21. • • • • • • • • •
Flow Chart for R.ankin;J sites for Mitiqatiat Decisiat
~ ............... .
Cx::.l!p!riscr1 of SUsitna River Natural, stage 1 1996 an:l
stage 2 2002 streamflOW& E)(rseded 97t of the time at
59
60
65
Gold CJ::-Mk. • • • • • • • • • • • • • • • • • • • • • • 67
Figure 23.
Figure 24.
Figura 25.
Figure 26.
Figura 27.
Figura 28.
Figure 29.
Figure 30.
Figure 31.
usr OF FIQJRES (o:nt.i.nued)
a:zrparisa'ls of SUSitna River Natural, stage l 1996 arrl
stage 2 2002 streamflows Exoeeded 50% of the ti:me at
Gold creek. • • • • • • • • • • • • •
Cc:llp!riscrls of susitna River Natural, stage l 1996 arrl
stage 2 2002 stream!l.OWB :E:)ooeeded 6% of the time at
(;()ld creek. • . • • • • • • • . • . • . • • • • •
Sillulated Natural ani stage 2 2002 SUsitna River
'l'elp!ratures at River Mile 150. . 0 0 0 0 0 0 0 0 0 0
Sillul.ated Natural ani stage 2 2002 SUSitna River
'l'elp!ratllres at River Mile 130. 0 0 0 0 0 0 0 0 0 0 0
Sillulated Natural ani stage 2 2002 SUsitna River
'l'elp!ratures at River Mile 100. 0 0 0 0 0 0 0 0 0 0 0
0 0
0 0
0 0
~ of flow duratim a.n:ves for sillul.ated stage l
1996 ani sillul.atad stage 2 2002 Energy Deman:! streamflows
for weeks 45 to 49 based m mean weekly flows for 34
68
69
0 7l
0 72
0 73
years of record • • • • • • • • • • • • • • • • • • . 74
Ccllpari..scl1s of SUSitna River Natural, stage 2 2002 arrl Stage
3 2008 streamflows Exoeeded 97% of the ti:me at Gold creek • 77
Ccllpari..scl1s of SUSitna River Natural, stage 2 2002 arrl Stage
3 2008 streamflows F:xreEded 50% of the time at Gold Creek • 78
Cc:llp!ri..soos of SUsitna River Natural, stage 2 2002 ani Stage
3 2008 streamflows ~ 6% of the ti:me at Gold Creek. • 79
viii
Figure 32.
Figure 33.
Figure 34.
Figure 35.
Figure 36.
Figure 37.
LISr OF FIGURES (a:rrt:.i.nued)
Cc:lrpari.sc:rls of susitna River Natural, stage 3 2008, an:i
stage 3 2020 streamflows Exr:e=ded 97\ of the time at
Gold Cl:'eek. • • • • • • • • • • • • • • • • • • • • • • 8 0
~of SUsitna River Natural an:i stage 3 2008,
an:i stage 3 2020 st::rel!lmfl.OW9 Evneeded sot of the time
at Gold Cl:'eek • • • • • • • • • • • •
~of SUsitna River Natural, stage 3 2008, an:i
stage 3 2020 st:reamfiOWB Exceeded 6t of the time at
81
(;old Cl:'eek. • • • • • • • • • • • • • • • • • • • • • • 82
Si.m.J.l.ated stage 3 2020 SUsitna River ~tures trcm
River Mile 150 to 80. • • • • • • • • • • • • • • • • • 83
~ of flow duratioo cmves for s:i:lll.1lated stage
2 2002 am si.m.J.l.ated stage 3 2008 Energy Deman:i st:ream-
fiOWB for weeks 45 to 49 based oo mean weekly fiOWB for
3 4 year'S ot r-ec:x::xrd. • • • • • • • • • • • • • • • • • • • • a 5
~of flow duratioo cmves for silll..ll.ated stage 3
2008 an:i silll..ll.ated stage 3 2020 Energy Deman:l streamflows
for weeks 45 to 49 based oo mean weekly flows for 34 years
of r-ec:x::xrd • • • • • • • • • • • • • • • • • • • • • • • • • a 6
ix
1.0 INTRODUCTION
1.1 -Backgroynd
The Alaska Power Authority submitted a License Application to the Federal
Energy Regulatory Commission for the proposed Susitna Hydroelectric Project in
February 1983. The License Application proposed a two-stage project. The
first stage would consist of a dam at the Watana site built to an elevation of
2205 feet and the second a dam at the Devil Canyon site built to an elevation of
1465.
In support of the FERC review process a Fish Mitigation Plan (WCC 1984) based
on data available at the time was developed for anticipated impacts resulting
from the construction and operation of the two stages. In May 1985 the Alaska
Power Authority's Board of Directors voted to revise the project that was
presented in the License Application. Construction of the project was . proposed
in three stages rather than the previously proposed two stages. Stage I would
be a dam constructed at the Watana site to an elevation of 2025 resulting in a
full pool elevation of 2000 ft. Stage 2 would be similar to the second stage at
Devil Canyon in the License Application. Stage 3 would raise the full pool
elevation of Stage I to 2185 ft, or the elevation of Watana as proposed in the
License Application.
The proposed staging of the project would result in impacts that differ in
magnitude as well as time of occurrence from those identified in the License
Application. Accordingly, this necessitated development of a revised fish
mitigation plan that includes measures that adequately address these changes in
impacts.
1.2 -Approach to Mitigation
The Alaska Power Authority's (APA) goal for Susitna Hydroelectric Project fish
mitigation is to maintain the productivity of natural reproducing populations
(APA 1982). This is consistent with the mitigation goals of the U.S . Fish and
Wildlife Service (USFWS) and the Alaska Department of Fish and Game (ADF&G)
(APA 1982, ADF&G 1982, USFWS 1981). The APA plans to either maintain
existing habitat or provide replacement habitat of sufficient quant i ty and qua li t y
to support this productivity. Where it is not feasible to achieve this goal, APA
will compensate for the impact with propagation facilities.
The development of the fish mitigation plan will follow a log ical step-by-st ep
process. Figure 1 illustrates this process and identifies the major components
(APA 1983). The options j)roposed to mitigate for impacts of the Susitna
Hydroelectric Project will be analyzed according to the hierarchical scheme
shown in Figure 2.
Proposed mitigation options are grouped into two broad categories based on
d i fferent approache~
Modifications to design, construction, or operation of the project
Resource management strategies
The first approach is project specific and emphasizes measures that avoid or
mini01ize adverse impacts according to the Fish and Wi ldlife Mitigation Policy
established by the APA (1982) and coordinating agencies (ADF&G 1982, U SFWS
1981). These measures involve adjusting or adding project features during
design and planning so that mitigation becomes a built-in component of project
actions.
If impacts cannot be mitigated by t he first approach, rectification, reduction or
compensation measures will be implemented. This type of mitigation will invo lve
management of the resource rather than adjustments to the project, and will
require concurrence of resource management boards or agencies with j urisdiction
over resources within the project area.
Mitigati on planning for the Susitna Hydroelectric Project has emphasized both
approaches. The sequence of option analysis from a voidance through com-
pensation has been applied to each impact issue. If full mitigation can be
achieved at a high priority option, lower options may not be considered. Iu
the development of mitigation plans, measures to a void, minimize, or rec ti fy
potential impacts are treated in greatest detail.
2
IDENTIFICATION OF
IMPACTS AND GOALS OF PLAN
OPTION ANALYSIS
NEGOTIATION OF ACCEPT ABLE PLAN
l
IMPLEMENTATION OF PLAN
MONITORING OF PLAN
PLAN MODIFICATION
COMPLETION OF MITIGATION
TERMINATION OF MONITORING I
MITIGATION PLAN DEVELOPMENT AND IMPLEMENTATION
Figure 1
A LA S KA P O WER AU THO RI TY
SUS I TNA HYDROELECTRI C P ROJ ECT
Woodw•rd-Ciyde Consult•nts
AND
ENTRIX , INC.
3
H A R Z A -EBAS CO
SUS ITN A JO I NT V E N T UR E
PARTIAL AVOIDANCE ~~----A_v_oi"To_AN_c_E_~I~----~~ TOTAL Av o roANc E
I
PARTIAL RECT I FICATION~
PARTIAL COMPENSATION ~
NO ;VOIDANCE
1
MINIMIZATION
I
NO MINIMIZATION
1
RECTIFICATION
NO R!CT~F!CATION
l
REDUCTION
I
NO REDUCTION
l
COMPENSATION
I
NO COMPENSATION
UNMITIGATED/LOSS
RESIDUAL IMP ACT
t------f' SOME MINIMIZATION
1---..,. TOTAL RECTIFICATION
.....,_ __ ~SOME REDUCTION
~-~TOTAL COMPENSATION
OPTION ANALYSIS
Figure 2
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodward-Clyde Con.ultanta
AHD
EHTRIX, INC.
4
HAAZA -EBASCO
SUSITNA JOINT VENTURE
Mon i toring and maintenance of mitigation features to reduce impacts over t i me
are recognized as integral parts of the mitigation process. The monitoring
program is being developed and will be appl i ed to fisher y resources and their
habitat.
1.3 -~
This report presents analyses of mitigation options that can be used in
developing an acceptable mitigation plan for impacts resulting from each stage of
the proposed three-stage construction and operation of the Susitna
Hydroelectric Project. Options are presented for impacts on fish resources and
habitats between Devil Canyon and Talkeetna.
Primary consideration is given to mitigation measures for impacts to sensitive
habitats supporting chum salmon spawni ng and incubation and juvenile chinook
salmon rearing and overwintering. Project flow releases are the primary means
of mitigating for chinook juveniles and serve as partial mitigation for chum
spawning. Additional chum salmon spawning and juvenile chinook rearing
mitigation is accomplished by structural modification of presently utilized side
sloughs to maintain productive spawning, incubation and rearing habitat. The
most heavily used sloughs and side channels for spawning by chum salmo n
during the 1981-1984 study period were selected for detailed analysis; these
include sloughs 8A, 9, 98, 9A, 11. and 21. and Upper Side Channel 11 and
Side Channel 21 (Barrett et al. 1985). However, the analyses are appl icable to
other sloughs in the middle Susitna River where physical impacts are expected
to be similar. Artificial propagation with stream-side incubation pits is
proposed to compensate for losses should the · above measures prove
unsuccessful.
Impacts to species given secondary consideration (coho, sockeye and pink
salmon and rainbow trout, Arctic grayling, burbot, and Dolly Varden) are also
exami ned. Mi tigation measures proposed for the primary species are evaluated
as to their effectiveness in offsetting impacts to the secondary species.
2.0 GENERAL IMPACT ASSESSMENT
Construction and operation of the Susitna Hydroelectric Project would alter the
natural physical processes of the Susitna watershed that determine the seasonal
and annual variations in water supply, and sediment and chemical yields to the
middle Susitna River. These physical processes, in turn, exert a controlling
influence on the principal physical habitat components (streamflow, channel
structure, water temperature and water quality) that ultimately determine the
availability of fish habitat in this reach. The physical changes effected by the
project would be qualitatively similar for all stages of the project, however, the
magnitude of these changes and corresponding impacts on fish resources and
habitats would vary with each stage of development and energy demand level.
The impact assessments presented in this section link the major predicted
physical changes with habitat utilization to provide a qualitative statement of
impacts likely to result from the Susitna Hydroelectric Project. This linkage is
facilitated by assessing the degree of influence the project would have on the
morphologic, hydrologic. and hydraulic characteristics of each of the five major
aquatic habitat types of the riverine environment identified in the middle
Susitna River. The response of fish habitat and species utilization patterns to
those physical changes are then predicted.
The process of assessing impacts to habitat types and species/life stages
associated with those habitat types also allows identification of evaluation
species for which mitigation measures need to be implemented to maintain their
productivity. Impacts specific to evaluation species during each of the three
stages of project development and intra-stage energy demands and associated
mitigation measures for these impacts are addressed quantitatively in Section
4.0.
2.1 -Utilization Within Habitat Types
A detailed discussion of the seasonal physical characteristics and utilization
patterns of the various habitat types is found in Jennings (1985). Utilization
of these habitats by salmon and resident species i ~ briefly summarized in this
section.
6
2.1.1 Mainstem and Sjde Channel Habitats
(A) Salmon Specjes
The mainstem in the middle Susitna river is used by each of the five
species of salmon for one or more of the principal life stage activities:
migration, spawning, overwintering, and rearing. The upstream
migration of adult salmon occurs during the summer high flow season
(June to September). Based on 1981 through 1984 escapement
estimates less than s percent of the total Susitna River salmon
escapement migrated within the Talkeetna-to-Devil Canyon reach.
Spawning by coho, chum, and sockeye in middle river mainstem and
side channel habitats amounts to only about 5 percent of the total
salmon spawning in this reach of the river.
Juvenile salmon use mainstem and side channels for movement and
outmigration, rearing, and overwintering. Side channels in particular
are important areas for chinook rearing.
(B) Resjdtnt Species
Most resident species use the mainstem and side channels as
migrat ional corridors. Some species, such as burbot and round
whitefish, also spawn in these habitats.
Rainbow trout, Arctic grayling and burbot appear to make extensive
use of the mainstem during winter. Other species, such as Dolly
Varden, whitefish and longnose sucker, likely overwinter in the
mainstem. However, overwintering areas have not been identified for
these species.
Juvenile burbot, round whitefish and longnose sucker rear primarily
in mainstem and side channel habitats. Some Arctic grayling and
rainbow trout juveniles also use these habitats.
7
2.1.2 Side Slough and Uoland Slough Habitats
(A) Salmon Species
Slough habitat in the middle Susitna River supports spawning f o r
sockeye, coho, pink and chum salmon. Results of escapement and
spawning surveys from 1981 through 1984 indicate that chum and
sockeye are substantially more numerous in sloughs than pink and
coho. In 1984, about 25 percent of all salmon spawning in the middle
Susitna River occurred in slough habitats.
Sloughs also function as important rearing and overwintering areas
for juvenile salmon. Sockeye juveniles rear primarily in natal side
sloughs in the early summer and move into upland sloughs by
mid-summer. Some overwintering occurs in the sloughs. The sloughs
provide temporary rearing habitat for chum salmon of 1-3 months
prior to their outmigration from the middle reach by mid-July.
The extent of slough utilization by j uvenile pink is limited by their
short term residency in freshwater (ADF&G 1983a, Schmidt et a!.
1984).
Some juvenile coho move from natal tributaries to rear in upland and
side sloughs. Juvenile coho apparently prefer clear water and lower
velocities (Schmidt et al. 1984). These conditions usually occur in
upland sloughs more frequently than in side sloughs. Some juvenile
coho also use sloughs for overwintering.
Juvenile chinook used side sloughs and upland sloughs for rearing in
relatively low densities in 1983 (Schmidt et al. 1984). However,
~loughs apparently provide important feeding areas during the fall ,
salmon-spawning period when juvenile chinook move into sloughs to
feed on salmon eggs (Schmidt et al. 1984). Sloughs may also be
important overwintering habitat for juvenile chinook.
8
(B) Resident Species
Slo.ughs are rearing areas for some resident fish. Rainbow trout,
Arctic grayling and round whitefish use sloughs and slough mouths
for rearing, while some burbot rear in slough mouths (Schmidt ct al.
1984). These fish apparently feed on salmon eggs in sloughs during
the salmon-spawning period. Spawning in sloughs by resident fish
appears to be limited. Burbot and longnosc sucker may spawn in
slough mouths (Schmidt ct at. 1984). The extent of overwintering in
sloughs by resident fish is unknown.
2.1.3 Tributary and Tributary Mouth Habitats
(A) Salmon Species
Tributaries serve as the primary spawning habitat for chinook, coho
and pink salmon (Barrett ct at. 1984, 198S). In 1984, about 70
percent of all salmon spawning upstream of RM 98.6 (68,700 fish )
occurred in tributaries (Barrett ct at. 198S). About one-third of the
chum salmon escapement upstream of Talkeetna spawned in tributaries
during 1984 (Barrett ct at. 198S). Tributaries arc rarely used by
adult sockeye salmon (Barrett ct al. 1984, 198S).
Chinook, pink, chum and coho salmon frequently spawn at tributary
mouths while sockeye salmon spawning appears limited in this habitat
type (Barrett ct at. 198S). Index counts of spawning salmon in
tributary mouth habitats arc unavailable, as counts arc included in
tributary counts. It appears that more spawning occurs in
tributaries than in tributary mouths (Barrett ct at. 198S). Water
depth and velocity may limit spawning in tributary mouths (Sandone
ct al. 1984).
Juvenile sockeye utilize tributary habitat incidentally (Schm idt et at.
1984). In 1983, few juvenile sockeye were captured i n tributary
habitat.
9
Tributaries likely provide rearing habitat for chum salmon for about
one to three months (Schmidt et al. 1984).
Tributaries serve as the primary coho natal areas upstream of
RM 98.6. Some juvenile coho use tributaries for rearing throughout
the summer, while others redistribute downstream to other rearing
habitats, including tributary mouths (Schmidt et al. 1984). This
redistribution occurs throughout the summer as fish become more
mobile. Tributary mouths apparently provide important rearing areas
for age-0+ coho (ADF&G 1983a). Some of the larger tributaries may
provide overwintering habitat.
Tributaries upstream of RM 98.6 are the primary natal areas for pink
salmon (Barrett et al. 1984, 198S). However, tributary utilization by
juvenile pink is limited because they move downstream to the ocean
shortly after emergence (Schmidt et al. 1984).
Tributaries arc important rearing areas for chinook in the spring and
early summer (Schmidt ct al. 1984). The redistribution of some
juveniles from tributaries to other rearing habitat, including the
mainstem, sloughs and tributary mouths, occurs throughout the
summer as fish become more mobile (Schmidt et al. 1984). Tributary
mouths apparently are important rearing areas for juvenile chinook.
Juvenile chinook apparently use tributaries for overwintering.
(B) Resident Soecies
In the Talkeetna-to-Devil Canyon reach, tributaries are the primary
spawning and rearing areas for rainbow trout and Arctic grayling
(Schmidt et al. 1984). The larger tributaries in this reach, such as
Portage Creek, may provide overwintering habitat for some rainbow
trout and Arctic grayling (Schmidt et al. 1984). However, it appears
that overwintering in tributaries is limited (Schmidt et al. 1984).
Round whitefish, humpback whitefish, Dolly Varden and longnose
sucker likely spawn in tributary or tributary mouth habitats (ADF&G
10
1983a, Schmidt et al. 1984). Juvenile Dolly Varden are thought to
rear in the upper reaches of tributaries. Tributary mouths are
important rearing and feeding areas for many resident species, such
as rainbow trout, Arctic grayling and whitefish (ADF&G 1981, 1983b,
Schmidt et al., 1984).
2.2 -Relationship Between Physjca! Changes and Habitat Utilization
Of the physical habitat components that determine the availability of fish
habitat, streamflow is the most important because of its direct relationship to all
physical processes influencing fish habitat in the middle river. Under natural
conditions, mainstem discharges are high from late May through early September
and decrease during September and October to reach low flow levels which
continue throughout the winter. Under project operation, flow would be more
uniform throughout the year with higher than natural flows in winter and lower
than natural in summer.
Project operation would alter the natural temperature regime by delaying the
temperature rise during early summer and extending warm water temperatures
into fall. The warmer water temperatures during the fall are expected to delay
development of the ice front from two to seven weeks (Harza-Ebasco 1985). In
addition, the warmer water temperatures released during the winter would
result in open water conditions for a variable distance below the dams. The
upstream progression of the ice front would vary with volume and temperature
of release water and year-specific climatic conditions.
The proposed impoundment area is expected to entrap nearly all the suspended
sediment currently being transported to the middle Susitna River. Reduced
mid-summer turbidities would likely result from such a reduction in suspended
sediment. Winter mainstem turbidities, however, are expected to be higher
than natural.
The degree of impact these changes in physical processes would exert on each
of the habitat types would depend on the level of influence mainstem conditions
have on the physical characteristics of the various habitat types.
1 1
2.2.1 Mainstem and Sjde Channel Habitat Tyoes
Mainstem habitat type is comprised of those portions of the Susitna R iv er
that normally carry water throughout the year whereas side channels
convey flow during the open water season except during periods of low
flow . Therefore, mainstem and to a lesser extent side channel habitat
types would be directly affected by changes in mainstem flow conditions.
In contrast to natural flows, regulated summer flows would provide
relatively stable habitat conditions in these two habitat types; however,
the amount of habitat available may be less than that available under
natural conditions for some life stages. Mainstem and side channel habitats
would also be directly affected by temperatures and seasonal changes in
turbidity levels and associated project released flows.
2.2.2 Sjde Sloughs and Uolapd Sloughs
The project flow regime would cause one or more of the following physical
changes in side sloughs and upland sloughs of the middle Susitna River:
o Reduced backwaters in spring, early summer and in winter
upstream of the ice-covered areas.
o Increased backwaters in fall and in winter in areas downstream
of the ice-front.
o Reduced frequency of breaching in spring and early summer.
o Increased frequency of breaching in winter in ice-covered areas.
o Reduc ed groundwater upwelling during spring and summer and
in w i n ter upstream of the ice cover.
Each of the above physical changes is discussed in relation to current and
potential utilization of these habitat types by salmon and resident species.
12
(A) l<.educed Backwater
Backwaters at slough mouths under natural conditions provide greater
depths in the affected zone than would be provided by local slough
flow. Project flows would substantially reduce the backwater zone in
some sloughs during spring and early summer resulting in a decrease
in the surface area. Depths would likely remain suitable for rearing
and outmigration of juvenile salmon. The degree of loss would be
dependent on the relative spatial distribution of available habitat
under natural and project conditions. During fall and winter in areas
downstream of the ice front. increased backwaters resulting from
increased project flows and ice staging would sustain incubating
salmon embryos that otherwise might be dewatered under natural
conditions. The increased backwaters would also provide additional
rearing and outmigrating habitat. assuming no deleterious effects due
to overtopping in winter.
(B) Breaching Flows
Breaching flows in side sloughs provide habitat in addition to that
provided by local flow by increasing the amount of area with suitable
depths for various life stage activities. Project flows would
substantially reduce the frequency of breaching flows in spring and
early summer. This may result i n difficulties in the movements and
outmigration of juvenile salmonids. The low utilization of these
habitat types by resident species would result in little or no impacts.
During winter. the higher than natural flows and associated staging
in the ice-covered areas would result in breaching or overtopping of
sloughs and the influx of near-zero degree water. This may retard
the development of embryos and reduce the quality of overwintering
habitat.
(C) Uowe!ljng
Reductions in the rate of upwelling during winter would decrease the
quality and quantity of habitat for lif ~ stages that prefer these areas.
13
Chum salmon embryos, for example, appear to depend on the rela-
tively warmer temperatures associated with groundwater upwelling for
successful incubation. In the fall, many chinook salmon juveniles
move into areas with a groundwater source to overwinter (Roth and
Stratton 1985). Reduction in upwelling in the early summer may be
of little significance. Increases in the rate of upwelling over natural
conditions would occur with the high flows i n fall (October and
November) and winter in areas downstream of the ice front.
2.2.3 Tributary and Tributary Mouth Habitats
Tributary habitat would be unaffected by alteration of mainstem flows.
Under project operational flows access into tributaries is not anticipated to
be a problem for returning adult salmon (Trihey 1982).
Tributary mouth habitat is the area bounded by the uppermost point of
mainstem backwater effect in a tributary and the area of clearwater plume
from tributary flows into the mainstem. The areal extent and physical
characteristics of this habitat type are a function of mainstem and
tributary conditions. The total area of tributary mouth habi tat will be
greater and more stable under lower regulated mainstem flows during
project operation (Klinger and Trihey 1984). Salmon and resident species
utilizing this habitat type would benefit from these changes.
2.3 -Selection of Evaluation Species
All three mitigation policies (APA, ADF&G and USFWS) i mply that project
impacts on the habitats of certain sensitive fish species will be of greater
concern than changes in distribution and abundance of less sensitive species.
Sensitivity can be related to high human use value as well as susceptibility to
change because of project impacts. Statewide policies and management
approaches of resource agencies suggest that concern for f ish and wildlife
species with commercial, subsistence, or other consumptive uses is greater than
for species without such value. These species are often numerous, and utilize
a wide range of habitats, as well as having high human use value. Such
characteristics often result in these species being selected for careful evaluation
14
when their habitats are subjected to alternative uses. By avoi d i ng or
min i mizing alterations to habitats utilized by these species, the impacts to other
less sensitive species that utilize similar habitats may also be avoided or
reduced.
The evaluation species were selected after initial baseline studies and impact
assessments had identified the important species and potential impacts on
available habitats throughout the year.
Since the greatest changes in downstream habitats are expected in the reach
between Devil Canyon and Talkeetna, fish using that portion of the river were
considered to be the most sensitive to project effects. Because of differences
in their seasonal habitat requirements, not all species would be equally affected
by the proposed project. Of the species in the middle Susitna River, chum and
sockeye salmon appear to be the most vulnerable because of their dependence
on slough habitats for spawning, incubation and early rearing. Of these two,
chum salmon are the dominant species. Chinook and coho salmon are less likely
to be impacted by the project because two critical life stages, spawning and
incubation, occur in habitats that are not likely to be altered by the project.
Similarly, while some pink salmon spawn in slough habitats in the reach between
Devil Canyon and Talkeetna, most of these fish utilize tributary habitats. The
mitigation measures proposed to maintain chum salmon productivity should allow
sockeye and pink salmon to be maintained as well. Project effects on the
rearing life stage of juvenile salmon, particularly chinook salmon, are also of
concern. The chinook juveniles rear in the r iv er up to two years and coht•
salmon juveniles up to 3 years prior to out-migration. Much of the coho
rearing apparently occurs in clear water areas, such as in sloughs and
tributary mouths, with the more abundant chinook rearing in turbid side
channels as well as clear water areas. Maintenance of chi•10ok rearing habitat
should provide sufficient habitat for less numerous resident species with similar
life stage requirements.
In summary, the primary and secondary evaluation species and life stages
selected for the Susitna Hydroelectric Project in the Devil Canyon to Talkeetna
Reach are:
1 s
PRIMARY
Chum Salmon
Spawning adults
Embryos and pre-emergent fry
Chinook Salmon
Rearing juveniles
SECONDARY
Chum Salmon
Returning adults
Rearing juveniles
Out-migrant juveniles
Chinook Salmon
Returning adults
Out-migrant juveniles
~; e Salmon
.<.eturning adults
Spawning adults
Embryos and pre-emergent fry
Rearing juveniles
Out-migrant juveniles
Coho Salmon
Returning adults
Rearing juveniles
Out-migrant juveniles
Pjnk Salmon
Returning adults
Spawning adults
Embryos and pre-emergent fry
Out-migrant juveniles
16
Arctic Grayling
-Adults
-Juveniles
Rainbow Trout
-Adults
-Juveniles
Dolly Varden
-Adults
Burbot
-Adults
-Juveniles
1 7
3.0 MITIGATION OPTIONS
A Fish Mitigation Plan was prepared and distributed to agency personnel in
November 1984. This was followed by a workshop on the subject documen t in
December 1984. At the request of APA, participating resource agencies and
interveners submitted comments on the three principal mitigation options
proposed in the document: flow release, habitat modification and artificial
propagation.
In general, the Alaska Department of Fish and Game, National Marine Fisheries
Service and the Fish and Wildlife Service concurred that flow release combined
with habitat modification is a feasible approach in achieving APA's goal of no
net loss of habitat value. Concerns, however, were expressed by all three
agencies on the lack of emphasis placed on flow release and the effectiveness of
habitat modifications in Southcentral Alaska. Artificial propagation was viewed
by the agencies as a mitigation option of last resort should the preferred
mitigation options fail.
Rational for development of the APA's selected flow regime and agency comments
on this and the other mitigation options are addressed below where appropriate.
3.1 -Flow Release
The aquisition of additional information on the relationships between physical
processes and habitat utilization in the middle river subsequent to submittal of
the License Application has permitted refinement of the original Case C flow
regime. This resulted in the developm<:nt of eight environmental flow cases,
each designed to achieve specific environmental goals (Harza-Ebasco 1984).
These environmental flow cases can be grouped into three broad categories of
which Case C, Case EV, and Case EVI are representative. These three flow
regimes were evaluated and compared in the Fish Mitigation Plan (WCC 1984).
Case C emphasized providing flows that allowed access into sloughs for
spawning. Case EVI, the APA's preferred regime, was designed to minimize
impacts to chinook rearing while Case EV was designed to minimize impacts to
chum salmon spawning and chinook salmon rearing.
18
An evaluation of CASE EVI indicated that although the flows unde r C ase EV
were established to minimize impacts to chum spawning, habitat mod ifica t ion
measures would be necessary to rectify the residual impacts. Furthermore, the
effort expended on habitat modification measures necessary to offset the
residual i mpacts to spawning habitat under the Case EV regime would not be
substantially greater than these for Cue EVI. The primary difference between
the two regimes, therefore, would be the degree to which impacts to chinook
juvenile habitat are minimized or avoided. Analyses are currently underway to
forecast the mainstem flows that would provide the optimam summer rear i ng
flows for juveniles. The availability of the results of these anal y ses will
provide the opportunity to direct attention to the priority mitigation option,
flow release. The lack of progress on this option has been a concern
expressed by the resource agencies.
3.2 -Habitat Modification
A number of habitat modification measures were presented in the Fish Mitigation
Plan for review and comment by the resource agencies. The measures within
this option focus primarily on rectifying impacts to chum salmon spawning
habitat although secondary benefits would accrue ~o rearing and overwintering
habitat of juvenile chinook salmon as well as life stages of other salmon and
resident species. Those measures considered by APA and the resource agencies
to have the greatest likelihood of success are described below in order of
priority and will be incorporated into the updated mitigation plan presented in
Section 4 .0 .
3.2.1 Slough E3cavatjon
Mechanical excavation of certain reaches of sloughs would improve fish
passage and fish habitat within the sloughs. At slough mouths, excavation
would provide fish access when backwaters are negligi u le during low
mainstem discharges. Mechanical excavation can be used to facilitate
passage within sloughs by channelizing the fl 0 w or deepening the thalweg
profile at the passage reach.
19
On a larger scale, mechanical excavation to lower the profile of the ent i re
slough could increase the amount of upwelling in the slough. A gre ater
head between the mainstem and the slough bed would result in additional
local flow in the slough.
An additional benefit of the excavation process would be the opportunity to
improve the substrate in the slough. Replacement of existing substrate
with suitable spawning gravels would provide additional spawning habitat.
Sorting of the existing substrate will be undertaken to remove unsuitable
particle sizes. The excavation process would be designed to develop
additional spawning and rearing habitat.
An estimate of the cost to excavate a typical slough mouth in the middle
portion of th: Susitna River is $26,000. An estimate of the cost to lower a
typical slough profile by 2 feet for a length of 2,000 feet in the middle
section of the Susitna River is $34,000.
3.2.2 Channel Barriers
Fish access through passage reaches is also improved by creating a series
of pools. Barriers are placed to break the flow on long, steep passage
reaches and create pools between obstacles. Fish passage over the
obstacles is accomplished if sufficient steps of decreased barrier height are
provided to permit surmounting the original barrier (Bell 1973).
Channel barriers are used on long slopes to create fish resting pools, as
shown in Figure 3. These barriers with heights of 10 to 14 inches act as
weirs, with a section of decreased height to improve fish passage between
pools . The barriers arc constructed of various materials. Concrete
highway curbs anchored to the bed with rcbar (Figure 3) or cobbles and
boulders placed to create a sill may be used. Logs may also be attached
to the banks and anchored securely to the bed to prevent movement at
high discharges. Gabions shaped as shown in Figure 3 may also be used
(Lister ct al. 1980).
20
'LOW-
OAIION UIUUI"
r ,. 1-----•u.,••c•O•
HIGHWAY CUill IAilllll"
2
__ 7 __ 7 __ 7~7~~?--~J~t: ~~-~---;~;--7~~;~;--:r-~l-
HOW .__
ICATVIUL Ol,TH 0' 'LOW
TY'ICAL ILO'I
Fish Passage Mitigation Utilizing Barriers
Figure 3
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Wooctwa,.Ciyda Conauttanta
AHO
!NTNX.INC.
21
HARZA·E8ASCO
SUSITNA JOINT VENTURE
Channels are constrained in width to form effective pools. For a wide
channel. channel widths are modified where a pool and weir structure is
des i red.
Estimates of costs per barrier on the basis of a two barrier system are
listed below. Each slope will require more than one barrier to create a
series of pools. As more barriers are built on a site. the cost per barrier
will decrease because of the economies of scale; the major cost involved in
the construction of the barrier is the cost of transporting equi pment.
Barrier
Concrete highway curbs
Rock sill
Gabions
Anchored logs available on site
Anchored logs not available on site
3.2.3 Cbapncl Width Modifications
Co~t/Barrier
s 12.000
16.000
12.000
11.000
12.000
Channeling slough flow will improve fish access through passage reaches
by constricting the width and increasing the depth of the channel. This
technique is especially useful in modifying short. wide passage reaches
(Figure 4). Wing deflectors extending out from the channel bank or rock
gabions restructuring the cross section of the natural channel may be used
to constrict the flow width (Bell 1973).
In determining the modified width for the channel. a maximum velocity
cri teria of 8 fps was used to permit fish access through the reach (Bell
1973).
(A ) Wing Deflectors
Wing deflectors are used to divert the flow in a channel. Two wing
deflectors placed on opposite banks will funnel the flow from a wider
to a narrower cross !ection as shown in Figure 4. The narrowed
channel is tiesigned to provide fish passage at the minimum flow. At
22
~
I
I
j_
'l OW -
PlAN V IEW
WING OEFI.fCTOit
........
0 0 0
0
"00~ 0
Q 0 0 0
.. LA• Y .. W
T YPICAL PA88AQif IIIACM OP kOUQH ALOtiQ
MIODLE 8EC:TIO .. M TtM 8USIT .. A IIIYEII
•r~NQ 0 1,\.IC TOA ,. ...... I.~OQI COIILI 'U
~~
W I NG DEI'UCTOII
•oc •~c • .....,,
._.oo-., o• '"•••-... k~ O••'-•••oa I
rr=---o ·~·' c .. ·-·~
-----~ . =::;~ . .-•or• ,, .... , .. :1
Fish Passage Mitigation by
Modifyin1 Channel Width
AlASKA POWER AUTHORI T Y
SUSITNA HYDROElECTRIC PROJECT
Figure 4
Woo.,.a....CI~a COftaultanta
AND
IHTNX.INC.
HUUA ·fiASCO
SUSITNA JOINT YENTUIU
higher flows, the wing deflectors are inundated; fill between the
banks and the wing deflector w alls is sized to prevent scouring at
higher discharges. Fill will typically be composed of large cobbles
available at the sloughs.
Wing deflector walls are constructed either of rock or gabions formed
of wire mesh and filled with cobbles. Another alternative is the use
of 12-inch-diameter timbers, anchored to the banks and channel bed.
A wing deflector costs $31,000 when constructed of rock,
approximately $24,000 when constructed with gabions, and $22,000 if
timber logs available on site are used. For sites where timber is not
available, a log wing deflector would cost $23,000. Estimates are
based on a typical passage reach of approximately 200 feet for a
slough on the middle Susitna River (Figure 4).
(B) Rock Gabion Channel
Reshaping the original cross section of the channel with rock gabions
is an alternative method of channelizing the slough flow. The channel
is excavated and gabions are used to establish the new configuration.
The new channel shape is designed to maximize depth at minimum
flows; at higher discharges, the gabions prevent scouring of the
channel banks. Figure 4 illustrates a typical cross section for a
reshaped passage reach. For long passage reaches, resting areas are
created by widening the channel between the rock gabions forming
the minimum discharge channel. The gabions are provided throughout
the length of the passage reach and protected upstream by riprap or
wing wall gabions. The gabion banks extend higher than the height
of the maximum slough discharge to prevent collapse from erosion.
The gabions composing the channel banks prevent scouring of the
banks; the channel will be more stable than a similar channel modified
by wing deflectors. For passage reaches with greatly varying
discharges, the added stability of the rock gabion channel is an
advantage. The cost of constructing the gabion channel is
approximately $60,000 f o r a typical passage reach 200 feet in length.
24
3.2.4 Prevention of Sloua,b Oveuopoina,
Project flows are higher than natural discharges in the winter. Ice
staging at these discharges would result in an increase in mainstem stage
and increase the probability of overtopping of sloughs downstream of the
ice cover front.
An influx of cold mainstem water into the incubating area of the Slough 8A
in 1982 caused adverse impacts (ADF&G 1983b). To prevent overtopping,
the height of the .slough berms would be increased as shown in Figure 5.
Cost estimates per berm range from $24,000 to $161,000 or higher
depending on the slough head configurations and the mainstem stage.
3.2.5 Gated Water Supply System
In the absence of large flows i n sloughs and side channels, debris
buildup, siltation, and algal growth may create passage restrictions and
decrease available spawning habitat. Side sloughs and side channels are
breached under natural conditions with a frequency from 1 to 4 years.
The large breaching flows remove obstacles caused by debris and scour
the channel bed. Flows of SO cfs or greater may be required for the
removal of debris and channel scouring. Under project conditions,
breaching of the sloughs and side channels will occur less frequently in
spring and summer months and may not provide sufficient flushing of the
channel. A gated pipeline extending under the berm at the head of a
slough or side channel could provide large quantities of flow under
unbreached conditions.
The gated water supply system consists of a 3 ft diameter corrugated pipe
wi t h a gate' valve structure. The pipe intake is protected by a riprap
cover to prevent the entrainment of fish and debris. The riprap will
stabilize the bank of the berm at the intake by preventing scour. Large
riprap at the outlet will create turbulent conditions for improved air
entrainment and the dissipation of energy to prevent excessive channel bed
erosion. The gate valve structure will enable the manual opening 'Jf the
25
R M~INSTEM
.---SUSITN~ RIVE
PLAN VIEW
vLENGTH OF BERM
-
CROSS SECTIONAL VIEW
LARGE ROCK FAC I NG
Overtopping Prevention Mitigation by Increasing Berm Height
Figure 5
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Wooctward-Ctyda COfteutt.nta
AHD
INTRIX, INC.
HAAZA ·EIASCO
SUSITNA JOINT VENT U RE
pipe to allow large flows into the channel. In order to provide the
suggested SO cfs of slough flow, the pipe system will be operated at a
high mainstem discharge. To prevent the influx of turbid water during
chum spawning or near-freezing water during incubation, the pipe gate
valve will remain closed during the fall and winter months.
A gated water supply system to provide a minimum of SO cfs is feasible if
the head difference between the mainstem elevation and the slough bed is
large enough to drive water through the required pipe length. A 3 ft
head difference will deliver 60 cfs through a 4SOO ft or less pipe length.
A 1 ft head difference requires a pipe length of less than 1300 ft. Given
the head difference and pipe length requirements, a gated water supply
system is feasible at Sloughs 9, 11, and 21. The estimated cost of a
system with a pipe length of 2SOO ft is $100,000.
3.3 -Artificial Propagation
In the Fish Mitigation Plan. artificial propagation was proposed as a means of
maintaining the productivity of chum salmon populations should the highest
priority options prove unsuccessful. At the time the plan was drafted,
streamside egg incubation boxes were chosen as the preferred method for
achieving this goal. As discussed in the plan, incubation boxes require a
reliable water sQpply with appropriate water quality characteristics. particularly
water tempcrat\.\re. The temperature regime of the ident:fied source water,
Deadhorsc Creek at Curry Station, appeared to be somewhat cooler than the
incubation temperatures encountered by chum salmon embryos incubating in side
sloughs (Vining et al. 198S). It was suggested that the Deadhorsc Creek
temperature regimes be matched with a stock of chum salmon that
under a simil"r regime, tributary spawners for example, to ensure
emergence of fry occurs at a time that coincides with natural emergence.
spawned
that
Since
that plan was presented, an alternative technique for artificially incubating
eggs currently in usc in British Columbia was evaluated. This technique
consists of an incubation pit that is buried in the ground and is constructed
with an open bottom enabling it to intercept groundwater flow.
27
The incubation pit consists of a wooden box 10 x 20 x 5 ft deep set to a depth
of 3 feet below the lowest water table elevation. A slotted wood floor installed
in the bottom of the box approximately 6 inches above the base i ntercepts the
groundwater flow.
The incubation pit can accommodate a monolayer of 500,000 eggs and requires a
flow rate of approximately 50 gpm. The advantages of the incubation pit over
the traditional egg incubation box include 1) a wide range of potential sites for
installati on, 2) direct installation in a slough eliminat ing the need to construct
rearing ponds, 3) a constant reliable water source somewhat independent of
weather conditions, and 4) access to the same source of upwelling groundwater
that surrounds naturally i ncubating embryos.
28
4 .0 FRAMEWORK FOR MIDDLE SUSITNA RIVER FISH MITIGATION PLAN
The recently adopted three-staged construction plan for the Susitna
Hydroelectric Project not only provides decision points for project development
based on energy demands but also permits formulation of a mitigation plan that
is tailored to the impacts associated with reservoir filling and each stage of
project development. The magnitude of impacts to the evaluation species/life
stages that would accompany reservoir fillins and each stage of operation would
vary as would the level of mitigation effort necessary to mitigate for these
impacts. For example, with the exception of the filling stage, impacts to chum
salmon spawning would generally increase with each stage and the energy
demand within each stage. Conversely, incubation conditions would improve
with project development as the frequency of winter overtopping in some
sloughs would decrease, particularly with Stage 3 and year 2020 energy
demands. This section presents a framework for impact and mitigation option
analysis that will facilitate incorporation of additional information as it becomes
available and will eventually lead to development of a detailed and acceptable
mitigation plan.
4.1 -Stue 0996-2001)
4 .1.1 Impact Analysis
(A) Fj!ljog • 1995
Impoundment of water from the Susitna River for the Watana reservoir
is presently scheduled to commence in May 1995 with the spring
runoff. Coincident with the initiation of reservoir filling would be
the institution of Case E-VI flow constraints. During the open water
season, flow releases would be at or near E-VI m i nimum levels in
May, June, September, and October. Flow release levels during July
and August would depend on the hydrologic conditions of that year.
Preliminary esti mates of monthly average regulated flow releases for
May through October arc compared to natural flows for the same
periods under dry, average, and wet hydrologic conditions (90, 50,
10 percent excecdence) (Figure 6). Under dry conditions flow
29
19M 1995
40000
36000
30000 -. "" .. ... u 25000 --', ~ u 1' .. I ~ ... .. .. 20000 \ ·~ "'
&. u
.:! ' Q 16000 ': .. \ J~,~· ~\ \
10000 ~ rr -r, ' J 6000 J ~ ~' "'Il ~-r-
b t:::-. ~ ~ 0 M AM J J A S 0 N 0 J F M A M J J A S 0 N 0 J F
Months
10% Exceedance
----SO% Exceedance
- - -90% Exceedance
Susitna River Flows at Gold Creek Under Natural (1994) and
Filling of Reservoir (1995) Regimes with Case E-VI Flow
Requirements.
Fig1.1re 6
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woo4ward-Ciyda ConM~tt.nta
ANO
INTRIX. INC.
11)
HAAZA ·EIASCO
SUSITNA JOINT VENTURE
releases in July and August would be at E-VI dry year minimum of
8,000 cfs. In an average year July and August flows would be about
11,:400 and 12,400 cfs, somewhat higher than E-VI minimum (9 ,000
cfs) yet substantially reduced from average natural flows of 24,000
cfs and 22,000 cfs. In a wet year flow releases wculd increase to
19,400 and I 5,200 cfs, closer to the average natural condition.
During the first winter following filling, November 1995 -March 1996,
the reservoir level would be held constant so that releases would
match inflow. Power generation would commence in April 1996.
Downstream water temperatures from May through October are
expected to be similar to pre-project temperature, although some time
lag would occur.
Turbidity levels during filling would decrease in the open water
season and increase over natural levels during the ice-covered
months.
(i) Primary Evaluation Species
Chum Salmon
Adult Spawning
Detailed analysis of maii£stem flows required for successful
passage into the major chum salmon spawning sloughs have
been conducted by ADF&G (Blakely et al. 1985). However,
a quantitative assessment of the availability of successful
passage conditions during reservoir filling using this
information is not possible for average and wet years since
the available flow data, mean monthly flows, mask the
monthly variability in flows caused by short-term rainstorm
events that often provide passage. It can be assumed,
however, that since the mean monthly flows for filling are
less than those for natural conditions in August and
September for average and wet conditions that the
31
frequency of successful passage conditions would be
reduced. In a dry year with E-VI minimum flows during
the spawning period and assuming no local runoff (no
variability around the minimum flow value) passage would be
possible at only two passage reaches of the seven sites
evaluated -one in Slough SA and one in Side Channel 21.
Embryos and Pre-Emeuent fry
Incubation conditions during the winter following the
summer filling period would be similar to natural conditions
and no project-induced impacts are expected to embryos and
pre-emergent fry.
Chinook Salmon
Juvenile Rearina
Chinook salmon juveniles rear principally in tributaries and
side channels in the open water season (Schmidt et al.
1984). The filling flow during this period would reduce the
amount of rearing habitat in currently utilized side
channels. Tributary habitat would be unaffected.
Additional rearing habitat may become available in other
middle Susitna River areas. This is the subject of ongoing
analysis. the results of which should become available in
early fall. 1985.
(ii) Secondary Evaluation Species
Chum Salmon
Returning Adults
Chum salmon migrate up
areas during the summer.
32
the Susitna
The 9.000
River to spawning
cfs minimum flows
during filling (8 ,000 i n a dry year) would not impede their
upstream migration.
Juvenile Rearing
Chum salmon rearing occurs in natal areas, primarily
sloughs and tributaries, during the early summer (May to
first part of June). In mid-summer (late June and July),
densities remain high in tributaries and increase in upland
sloughs. During outmigration, which is generally complete
by the end of July, juvenile chum usc mainstem areas for
short-term rearing. Filling flows would decrease the
amount of rearing habitat in side sloughs through the
elimination of overtopping conditions and to a lesser extent
a reduction in backwaters. Similarly, the backwater in
upland sloughs would be reduced. The availability of
mainstem sites for short-term rearing is not expected to
decrease although the locations of suitable sites would
change with decreased flows.
Out-migrant Juveniles
Filling flows would reduce the frequency and amplitude of
spring runoff flows that can act as stimul i for outmigration
for chum salmon. These reductions are not expected to
impact seaward migrat i on because other factors such as
photoperioc', water temperature increases and physiological
condition also stimulate outmigration.
Chinook Salmon
Returning Adults
Filling flows during summer would not impede the upstream
migration of chinook salmon adults in the Susitna River and
into tributaries.
33
Out-miuant Juveniles
Age-l+ chinook salmon migrate out of the middle river by
July. As mentioned with chum salmon, this outmigration
would not be substantially affected by filling flows.
Sockeye Salmop
Returpjpa Adults
Filling flows would not impede the summer upstream
migration of sockeye salmon adults. Sockeye spawn in side
sloughs in the middle river similar to chum salmon.
Soawnjng Adults
The restricted access conditions to
channels discussed for chum salmon
sockeye.
Embryos and Pre-emergent Fry
sloughs and side
would also apply to
The incubation conditions during the winter following the
summer filling period would be similar to natural conditions
and no project-induced impacts are expected to embryos and
pre-emergent fry.
Rcarjoa Juveniles
Sockeye juveniles generally rear in natal side sloughs
during early summer and relocate to upland sloughs by
July. Reductions in the amount of habitat available in
these habitat types due to filling flows would result from
reduced backwater and breaching flows. The degree of
habitat loss ~ould be site specific.
34
Out-migrant Juveniles
Outmigration of sockeye salmon would not be impacted by
project filling flows.
Coho Salmon
Returning Adults
Filling flows during summer would not impede the upstream
migration of chinook salmon adults in the mainstem Susitna
River and access into tributaries.
Rearing Juveniles
Coho salmon rear primarily in tributaries and upland
sloughs. Project filling flows are not expected to impact
these habitats.
Out-mi&rant Juveniles
The outmigration of coho juveniles would not be impacted by
project flows.
Pjnk Salmon
Returning Adults
Filling flows during summer would not impede the upstream
migration of pink salmon adults in the mainstem Susitna
River.
Spawning Adults
A limited amount of pink salmon spawning occurs i n slough
habitats and filling could restrict access to these areas
during the spawning season.
35
Embryos and Pre-emergent fry
The similar-to-natural condition during
incubation months would preclude any
impacts of pink embryos and pre-emergent fry.
Out-migrant Juveniles
the winter
project-induced
Pink salmon fry migrate to Cook Inlet shortly after
emergence. For reasons discussed previously, the project
is not expected to interfere with outmigration.
Arctic Grayljpg
Arctic grayling rear in tributary mouths and overwinter in
mainstem habitat. Filling flow level would increase the
availability and stability of tributary mouth habitat for rearing
(Klinger and Trihey 1984). The winter flow regime would
approximate that of natural conditions so no impacts to
overwintering based on flow would be expected.
Rainbow Trout
Rainbow trout use side sloughs and tributary mouth habitats for
rearing and mainstem areas for overwintering. The i ncrease in
tributary mouth habitat during summer and the maintenance of
natural conditions in winter during filling should sustain rainbow
trout production at current levels.
Dolly Varden
Do ll y Varden's primary use of project affected habitats is
overwintering in the mainstem. Since winter flow during filling
would approximate natural conditions no impacts are anticipated.
36
Bur bot
Burbot use mainstem habitat for all life history stages, showing
a preference for turbid backwater sites and slough mouths. The
lower flows during summer filling would increase the areas with
low velocity, backwater characteristics. No project impacts
would occur during the winter months. Therefore, the project
filling flows would maintain sufficient habitat to support present
levels of burbot.
(B) Operation
Power generation for the Susitna Hydroelectric Project would
commence in April 1996 after approximately one year of filling.
Regulated flow releases have been simulated for the first year of
operation based on anticipated energy demands. Natural and Stage
1-1996 operating flows are compared at the 97, SO, and 6 percent
exceedance probabilities (Figures 7-9). The 1996 flow regime is
typical of project operation -higher flows in winter and during
periods of peak energy demand and lower flows in summer during the
filling process.
Water temperatures during Stage I would be 2-3°C colder than natural
in the spring. By mid-summer, project temperatures would be similar
to natural ones. In the fall and winter, warmer than natural
streamflow temperatures would result from the heat stored in the
reservoir. The difference between natural and project temperature is
inversely related to the distance from the dam. Figures 10-12
compare natural and simulated Stage 1 (2001) temperatures at three
locations below the dam.
The warmer winter water temperatures and higher than natural flows
would delay the formation of the ice front and result in its upstream
progression only to RM 136.5 in an average winter (1981-1982). The
higher flows would also increase the thickness of the ice cover and
37
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fROM "fAIOD 1110-1111
I . ITAOEO CONITRUCTION
ITAGE t
I . 'IIOJECTEO ENERGY
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fLOWI rOll ITAOI!D
CONITIIUCTION
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JAN FEB MAR APR MAY JUN JUL ACG SEP OCT NOV DEC
Honlh
Comparison• of Susitna River Natural and Stage 1 1996 Streamflow•
Exceeded 97% of the time at Gold Creek
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
...... ~ Cofteultenta
AND
Reference: Harza-Ebasco 198~ Figure 7
ENTfUX, INC.
HARZA ·EBASCO
SUSITNA JOINT VENTURE
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Honlh
Comparisons of Susitna River Natural and Stage 1 1996 Streamflow•
Exceeded 50% of the time at Gold Creek
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Reference: Harza-Eha•r0 !9!!~ Figure 3 ~" i ftiA, ;::c..
HARZA ·fBASCO
SUSITNA JOINT VENTURE
ol>o
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FIIOW PERIOD IUD-1111
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CONITIIUCTION •uo. 1
JAN fEB MA R APR NAY JUN ~UL AUG SEP OCT NOV DEC
Hon lh
Comparisons of Susitna River Natural and Stage 1 1996 Streamflows
Exceeded 6% of the time at Gold Creek
ALASKA POWER AUTH li RITY
SUSITNA HYDROELECTRIC PROJECT
Woodw .... CI-Coneultanta
AND
Reference: Harza-Ebasco 1985 Figure 9
ENTRIX, INC.
HARlA ·E8ASCO
SUSITNA JOINT VENTURE
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Monlh
Simulated Natural and Stage 1 2001 Susitna River Temperatures •t
River Mile 150
ALASKA POWER AUTHOAITY
SUSITNA HYDROELECTRIC PROJEC T
Reference: Harza-Ebasco 198S Figure 10
Woodword-Cirtle Conaultanto
AND
HARZA ·EBASCO
SUSITNA JOINT V E NTURE
ENTAIX, INC.
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NOTE I .
I . CLIWA TOLOOICAL ANO
HYOIIOLOOICAL DATA
f'IEIIIOO WAY 1111 -llf'T.
II II
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Simulated Natural and Stage 1 2001 Susitna River Temperatures at
River Mile 130
ALASKA POW ER AUTHORITY
SUSIT NA HYDROEL ECTRIC PROJE CT
Referen<.:e: Harza-Eba!co 1985 Figure 11
Woodward-Clyde Conaultanta
AND
HARZA -E8ASC.O
SUSITNA JOINT VENTUrlE
ENTRIX , INC.
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~UIIOO WAY ltlhii~T.
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Simulated Natural and Stage 1 2001 Susitna River Temperatures at
River Mile 100
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Reference: Harza-Ebasco 1985 Figure 12
WOCHiward-CI~e Conaultante
AND
HAAIA ·EBASCO
SUSITNA JOINT VEN T URE
ENTAIX , INC.
result in higher staging in the ice covered areas. Upstream of the
ice front the stage of the open water would be less than the effective
stage of the ice cover formed under natural condition.
Turbidity levels dur i ng Stage 1 would be less than natural in the
summer and greater than natural in the winter.
(i) Primarv Evaluation Species
Chum Salmop
Spawnjng Adults and Incubating Embryos
and Pre-Emenept Fry
Stage 1 -1996 project flows during the spawning season for
chum salmon (August 12 -September IS) would be less than
natural flows . Flow duration curves for natural and
simulated Stage 1 mean weekly flows based on 34 years of
record are compared for each week of the spawning period
(water weeks 45-49) in Appendix Figures 1-S. Natural and
simulated Stage 1 weekly flow duration curves based on the
maximum mean weekly flow for weeks 45-49 of each year for
the 34 years of record are presented in Figure 13 .
Although the flows are substantially greater than E-VI
minimum constraints, a reduction in the frequency of
occurrence of successful passage conditions and availability
of suitable habitat would occur. The extent of these
reductions for the major chum producing sloughs and side
channels (sloughs SA, 9, 9A, 11, 21 and Upper Side
Channel 11 and Side Channel 21) were analyzed. The
percent of time successful passage conditions would be
available at the passage reach of each slough was estimated
by selecting the exceedance value associated with the
minimum mainstem discharge that provided passage either
44
-en u. u -u
110 ..
Ill .c: u
"' 0
60,000 l
\ SO,OOO
• Natural flow at Gold Creek
a Simulated Stage I 1996 Energy Demand flow
\
40,000
~o.ooo
20,000
10,000
0
0 20 40 60 80 100
Percent Excccdance
Comparison of flow duration curves for natural and simulated
Stage 1 1996 Energy Demand streamflows for weeks 45 to 49
based on mean weekly flows for 34 years of record.
Figure 13
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodw•rd-Ciyde Conaurt.nta
AHD
ENTRIX, INC.
45
HARZA·EBASCO
SUSITNA JOINT VENTURE
through backwater, contro:l ing breaching flows or local
flow (excluding direct surface runoff}. The results of
these analyses are presented in the discussion of individual
sloughs below.
Stage 1 -1996 project flows during the incubation period
for chum salmon would be higher than natural from October
through April. As the winter ice cover forms, the staging
associated with the higher than natural flows would result
in increased upwelling benefitting incubation but would also
result in near-0°C mainstem water overtopping sloughs and
possibly retarding the growth and delaying the emergence
of embryos that ordinarily incubate at 2-3°C. This
upstream progression of the ice front and potential for
overtopping would range from RM 127 to RM 145 for Stage
-1996 depending on year-specific meteorological conditions.
Increasing the height of berms at the slough head was
proposed in the Fish Mitigation Plan (WCC 19S4} as a
method to prevent the overtopping of sloughs during
winter. While this may be beneficial for incubation it would
reduce the frequency of successful passage conditions
resulting from breaching flows during the spawning season.
In the analysis of Stage 1-1996 flow effect on passage
conditions that follows, both unbermed and bermed
conditions for each slough are considered.
Slough SA
Relative Utilization
During the 19Sl-19S4 studies, the mean peak counts of
chum salmon and sockeye salmon in Slough SA were 478
(range: 37-917) and 110 (range 67-177). The mean
estimated total escapements to the slough were 1009
46
chum (range: 112-2383) and 247 sockeye (range:
131-532) (Barrett et al. 1985). Slough 8A mean chum
and sockeye escapements comprised 14 .9 and 14.3
percent of the total escapement to sloughs in the
middle Susitna River.
Impact Mechanism
The frequencies of occurrence of successful passage
conditions at each passage reach of Slough SA under
natural, Stage unbcrmcd, and Stage I bcrmcd arc
graphically depicted for each week and for all weeks
combined of the spawning period in Figure 14. The
prevailing mechanism for passage (backwater, local
flow or breaching) and associated frequency values are
listed for each week and for the entire period in
Appendix Tables I to 6 .
Under natural and Stage I flow regimes, the frequency
of successful passage conditions decreases progress-
ively with each week of the spawning season as
mainstcm flows decline. The differences between
natural and Stage 1 flows are greatest, although not
substantial, at the beginning of the spawning season
(Week 45) and gradually narrow by the last week
(Week 49). This is attributable to the passage
provided by the relatively high breachir.g discharges
at Slough SA, 27 ,000 and 33,000 cfs, which oc;ur at a
greater frequency with natural flows than with project
flows early in the season. Later in the season the
frequencies of these flows arc at or near zero for both
natural and project flows. A similar pattern is evident
with both a bermcd and unbcrmed slough. The most
noteworthy decrease in frequency of successful
pass11.ge occurs at Passage Reaches VII-X where the
natura l freq u ency of I 5 percent for the entire periods
47
0 Natural §Stage 1 -Unbermed
I Stage 1 -Bermed
p
E
R c
E
N
T
too
Percent of Time Successful
Passage Occurs Under
Natural and Stage 1 Flows
at Slough SA
Figure l4
WEEK 45
WEEK 46
WEEK 47
'Ai:EK 48
'Ai:EK 49
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodward-Ct,.te COftiUfUnta H A A Z A • E I A S C 0
AND SUSITNA JOINT VENTUfU
lNTNX.INC.
4.R
(weeks 45-49) drops to 0 percent for the Stage
bermed conditi on.
The probability of Slough 8A overtopping in the w i nter
is high under Stage 1-1996 flows. The length, height,
locations, and costs of berms necessary to prevent the
likelihood of overtopping will be assessed in an
upcoming summer field program.
Stough 9 -98
Relative Utilization
During the 1981-1984 studies, the mean peak counts of
chum and sockeye salmon in Slough 9 (including 98)
were 312 (range: 175-423) and 28 (range: 2-91). The
mean estimated total escapements to the slough were
531 chum (range: 430-645) and 70 sockeye (range:
0-230) (Barrett et at. 1985). Slough 9 and 98 mean
chum and sockeye escapements comprised 7.8 and 4.0
percent of the total mean escapement to sloughs in the
middle Susitna River.
Imoact Mechanism
The frequencies of occurrence of successful passage
conditions at each passage reach of Slough 8A under
natural and Stage I flows with the slough bermed and
unbermed are grap~ically depicted for each week and
for all weeks of the spawni ng period combined in
Figure 15 . The prevaili ng mechani sm for passage and
associated frequency values are l isted for each week
and for the period in Appendix Tables 7 to 12 .
In general, the reduction in frequency of passage from
natural to an unbermed slough under Stage 1 for each
49
O Natural I; Stage 1 -Unbermed
I St•ge 1 -Bermed
1
p 1
E
R c
E
N
T
PR II
Percent of Time Successful
Passage Occurs Under
Natural and Stage 1 Flows
at Slough 9
Figure 15
V\EEKS 45-49
WEEK 45
WEEK 46
WEEK 47
V\EEK 48
V\EEK 49
Ill IV v
ALASKA POWER AUTHORITY
SUSITPU HYDROELECTRIC PROJECT
WooctwaN-C~e COftaultanta
ANO
INTNX,INC.
50
HAAZA ·EIASCO
SUSITNA JOINT VENTUAE
week and for the entire period would not likely be
sufficient to alter present u ti lization patte r ns.
However, given the relatively low breach in g discha . ge
{19,000 cfs), a bermed slough would substantially
reduce the frequency of passage from natural
conditions at Passage Reaches 11-V. Passage i n to
Slough 9B through Slough 9, in particular, is
dependent on breaching flows.
Slough 9 would likely be overtopped in most years of
operation. The length, height, locations and cost:. of
berms necessary to prevent overtopping will be
assessed in an upcoming summer field program.
Slough 9A
Relative Utilization
During the 1981-1984 studies, the mean peak count of
chum salmon in Slough 9A was 17 (range: 105-303)
while the mean estimated total escapement to the slough
was 246 chum (range 86-528) (Barrett et al. 1985).
Slough 9A mean chum and sockeye escapement
comprised 3.6 and 0.1 percent of the total escapement
to sloughs in the middle Susitna River.
lmoact Mechanism
The frequencies of occurrence of successful passage
conditions at each passage reach of Slough 9A under
natural and Stage 1 flows with the slough bermed and
unbermed are graphically depicted for each week and
for all weeks of the spawning period combined in
Figure 16 . The prevailing mechanism for passage and
associated frequency values are listed for each week
and for the period in Appendix Tables 13 to 18.
S I
p
E
R c
E
N
T
D Natural i Stage 1 -Unbermed
I Stage 1 -Bermed
100-,.. ,.. ,.. ... ,.. ,.. .
.
-
• • o~~-U~~.--~~~~~~~.--1oo-"' "" .. "' "' -
~
~
~
~
'AEEKS 45-49
-~ WEEK 45
-.
0~~~~~~~~~~~·~~~~-1 oo-,... ,.. ~ ,.. ,... ,.. .. ,.. ,. ,.. ~ ~ .
-• WEEK 46 --
-
Ill O~~~LLBL~~aL~~~~~~~~~.
100• -r-,.. . ,...., ,.. ~ ,.
-~ WEEK 47
oJU:JI-L~-LBL~~~L-~~~~_.~·L-~~-
1oo--,.. --,... ,.. ,.. .
0-~BL~~~--~~~~~~~~_.~_u~ .. --~~~
100-"" : -
~
~ 'AEEK 49
-,.. -
,.. ,.
~ ,.. ,..
-I I l o~~UL~~s_~~~~~~~~~
PR 1 11 Ill IV V VI VII VIII IX X XI
Percent of Time Successful
Passage Occurs Under
Natural and Stage 1 Flows
at Slough 9A
Figure 16
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
WCHHiward-Cird• Couultanta
AND
INllft.INC.
52
HAAZA·EIASCO
SUSITNA JOINT VENTURE
The low breaching flow ( 13,500 cfs) and low mainstem
discharges that provide the local flow necessary for
passage at most passage reaches account for the sl igh t
and inconsequential reductions in passage frequencies
from the natural to project flows. Even with a bermed
slough only two passage reaches, VIII and XI,
experience substantial declines in the frequency of
passage.
Slough 9A with its low breaching flow is predicted to
be overtopped in most years. The length, height,
locations and costs of berms necessary to prevent
overtopping will be assessed in an upcoming field
program.
Slough II
Relative Utilization
During the 1981-1984 studies, the mean peak counts of
chum salmon and sockeye salmon in Slough 11 and
Upper Side Channel 11 were 674 (range: 238-1586) and
540 (range: 248-893). the mean estimated total
e3capements to the slough were 1572 chum (range:
674-3,481) and 1,166 sockeye (range: 564-1 ,620)
(Barrett et al. 1985). Slough II and Upper Side
Channel II mean chum and sockeye escapements
comprised 23 .2 and 67.3 percent of the total
escapement to sloughs in the middle Susitna River.
Imoact Mechanism
The frequencies of occurrence of successful passage
conditions at each passage reach of Slough 11 under
natural flows and Stage I flows with the slough bermed
and unbermed are graphically depicted for each week
S3
and for all weeks combined of the spawning period in
Figure 17. The prevailing mechanism for passage and
associated frequency values are listed for each week
and for the period in Appendix Tables 19 to 24.
Project flows would reduce the frequen'· y of successful
passage only to a minor
relatively high breaching
indicates that it contributes
Construction on berms at
degree in Slough 11 . The
discharge at this site
infrequently to passage.
this slough would reduce
passage in the upper passage reaches by about 6
percent. The other passage reaches would be
unaffected.
Slough 11 is predicted to be overtopped in years of
average or colder meteorological conditions.
Uooer Side Channel 11
Relative Utilization
(see Slough II)
Imoact Mechanism
The frequencies of occurrence of successful passage
conditions at each passage reach of Upper Side
Channel 11 under natural flows and Stage I flow with
the side channel bermed and unbermed are graphically
displayed for each week and all weeks of the spawning
period in Figure 18. Insufficient data were available
to evaluate the influence of mainstem discharge on local
flow and backwater effects at Passage Reach II
(Appendix Tables 19-24).
54
0 Natu ral EJ1 Stage 1 -Unbermed
I Stage 1 -Bermed
p
E
R c
E
N
T
PR I II Ill
Percent of Time Successful
Passag_e Occurs Under
Natural and Stage 1 Flows
at Sl->ugh 11
Figure 17
IV
\1\fEKS 45-49
WEEK 45
WEEK 46
WEEK 47
\1\fEK 48
\1\fEK 49
v VI VII
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodwafti.Ctyde Conaultanta H A A Z A • E I A S C 0
ANO SUSITNA JOINT VENTURE
INTNX, INC.
-frNatural i Stage 1 -Unbermed
I Sta1e 1 -Bermed
p
E
R c
E
N
T
Percent of Time Successful
Passage Occurs Under
Natural and Stage 1 Flows
at Upper Side Channel 11
Fiaure 18
56
\N:EKS 45-49
WEEK 45
WEEK 46
WEEK 47
\N:EK 48
\N:EK 49
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
HAAZA·EIASCO
SUSITNA JOINT VENTUAE
The difference in the percent of time passage is
available under natural and Stage project flows based
on breaching flows would not likely affect the
utilization of this site to a large degree. The lack of
data mentioned previously does not all a discussion of
passage condition with the side channel bermed.
This site is predicted to be overtopped under Stage 1
flow with average or colder meteorological conditions.
The len&th, height, location and cost of berms to
prevent overtopping will be assessed in an upcoming
field program in conjunction with Slough 11 and with
which it is contiguous.
Slough 21
Relative Utilization
During the 1981-1984 studies, the mean peak counts of
chum salmon and sockeye salmon in Slough 21 and Side
Channel 21 were 921 (range: 274-2,354) and 103
(range 38-197). The mean estimated total escapements
to the slough were 1,7780 chum (range: 481-4,245) and
150 sockeye (range: 63-294) (Barrett et al. 1985).
Slough 21 and Side Channel 21 mean chum and sockeye
escapements comprised 25 .9 and 8.7 percent of the
total escapement to sloughs in the middle Susitna
river.
Impact Mechanism
The frequencies of occurrence of successful passage
conditions at each passage reach of Slough 21 under
natural flows and Stage I flow with the slough bcrmed
and unbcrmcd arc graphically displayed for each week
and for all weeks combined of the spawning period in
S1
Figure 19. The prevaili ng mechanism for passage and
associated frequency values are l isted for each week
and for the period in Appendix Tables 25 to 30.
Project flows would reduce the frequency of passage
only slightly for an unbermed slough and for a bermed
slough at Passage Reaches I and II. Passage at
Passage Reaches IIIL and IIIR for a bermed cond i tions
would be reduced about 29 percent from the natural
condition.
Slough 21 has a low probability of overtopping which
would only occur in the coldest of years. Berming of
this slough would therefore not be a high priority.
Side Chapnel 21
Relative Utilization
(see Slough 21}
Impact Mechanism
The frequencies of occurrence of successful passage
conditions at each passage reach of Slough 21 under
natural flow and Stage I flows w i th the side c hannel
bermed and unbermed are graphicall y displayed for
each week and for all weeks combined of the spawn i ng
period in Figure 20. The prevail ing mechani sm and
values are also listed for each week and for the period
in Appendix Tables 25 to 30.
Due to the low breaching flow (1 2,000 cfs) that affects
the majority of passage reaches in the side channel,
project flows would slightly reduce the frequency of
successful passage in an unbermed condition. For a
sa
0 Natural i Stage 1 -U nbermed
I Sta1e 1 -Bermed
1
l
p 1
E
R c
E
N
T
II
Percent of Time Successful
Passag_e Occurs Under
Natural and Stage 1 Flows
at Slough 21
Figure 19
~EKS 45-49
WEEK 45
WEEK 46
WEEK 47
~EK 48
~EK 49
IIIR IIIL
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJEC T
Woodwaf'd.C~• Conauttanta
AND
INTNX.INC.
59
HAAZA·EIASCO
SUSITNA JOINT VENTURE
0 Natural Ia Stage 1 -Unbermed
1 Stage 1 -Bermed
p
E
R c
E
N
T
10
O PR I II Ill IV
Percent of Time Successful
Passage Occurs Under
Natural and Stag_e 1 Flows
at Side Channel ~1
Figure 20
'AEEKS 45-49
WEEK 45
·WEEK 46
WEEK 47
V\£EK 48
V\£EK 49
V VI VII VIII IX
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Wooctw•~• Cofteult.anta
AND
INTRIX.,Ife
60
HARZA·EIASCO
SUSITNA JOINT VENTURE
bermed condition, local flow or backwa t er effects wou ld
mai ntain passage at a high frequency for Passage
Reaches 1-V . Substantial reductions in frequenc y
would occur at Passage Reaches VI and VII.
The ice front would not progress as far as Side
Channel 21 in an average winter; however, in the
colder winter it would and overtoppi ng may result.
Based on this low probability, bermi ng may not be
necessary.
Chinook Salmon
Rearing Juveniles
The open water flow regime during Stage 1 provides higher·
flows than filling yet lower flows than natural. In general,
the flows are substantially greater than the E-VI minimums
which were designed to minimize impacts to juvenile chinook
rearing. As results of an ongoing study of juvenile
chinook rearing habitat-flow relationship are made available
in fall 1985, impacts of Stage I flows can be assessed.
Impacts to juvenile chinook overwintering habitat resulting
from overtopping of sloughs and side channel is also of
concern. As information on the extent of overtoppi ng that
may occur with Stage I flows is acquired in the summer
field program, potential impacts to juveniles chinook rearing
in these areas may, in part, be addressed.
(ii) Secondary Evaluation Soecjes
In the evaluation of the effect of project filling flows on the
habitat of the secondary evaluation species, no significant
impacts were identified. Since Stage I open water flows lie
between filling and natural flows, no impacts are anticipated.
61
The Stage winter flows, however, are substantially greater
than filling and natural flows. The higher flows accompanied by
ice staging in winter would increase depths, wetted surface area
and the number and extent of backwater sites in the mainstem
side channels and slough mouths. This potential increase in
overwintering habitat may offset habitat lost from overtopping of
some sloughs.
4.1.2 Mitigation
(A) Filling
The primary impact identified during filling flows is restricted access
into sloughs by adult chum salmon. The extent of this impact would
depend on hydrologic conditions of that year. During a wet yc:tr,
impacts would likely be minimal. Assuming a worst case dry year ·
(based on the hydrologic record during filling up to August of that
year) E· VI minimum flows would be provided during the spawning
season.
Under E· VI minimum flows extensive modification of most sloughs
would be required to maintain the average natural access conditions.
These modifications would be in excess of those required for Stage 1,
2, and Stage 3-2008 operational flows.
The E-VI minimum flows during filling as compared to the
substantially higher operational flows of subsequent years can be
compared to the natural occurrence of dry years. For example, the
E-VI minimum flow during August, 9,000 cfs, is greater than the
maximum weekly average flow during the 1969 spawning period of 7399
cfs.
It is suggested therefore that if 1995 were a dry or average year and
mitigation measures designed for 1996 operational flows are not
complete or are insufficient, temporary low cost measures be employed
62
to improve passage such as manually modifying critical passage
reaches or physically transporting fish into the sloughs.
As mentioned previously, impacts to juvenile chinook rearing are in
the process of being evaluated and should any be i dentified
appropriate measures will be developed.
Impacts to secondary evaluation species, other than those that would
be mitigated for by measures for chum salmon, are not anticipated.
(B) Ooeration
(i) Primary Evaluation Soecies
Chum Salmop
Soawpipa Adults and Incubating Embryos and Pre-
Emergept Fry
The principal impacts identified for chum salmon spawning
resulting from Stage I flows would be a reduction in the
frequency of successful passage conditions in sloughs and a
reduction in the quality of incubation habitat due to sloughs
being overtopped with near 0°C water.
Since Stage 1-1996 operational flows would generally be well
within the bounds of E-VI minimum and maximum flow
constraints, Case E-VI would be considered of little
mitigative value during this early stage with respect to the
identified impacts. However, Case E-VI constraints on
limiting the amoun! of daily and weekly fluctuations would
be of importance in maintaining a c;table habitat.
Habitat modification is the mitigative option of choice to
rectify impacts to chum salmon spawning and incubation
63
habitat. Various measures to maintain these habitats were
described in Section 3.0.
The increase in icc staging with Stage I flow compared with
that described for the License Application project may
necessitate construction of more extensive berms than those
described in the Fish Mitigation Plan (WCC 1984). As
mentioned previously the length, height, location and cost
of additional bcrming that may be necessary at the seven
sites examined for passage may prove to be excessive and
not cost-effective. In such cases, mitigation efforts should
be directed to other sites.
A set of criteria has been developed to establish a means of
ranking sloughs for modification on a benefit-cost basis.
The criteria applied to each slough include the relative
utilization, the frequency of overtopping, the extent of
berming required to prevent overtopping, and the location
and extent of passage reach modifications. The usc of
these criteria in a decision making flow chart is presented
in Figure 21. As indicated in the chart, a slough with
higher relative utilization, low probability of winter
overtopping, and minor passage reach modification
requirements would receive the highest ranking. As
information on the extent of bcrming necessary for each site
is acquired, this set of criteria will be applied to each of
the maj or chum salmon producing sloughs.
If the cost of modifying one or more of these sloughs is
excessive, alternative sites will be evaluated for modification
as replacement habitat. A sufficient number of sites will be
modified to insure there is no net loss of habitat value.
64
(1\
U1
RELATIVE UTILIZATION OF SLOUGHS
Frequency or Winter Overtoppinq
I I
.Lmt IUgj)
I
Bera
Conatru~&tigo
I
I
I
tUruu: H..AJM
I I
Slouqh Slouqh Slouqh
Moditicotion H2!UU!<At12D H2ll1U!<At12D n n ~
ll1.nsu: H..AJM tUruu: HA.1.l2.t H.1nl21: HA12x
I I I I I I
l • l ) 4 9 10
Flow Chart for Rankin1 Sitea
for Mitigation Deci&ion Making
Frequency or Winter OvertoppinC)
I
Slouqh
H2ll1U!<It12D n
l!..in2l: lli.1.Q..[
I I
!> 6
I
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ll1.nsu: ~
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ll1.nsu: ~ ll.1ruu: lli.1.Q..[
I I I I
7 • ll u
• The 11naller cllc raall val"e ac a sice, chc •ore cou·cffccrovc would '-
miciaacioa work ac che aile.
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Figure 21
Woodwant-CI~• COflaultanta
AND
ENTRIK, INC.
HARZA ·EBASCO
SUSITNA JOINT VENTURE
Chinook Salmon
Juvenile Rearinll
Juvenile chinook rearing habitat-flow relationships will be
made available in fall, 1985 at which time any impacts that
may result from project operation wili be evaluated and
appropriate mitigation measures proposed.
(ii) Secopdary Evaluation Soecics
Mitigation measures proposed for chum salmon spawning will also
mitigate for impacts to sockeye salmon spawning habitat. No
other impacts have been identified for the other evaluation
species for which mitigation measures need to be implemented.
4.2 -Stage 2 (2002-2008)
4.2.1 Impact Analysis
Power generation with Stage 2 (Devil Canyon) completed would commence in
2002. Regulated flow releases have been simulated for the first year of
Devil Canyon-Watana operation based on anticipated 2002 energy demands.
Natural, Stage 1-1996 and Stage 2-2002 flow regimes arc compared at the
97, 50, and 6 percent cxcecdancc probabilities in Figures 22-24. Stage 2
flows would generally be greater than Stage 1 flowc: during March and
April and in late July and August and will be slightly less than Stage
flows in late fall to mid-winter in average and wet years. The opposite
would occur in dry years (97 percent exceedencc), with Stage 2 flows less
than Stage 1 flows in summer and greater in winter. In contrast to Stage
1 flow, Stage 2 flows would reach Case E-VI midmum flow requirements
during the spring filling period. The drier the year, the greater length
of t i me flows would be at the minimum level.
Streamflow temperatures during Stage 2 operation would depend to some
degree on the depth of drawdown and the use of multilevel intakes in Devil
66
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THOUSANDS
2 5
2 0
E -VI WAXIWUW flOW
IIEOUIAEWENTII
WAXIWUW fl0W•31.000 olo
'---------< l···-IS
10
5
0
-_..!.~ ... ,..~····
E -VI WINIWUW HOW
AEOUIAEWENJe
/
+----.----r----r----r---.----.--~---,----,---,----.--~
JAN FEB MAR APR HAY JUN JUL AUG SEP OCT NOV DEC
Ho nlh
NATUAAl C-T.oet
PLOWe-·T-
CONeTIIUC,_
.TA .. I
•&.owe,_ •'~• CONeTRUC:T.oet •u••
Comparisons of Susitna River Natural, Stage 1 1996 and
Streamflows Exceeded 97% of the time at Gold Creek.
Stage 2 2002
Reference: Harza-Ebasco 1985 Figure 22
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJEC T
Woo4w~ COIWUit.ftta
AHD
EHTRIX , INC.
HARZA ·EBASCO
SUS IT NA JO IN T V E NTURE
"' CD
D
•
c
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a ,.
g
•
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c
f
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THOUSANDS
30
25
20
15
19
5
0
CAIE E -VI MAXI .. Utol fLOW
REOUIIIEMENTI
MAXIMUM•36.000 cia
CAIE E -VI MINIMUM flOW
AEOUIAEM£NT8
LIUNO
MATUitAL C~IOM
PLO.IPCMt aT-D
COMaTIMICTIOII
.TAM I
PLO.aPCIIIa'f-O
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ITA .. I
JAN FEB MAR APR NAY JUN JUL AUG SEP OCT NOV DEC
Monlh
Comparisons of Susitna River Natural, Stage 1 1996 and Stage 2 2002
Streamflowa Exceeded 50% of the time at Gold Creek. r-----~~-L-A_s_K_A_P_o_w_E_R_A_u_T_H_o_R_tT-v-----t
Reference: Harza-Ebasco 1985 Figure 23
SUSITNA HYDROELECTRIC PROJECT
Woodw.....C~C............_
AND
ENTRIX, INC.
HARZA ·EBASCO
SUSITNA JOINT VENTURE
(1\
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60
50
30
20
10
0
C:Ael! 1!-VI MAICIMUM flOW
IIIOUIIII!MINTe
I I I
. . .
C:Ael I-VI -IMUM fLOW
IIIOUIIIEMENTe
I
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~ •r., • r. ;,
.JAN FEB MAR APR MAY ..JUN ._llll AUG SEP OCT NOV DEC
Month
Comparisons of Susitna River Natural, Sta1e 1 1996 and Sta1e 2 2002
Streamflow• Exceeded 6% of the time at Gold Creek. ALAsKA PowER AuTHoR 1 Tv
Reference: Harza-Ebasco 191.S Fiaure 24
SUSITNA HYDROELECTRIC PROJECT
....... c .... c:..oulleftlo
AND
ENTRIX, INC.
HAAZA -f8ASCO
SUSITNA JOINT VENTURE
Canyon operation. In general, release temperatures would be cooler than
Stage 1 in April through September (about 2-S°C less than natural) and
warmer . than Stage 1 from September to April (about 2-6°C greater than
natural) (Harza-Ebasco 1985). The temperature regimes for three locations
downstream of Devil Canyon RM 100, 130, and ISO arc presented for a 50
ft drawdown and 2 levels of intakes in operation in Figures 25-27. The
upstream progression of the icc front in Stage 2 would be to about RM 131
based on average climatological conditions (1981-1982).
Turbidity during Stage 2 is expected to be at similar levels and exhibit
the same annual variations as described for Stage 1.
(i) Prjmary Evaluation Species
Chum Salmon
Adult Spawnjng and Incubating Embryos
and Pre-Emergent Fry
Flow duration curves for simulated Stage 1-1996 and Stage
2-2002 mean weekly flows based on 34 years of hydrologic
conditions arc compared for each week of the spawning
period in Appendix Figures 6-10. Simulated Stage 1 and
Stage 2 flow duration curves based on the maximum mean
weekly flow for weeks 45-49 of each year for the 34 years
of record arc presented in Figure 28 . The Stage 2 flows
above about 30,000 cfs that arc important for passage would
occur at a greater frequency than similar Stage flows.
Stage 2 flows greater than 40,000 cfs would occur at lesser
frequency.
Slough modifications measures implemented under Stage I
would have altered the natural conditions and consequentl y
a comparison of th.; percent of time passage occurs under
natural and Stage 2 flows is not feasible. The slightly
70
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~l vn 1• h
Simulated Natural and Stage 2 2002 Suaitna River Temperature• at
River Mile 150 ----=---------------
ALASI<A POW E A AUTHORITY
SUSITNA HYOROELECTAIC PAOJECT
Reference: Harza-Ebasco 198~ Figure 25
Woo4want-Ciyde c ... auttante
ANO
HARZA ·E8ASCO
SUSITNA JOINT VlNTU"l
ENT,.IX . INC.
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Simulated Natural and Stage 2 2002 Susitna River Temperatures at
River Mile 130
ALASKA POWER AUTHORITY
SUSITNA HYDROElECTRI C PROJECT
HAAlA f8ASCO
Reference: Harza-Ebasco 1985 Figure 26
Wooclwerd-CIVde Coneultente
AND SUSITNA JOINT VENTURE
ENTAIIC, INC
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MAY JUN J UL AUG S[P OCT NOV Dfl) JAN fEB MAR APR HAY JUN JUL AUG S[P
Honlh
Simulated Natural and Stage 2 2002 Suaitna River Temperatures at
River Mile 100 ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
HARIA ·EBA S CO
Reference: Harza-Ebasco 198S Figure 27
Wooclwa..C~a COftMittar 'e
AND SUSITNA JOINT VENTURE
ENTRIX, INC.
-V)
1.1. u -u
QD .. • -'= v
"' 0
60,000
50 ,000
40,000
30,000
20,000
10 ,000
0
0 20
• Simulated Staae 1 1996 EneriY Demand now
0 Simulated Staae 2 2002 EncriY Demand now
40 6(1 ao 100
Percent Exceedance
Comparison of flow duration curves for simulated Stage 1 1996
and simulated Stage 2 2002 Energy Demand streamflows for weeks
45 to 49 based on mean weekly flow• for 34 years of record.
Fi1ure 28
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
WoodwaN-Cfrda Conaultanta
AND
lHTNX.INC.
74
HARZA ·EIASCO
SUSITNA JOINT VENTURE
hiaher flows provided by Staae 2 would, however, maintain
or enhance passaae at the modified sloughs.
The construction of berms to prevent sloughs from being
overtopped by mainstem flows during Stage I would insure
against similar impacts during Stage 2.
Chinook Salmon
Rearing Juveniles
It is anticipated that analyses on flow requirements for
juvenile chinook rearing would have been available prior to
2002 and that an acceptable flow regime would be in effect.
(ii) Secondary Evaluation Species
The Stage 2 flow regime would not result in any additional
impacts to the secondary evaluation species.
4.2.2 ~
The lack of additional adverse impacts resulting from Stage 2 operation
would limit mitigation efforts to maintaining and monitoring the
effectiveness of mitigation measures implemented during Stage 1.
4.3 • Stage 3 (2008-2020)
4.3.1 Impact Analysis
(A) fi!ljng
The details of Stage 3 filling flows are not available at this time.
However, it is anticipated that filling will coincide with construction
over a 2 or 3 year period. The level of filling would be determined
by the crest elevation of the dam. The spring and summer flows
7S
durina the multi-year fillina process would likely be less than those
simulated for Staae 2-2002 and Stage 3-2008 eneray demands but
greater than E-VI minimum levels. As information ~:. Stage 3 filling
becomes available anticipated impacts and appropriate mitigation
measures will be incorporated into this document.
(B) 2008 Energy Qemand
Power generation with Watana Dam constructed to its full height would
commence in 2008 or within a few years thereafter. Regulated flow
releas~s have been simulated for the first year of operation based on
anticipated 2008 energy demands. Natural, Stage 2-2002 and Stage
3-2008 operating flows are compared at the 97, SO, and 6 percent
cxcecdcncc probabilities in Figures 29-31. Stage 3-2008 flows would
be similar to or slightly higher than Stage 2 flows in the winter and
spring (November through May). In the summer during average or
wet hydrologic conditions Stage 3 flows would be similar to or slightly
less than Stage 2 flows. In the driest years, Stage 3-2008 and Stage
2 flows would be maintained at the E-VI minimum during the
spring-summer filling period.
(C) 2020 Energy Qemand
Regulated flow releases have been simulated for Stage 3-2020 energy
demand. Natural, Stage 3-2008, and Stage 3-2020 operation flows are
compared at the 97, SO, and 6 percent cxceedcnce probabilities in
Figures 32-34. In years with a veragc and wet hydrologic conditions
Stage 3-2020 flows would be a bout 2000 cfs higher than Stage 3-2008
from mid-October through May. In the summer months, Stage 3-2020
flow would be at or ncar Case E-VI minimum except during the
wettest of years.
Streamflow temperatures under Stage 3 flow regimes would be about
O.S to I °C warmer than Stage 2 in the winter and similar to Stage 2
in the summer (Figure 3S).
76
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THOUSANDS
25
2A
15
10
5
f-VI .. AICIWUioot flOW
IIEOUIRE .. ENTI
\
~-
.. A)(I .. U., fLOW•:ti,OOO cle
E -VI .. JNJ .. U .. flOW
IIEOUIRE .. ENTI
0 4---~~---.,~--~---~,----.----,,,
.. -....... .. -.. .,.. .. -_,.,.
~-. . .
JAN FEB MAR APR MAY .JUN &II. AUG SEP OCT NOV DEC
Month ~
liM-
NATUIIAl ~,....
nowe '011 ......
CO.'NMOT ... eu.• 1
f'LOWe '011 .......
GO. a T..UC:ncMI
eTA .. I
Comparisons of Susitna River Natural. Stage 2 2002 and Stage 3 2008
Streamflow& Exceeded 97o/o of the time at Gold Creek. _____ A_L_A....;S;;..K_A_P_o_w_e _R_A_u_r_H_O_R_I_T_v ___ _
Reference: Harza-Ebasco 198S Figure 29
SUSITNA HYDROELECTRIC PROJECT
••~c-...~
AND
I!NTAIX, INC.
HAAZA ·f8ASCO
SUSITNA JOINT VENTU .. E ,
-...J co
D
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h
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THOUSANDS
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25
20
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CAl! !-VI MAXIMUM flOW
REOUIREMENl S
·------"--\ .. ·. -.
5
' -----
MAXIMUM•JI .OOO ale
CAIE E -VI MINIMUM flOW
R!OUIREM!Nf&
LI .. MD
MA TURAL co.etfiOII
noweHN~eTAMD
CONeT-.,c:TIOII
eTAM I
PlOWe POll eTAMD
CON8T-.,c:TION ., ....
JAN f£8 MAR APR HAY ~UN JUL AUG SfP OCT NOV DEC
Monlha
Comparisons of Suaitna River Natural, Stage 2 2002
Streamflows Exceeded 50% of the time at Gold Creek.
and Stage 3 2008
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
w ..... .,.. c~ C•R• ,,_ .. HAAZA ·E8ASCO
SUSITNA JOINT VENTu.-£. Reference: Harza-Ebasco 1985 Figure 30 AND
INTft!IC,INC.
D
•
c
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r
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•
n
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f
•
THOUSANDS
60
50
40
30
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CAIE 1!-YI WA~IWUW FLOW
RI!OUIIIEWENYI
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ITAII I
.JAN FEB HAR APR HAY ..JUN ..JUL AUG SEP OCT NOV O(C
Honlh
Comparison& of Susitna River Natural, Stage 2 2002
Streamflows Exceeded 6% of the time at Gold Creek.
and Stage 3 2008
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Figure 31
........ c.,.. C...........te
AND
HAAlA ·EIIASCO
SUSITNA JOINT VENTURE
Reference:: Harza -E basco 198~ fNT"IX, INC.
0
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.....
1. HYOIIOLOOICAL OATA
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JAN FEB MAR APR HAY JUN JUL AUG SEP OCT NOV DEC
Month•
c ·omparisons of Susitna River Natural, Stage 3 2008,
and Stage 3 2020 Stre•mflowa Exceeded 97% of the
time at Gold Creek
Reference: Harza-Ebasco 198.S Figure 32
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woo4w...Cird• c .............
AND
ENTAIX , INC .
HARZA ·EBASCO
SUSITNA JOINT VENTURE
THOUSANDS
30 -.--------------.-----------,r---------, -y •• ,
UA XIUUU•ai.OOO olo
D
•
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•
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IIEOUIAEWENU
·-·-·---
·---.
.,
,/ ·-·-.
I .·
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IIEOUIIIIUINTI
1. HYDIIOLOGIGAL DATA
fiiOM ~EIIIOO 1110-1 111
I . ITAGID CONITIILIGT.,_
ITACU I
I . ~IIOJICTIO INitteY
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~-y~
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CONITIIUCTIOM
(2001 ~' DBMNDel
JAN fEB HAR APR MAY JUN JUL AUG SEP OCT NOV OEC
Honlh•
Comparisons of Susitna River Natural and Stage 3 2008,
and Stage 3 2020 Streamflow• Exceeded 50% of the
time at Gold Creek
Reference: Harz~-Ebasco 1985 Figure 33
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodward-Clyde Conaultenta
AND
ENTRilC, INC.
HARZA ·EBASCO
SUSITNA JOINT VENTURE
00
N
D
•
c
h
0
r
g
•
n
c
f
•
THOUSANDS
60
50
40
30
20
10
OAII I-VI MAXIMUM 'LOW
fiiOUIIUMINTI
--·-·-·-·-----..
. . . .
I
*'" ..
I . HYDfiOLO..CAl. OATA '"ow ~111100 tea•-, •••
1 . ITAQIO COIIITfiUCTICNI
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, ,::.J j NWANOI '0111 ·-·-' . ·.,,it:< 4 . I·VI 'LOW 1110'-anne
·~ ·;I LICIINO
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•.; 4"' --"' ... ..,.. ......
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. :'t7~~ ~~'!.-:;::n:.--
:~, (JON...,... oeu -•
.lf
/ ........ ·-..
. ...........
JAN FEB HAR APR HAY JUN JUL AUG SEP OCT NOV DEC
Month•
Comparisons of Su1itna River Natural, Stage 3 2008,
and Stage 3 2020 Streamflow& Exceeded 6% of the
time at Gold Creek
Reference: Harza-Ebasco 1985 Figure 34
ALASKA POWER AUTHORITY
SUStTNA HYDROELECTRIC PROJECT
Wooctw•rd-CI~• Conautt.nta
AND
ENTAIX, INC .
HAAZA ·EBASCO
SUSITNA JOINT VENTURE
WATER WEEKS CrLOJJED AT UID ·WUKI
J1 u n )4 U )6 SF » ,, 40 41 41 4) 44 U 46 4F 41 ~· ~ ~ U I I ) 4 II I 7 I I 10 II II IS H IS 16 IF 16 ., 10 II II U 14 ISH U H H 10
190
_ 1 I I I
NOTES ·
WAJANA-I. TEW .. EAA TURfS IN •c .
DEYil
CANYON
c w > «
170 -
160-
llr.t£
\
l
\
\
\ \
l I
\ ~
\ \
~' ! I '
Simulated Stage 3 2020 Susitn• River Temperature• from
River Mile 150 to 80.
2 . ICE SIWULA TION HOT
WADE fOA THIS CASE.
TfWPEAA TUAE S FOA
N0VfW8EA H :~OUOH
WAACH SHC ULO NOT
8F. USEO.
I. IMI ltal C&.IMAWE DAIA
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodw•rd-Ciyde c ... ....._,.,.
Rc:fc:rence: Harza-Ebasco 1985 Figure 35 AND
ENTAIX, INC
HARZA ·f8ASCO
SUSIJNA JOINT VfNTUflllf
Seasonal turbidity levels under Stage 3 would exhibit seasonal
variations similar to Stage 2.
(i) Prjmarv Evaluation Species
Chum Salmon
Spawnjng Adults
Comparisons of Stage 2·2002, Stage 3·2008 and Stage 3-2020
mean weekly flow duration curves for each week of the
spawning period are shown in Appendix Figures 11-20.
Similar comparisons based on the maximum mean weekly flow
for weeks 45-49 of each year for the 34 years of record are
presented in Figures 36 and 37. The percentage of time
flows that provide passage occur is similar for Stage 2-2002
and Stage 3·2008. However, there is a marked reduction in
the frequency at which flows necessary for passage is
provided in under the Stage 3-2020 energy demand as
compared to the Stage 3·2008 energy demand. The
transition from adequate flows in 2008 to the reduced flows
during the spawning period in 2020 would occur over a
period of 12 years. This time period would allow
assessment of any impacts that may result from these flow
reductions. There is also the possibility that the patterns
of utilization of different habitat types may occur during
this interval without a net decrease in productivity.
Attempting to assess impacts in 2020 based on current
utilization patterns would therefore not be productive.
Provision will be made in a long-term monitoring program to
assess changes in productivity of the evaluation species.
There are no anticipated impacts to the incubation life stage
of chum salmon resulting from Stage 3 development.
84
-V)
I.L. u -u
CIO .. • .c u
"' 0
60,000
50,000
40 ,000
30,000
20,000
10,000
0
0
• Simulated Staae 2 2002 Eoeray Demand flow
a Simulated Staac 3 2001 Eoeray Demand flow
20 40 60 80
Percent Exceedaoce
100
Comparison of flow duration curves for c;imulated Stage 2 2002
and simulated Stage 3 2008 Energy Demand streamflows for weeks
45 to 49 based on mean weekly flows for 34 years of record.
Figure 36
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodward-Clyde Conaulunta
AHD
ENTNX,INC.
85
HAAZA·EISASCO
SUSITNA JOINT VENTURE
-{I)
1.1. u -u
CIO .. • .c u
"'
0
60,000
50,000
40 ,000
30,000
20,000
10,000
0
0
.. Simulated Stage 3 2001 EneriY Demand flow
o Simulated Staae 3 2020 EneriY Demand flow
20 40 60 ao
Percent Exceedance
100
Comparison of flow duration curves for simulated Stage 3 2008
and simulated Stage 3 2020 Energy Demand streamflows for weeks
45 to 49 based on mean weekly flows for 34 years of record.
Figure 37
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodwerd-Cird• Conault.nta
AND
INTAtX,INe
86
HAAZA ·EBASCO
SUSITNA JOINT VENTURE
Chinook Salmon
Rearjna Juveniles
It is anticipated that the mitigation measures applied to
chinook rearing in Stage 1 would also mitigate for Sta&e
3·2020 flows.
(ii) Secondary Evaluation Specjes
No additional impacts are anticipated for the Stage 3 flow
regimes.
4.3.2 Mitigation
During Stage 3 of the projects, the long-term monitoring program would
identify impact to the evaluation species and appropriate mitigation
measures would be implemented as needed.
4.4 • Scheduling of Mitigation
4.4.1 Flow Release
Case E· VI flow constraints, or a similar negotiated flow regime would be
instituted in May 1995 during the first year of filling. The constraints of
this flow regime would then be in effect for the duration of the project.
4.4 .2 Structural Modification of Habitats
Modifications of slough and side channel habitats to accommodate spawning
by chum salmon and to a lesser extent rearing of juvenile salmon would be
scheduled according to the timing of impacts identified with each stage of
project development. With the exception of filling flows impacts to chum
salmon spawning and incubation habitat aduring Stage l, Stage 2 and
Stage 3-2008 energy demands would be similar.
87
The: construction of berms to prevent overtopping take: priority over
modifications within sloughs since: the: berms will also serve: to protect
these: modifications. If proposed berm construction were: extensive it could
be: initiated during the: construction phase: of Watana and also take:
advantage: of previously mobilized equipment to reduce: costs. Candidate:
si tc:s for pre-operational bc:rming would be those sites that do not depend
on breaching conditions during the spawning season for passage (e .g.
Slough II). Berming of such a site would eliminate the need for immediate
slough modifications. The flows during the winter following the first
summer of filling in 1995 would be at natural levels and berming would not
be necessary to protect incubating embryos. All proposed berming would
be completed by the winter of 1996-1997. Modification of sloughs and side
channels could also be staggered over a multiyear period if necessary. A
full scale modification of a slough would require about two weeks time.
Minor modification could be accomplished in a few days or less.
Modification to slough and side channel would generally occur between June
I and July IS, after most fry or juvenile ~ have left their natal areas and
before adults have returned to spawn. The timing may be adjusted on a
site specific basis. Modification to sloughs and side channels should be
completed by summer, 1996 or if possible by summer 1995.
As information on the extent of berming required for different sites is
acquired this summer and specific sites or parts of sites are selected for
modification, a detailed scheduling program will be developed.
Should additional modification measures be necessary during the later
stages of the project, scheduling would be on an as-needed basis and at
the least sensitive time of the year for the particular activity.
4.5 -Monitoring
A monitoring program is recognized as an essential project mitigation feature,
particularly in a staged development in which the impacts will vary over time.
A detailed monitoring program is currently being developed as a separate
88
document that will address impacts and mitigation measures presented in this
volume and the other two volumes of this three volume mitiaation series.
The middle · Susitna River portion of the monitoring program will focus on
(I) monitoring salmon population and production levels to ensure that the
predicted level of impact is not being exceeded and (2) evaluating the
effectiveness of the implemented mitigation measures. These two areas of focus
are outlined below.
4.S.l Monjtorjna of Salmon Populations
Salmon populations in the Devil Canyon to Talkeetna reach will be
monitored to assess whether populations maintain historical levels during
the operation phase. Monitoring will consist of enumerating returning
adults and estimating fry and smolt production. The adult monitoring
program will include:
1) Monitoring the long-term trend in catches at fixed fishwheel
stations.
2) Monitoring the long-term trend in spawning ground counts.
3) Monitoring the long-term trend in age and size composition of
spawning adults.
4) Relating the above trends to physical, chemical and biological
changes in the system, including changes induced by the
project.
The juvenile salmon monitoring program will provide estimates of fry and
smolt production in the middle Susitna River over a pe1 iod of years
encompassing natural and with-project conditions. Production estimates
and changes in production patterns over the years can be compared
directly with changes in physical conditions due to project operation.
Factors affecting smolt production estimates will be evaluated by:
89
1) Obtainina data on survival rates from eu deposition to fry-smolt
production.
2r Monitorina lona-term trends in the timina of emergence and
outmigration of juvenile salmon by use of tauina of young fish
and recapture in outmiarant traps.
3) Monitorina lona·term trends in the development, arowth and
relative condition of young salmon.
Pre-project data will be compared to with-project data to determine whether
substantial changes are occurrina as a result of the project. In addition,
the data collected from the above studies, data from the commercial fish
harvest, sportfish harvest surveys,and subsistence fishina will be
considered in the overall evaluation of the salmon resources.
4.5.2 -Mitigation Monitoripa
Mitigation features to be monitored for evaluation of the level of mitigation
being achieved include:
-Slough modifications
-Replacement habitats
-Incubation pits
The monitoring activity will include evaluating the operation and
maintenance procedures to ensure that the facilities are operating
effectively. If a mitigation feature is not meeting the intended level of
effectiveness, modifications to the mitigation feature will be made to
increase its effectiveness.
(A) Monitoring Slough Modifications
The various measures incorporated for slough habitat maintenance will
be monitored to assess whether they arc meeting their intended
function and are operating properly. Methods used to evaluate the
90
slouab mitiaation features will be consistent with methods currently
beina used to assess baseline conditions of the parameters to be
monitored.
Mitigation features desianed to allow adult salmon passage into and
within the sloughs will be annually inspected after breakup to identify
and conduct needed repairs prior to the adult return. Annual
monitoring of returning adults will allow identification of additional
passage problems. Appropriate corrective actions will be taken.
Modifications to slouahs designed to maintain spawning areas will be
annually inspected prior to the spawning season to verify that the
area contains suitable spawning conditions such as upwelling, amount
of flow, depth of water, and suitable substrate. Areas that become
overly silted will be cleaned. If slough flows diminish so that
spawning is no longer possibie, appropriate corrective actions will be
taken.
The number of spawning adults returning to the sloughs will be
monitored annually to measure changes in distribution to assess if the
combination of minimum flow and slough modifications is maintaining
natural production. This monitoring will also serve to assess whether
the capacity of the modified areas is being exceeded. Appropriate
remedial actions will be taken when spawning sites are inadequate.
Fry production will be monitored annually to evaluate incubation
success. Fry monitoring will include an assessment of out-migration
timing and success.
The annual slough monitoring will include an evaluation of general
slougb conditions including vegetative encroachment, beaver
occupation, and general condition of the spawning and rearing areas.
Appropriate remedial actions will be performed to maintain slough
productivity.
91
Representative slouahs will be monitored for temperature and slough
flow . Monitoring of the physical processes will be continued until
slough conditions stabilize under the regulated flow regime. This
monitoring will be used in part to assess whether further
modifications to the physical habitat must be made to maintain slough
productivi t y .
(B) Monitoring Reolacement Habitats
Replacement habitats which develop as a result of th~ lower and more
stable project mainstcm flows during the spawning season will be
monitored to quantify usc of these areas by adult salmon. Monitoring
methodology will be similar to that currently used to evaluate
spawning habitats and will include standard physical and chemical
measurements as well as biological analyses.
(C) Monitoring of Artificial Prooagation
Stream-side incubation pits, if utilized, will be monitored to evaluate
their effectiveness in producing the number of returning chum salmon
for which they were designed.
92
REFERENCES
Alaska Department of Fish and Game. 1982. Statement of Policy on Mitigation of
Fish and Game Habitat Disruptions. Juneau.
Alaska Department of Fish and Game. 1981. Susitna Hydro Aquatic Studies •
Phase I Final Draft Report: Resident Fish Investigation on the Lower
Susitna River. Prepared for Acres American, Inc. Buffalo, NY 166 pp.
Alaska Department of Fish and Game. 19S3a. Susitna Hydro Aquatic Studies.
Phase II Basic Data Report. Volume 3: Resident and juvenile anadromous
fish studies below Devil Canyon, 1982. 177 pp.
Alaska Department of Fish and Game. 1983b. Susitna Hydro Aquatic Studies •
Phase II Data Report. Winter aquatic studies (October 1982 -May 1983),
Anchorage, AK.
Alaska Power Authority. 1982. Susitna Hydroelectric P !oject: Fish and Wildlife
Mitigation Policy. Alaska Power Authority. Anchorage, AK.
Alaska Power Authority. 1983. Application for license for major project,
Susitna Hydroelectric Project, before the Federal Energy Regulatory
Commission. Vol. 6A. Exhibit E, Chap. 3. Alaska Power Authority.
Susitna Hydroelectric Project.
Barrett, B.M, F.M Thompson, and S.N . Wick . 1984 . Report No. I. Adult
anadromous fish investigations: May October 1983. Susitna Hydro
Aquatic Studies. Alaska Department of Fish and Game. Anchorage, Ak.
Barrett, B.M, F.M Thompson, and S.N. Wh.:k . 1985. Report No. I. Adul t
anadromous fish investigations: May -October I 984. Alaska DeiJartment
of Fish and Game. Anchorage, AK. Draft.
93
Bell. MC. 1973. Fisheries Handbook of Engineering Requirements
Biological Criteria (Revised 1980). Prepared for Fisheries-Engineering
Research Proaram, Corps of Engineers, North Pacific Division. Portland,
Oregon.
Blakely, J .S., J .S. Sautner, L.A. Rundquist and N .E. Bradley. 1985
and
Addendum to Alaska Department of Fish and same Report No. 3, Chapter
6: Salmon Passage Validation Studies Auaust -October, 1984.
Harza-Ebasco Susitna Joint Venture. 1984. Evaluation of Alternative Flow
Requirements. Anchorage, AK.
Harza-Ebasco Susitna Joint Venture. 1985. Stlged Construction Pre-Filing
Consultation Package. Susitna Hydroelectric Project. Prepared for the
Alaska Power Authority. Text and Appendix A (Physical Habitat
Simulation Exhibits}.
Jennings. T .R. 1985. Fish Resources and Habitats in the Middle Susitna River.
Instream Flow Relationships Technical Report Series: Technical Report No.
I. Prepared for the Alaska Power Authority. Anchorage, AK.
Klinger, S. and E.W. Trihey. 1984. Response of Aquatic Habitat Surface Areas
to Mainstem Discharge in the Talkeetna to Devil Canyon Reach of the
Susitna River, Alaska. Final Report prepared for the Alask~ Power
Authority.
Lister, D.B . & Associates, Ltd. 1980b. Stream Enhancement Guide. Province of
British Columbia, Ministry of Environment, Vancouver, BC, Canada.
Roth, K . and M Stratton. 1985 . The Migration and growth of juvenile salmon
in the Susitna River. Draft Report No 7, Part 1. Alasksa Department of
Fish and Game. Anchorage, AK.
94
Sandone, G ., D. Vincent-Lana. and A. Hoffman. 1984 . Chapter 8: Evaluations
of Chum Salmon-Spawnina habitat in selected tributary-mouth habitats of
the middle Susitna River. In Report No. 3: Aquatic Habitat and lnstream
Flow lnvestiaations (May October 1983), by C. Estes and D.
Vincent-Lang, eds. Alaska Department of Fish and Game. Anchorage, AK.
Schmidt, D.C ., S.S. Hale, and D.L. Crawford (eds.). 1984. Resident and
Juvenile Anadromous Fish Investigations (May • October 1983). Alaska
Department of Fish and Game. Su Hydro Aquatic Studies Report Series
No. 2. Alaska Department of Fish and Game. Anchorage, Alaska.
Trihey, E.W. 1982. Preliminary assessment of access by spawning salmon to
side slough habitat above Talkeetna. Prepared for Acres American, Inc.
Buffalo, NY. 26 pp.
U.S . F ish and Wildlife Service. 1981. Endangered and Threatened Wildlife and
Plants. Federal Register SO CFR 17.11 and 17 .12. January 1, 1982.
Vining, L.J ., J .S. Blakely, and G .M. Freeman. 1985. An evaluation of the
incubation life stage of chum salmon in the middle Susitna River, Alaska.
Vol. 1, Rept. No. S, Winter aquatic investigations: September 1983 • May
1984. ADF&G Susitna Hydro Aquatic Studies, Anchorage, AK. 130 pp. +
Appendices.
Woodward-Clyde Consultants. 1984. Fish Mitigation Plan. Susitna Hydroelectric
Project. Prepared for Alaska Power Authority.
95
APPENDIX
96
APPENDIX FIGURES
97
.-.
~
1.1.. u ._.
u ao ..
Cll .c
()
"' a
60,000
• Natural rtow at Gold Creek
a Simulated Stage I 1996 Eneray Demand flow
50,000
40,000
30,000
20,000 ~
10,000
0
0 20 40 60 80 100
Percent Exceedancc
Comparison of flow duration curves for natural and simulated
Stage 1 1996 Energy Demand streamflows for week 45 based on
mean weekly flows for 34 years of record.
Appendix Figure 1
ALASKA POWER AUTHOR I TY
SUSITN-' HYDROELECTRIC PROJE C T
Wooctw•rd·Ciyde Conaulbnts
AHD
ENTRIX. INC.
98
HARZ4 ·E84SCO
SUS IT NA JO I NT VENTURE
~
LL. u -u
110 ..
til
J: u ...
Cl
60,000
• Natural flow at Gold Creek
a Simulated Staae 1 1996 Eneray Demand flow
50,000
40,000
30,000
20,000
10,000
0
0 20 40 60 80 100
Percent Exceedance
Comparison of flow duration curves for natural and simulated
Stage 1 1996 Energy Demand streamflows for week 46 based on
mean weekly flows for 34 years of record.
ALASKA POWER AUTHC:11T Y
SUSITNA HYDROELECTRIC PROJECT
Woodward·Ciyde Contultanta , R l A . e a A s c 0
Appendix Figure 2 AND su . ..A JOINT veNH ~e
~----------------------------~-------~-T_N_x._INC--------~-----------------__J
..-.
~
Llr. u ._,
u
CliO ..
al .c u ...
0
60,000
• Natural flow at Gold Creek
50,000 a Simulated Stage I 1996 EneriY Demand flow
40,000
30,000
20,000
10,000
0
0 20 40 60 80 100
Percen t Ex ceedance
Comparison of flow duration curves for natural and simulated
Stage 1 1996 Energy Demand streamflows for week 4 7 based on
mean weekly flows for 34 years of record.
Appendix Figure 3
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodward-Clyde Consulunta HARZA ·E8ASCO
SUSITNA JOINT VENTURE AND
OIITAIX, INC.
1 00
.-.
V') u. u _..
u
all .. • .If! u ...
0
60,000
• Natural flow at Gold Creek
50,000 a Simulated Staac 1 1996 Eneru Demand flow
40,000
30,000
20,000
10,000
0
0 20 40 60 80 100
Percent Exceedance
Comparison of flow duration curves for natural and simulated
Stage 1 1996 Energy Demand streamflows for week 48 based on
mean weekly flows for 34 years of record.
Appendix Figure 4
AlASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodwartf.Cfrd• Conautt.nta
AND
ENTAil, INC.
101
HAAZA·EBASCO
SUSITNA JOINT VENTURE
.......
Cl)
u. u ........
u
Gill .. • .c: u
-~ ~
60,000
so .ooo • Natural flow at Gold Creek
a Simulated Staae 1 1996 Ener&Y Demand rtow
40,000
30,000
20,000
10,000
0
0 20 40 60 so 100
Percent Exceedance
Comparison of now duration curves for natural and simulated
Stage 1 1996 Energy Demand streamnows for week 49 based on
mean weekly flows for 34 years of record.
Appendix Figure 5
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodw•rd-Ciyde Consutt.nts
AND
IENTJO, INC.
102
HAAZA ·EBASCO
SUSITNA JOINT VENTURE
--V)
Ll. u .._,
u
QID .. • .c u ..
0
60,000
50,000
40,000
30,000
20,000
10,000
0
0 20
• Simulated Staae 1 1996 EneriY Demand rtow
a Simulated Staae 2 2002 Ener&Y Demand (low
40 60 80 100
Percent Exceedance
Comparison of flow duration curves for simulated Stage 1 1996
and simulated Stage 2 2002 Energy Demand streamflows for week
45 based on mean weekly flows for 34 years of record.
Appendix f!gure 6
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodward-Clyde Con•ulbnts
ANO
!NTRfX. INC.
103
H A A 2' A · E 8 A S C 0
SUSITNA o~'OINT VENTURE
.......
V)
1.1. u ._,
u
CIO ..
~ ..: u
"' ::::l
60,000
50,000
40,000
30,000
20,000
10,000
0
0 20
• Simulated Stage I 1996 Energy Demand flow
0 Simulated Stage 2 2002 Eneray Demand flow
40 60 80 100
Percent Exceedance
Comparison of flow duration curves for simulated Stage 1 1996
and simulated Stage 2 2002 Energy Demand streamflows for week
46 based on mean weekly flows for 34 years of record.
Appendix Figure 7
AlASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodw•rcf.Circf• Con1ulunta
AHO
lNTRtX, IHC.
104
HAFIZA ·E8ASCO
SUSITNA JOINT VENTURE !
.-.
II)
1.1. u _..
u ao
"' • ~ u ...
0
60,000
50,000
40,000
30,000
20,000
10,000
0
0 20
a Simulated Stage I 1996 Energy Demand flow
a Simulated Stage 2 2002 Energy Demand flow
40 60 80 100
Percent Exceedance
Comparison of flow duration curves for simulated Stage 1 1996
and simulated Stage 2 2002 Energy Demand streamflows for week
47 based on mean weekly flows for 34 years of record.
Appendix Figure 8
ALASKA POWER AUTHORqy
SUSITNA HVOROELECTRIC PROJECT
Woodwercf..Ctyde Conaultanta HARZA ·EBASCO
SUSITNA JOINT VENTURE AND
ENTftiX. INC.
105
.-
(I)
"" u --u
110 .. • .c
<J ...
0
60,000
so,ooo
40,000
30,000 \
20,000
10,000
0
0
• Simulated Staae 1 1996 Eneray Demand flow
0 Simulated Staae 2 2002 Eneray Demand flow
20 40
I
60
Percent Exceedance
so 100
Comparison of flow duration curves for simulated Stage 1 1996
and simulated Stage 2 2002 Energy Demand streamflows for week
48 based on mean weekly flows for 34 years of record .
Appendix Figure 9
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodwarcf.Cirde Consultants
AHO
ENTRIX, INC.
106
HAAZA ·EIASCO
SUSITNA JOINT VENTURE
,-.
Ill
LL. u _.
u
CIO .. • .c u
"' 0
60,000
so .ooo
40,000
30,000
20 ,000
10,000
0
0
• Simulated Staae 1 1996 Eneray Demand flow
a Simulated Stage 2 2002 Eneray Demand flow
20 40 60 so
Percent Exceedance
100
Comparison of flow duration curves for simulated Stage 1 1996
and simulated Stage 2 2002 Energy Demand streamflows for week
49 based on mean weekly flows for 34 years of record.
Appenc:H~ Figure 10
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
ENTAIX. INC.
HARZA·EIASCO
SUSITNA JOINT VENTURE
-Cl)
LL. u -u
CliO .. • .c
CJ
"' 0
60,000
so.ooo
40,000
30,000
20,000
10,000
0
0 20
6 Simulated Staae 2 2002 EneriY Demand now
a Simulated Staae 3 2001 Eneray Demand now
60 80 10~
Percent Exceedance
Comparison of flow duration curves for simulated Stage 2 2002
and simulated Stage 3 2008 Energy Demand streamflows for week
45 based on mean weekly flows for 34 years of record.
Appendix Figure 11
ALASKA POWER AUTHORITY
SUSITNA HYOROELECTFHC PROJECT
Woodwa,.Ciyde C4naultanb HAAZA ·EBASCO
SUSITNA JOINT VENTURE
INTNX,INC.
__ 1_08
-V)
1.1. u
'-'
u
CliO ..
ell .c
(,) .,
0
60,000
50 ,000
40,000
30,000
20,000
10,000
0
0 20
.. Si mulated Stage 2 2002 Energy Demand flow
a Simulated Stage 3 2008 Energy Demand flow
40 60 80 tO O
Percent Exceedance
Comparison of flow duration curves for simulated Stage 2 2002
and simulated Stage 3 2008 Energy Demand streamflows for week
46 based on mean weekly flows for 34 years of record.
Appendix Figure 12
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodward-Clyde Conaulunta
AHD
ENTAIX, INC.
109
HAAZA ·EBASCO
SUSITNA JOINT VENTURE
.......
V'l
LL. u
'-'
u ao .. • .c u
"' c
60,000
.50,000
40,000
30,000
20,000
10,000
0
0 20
• Simulated Stage 2 2002 Energy Demand flow
a Simulated Stage 3 2001 Energy Demand flow
40 60 &0 100
Percent Exceedance
Comparison of flow duration curves for simulated Stage 2 2002
and simulated Stage 3 2008 Energy Demand streamflows for week
4 7 based on mean weekly flows for 34 years of record.
Appendix Figure 13
ALASKA POWER AUTHOqiTY
SUSITNA HYDROELECTRIC PROJECT
W~odw•rdoCIJde Conautbnll
AHO
ENTAil, INC.
l lO
HAAZA ·EBASCO
SVSITNA JOINT VENTURE
-<I)
1.1. u .......
u
CIID .. • .c
()
"' 0
60,000
so.ooo
40,000
30,000
20,000
10,000
0
0 20
• Simulated Stage 2 2002 Ene r gy ~emand flow
a Simulated Stage 3 2008 Energy Demand flow
40 60 ao
Percent Exceedance
100
Comparison of flow duration curves for simulated Stage 2 2002
and simulated Stage 3 2008 Energy Demand streamflows for week
48 based on mean weekly flows for 34 years of record .
Appendix Figure 14
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PRO J ECT
Woodward-Clyde Consultants
ANO
lNTRIX, tHC.
111
HARZA ·EBASCO
SUSITNA JOINT VENTURE
..-.
V)
u. u .._,
u ao .. • .c u
"' 0
60,000
so.ooo
40 ,000
30,000
\
20,000
10,000
0
0
• Simulated Staae 2 2002 Eneray Demand flow
a Simulated Staae 3 2020 Ener&Y Demand flow
20 40 60 ao
Percent Exceedance
100
Comparison of flow duration curves for simulated Stage 2 2002
and simulated Stage 3 2008 Energy Demand streamflows for week
49 based on mean weekly flows for 34 years of record.
Appendix Figure 15
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodward-Clyde Con•uttanta
AHO
ENTRIX, INC.
HAAZA ·EIASCO
SUSITNA JOINT VENTUAE i
.......
Cl)
1.1. u --u
CID .. • .c u ...
Cl
60,000
50,000
40,000
30,000
20,000
10,000
0
0 20
• Simulated Staae 3 2008 Ener&Y Demand flow
a Simulated Staae 3 2020 Eoer&Y Demnd flow
40 60 ao 100
Percent Exceedaoce
Comparison of flow duration curves for simulated Stage 3 2008
and simulated Stage 3 2020 Energy Demand streamflows for week
45 based on mean weekly flows for 34 years of record.
Appendix Figure 16
AL.ASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodward-Clyde Consultanta
AHO
INTJU,IHC.
ll3
HARZA ·EIIASCO
SUSITNA JOINT VENTURE
,-..
II)
""' u ._,
u
Qlll .. • .c u ...
:::::l
60,000
so.ooo
40,000
30,000
20,000
10,000
0
0 20
a Simulated Staae 3 2001 Encr&Y Demand flow
o Simulated Staae 3 2020 EnerJY Demand flow
40 60 so 100
Percent Exceedance
Comparison of flow duration curves for simulated Stage 3 2008
and simulated Stage 3 2020 Energy Demand streamflows for week
46 based on mean weekly flows for 34 years of record.
Appendix Figure 17
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodward-Cfrde Conauttanta
AND
~NTJU,IIC.
114
HAAZA -EIASCO
SUSITNA JOINT VENTURE
--en u. u .._,
v
CIO .. • .c u ...
c
60,000
so.ooo
40,000
30,000
20,000
10,000
0
0 20
• Simulated Staae 3 2001 EneriY Demand flow
a Simulated Staae 3 2020 Eneray Demand flow
40 60 so 100
Percent Exceedance
Comparison of flow duration curves for simulated Stage 3 2008
and simulated Stage 3 2020 Energy Demand streamflows for week
47 based on mean weekly flows for 34 years of record.
Appendix Figure 18
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodward-Circle Conaultanb HARZA ·EIASCO
SUSITNA JOINT VENTURE
--V)
1.1. u _.
u
CliO ..
Ill .s: u
"' 0
60,000
50,000
40,000
30,000
20,000
10,000
0
0
• Simulated Stage 3 2008 Eneray Demand flow
a Simulated Staae 3 2020 Ener&Y Demand flow
20 40 60 80
Percent Exceedance
100
Comparison of flow duration curves for simulated Stage 3 2008
and simulated Stage 3 2020 Energy Demand streamflows for week
48 based on mean weekly flows for 34 years of record.
Appendix Figure 19
ALASKA POV.ER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
Woodward-Clyde Conaulunta
AHO
ENTJU.INC.
116
HAAZA·EBASCO
SUSITNA JOINT VENTURE
,_
V)
1.1. u --u
110 ... • .c u
"' 0
60,000
so.ooo
40 ,000
30,000
20,000
10 ,000
0
-·------..,
• Simulated Staae 3 2008 Eneray Demand flow
a Simulated Staae 3 2020 Eneray Demand flow
"\:::
'-··~::::::: II~
ll I I I I.-_ I I I I
~-----------------------~1 ---ri ----~~--~~---------,
0 2 0 40 60 ao 100
Percent Ex ceedance
Comparison of flow duration curves for simulated Stage 3 2008
and simulated Stage 3 2020 Energy Demand streamflows for week
49 based on mean weekly flows for 34 years of record.
Appendix Figure 20
ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJEC T
Woodw•rcf.Cirde Con1ultanb
AND
ENTAil, INC.
117
HARZA ·E8ASCO
SUS I TNA JOINT VENTURE
APPENDIX TABLES
118
Appendix Table 1. Percent of time successful paaaaqe occurs under natural
and Staqe 1 mainstem discharqes durinq week 45 at Slouqh
BA.
Mainatem Discharqe for
~y~~e~I~Yl fAI~Ig. f~J::~!mt 2: Iim~·
Paasaqe Local Unbermed Bermed
Slouqh Reach Backwater Flow Breachinq Natural Staqe 1 Staqe 1
BA I 7,700 5,500 27,000 100 100 100
II 16,000 >60,000 27,000 88 53 53
III 19,000 >60,000 27,000 65 47 47
IV 25,000 >60,000 27,000 15 15 15
v 30,000 >60,000 27,000 12 12 12
VI 59,000 13,500 33,000 97 65 65
VII >60,000 >60,000 33,000 9 9 0
VIII >60,000 >60,000 33,000 9 9 0
IX >60,000 >60,000 33,000 9 9 0
X >60,000 >60,000 33,000 9 9 0
*Percent of time corresponds to the minimum of the three required dis-
char qes for successful passaqe provided by either backwater, local flow,
or breachinq.
119
Appendix Table 2. Percent ot time successful passage occurs under natural
and Stage 1 mainstem discharges during week 46 a ~: Slough
BA.
Mainstem Discharge tor
SY~~estfYl ~1111g1 ~e~::c~nt Qf Iime*
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
BA I 7,700 5,500 27,000 100 100 100
II 16,000 >60,000 27,000 79 62 62
III 19,000 >60,000 27,000 59 44 44
IV 25,000 >60,000 27,000 12 15 15
v 30,000 >60,000 27,000 9 9 9
VI 59,000 13,500 33,000 91 71 71
VII >60,000 >60,000 33,000 6 6 0
VIII >60,000 >60,000 33,000 6 6 0
IX >60,000 >60,000 33,000 6 6 0
X >60,000 >60,000 33,000 6 6 0
•Percent ot time corresponds to the minimum of the three required dis-
charges for successful passage provided by eit:ner backwater, local flow,
or breaching.
120
Appendix Table 3, Percent ot time successful passage occurs under natural
and Stage 1 mainatem discharges during week 47 at Slough
SA.
Mainstem Discharge tor
§y~~!SI!Yl ~AI§Ag! ~e~~ent 2! time•
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
SA I 7,700 5,500 27,000 100 100 100
II 16,000 >60,000 27,000 53 41 4l
III 19,000 >60,000 27,000 41 32 32
IV 25,000 >60,000 27,000 15 12 12
v 30,000 >60,000 27,000 6 9 6
VI 59,000 13,500 33,000 77 68 68
VII >60,000 >60,000 33,000 6 6 0
VIII >60,000 >60,000 33,000 6 6 0
IX >60,000 >60,000 33,000 6 6 0
X >60,000 >60,000 33,000 6 6 0
•Percent ot time corresponds to the minimum o! the three required dis-
charges for successful passage provided by either backwater, local flow,
or breaching.
121
Appendix Table 4. Percent ot time successful passage occurs under natural
and Stage 1 mainstam discharges during week 48 at Slough
SA.
Mainstem Discharge for
~ygc~s!tYl ~~ssagt ~e[gent Q! Iime*
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
SA I 7,700 5,500 27,000 100 100 100
II 16,000 >60,000 27,000 47 41 41
III 19,000 >60,000 27,000 18 18 18
IV 25,000 >60,000 27,000 9 9 9
v 30,000 >60,000 27,000 9 9 0
VI 59,000 13,500 33,000 50 47 47
VII >60,000 >60,000 33,000 0 0 0
VIII >60,000 >60,000 33,000 0 0 0
IX >60,000 >60,000 33,000 0 0 0
X >60,000 >60,000 33,000 0 0 0
*Percent of time corresponds to the minimum of the three required dis-
charges for successful passage provided by either backwater , local flow ,
or breaching.
122
Appendix Table 5. Percent ot time •uccesstul passaqe occurs under natural
and Staqe 1 mainstem discharqes durinq week 49 at Slouqh
SA.
Mainstem Discharqe tor
Su~~eslfYl ~IIIAgl ~·~~en~ 2! ~ime•
Passaqe Local Unbermed Bermec
Slouqh Reach Backwater Flow Breachinq Natural Staqe 1 Staqe 1
SA I 7,700 5,500 27,000 100 100 1011
II 16,000 >60,000 27,000 29 27 2 '7
III 19,000 >60,000 27,000 15 15 15
IV 25,000 >60,000 27,000 3 0 )
v 30,000 >60,000 27,000 3 0 I )
VI 59,000 13,500 33,000 56 56 Sl i
VII >60,000 >60,000 33,000 0 0
VIII >60,000 >60,000 33,000 0 0 c
IX >60,000 >60,000 33,000 0 0 0
X >60,000 >60,000 33,000 0 0 0
*Percent ot time corresponds to the minimum ot the three required dis-
charqes tor successful passaqe provided by either backwater, local flow,
or breachinq.
123
Appendix Table 6. Percent ot time successtul passage occurs under natural
and Stage 1 mainstem discharges during weeks 45-49 at
Slough SA.
Mainstem Discharge tor
Suc~es§fYl f~ss~ge fe[cen~ Qf Iime*
Passage Local Unbermed Bermed
S l ough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
SA I 7,700 5,500 27,000 100 100 100
II 16,000 >60,000 27,000 97 77 77
III 19,000 >60,000 27,000 82 68 68
IV 25,000 >60,000 27 ,000 29 27 27
v 30,000 >60,000 27,000 24 21 18
VI 59,000 13,500 33,000 97 82 82
VII >60 ,000 >60,000 33,000 15 15 0
VIII >60,000 >60,000 33,000 15 15 0
IX >60,000 >60,000 33,000 15 15 0
X >60,000 >60,000 33,000 15 15 0
*Percent ot time corresponds to the minimum ot the three required dis-
charges tor successtu1 passage provided by either backwater, local flow,
or breaching.
124
Appendix Table 7. Percent ot time successful passage occurs under natural
and Stage 1 mainatem discharges during week 45 at Slough
9.
Mainatem Discharge tor
---~y~~!llf~l fllllgl ftl:~~mt 2f :time•
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
9 I 11,600 27,000 19,000 97 85 85
II 22,300 58,000 19,000 65 47 18
III 25,500 >60,000 19,000 65 47 15
IV 25,500 5Q ,('I00 19,000 65 47 15
v 34,400 >60,000 19,000 65 47 9
*Percent ot time corresponds to the minimum ot the three required dis-
charges tor successful passage provided by either backwater, local flow,
or breaching.
125
Appendix Tabla 8. Percent ot time successful passage occurs under natural
and Stage 1 mainstaa discharges during weak 46 at Slough
9.
Mainstem Discharge tor
~y~~esgfyl fAIIA91 ~~[~en~ of time*
Passage Local Un.bermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
9 I 11,600 27,000 19,000 97 85 85
II 22,300 58,000 19,000 59 44 21
III 25,500 >60,000 19,000 59 44 15
IV 25,500 58,000 19,000 59 44 15
v 34,400 >60,000 19,000 59 44 6
*Percent ot time corresponds to the minimum ot the three required dis-
charges tor successful passage provided by either backwater, local flow,
or breaching.
126
Appendix Table 9. Percent ot time successtul passage occurs under natural
and Stage 1 mainstem discharges during week 47 at Slough
9.
Mainstem Discharge tor
~u~~~~lfYl E~ISAg! f![~!Dt Qf Iime•
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
9 I 11,600 27,000 19,000 94 77 77
II 22,300 58,000 19,000 41 32 18
III 25,500 >60,000 19,000 41 32 12
IV 25,500 58,000 19,000 41 32 12
v 34,400 >60,000 19,000 41 32 6
*Percent ot time corresponds to the minimum ot the three required dis-
charges tor successtul passage provided by either backwater, local !low,
or breaching.
127
Appendix Table 10. Percent ot time successtul passage occurs under natural
and Stage 1 mainstem discharges during week 48 at
Slough 9.
Mainstem Discharge tor
SY~~IIIfYl f1111g1 fiJ::~IDt Qf l:iml*
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Sta ge 1
9 I 11,600 27,000 19,000 71 77 77
II 22,300 58,000 19,000 18 18 15
III 25,500 >60,000 19,000 18 18 9
IV 25,500 58,000 19,000 18 18 9
v 34,400 >60,000 19,000 18 18 0
*Percent ot time corresponds to the minimum ot the three required dis-
charges tor successtul passage provided by either backwater, local !low,
or breaching.
128
Appendix Table 11. Percent ot time successful passage occurs under
natural and Stage 1 mainstem discharges during week 49
at Slough 9.
Mainstem Discharge tor
5Y~~IIIfYl ~1111g1 ~~[~IDt Qf Iimg*
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
·-
9 I 11,600 27,000 19,000 65 77 77
II 22,300 58,000 19,000 15 15
III 25,500 >60,000 19,000 15 15
IV 25,500 58,000 19,000 15 15
v 34,400 >60,000 19,000 15 15
*Percent ot time corresponds to the minimum ot the three required dis-
charges tor successful passage provided by either backwater, local tlow,
or breaching.
129
6
0
0
0
Appendix Table 12. Percent ot time successtul passage occurs under natural
and Stage 1 mainstem discharges during weeks 45-49 at
Slough 9.
Mainatem Discharge tor
~y~~~llrYl fAIIAgl ~e[~en~ 2: :rime•
Passage Local Unbermed Bermed
Slough Reach Back\olater Flow Breaching Natural Stage 1 Stage 1
9 I 111 600 27,000 19,000 97 91 91
II 22,300 58,000 19,000 82 68 35
III 25,500 >60,000 19,000 82 68 15
IV 25,500 58,000 19,000 82 68 27
v 34,400 >60,000 19,000 82 68 15
*Percent ot time corresponds to the minimum ot the three required dis-
charges tor successtul passage provided by either back\olater, local tlow,
or breaching.
130
Appendix Table 13. Percent of time •ucces•tul pasaaqe occur• under natural
and Staqe 1 mainatea diacharqes durinq weex 45 at Slouqh
9A.
Mainstem Diacharqe tor
SY~~!SI,Yl fAIIA9. f!l:~IDt 2' ~ime*
Passaqe Local Unbermed Bermed
Slouqh Reach Backwater Flow Breachinq Natural Staqe 1 Staqe 1
9A I 11,500 15,000 13,500 97 88 88
II 15,000 7,500 13,500 97 100 100
III 22,300 11,000 13,500 97 91 91
IV 27,000 11,000 13,500 97 91 91
v 33,500 12,500 13,500 97 80 80
VI 44,600 18,000 13,500 74 65 50
VII 47,300 15,000 13,500 94 65 56
VIII >60,000 31,500 13,500 94 65 9
IX >60,000 15,000 13,500 94 65 56
X >60,000 12,500 13,500 97 80 80
XI >60,000 50,000 13,500 94 65 0
*Percent ot time corresponds to the minimum of the three required dis-
charqes for successful passaqe provided by either backwater, local flow,
or breachinq.
131
Appendix Table 14. Percent ot time successtul passage occurs under natural
and Stage 1 mainstem discharges during week 46 at Slough
9A.
Mainstem Discharge tor
~y~~~~~:Yl fas~A91 f~[i~Dt 2: time•
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
9A I 11,500 15,000 13,500 97 85 85
II 15,000 7,500 13,500 97 100 100
III 22,300 11,000 13,500 97 91 91
IV 27,000 11,000 13,500 97 91 91
v 33,500 12,500 13,500 97 77 77
VI 44,600 18,000 13,500 97 71 50
VII 47,300 15,000 13,500 91 71 65
VIII >60,000 31,500 13,500 91 71 6
IX >60,000 15,000 13,500 91 71 65
X >60,000 12,500 13,500 97 77 77
XI >60,000 50,000 13,500 91 71 0
•Percent ot time corresponds to the minimum ot the three required dis-
charges tor successtul passage provided by either backwater, local flow,
or breaching.
132
Appendix Table 15. Percent ot time successful passaqe occurs under natural
and Staqe l mainstem discharqes durinq week 47 at Slouqh
9A.
Mainstem Discharqe tor
SY~~e~styl ~AS!A91 ~~[~tnt 2! Iime•
Passaqe Local Unbermed Bermed
Slouqh Reach Backwater Flow Breachinq Natural Staqe 1 Staqe 1
9A I 11,500 15,000 13,500 88 82 82
II 15,000 7,500 13,500 97 100 100
III 22,300 11,000 13,500 94 94 94
IV 27,000 11,000 13,500 94 94 94
v 33,500 12,500 13,500 85 85 85
VI 44,600 18,000 13,500 77 68 35
VII 47,300 15,000 13,500 77 68 47
VIII >60,000 31,500 13,500 77 68 6
IX >60,000 15,000 13,500 77 68 47
X >60,000 12,500 13,500 85 74 74
XI >60,000 50,000 13,500 77 68 0
•Percent of time corresponds to the minimum ot the three required dis-
charqes tv~ successful passaqe provided by· either backwater, local flow,
or breachinq.
133
Appendix Table 16. Percent ot time auccesatul passaqe occur• under natural
and Staqe 1 •ainstea discharqea durinq week 48 at Slouqh
9A.
Mainstem Discharqe tor
~~,,111,~1 fllllgl flt,IDt 2' Iiml*
Passaqe Local Unbermed Bermed
Slouqh Reach Backwater Flow Breachinq Natural Staqe 1 Staqe 1
9A I 11,500 15,000 13,500 71 77 77
II 15,000 7,500 13,500 97 100 100
III 22,300 11,000 13,500 79 88 88
IV 27,000 11,000 13,500 79 88 88
v 33,500 12,500 13,500 62 62 62
VI 44,600 18,000 13,500 50 47 29
VII 47,300 15,000 13,500 50 47 44
VIII >60,000 31,500 13,500 50 47 0
IX >60,000 15,000 13,500 50 47 44
X >60,000 12,500 13,500 62 62 62
XI >60,000 50,000 13,500 50 47 0
•Percent ot time corresponds to the minimum ot the three required dis-
charqes tor successful passaqe provided by either backwater, local tlow,
or breachinq.
134
Appendix Table 17. Percent ot time successful passage occurs under nat ural
and Stage 1 mainstem discharges during week 49 at Slough
9A.
Mainstem Discharge tor
~y~~~~~~Yl fi~SAgl fet!ant 2~ Iime•
Passage Local Unbermed Berm!d
Slough Reach Backwater Flow Breaching Natural Stage 1 Staga 1
9A I 11,500 15,000 13,500 65 82 82
II 15,000 7,500 13,500 94 97 97
III 22,300 111000 13,500 71 88 88
IV 27,000 11,000 13,500 71 88 88
v 33,500 12,500 13,500 62 62 62
VI 44,600 18,000 13,500 56 56 21
VII 47,300 15,000 13,500 56 56 29
VIII >60,000 31,500 13,500 56 56 29
IX >60,000 15,000 13,500 62 62 52
X >60,000 12,500 13,500 62 62 •52
XI >60,000 50,000 13,500 56 56 0
•Percent of time corresponds to the minimum of the three required dis-
charges tor successful passage provided by either backwater, local flow,
or breaching.
135
Appendix Table 18. Percent ot time •uccesstul passage occurs under natural
and Stage 1 mainstem discharges during weeks 45-49 at
Slough 9A.
Mainstem Discharge tor
Su~~es~tYl f~~~Ag! f~r~~nt Q: Iime*
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
9A I 11,500 15,000 13,500 97 91 91
II 15,000 7,500 13,500 97 100 100
III 22,300 11,000 13,500 97 94 94
IV 27,000 11,000 13,500 97 94 94
v 33,500 12,500 13,500 97 85 85
VI 44,600 18,000 13,500 97 82 71
VII 47,300 15,000 13,500 97 82 77
VIII >60,000 31,500 13,500 97 82 15
IX >60,000 15,000 13,500 97 82 77
X >60,000 12,500 13,500 97 85 85
XI >60,000 50,000 13,500 97 82 0
•Percent ot time corresponds to the minimum of. the three required dis-
charges for successful passage provided by either backwater, local flow,
or breaching.
136
Appendix Table 19. Percent ot time successful passage occurs under natural
and Stage 1 mainstem discharges during week 45 at Slough
11 and Upper Side Channel 11.
Mainstem Discharge for
~YQQesstyl ~A~sag~ ~§[cent ot Iime•
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
11 I 16,500 28,000 42,000 88 52 52
II 19,400 <8,500 42,000 97 97 97
III 33,400 >60,000 42,000 9 9
IV 40,300 48,000 42,000 6 6
v >60,000 >60,000 42,000 6 3
VI >60,000 >60,000 42,000 6 3
VII >60,000 >60,000 42,000 6 3
usc 11 I 44,000 a 16,000 88b 53b
II a a 16,000 sac 53c
•Percent of time corresponds to the minimum of the three required dis-
charges for successful passage provided by either backwater, local flow,
or breaching.
a Mainstem discharges not evaluated as data insufficient for analysis.
b Percent exceedence evaluated for backwater and breaching mainstem
discharges only.
c Percent exceedence evaluated for breaching mainstem discharge only.
d Percent exceedence not evaluated as data insufficient for analysis.
137
9
6
0
0
0
ob
d
Appendix Table 20. Percent ot time auccesstul paasaqe occurs under natural
and Staqe 1 mainatem diacharqes durinq week 46 at Slouqh
11 and Upper Side Channel 11.
Mainstem Discharqe tor
~u~cesstul ~~ssagg ~~t~ent o: Iime•
Passaqe Local Unbermed Bermed
Slouqh Reach Backwater Flow Breachinq Natural Staqe 1 Staqe 1
11 I 16,500 28,000 42,000 74 56 56
II 19,400 <8,500 42,000 97 97 97
III 33,400 >60,000 !.2,000 6 6
IV 40,300 48,000 42,000 3 0
v >60,000 >60,000 42,000 3 0
VI >60,000 >60,000 42,000 3 0
VII >60,000 >60,000 42,000 3 0
usc 11 I 44,000 a 16,000 79b 62b
II a a 16,000 79c 62c
*Percent ot time corresponds to the minimum of the three required dis-
charges tor successful passaqe provided by either backwater, local flow,
or breachinq.
a Mainstem discharqes not evaluated as data insufficient for analysis.
b Percent exceedence evaluated tor backwater and breaching mainstem
discharges only.
c Percent exceedence evaluated for breaching mainstem discharge only.
d Percent exceedence not evaluated as data insufficient for analysis.
138
6
0
0
0
0
ob
d
Appendix Table 21. Percent of time successful passage occurs under natural
and Stage 1 mainstem discharges during week 47 at Slough
11 and Upper Side Channel 11.
Mainstem Discharge for
SY~~~~I!Yl ~A!S~gg ~u:~~nt 2! Iime*
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
11 I 16,500 28,000 42,000 53 41 41
II 19,400 <8,500 42,000 97 97 97
III 33,400 >60,000 42,000 6 6
IV 40,300 48,000 42,000 3 3
v >60,000 >60,000 42,000 3 3
VI >60,000 >60,000 42,000 3 3
VII >60,000 >60,000 42,000 3 3
usc 11 I 44,000 a 16,000 53b 41b
II a a 16,000 53c 41c
*Percent of time corresponds to the minimum of the three required dis-
charges for successful passage provided by either backwater, local flow,
or breaching.
a Mainstem discharges not evaluated as data insufficient for analysis.
b Percent exceedence evaluated for backwater and breaching mainstem
discharges only.
c Percent exceedence evaluated for breaching mainstem discharge only.
d Percent exceedence not evaluated as data insufficient for analysis.
139
6
3
0
0
0
ob
d
Appendix Table 22. Percent of time •uccessful passage occurs under natural
and Stage 1 •ainste• discharges during week 48 at Slough
11 and Upper Side Channel 11.
Mainstem Discharge for
SY~~~!I!Yl fAI§Agg f~~~~n~ 2! lim~·
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
11 I 16,500 28,000 42,000 41 35 35
II 19,400 <8,500 42,000 94 97 97
III 33,400 >60,000 42,000 0 0
IV 40,300 48,000 42,000 0 0
v >60,000 >60,000 42,000 0 0
VI >60,000 >60,000 42,000 0 0
VII >60,000 >60,000 42,000 0 0
usc 11 I 44,000 a 16,000 47b 41b
II a ·1 16,000 47c 41c
•Percent of time corresponds to the minimum of the three required dis-
charges for successful passage provided by either backwater, local flow,
or breaching.
a Mainstem discharges not evaluated as data insufficient for analysis.
b Percent exceedence evaluated for backwater and breaching mainstem
discharges only.
c Percent exceedence evaluated for breaching mainstem discharge only.
d Percent exceedence not evaluated as data insufficient for analysis.
140
0
0
0
0
0
ob
d
Appendix Table 23. Percent of time successful passage occurs under natural
and Stage l mainstem discharges during week 49 at Slough
11 and Upper Side Channel 11.
Mainstem Discharge for
~y~~~~~~~l ~A~SA91 ~~[~IDt Q~ Iime*
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
11 I 16,500 28,000 42,000 29 27 27
II 19,400 <8,500 42,000 97 97 97
III 33,400 >60,000 42,000 0 0
IV 40,300 48,000 42,000 0 0
v >60,000 >60,000 42,000 0 0
VI >60,000 >60,000 42,000 0 0
VII >60,000 >60,000 42,000 0 0
usc 11 I 44,000 a 16,000 29b 27b
II a a 16,000 29c 27c
*Percent of time corresponds to the minimum of the three required dis-
charges for successful passage provided by either backwater, local flow,
or breaching.
a Mainstem discharges not evaluated as data insufficient for analysis.
b Percent exceedence evaluated for backwater a.nd breaching mainstem
discharges only.
c Percent exceedence evaluated for breaching mainstem discharge only.
d Percent exceedence not evaluated as data insufficient for analysis .
141
0
0
0
0
0
ob
d
Appendix Table 24. Percent ot time successtul passage occurs under natural
and Stage 1 mainstem discharges during weeks 45-49 at
Slough 11 and Upper Side Channel 11.
Mainstem Discharge tor
~u~~~~lrYl ~a§sAgl ~~~::cent 2r Iim!il*
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
11 I 16,500 28,000 42,000 94 74 74
II 19,400 <8,500 42,000 97 97 97
III 33,400 >60,000 42,000 15 15 15
IV 40,300 48,000 42,000 12 9 9
v >60,000 >60,000 42,000 9 6 0
VI >60,000 >60,000 42,000 9 6 0
VII >60,000 >60,000 42,000 9 6 0
usc 11 I 44,000 a 16,000 97b 77b ob
II a a 16,000 97c 77c d
•Percent of time corresponds to the minimum ot the three required dis-
charges for successful passage provided by either backwater, local flow ,
or breaching.
a Mainstem discharges not evaluated as data insufficient for analysis.
b Percent exceedence evaluated tor backwater and breaching mainstem
discharges only.
c Percent exceedence evaluated tor breaching mainstem discharge only.
d Percent exceedence not evaluated as data insufficient for analysis.
142
Appendix Table 25. Percent of time successful passage occurs under natural
and Stage 1 mainstem discharges during week 45 at Side
Channel 21 and Slough 21.
Mainstem Discharge tor
SY~~~§ItYl fAS~Age f~x:cent ot Iime*
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
sc 21 I 7,800 5,000 12,000 100 100 100
II 10,300 15,000 12,000 97 91 91
III 13,000 15,000 12,000 97 82 68
IV 20,000 15 ,000 12,000 97 82 56
v 25,900 15,000 12,000 97 82 56
VI 32,100 48,000 12,000 97 82 9
VII 45,900 >60,000 12,000 97 82 0
VIII 50,000 28,000 24,0 00 21 21 12
IX 51,400 22,000 24,000 32 21 21
Sl 21 I 51,400 22,000 25,800 32 21 21
II 54,900 5,000 25,800 100 100 100
IIIL >60,000 >60,000 25,800 15 15 0
IIIR >60,000 >60,000 29,000 >12 >12 0
•Percent of time corresponds to the minimum of the three required dis-
charges for successful passage provided by either backwater, local flow,
or breaching.
143
Appendix Tabla 26 . Percent ot time auccaastul paaaaqa occurs under natural
and Staqa 1 mainstem discharqas durinq week 46 at Side
Channel 21 and Slouqh 21.
Mainstem Discharqe tor
SY~C!S~fYl f~S§~g~ fe~~en~ of rime•
Passaqe Local Unbermed Bermed
Slouqh Reach Backwater Flow Breachinq Natural Staqe 1 Staqe 1
sc 21 I 7,800 5,000 12,000 100 100 100
II 10,300 15,000 12,000 97 91 91
III 13,000 15,000 12,000 97 79 74
IV 20,000 15,000 12,000 97 79 65
v 25,900 15,000 12,000 97 79 65
VI 32,100 48,000 12,000 97 79 6
VII 45,900 >60,000 12,000 97 79 0
VIII 50,000 28,000 24,000 18 15 6
IX 51,400 22,000 24,000 27 21 21
Sl 21 I 51,400 22,000 25,800 27 21 21
II 54,900 5,000 25,800 100 100 100
IIIL >60,000 >60,000 25,800 12 15 0
IIIR >60,000 >60,000 29,000 9 6 0
*Percent of time corresponds to the minimum ot the three required dis-
charqes for successful passaqe provided by either backwater, local flow,
or breaching.
144
Appendix Table 27. Percent ot time successtul passage occurs under natural
and Stage 1 mainate• discharges during week 47 at Side
Channel 21 and Slough 21.
Mainstem Discharge tor
~yc~esstul ~ass~g§ ~ercen~ 2! Iime*
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
sc 21 I 7,800 5,000 12,000 100 100 100
II 10,300 15,000 12,000 97 88 88
III 13,000 15,000 12,000 85 74 71
IV 20,000 15,000 12,000 85 74 47
v 25,900 15,000 12,000 85 74 47
VI 32,100 48,000 12,000 85 74 6
VII 45,900 >60,000 12,000 85 74 0
VIII 50,000 28,000 24,000 15 12 9
IX 51,400 22,000 24,000 24 18 18
Sl 21 I 51,400 22,000 25,800 24 18 18
II 54,900 5,000 25,800 100 100 100
IIIL >60,000 >60,000 25,800 12 12 0
IIIR >60,000 >60,000 29,000 6 6 0
•Percent ot time corresponds to the minimum ot the three required dis-
charges for successful passage provided by either backwater, local flow,
or breaching .
145
Appendix Table 28. Percent ot time •ucc•••tul passage occurs under natural
and Stage 1 mainstem discharges during week 48 at Side
Channel 21 and Slough 21.
Mainstem Discharge tor
~Y~~es~:ul ~~sg~g1 ~~~~ent 2: Iime•
Passage Local Unbermed Bermed
Slough Reach Backwater Flow Breaching Natural Stage 1 Stage 1
sc 21 I 7,800 5,000 12,000 100 100 100
II 10,300 15,000 12,000 85 91 91
III 13,000 15,000 12,000 65 68 50
IV 20,000 15,000 12,000 65 68 44
v 25,900 15,000 12,000 65 68 44
VI 32,100 48,000 12,000 65 68 0
VII 45,900 >60,000 12,000 65 68 0
VIII 50,000 28,000 24,000 9 9 6
IX 51,400 22,000 24,000 15 15 15
Sl 21 I 51,400 22,000 25,800 15 15 15
II 54,900 5,000 25,800 100 100 100
IIIL >60,000 >60,000 25,800 9 9 0
IIIR >60,000 >60,000 29,000 6 3 0
•Percent ot time corresponds to the minimum ot the three required dis-
charges for successful passage provided by either backwater, local flow,
or breaching.
146
Appendix Table 29. Percent of time successful passage occurs under natural
and Stage 1 mainstem discharges during ~eek 49 at Side
Channel 21 and Slough 21.
Mainstem Diacharqe for
Su~~esstul fas~Age f!n::cen~ ot Iime*
Passage Local Unbermed Berm!d
Slough Reach Backwater Flow Brea.chinq Natural Stage 1 Stag! 1
sc 21 I 7,800 5,000 12,000 100 100 100
II 10,300 15,000 12,000 74 88 88
III 13,000 15,000 12,000 62 71 56
IV 20,000 15,000 12,000 62 71 29
v 25,900 15,000 12,000 62 71 29
VI 32,100 48,000 12,000 62 71 0
VII 45,900 >60,000 12,000 62 71 0
VIII 50,000 28,000 24,000 3 0 0
IX 51,400 22,000 24,000 6 6 6
51 21 I 51,400 22,000 25,800 6 6 6
II 54,900 5,000 25,800 100 100 1)0
IIIL >60,000 >60,000 25,800 3 0 0
IIIR >60,000 >60,000 29,000 3 0 0
•Percent of time corresponds to the minimum of the three required dis-
charges for successful passage provided by either backwater, local flow,
or breaching.
147
Appendix Table 30. Percent ot time successtul passage occurs under natursl
and Stage 1 mainstem discharges during weeks 45-49 at
Side Channel 21 and Slough 21.
Mainstem Discharge tor
~uccess:ul Eass~g~ Eetcent o: Iime•
Pass~ge Local Unbermed Berned
Slough Reach Backwater Flow Breaching Natural Stage 1 Sta;e 1
sc 21 I 7,800 5,000 12,000 100 100 100
II 10,300 15,000 12,000 97 97 97
III 13,000 15,000 12,000 97 91 82
IV 20,000 15,000 121000 97 91 77
v 25,900 15,000 121000 97 91 77
VI 321100 48,000 121000 97 91 15
VII 45,900 >601000 121000 97 91 0
VIII 50,000 28,000 24,000 32 27 18
IX 51,400 22,000 241000 47 38 38
Sl 21 I 511400 22,000 251800 47 38 38
II 541900 51000 251800 100 100 100
IIIL >601000 >601000 251800 29 27 0
IIIR >601000 >60,000 291000 >28 >18 0
•Percent ot time corresponds to the minimum of the three required dis-
charges for successful passage provided hy either !.J ackwater 1 local flc ,w 1
or breaching.
148