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HomeMy WebLinkAboutAPA4000............. SUSITNA HYDROELECTRIC PROJECT FEDERAL ENERGY REGULATORY COMMISSION PROJECT No.7114 APRIL 1985 DOCUMENT No." LASKA POWER AUTHORITY_--..II ~~~~rn3~®©@ JOINT VENTURE A FRAMEWORK FOR THE ASSESSMENT OF CHINOOK SALMON REARING IN THE MIDDLE SUSITNA RIVER UNDER ALTERED FLOW,TEMPERATURE AND SEDIMENT REGIMES TK. 1425 .S8 F12 Do.4000 ,~EWT&.A 18UIEY Ii ASSOCIATES -~---.. TRACT 1"'0 [}{]&~~&c §[ID&®©@ SUSITNA JOINT VENTURE 711 H STREET ANCHORAGE,ALASKA 99501 TEL.(907)272 5585 RECEIVED MAY 10 1985 May 9,1985 1 .8.2/4.3.1 .ALASKA POWER AUTHORI"Ji( Mr.James B.Dischinger Project Manager Alaska Power Authority 334 West 5th Avenue Anchorage,Alaska 99501 CONFIDENTIAL:PRIVILEGED WORK PRODUCT PREPARED IN ANTICIPATION OF LITIGATION;RESTRlCTED D1STRIi3UTION Subject:Susitna Hydroelectric Project (11)A Framework for the Assessment of Chinook Salmon Rearing in the Middle Susitna River Under Altered Flow, Temperature and Sediment Regimes and (12)Response of Aquatic Habitat Surface Areas to Mainstem Discharge in the Talkeetna-to-Devil Canyon Reach of the Susitna River, Alaska Dear Mr.Dischinger: Enclosed for your review and comment is a draft copy of (11)A Framework for the Assessment of Chinook Salmon Rearing in the Middle Susitna River Under Altered Flow,Temperature and Sediment Regimes and (12)Response of Aquatic Habitat Surface Areas to Mainstem Discharge in the Talkeetna-to-Devil Canyon Reach of the Susitna River,Alaska. There are also copies of the above mentioned reports enclosed for your transmittal for ADF&G SuHydro. Please return your comments to me by May 31,1985. Very truly yours, W.E.Larson Project Director klk F1Ia No. Enc:as noted cc w/o Enc: ~F~p~ani,Power L.GlIlFertson,HE J.Thrall,HE Authority Resp. Keyword. 425471/5 ..•.._--_.-.._----------- DAlE IJOB NO May 10,1985 ATTENTION Dr.Dana Schmidt AE Draft Reports (907)276-0001 (907)277-7641 ALASKA POWER AUTHORITY 334 liVest 5th Avenue, 2nd Floor Anchorage,Alaska 99501 TO SuHydro Aquatic Studies 630 East Tenth Avenue,3rd Floor Anchorage,Alaska 99501 o SamplesoPlans o _ o Prints o Change order o Shop drawings o Copy of letter GENTLEMEN: WE ARE SENDING YOU CXAttached 0 Under separate cover via the following items: o Specifications COPIES DATE NO.DESCRIPTION 1 April 85 A Framework for the Assessment of Chinook Salmon Rearing in the Middle Susitna River Under Altered Flow,Temperature and Sediment Regimes Response of Aquatic Habitat Surface Areas to Mainstem Discharge in the Talkeetna-to-Devil Canyon Reach of the Susitna Rive Alaska THESE ARE TRANSMITTED as checked below: o Resubmit copies for approval o Submit copies for distribution o Return corrected prints o Approved as submitted o Approved as noted o Returned for corrections o o For approval o For your use o As requested ~For review and comment o FOR BIDS DUE 19 0 PRINTS RETURNED AFTER LOAN TO US REMARKS _ COPYTO---------S-,GNED~/Z$1~ If enclosures are not as noted,kindly notify us at once.E~arCheglanl Document No._ Susitna File No.4.3.1.3 TK H'LS .S5 FL.J+'2 no.1-\000 SUSITNA HYDROELECTRIC PROJECT A FRAMEWORK FOR THE ASSESSMENT OF CHINOOK SALMON REARING IN THE MIDDLE SUSITNA RIVER UNDER ALTERED FLOW,TEMPERATURE AND SEDIMENT REGIMES Report by E.Woody Trihey &Associates Alexander M.Milner Under Contract to Harza-Ebasco Susitna Joint Venture Prepared for Alaska Power Authority Draft Report April 1984 ARLIS Alaska Resources Library &InformatlOn ServIces Anchorage.Alaska TABLE OF CONTENTS 1•I NTRODUcr I ON •••••••••••••••••••••••••••••••••••••••••••••• 2.OVERVIEW OF CHINOOK SALMON ESCAPEMENT OF THE SUSITNA RIVER DRAINAGE ••••••••••••••~•••••••••••••••••••••7 3.DISTRIBUTION OF REARING JUVENILE CHINOOK SALMON IN THE MIDDLE SUSITNA RiVER •••••••••••••••••••••••••••••••11 4.FACTORS THAT INFLUENCE JUVEN ILE REAR ING CH INOOK SALMON IN THE MIDDLE SUSITNA RIVER ••••••••••••••••••••••••18 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 I ntrod uct I on •••••••••••••••••••••••••••••••••••••••••18 F I ow Reg I me ••••••••••••••••••••••••••••••••••••••••••18 Discharge/Velocity •••••••••••••••••••••••••••••••••••20 Water Depth ••••••••••••.•••••••••••••••••••••.•••••••25 Cover 26 Food Ava II ab III ty ••••••••••••••••••••••••••••••••••••28 Predation 35 Space Requ f rernents •••••••••••••••••••••••••••••••••••35 Temperature •••.••••.••••••••••••••••.•••••.••••.•••••37 Overwintering Surv Ivai •••••••••••••••••••••••••••••••39 5.EVALUATION OF WITH-PROJECT CONDITIONS •••••••••••••••••••••44 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 I ntrod uct I on •••••••••••'••••••••••••••••••••••••••••••44 F I ow Reg I me ••••••••••••••••••••••••••••••••••••••••••44 Discharge/Velocity •••••••••••••••••••••••••••••••••••45 Water Depth ••••••••••••••••••••••••••••••••••••••••••48 Cover ••••••••••••••••••••••••••••••••••••••••••••••••50 Food Avallablllty ••••••••••••••••••••••••••••••••••••53 Predat I on ••••••••••••••••••••••••••••••••••••••••••••54 Space Req u J ranents •••••••••••••••••••••••••••••••••••54 Temperature ••••••••••••••••••••••••••••••••••••••••••55 Overw Inter Ing Surv Iva I ••••••••••••••••••••••••.••••••57 0') 0')co N ~ ~ ooo LD LDr-- ('t) ('t) 6.REFERENCES ••••••••••••••••••••••••••••••••••••••••••••••••62 ARLIS Alaska Resources Library &InformatlOn ServIces Anchorage.Alaska .. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 1I ST OF FIGURES Susltna River drainage basin with major 2 tributaries and geographic features General habitat categories of the Susltna 4 River Relative abundance and distribution of 5 juvenile salmon within different habitat types of the middle Susltna River Density distribution of juvenile chinook 14 sal mon by macrohabltat type on the Susltna River between the Chulitna River confluence and Devil Canyon,May through November 1983 Juven lie ch Inook sal mon mean catch per cell 15 at side sloughs and side channels by sampling period,May through November 1983 Conceptual flow diagram of the factors 19 Influencing chinook salmon rearing In the middle Susltna River Facing-water velocity and probability of use 21 for juvenile chinook compiled from underwater observations In the Kenai River,miles 18-36, during 1981 Comparison between average weekly stream 36 temperatures for the Susltna River and Its tributaries Surface area responses to malnstem discharge 47 In the Tal keetna-to-Dev II Canyon reach of the Susltna"Rlver (RM 101 to 149) Comparison of the middle Susltna River 49 natural and with-project (Case D)exceedance flows (cfs)for the months May to October calculated from average weekly streamflows for the water years 1950-1983 Theoretical curve of turbidity against depth 51 of compensation pol nt Comparison of the middle Susltna River 58 natural and with-project (Case D)exceedance flows (cfs)for the months November to April calculated from average weekly streamflows for the water years 1950-1983 Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9 Table 10 Tab Ie 11 LIST OF TABLES Sus Itna River annual ch Inook sa I mon escape-8 ment and timing for 1983 by sub-basin Peak survey counts and percent distribution 10 of chinook salmon In streams above RM 98.6 In 1981-84 Typical Juvenile chinook densities from other 13 studies Average I engths of 0+ch Inook sa I mon dur I ng 16 1984 In the middle Susltna River Depth and ve I oc I ty preferences for juven II e 20 chinook from other studies Summary of monthly streamflow statistics for 23 the Susltna River at Gold Creek Comparison between measured surface water 40 temperatures (oC)In side sloughs and simulated average monthly malnstem temperatures Susltna hydroelectric project flow con-46 stralnts for environmental flow requirement case E-VI Simulated monthly mean temperatures (OC)for 55 the ma I nstem Sus Itna River,Dev II Canyon to Talkeetna Susltna River temperature ranges (OC)for the 60 period September through April under natural and with-project conditions Comparison of timing of freeze-up and Ice 61 break-up In the middle Susltna River under natural and with-project conditions 1.INTROOUCTION The Alaska Power Authority (APA)has proposed the construction of two dams on the Sus I tna River over a per I od of 15 years;Dev II Canyon Dam at river mile (RM)152 upstream of the estuary and Watana Dam at RM 184.The Susltna River,an unregulated glacial river,flows approximately 318 miles from the terminus of the Susltna Glacier In the Alaska Mountain Range to Its mouth In Cook Inlet,draining an area of 19,600 square miles (Figure 1).The setting,scope and technical specifications of the proposed Susltna hydroelectric project are given In the Instream Flow Relationships Report, Vol ume 1,prepared by E.Woody Tr I hey and As soc I ates (EWT&A)and Woodward Clyde-Consultants (1985). As part of the environmental assessment studies for the proposed project, Investigations have been conducted since 1974 to quantify fish resources and evaluate utilization of aquatic habitats In the Susltna River drainage basin.In 1980 the Susltna Hydroelectric Aquatic Studies program was Initiated,In which Investigations were concentrated on the middle Susltna River from Talkeetna to Devil Canyon (RM 98.6 -152).This section of the river Is considered to be the most susceptible to with-project Impacts. Anadromous salmon are usually prevented from moving upstream of Devl I Canyon by high water velocity.Below Talkeetna (RM 98.6)project Induced changes In streamf low,stream temperature and sed Iment concentration will be buffered by the Input of a number of large trlbutrrles,notably the Tal keetna,Chu Iitna and Yentna rivers,wh I ch wIII be unaffected by construction and operation of the project. INIFigure1.suSSRiverdrainagebasinwithmajortrIbutariesandgeographicfeauer.(UniversItyofAlaska,ArcticEnvIronmentalInformationandDataCendr984b). Within the middle Susltna River,evaluation species have been selected for study.This procedure Is In accordance with Alaska Power Authority,Alaska Department of Fish and Game,and U.S.Fish and WI IdI I fe Serv I ce gu I de I I nes for studying habitats of greatest concern,which are those utilized by commercially and recreational Iy Important fish species that are most likely to be significantly Influenced by the project.Six principal aquatic hab I tat types,based on morphol og I c,hydrol og I c and hydrau I I c characteristics,have been Identified within the Talkeetna-to-Devll Canyon reach of the Susltna River,namely;malnstem,side channel,side slough, upland slough,tributary,and tributary mouth.Their characteristics are summarized In Figure 2. The habitats that respond most markedly to variations In malnstem discharge are the side channel s and side sloughs and thus are the most likely to be 5 rgn I f Icant I y aI tered In a w Ith-project 5 I tuati on (K linger and Tr i hey _I'~I j .~,I';.~. {iF ~) 1984).The primary species and life stages selected for eval uatlon were ~:/'~( chum salmon (Oncorhynchus~)spawning adults and their Incubating ) ",td~I • Trlhey and Associates and Woodward-Clyde Consultants 1985),which typically embryos and ch I nook sa I mon (.oa.nMwytscha)rear I ng j uven II es (E.Woody ?IH l ~,,- ! \ uti I Ize the side channel and side slough habitats to the greatest extent_/' ,,--'----.----.--...."".",,-_.,,_•._.-.....--...-...-'_'-'0'''_''--••_-......f\ (Dugan,Sterr Itt,and Stratton ~~4).Ch I nook sa I mon are I mportant to both \\u-I f 1.L:.. the commercial and sport flshe~y.Coho (.Q..klsutch)fry principally rear J !:~~:".~~ I n the tr I butar I es and up I and sloughs whIt e sockeye (.0....nerka)make the -.........\ most use of the side sloughs and upland sloughs [(Figure 3).Juvenile chum salmon were selected as a secondary evaluation species for rearing habitat, as their freshwater residence period In side channels and side sloughs does not typically exceed three months (Jennings 1984). -3- I~I(...({,GENERALHABITATCATEGORlfSOftilESUSITNARIVERI)MAlnslrmH.lbll.llcon~iSlSofIhoW!portion~ofIheSu~ilnaRiverIhollnOll1uUycon·\leyslreamllowIhrO\lghoullheyear.BOIhsingleandmulliplechannelreJchesarrIncludedinIhisholbilal,alegory.GroundwaterandI/iOulolryinRowappear10bein·con)l~quenlialconllibulors10Iheoverolltcharacle",I;csofm.linslemhdlJ,lal.MolinslemhahilalisIypicallychalaClerizedbyhighwdlervclocilie~Jnd~It·armoredstreambeds.Substralesgenerallyconsi,lofboulderandcohlliesizemaleriollswilhInlerslilialspacesf.lledwilhasroul·likt'mixlureofsmallgrd"elsandslacialsands.Suspendc-dsedimentconcentralionsandlurbidilyarchfllhduringsummerdue10IheinRuenceofglacialmek·waler.SireamilowsrecedcineolrlyfolDandIhemainslemclearsapprl'ciablyInOclober.AnicecoverformsonIherivt'rinlaleNovembelorDecember.2)SidrChanneftt.lblt.tconsislsoflhoseportionsofIheSusilnolRiverIhalnormalyconveyslreamflowdurinaIheopenwalersea~onbUIbecolTll!apJ1feciolblyde~vollereddurinllpeliodsoflowflow.Sidechannelholuilollmayeai~1e~herinwell·de/inedoverflowchannds,orinpoorlydefinedwalercour~esRowinlllhlOuj;hpar·liaUysubmcrgl!dgroivelbolrsandislandsakIOlllhemJrKimofIhema,n,lemrivel.Sitlechannelslreambl.'delevalionsarelypic.JllyIo..."rIhanIhemeanmonlhlyWoller~urfolceelevollionsofIhcmainslemSu~ilnaRiverob~rvcddunn!!lune,July,andAususl.SideeholnnelhJhilalSarecholrolcleriudbyshallo..."rd"Plhs,10lM!rvelocilies,andsmallerslreolmbedmJlerialsIhanIheadjacenlhah,I,.1ofIhemaimlemriver.1)SidrSluuShH.bitatlslocaledinspling·fedoverll'lwchannelsbetweentheedgeofIhef1oodploiinandthemainslelnandsidechannelsofIheSusilnaKiveranel.susual·lyseparaledfroIOIhemainslemandsidechannelshywell·~elletaledbol"Ancx·posedalluviJIbermont'nseparalesIheheadofIheslc,ughfrommailhlemorsidt'channelflows.TheconlrollinKSlre~mlJedlslre,lI11han~..k'v,lhon.allh,'ujI,lreilmendofIht'sidesloullh~areslillhllylessIholnIhew,'ll'rsurfJceelo:"dllt""ufIhemeolnmonlhlyRowsofIhemdinslemSu~ilnaKiwrob,en.-edforIWH',July,andAUlluSI.AlIheinlermedialeandlow-flowpl'nods,Ihl!sidesloullhsCO/l\cycll'alWollerfromsmalllribul.uie,and/orupwellinKllroundwaterIADfll.GI'JIII(,1r)82bl.Thl'~eclearw.lIerinRoW'Saree~senljollconlnbulors10rIll't'xi,h.'IKe0/11mhdllll,.tIypl'.Tht'walersurfolcel'IevolliulIofIheSU~llnaKlv,'rIll'"..rolilycau;es.1h.I,\..wal,'r10e.lendwellupinloIhesloughfromilslowerend(,\DF&G1':I8Ic.I'JlJibl,henIhoughthissubslolnliolllJackwoltelt'aisl",IheSIOUIlIIsfunclionhydrol"lol.lllyverymuchlikesmallslream.systemsand~verdlhunJ'('dfl"'1oflheSloullh[holnnelollenconveyswaterindependenlofmaimlernbJd"'Jlerelft'clS.Alhi.:hIluwsIhewalersurfaceelev.llionofIhenuinslemrillelissulficienlloovertopIhtuppert'ndofIhesloullhIAOF&G1981c,1982h),Surfacewall'!lemperdluresinIhesidesloUKhsduringsum",elmonthsareprincipallyafunch"nofairIl'mlleralure.solalracliollion,dndIhelemperalureofIheluealrunolf.4)Upl.ndSioullhHabit.lldiffersfromIhesidesloullhhabirJIinIhallheup,lreamendofIhesloughisnolinlerconn('CledwilhIhesurfolcewdlersofIhemain>ll'lnSusilnaRiverorilssidechannels.Theseslough,arecharaClerizedhyIheprl",cnct'ofbl.'oIverdamsandanaccumulJlionofsillcoverinllihesub,lIolleresultin!!fromlheabsenceof",ainslemscoulinllflows.5)TribuLiryHabit.tconsislsofthefullcomplemenlofhydraulicandmurphologiccondilion~IhaloccurinIheIribularies.Theirseasonalslreamilow,sedull"nl,andIhermallellimesrl.'Retllh~inll'Kralion(IfIhehydwlollY.lleoloKY,.lnd(I""dll'ollhl'trihuiolrydrolina!ll',Thl'physic..1allrihultSofIrihulolryhdl,lloIlarcnOId'·I,,·rul,·nl"nmalflslemcondilions.6)TributaryMoulhHabil.ltealendsfromIheuppermoSIpoinlinIheIrobuLlryin·f1uencedbymolinsll'olrnSusilnaRiverorslouKhbolckwalereitel'!,10IhedownslreamexlentofIhe,ribu'dryplumewhichcdenlhinloIheniJin,ll!f11Su,ilnaRiver01sloullh(ADF&G1981c,1982h).7)bkeH.bilatcunsiSlSofvariouslenticenvironl"'?n15thaiOCCUIwilhintheSu~ilnaRiverclrJinalle.These~oIbilJISlangefromsnlolll,shallow.IsoloiledIJkt'sp"rch,'fIonIhelundrJ10Idrller,dl'eperIolkeswhichconnecl10Ihl!main.I,'mSu>tlnJRivl!rthroUllhwcll·defint'dtrilJuI.Jrysyslems,Thelakl!sreceivetheirWollerfromsprinlls.SUrf.ICCrunoff,anJ/orIribularies.Figure2.GeneralhabitatcategoriesoftheSusltnaRiver.(AlaskaDept.ofFishandGame,SusltnaHydroAquaticStudies1983a). SIDESLOUGHS8.lSSIDECHANNELSSOCKEYEUPLANDSLOUGHSTRIBUTARIES'UPLANDSIDESIDESLOUGHSCHANNELSSLOUGHS41.341.7COHOTRIBUTARIES52.3~e.2o40105060...Z"'30o0:1&1A.2060RELATIVEABUNDANCE50OFJUVENILESALMON40...ZLIJ3000:LIJQ.20SIDESLOUGHSSIDECHANNELSCHINOOKUPLANDSLOUGHS1)(____X)....~_0y'c:t",...s'~)RelativeabundanceanddistributionofjuvenilesalmonwithindifferenthabitattypesofthemiddleSusltnaRiver.(Schmidtetal.1984).CHUM'TRIBUTARIES'UPLANDSIDESIDESLOUGHSCHA~NELSSLOUGHSTRIBUTARIES1-III.--84.4I17.'I.......2.94.9J...,-II,-.-I-i..I89.el--I,_6.!521.7I.......I"12.2oFigure3.60105040o4060/050...Z"'30o0:LIJQ.20...Z"'30o0:~20I\JII The purpose of this preliminary draft report Is to provide a framework for evaluating chinook rearing In the middle Susltna River under with-project conditions when further data become available and appropriate analyses are ,~completed:,At present,this report contains an overview of juvenJle ~,.;I ':/..1_K 'Q:!"""'" chlnOOkA;tudle~to date,a comparatIve evaluatIon of the sIgnIfIcance of the prIncIpal envIronmental factors InfluencIng the rearIng of juvenIle chinook,and an extensive literature revIew.A subjective assessment has been made of how these factors may be al tered under wIth-project conditIons,and the lIkely consequences for juvenIle chinook.A future draft of this report wll I Include the fol lowIng analyses presently underway by EWT&A. (a)Modeling of streamflow varIabIlIty under with-project conditions and the potentIal effect on the quantity of suitable rearIng habitat• ."'.~"'p"i '.'i.,t ..~)T""',,,".,¥'~,I",.. (b)Weighted Usable Area (WUA)forecastsAfor juvenl Ie chinook habitat as related to malnstem discharge. rear Ing I ~",,- ". (c)An euphotic zone model assessing the effects of reduced turbidity on light penetratIon and the ImplicatIon for primary and secondary productIvity levels. (d)ExtrapolatIon of WUA forecasts for juvenl Ie chinook to the entire mIddle Susltna RIver. ~~A number of reports prepared by the Alaska Department of Fish and Game )(ADF&G)are Important to this analysis,Including the 1984 resident /juvenlle anadromous fIsh study,the 1984 food avatlabliity study,and the 1984/85 overwinterIng study. -6- -------------_._.... / / 2.OVERV I EW OF CH I NOOK SALMON ESCAPEMENT AND SPAWN I NG OF THE SUS I TNA RIVER DRAINAGE The Susltna River affords a migrational corridor and spawning and juvenile rearing areas for chinook,coho,chum,sockeye,and pink (.Q..gorbuscha) salmon from Its mouth on Cook Inlet (RM 0)to Devil Canyon (RM 152).From 1981 to 1984,95 percent of the commercial monetary value In the Upper Cook I n let fishery was der I ved from sockeye,chum,and coho catches.Ch I nook salmon contribution In 1984 was 1.65 percent. Approximately 10 percent of the total commercial chinook catch In Upper Cook Inlet Is Susltna River drainage stock,representing an average annual contribution of 1,160 fish from 1964 to 1984.Catches have decreased markedly since 1964,due to the adoption of later opening dates by the commercial fishery,thereby allowing the majority of spawning chinook sa I mon to reach the I r nata I streams.The river basin supports a com paratl ve I y larger annua I ch I nook sa I mon sport catch,whI ch averaged 7,950 fish from 1978 to 1983.The sport catch has Increased from 2,830 fish In 1978 to 12,420 fish In 1983 (Barrett,Thompson,and Wick 1984). Chinook salmon enter the Susitna River In late May to early June.In 1983, the minimum total escapement was 125,600 fish.Subdrainage escapement and <I w'",_ timing for 1983 are given In Table 1,tn which estimate methods and thel~'r A)(-'/'\r . associated I imttatlons ~summariz~d by Jennings (984).Approxlmatqly.--J 80 percent of the ch I nook sal mon were estl mated to have returned to the 'f:\:;::'c r C;.,+..~~Jc 'R rr,15'() Yentna .yb-ba&I~.Spawners In the middle river (Talkeetna-to-Devll Canyon reach)account for a small percentage of_the remaining escapement.In 1983 ---...:.-..._-:-,~-"......_-....-......-.'-' th Js percentage •as t'or 3,800 f ISh.~:maj or Ity of the spa.n Jn9 above ()~"C1 t",,"-7-~>Y3 \S 1""1 dt-,:;.,",Ie ......\e....";;..•."..1 '''/- --_.._--------_.___. Sub-Basin Lower Susltna River (RM 0 to 80),excluding Yentna River (RM 28) Yentna River (RM 28) Talkeetna (RM 97.1)and Chulitna (RM 98.6)rivers, Including Susitna River from RM 80 to 98.6 Talkeetna Station to Devil Canyon (RM 98.6 to 152) Total Susltna basin Numbers 56,300 44,700 16,100 (62,000) 8,500 (9,500) 125,600 TI mIng Mid June to mid July third week In June to third week In July Minimum estimates of escapement from ADF&G 1983 survey counts and conver- sion factor of 52 percent (Nielson and Geen 1981);numbers In parenthesis are 1982-83 average of ADF&G escapement estimates. Table 1.Susltna River annual chinook salmon escapement and timing for 1983 by sub-basin.(Adapted from Jennings 1984). -8- 1981a,1982;Barrett, ...U;,'\(~,t'l "'r i {J'y -rf\/., . .{,'_'(I:ii-l b::·".,l''.'c", RM 80 occurs Inthe larger·trlbutarf~,notably the Talkeetna and Chulitna \.....~.t.~III r;.'....!c.\''''.,\'I! rlver~In the past three years,an average of 34 chinook salmon have V\-t"'-- overcome the high velocities and spawned In tributaries abovenDevl1 Canyon. /l.et Jl".,))1,.I . t/ In the middle Susltna River,chinook salmon spawn only In tributary stream habitat.Portage Creek and Indian River account for over 90 percent of the spawners (Barrett,Thompson,and Wick 1984).Trlhey (1983)examined the hydraulic conditions In the mouths of these two tributaries and concluded that passage of spawning fish Is not likely to be Impaired at low malnstem discharges.Peak spawner survey counts In the tributary streams Indicate an average annual Increase of 87 percent between 1981 and 1984 <Table 2). i ( Spawning peakS--fel ~between July 24 and August 8 In each year (JU.aska Dept. "'-)--.....6 of EI sb and Bam-e,·,Sus 11'·na·~Hy-dre·~a.:t~Stu.d l,as T~k 1984).\,,~ The majority of chinook spawners aged 5 and 6 had migrated to sea In their second year of I I fee The n umber of eggs per fema Ie spaw ner has not been estimated for chinook salmon,but Beauchamp,Sneperd,and Pauley (1983)put fAil <.CJ{t!;~ the typical range as 3,000 to 6,000.No Information Is available on egg- to-fry survival,but Jennings (1984)summarized the factors affecting Incubation and their application to the middle Susltna River. -9- ------,--_._..__•.._-_.__.._._-----_.--._--~....._.- 1981 1982 1983 1984 River Peak ,Peak ,Peak \Peak ,,l..verage Stream Mi 1e Count Oistri-Count Di stri'Count Oi stri-Count Distri-'\ 1/bution 1/but ion 1/bution 1/bution D;stribution Whiskers Creek 101.1+0 0 :3 0.1 67 0.9 0.6 Chase Creek 106.9 15 0.6 15 0.3 3 1<0.4 Lane Creek 113.6 40 3.6 47 1 .9 12 0.3 23 0.3 0.8 5th of July Cr.123.7 3 0.1 0 0 17 0.2 0.2 5herman Creek 130.8 3 0.1 0 0 0 0 1< 4th of July Cr.131.1 56 2.3 6 0.1 92 1 .3 1.3 Cold Creek 136.7 21 0.9 23 0.5 23 0.3 0.6 Indian River 138.6 1+22 37.6 1,053 42.6 1 ,193 26.9 1,456 20.3 26.8 Jack Long Creek 144.5 2 0.1 6 0.1 7 0.1 O., Portage Creek 148.9 659 58.8 1,253 50.7 3,11+0 70.9 5;446 75.9 68.3 ." Cheechako Creek 152.5 16 0.7 25 0.6 29 0.4 0.6 Chinook Creek 156.8 5 0.2 8 0.2 , 5 0.2 0.2 Oevi 1 Creek 161.0 0 0 *0 0 * Fog Creek 176.1 0 0 0 0 2 ...* TOTALS~/1,121 .100.0\2,474 \00.2\4,432 100.0\7,180 99.9\99.9\ 1/Peak count includes live plus dead fish. 2/Percent distribution totals may not equal 100 due to rounding errors. *Trace Table 2.Peak surv~y counts and percent distribution of chinook salmon In streams above RM 98.6 In 1981-84.(Alaska Dept.of Fish and Game~ Susltna Hydro Aquatic Studies 1985). -10- ----------------~_----------- 3.DISTRIBUTION OF REARING JUVENILE CHINOOK SALMON IN THE MIDDLE RIVER As part of the Susltna Hydroelectric Aquatic Studies program.the juvenile anadromous habitat study was carried out by ADF&G.In 1981 and 1982 the focus was primarily on determining the relative abundance of each species and the types of habitat associated with rearing (Alaska Dept.of Fish and Game.Susltna Hydro Aquatic Studies 1983a).This general distribution data was then used In 1983 and 1984 to select specific sites for more detailed Investigations regarding the sultabl I Ity of selected habitat areas for juvenile chinook salmon.and for measuring rearing habitat response to changes In malnstem discharge. Young chinook salmon generally go to sea during their first year.normally after a few months of feeding In the river (Ricker 1972;Lister and Walker 1966).However.studies of juvenile chinook In Alaska rivers Indicate that migration mainly occurs after one winter In freshwater (Burger et al.1983; Kissner 1976;Meehan and Sniff 1962;Waite 1979).This Is principally the situation for juvenile chinook In the Talkeetna-to-Devll Canyon sub-basin of the Susltna River (Alaska Dept.of Fish and Game.Susltna Hydro Aquatic Studies 1981b;Dugan.Sterr Itt.and Stratton 1984). Juvenile chinook salmon In the Susltna River emerge from the gravel In March or April (Alaska Dept.of Fish and Game.Susltna Hydro Aquatic Studies 1983).Chinook fry spend up to two months fol lowing emergence In the vicinity of their natal areas.after which they may redistribute and frequently display a downstream migration (Burger et al.1983;Delaney.. Hepler.and Roth 1981;Miller 1970;Waite 1979).Throughout their operation In 1983 from mid May to the end of August.outmlgrant traps at RM -11- ,----------,---'"'",. 103 captured young of the year (0+)chinook,with a major peak In the mJddle of August.This peak may have been related to a discharge of 32,000 cubic feet per second (cfs)measured at Gold Creek on August 10 (Roth,.',.; Gray,and Schmidt 1984).Some chinook populations have been reported to slowly migrate downstream feedJng,rather than I IvJng,ltn dJstlnct reaches ~ of the river for extended periods of tJme (Beauchamp,Sneperd,and Pauley 1983)• channels (Dugan,Sterr Jtt,and Stratton 1984). RedlstrJbutlon of chinook fry In the mJddle Susltna River results In ~:J -\-if ( sloughs,and upland sloughs / _/ In the;$JdeHighestdensitiesaretypJcalIyfound Jncreased utll Jzatlon of sJde channels,side ) \,.:- ii' SJde sloughs become more J.~(~vc.'". Important as rearJng areas In September and October.TrJbutarJes become i-Iic from July onwards. less significant after November as low wJnter flows and Icing occur.The malnstem,sJde channels,side sloughs,and trIbutaries are used by juvenJle chinook as overwintering areas (Alaska Dept.of Fish and Game,Susltna Hydro Aquatic Studies 198'lb;Dugan,Sterr Itt,and Stratton 1984).Ri Is and Friese (1978)concluded that Juvenile chinook overwinter mainly In side channel s,as opposed to s I de sloughs,but thel r resu I ts were based on a smal I sample size and thus are probably Inaccurate. Population estimates of rearing Juvenile chinook by conventional methods have not been undertaken In the mJddle Susltna River.Indices of fish densJty In four macrohabltat types (side channels,side sloughs,upland sloughs,and tributaries)were obtained In 1983 using backpack electro- fishing units and beach seines to collect fish.Results,expressed as -12- catch per unit effort (CPUE)and defined as the number of fish per 300 square foot cell (6 feet (ft)wide by 50 ft long),are summarized In Figure 4. Highest densities of 0+juvenile chinook salmon were recorded In the tributaries from May through early August,attaining 24 fish per cel I,or 0.88 fish per square meter (m 2 ).Converse I y,averages of less th an one fish per cel I were found In some side and upland sloughs In May.Chinook fry (0+)densities Increased at malnstem associated macrohabltats In late July following redistribution from the tributaries.A comparison of side slough and side channel densities for 1983 Is given In Figure 5.The highest values of juvenile chinook salmon mean catch occurred In the side channels during August,with close to six fish per cell (0.2 flsh/m 2 ). Side slough densitIes In September and October may reach five times the values for earlier In the year.Typical chinook fry densities from a number of other studies are given In Table 3. Age 0+ 0+ 0+ FI sh/Area (no/lTJ2) 0.59 -1.35 0.44 -1.60 1.90 Region Idaho Idaho Idaho Reference Bjornn (1978) Sekullch and Bjornn (1977) Bjornn et al.(1974) Table 3.Typical juvenile chinook densities from other studies. -13- MainatemII9.3%OxbowOneEillhtSites\/8.2%Combined4.0%S10Ullh22WhiskersCreekS10UllhSideChannelOxbowOne10.7%----SideChannel10J17.9%TwelveSiteaCombinedSloullh9SIDECHANNELS6.7~UPLANDSLOUGHSCOM81NEDMACROHA81TATTYPESSIDESLOUGHS~FiveTributariesCombined10.4%TRIBUTARIESI-~IFigure4.DensitydistributionofJuvenilechinooksalmonbymacrohabltattypeontheSusltnaRiverbetweentheChulitnaRiverconfluenceandDevilCanyon,MaythroughNovember1983.Percentagesarebasedonmeancatchpercell.(Dugan,Sterrltt,andStratton1984). -l -l l.Ll U cr l.Lla. :I:o.... ~o z ~ l.Ll :l: 5.0 4.0 3.0 2.0 1.0 ~~~B(liA\O~~~CITIONS f?&l ~~OB~T~H/~~~~1T10NS *NO (!'!'ORT .·CHINOOK CATCH ...17:3, .., Figure 5.Juvenile chfnook salmon mean catch per cell at sfde sloughs and sfde channels by sampl fng period,May through November 1983. <Dugan,Sterr ftt,and Stratton 1984). -15- ----------------_._----- Average tota I I engths of 0+ch I nook for I nd I an River and ma I nstem associated habitats during 1984 are given In Table 4.No weight analyses are presently available to compare condition of juvenile chinook from d If ferent hab I tats. SI de Channel sl Time of Year Indian River Side Sloughs Late May 38 mm 41 mm July 1st -15th 49 mm 48 mm July 16th -31st 55 mm 52 mm August 1st -15th 59 mm 52 mm August 16th -31st 61 mm 56 mm Early September 64 mm 58 mm October 1st -15th 65.5 mm 61 mm Tab Ie 4.Average total Iengths of 0+ch Inook sal mon In mIIII meters (mm) during 1984 In the middle Susltna River.(Roth and Stratton In press)• Outmlgratlon of the 1+chinook smolts from the Talkeetna-to-Devll Canyon sub-basin occurs principally In May and June and Is completed by September. Average smolt length for 1981 and 1982 was 90 mm (Roth,Gray,and Schmidt 1984).Rising water temperatures may stimulate smolt outmlgratlon (Sano 1966).The critical temperature Influencing this movement for chinook appears to be 7 degrees centigrade (OC).When temperatures fal I below this value,outmlgratlon has been shown In other studies to slow or cease (Cederholm and Scarlet 1982;Raymond 1979).Photoperiod,discharge, magnetic fields,and lunar phases are also thought to Influence smolt -16- ---------_.----~._------_...._.-_..._._._--------------- ",I"L h {-I i CAl - migration (Godin 1980;Groot 1982).In l:;bn~rs of outmlgratlng chinook smolt from the\mlddle Susltna River wereA~lgnlflcantlycorrelated \ with malnstem dlscharge~(r2 =O~)(Roth,Gray,and Schmidt 1984). ,/9 -17- ----------,-~.'--'-'--- 4.FACTORS THAT INFLUENCE JUVENILE REARING CHINOOK SALMON IN THE MIDDLE SUSITNA RIVER 4.1 Introduction Stream habitat parameters have a significant influence on al I stages of the salmonld I ife cycle,Including upstream migration of adults,spawning, incubation of eggs and the rearing of Juvenile fish.Habitat requirements of juvenile anadromous fish in streams vary with species,age and time of year.For those species,like chinook,which spend an extended time rearing In freshwater,habitat quantity and quality determine the number of fish that survive to smoltlflcation;and hence,the productive capacity of the system. Figure 6 Is a conceptual flow chart of the factors likely to Influence the production of rearing juvenile chinook salmon In the middle Susltna River. Many of the factors are Interrelated,but nine of them are highlighted for discussion.These factors and their Interrelationships wil I be examined In regard to their effect on rearing chinook under preproject conditions. Section 5 examines how the with-project scenario may alter the significant factors and the possible imDI Icatlons for rearing chinook. 4.2 Flow Regime Streamflow is a major determinant of Juvenile rearing habitat for salmonlds (Reiser and Bjornn 1979),and Its effect Is manifested through a number of factors (Figure 6).Streamflow and longitudinal channel profile determine the extent of riffles,runs and pools In a section of stream.Bjornn et -18- ----------------"._..""---_~-------" SUBSTRATE Size and Extent of Glacial Fines in Interstitial Spaces SUSPENDED SEDIMENT TURBIDITY PRIMARY PRODUCTIVITY I INCIDENT LIGHT/DEPTH WATER DEPTH COVER RIPARIAN VEGETATION BENTHIC INVERTEBRATES / FOOD AVAILABILI' t TERRESTRIAL INVERTEBRATES \ DRIFT------ Figure 6.Conceptual flow diag:-am of the facters Influencing chinook selmer:re~ in the middle $usitna River. FLOW REGIME VELOCITY REARING JUVENILE CHINOOK SALMON WATER TEMPERATURE UPWELLING OVERWINTERING SURVIVAL ICE PROCESSES ·Y ring SPACE REQUIREMENTS INTERSPECIFIC & INTRASPECIFIC COMPETITION PREDATION al.(1974)showed that a reduction In stream pool area resulted In a loss of juvenile salmonld rearing capacity,and Thompson (1972),In developing streamflow optima for rearing habitat,recommended a 1:1 pool to riffle ratio.Dtv-e-rsi-<Fy-~-sTreamflowls Important to juvenile salmonl,.Q.s.. Juvenile chinook salmon are typically associated with pools along the margins of riffles or current eddies (Kissner 1976;Platts and Partridge 1978).Streamflow Is described and quantified by discharge and current velocity. 4.3 Discharge/Velocity In a study of chinook salmon In the Kenai River,Alaska,young of the year (0+)fish under 50 mm were typically found In velocities below 0.6 feet per second (ft/sec)(Burger et al.1983).Larger fish,In the range 50 to 100 mm,selected velocities under 1.1 ft/sec.Underwater observations showed that the optimum velocity was 0.3 ft/sec for the 55 to 95 mm length (Figure 7).Juvenile chinook were not observed In velocities exceeding 2.20 ft/sec.Velocity preferences of juvenile chinook from several studies are given In Table 5.The relationship between velocity and juvenile fish distribution depends on fish size,for as they become larger,they are able to move Into faster deeper water. ~'~~. ~I', I' Age Depth (ft)Velocity (ft/sec)Reference 0+0.5 -1.0 <0.5 Everest and Chapman (1972 ) 0+<2.0 0.3 Stuehrenberg (1975) 0+1.0 -4.0 0.2 -0.75 Thompson (1972) Table 5.Depth and velocity preferences for juvenIle chinook from other studies. -20- ------------~'-------" wen :J u.o >I- :::i iii ~oa:c.. 1.0 .8 .6 .4 .2 Number of fish examined (N)=163 Length range =55-85 mm o N ~~=~N ~~~~N ~~~0o000~~~~~N N N N N M WATER VELOCITY (f.p.s.) Figure 7.FacIng-water velocIty and probabIlity of use for Juvenile chInook compiled from underwater observations In the Kenai River,miles 18-36,during 1981.(Burger et al.1983). -21- Suchanek et al.(1984)report that In the mIddle Susltna RIver,lower ve I oc I tIes and sh aI lower depths are preferred by Juven II e ch I nook under turbId condItIons as compared to clear water.The greatest number of chInook per cell were captured at velocItIes between 0.1 and 0.3 ft/sec In turbId water greater than 30 NephelometrIc TurbidIty UnIts (NTU)and 0.4 to 0.6 ft/sec In low turb IdI ty waters I ess than 30 NTt,l./No adjustments for ......._.,~/ gear effIcIency dIfferences were made In calculatIng the mean number of chInook per cel I,as beach seInes were used to capture fIsh In turbid water,whIle In clear water electroflshlng was employed.Lorenz (1984) ? ( \ found that In small Alaskan streams,a hand held seIne had a hIgher catch ,-_..•-..._-------.---' efficIency per unIt effort than an electoshocker.The preference for lower velocIties may be due to fewer velocIty breaks from substrate beIng available In turbid side channels than are In clear water channels (Suchanek et al.1984) DIscharge In the Susltna River varies markedly with the time of year. /...I As Is typical of unregulated northern glac~rivers,the Susltna River has*"-"-4,) high turbId wate~durtng the summer and low clearwater flow during the winter.Changes In surface area of the major habitat types occur In response to malnstem dIscharge varIations (refer to Figure 9).A summary of mean,mInImum and maximum monthly dIscharges for the Gold Creek gaging station show 5 an annual mean of 9,650 cfs (Table 6).Average monthly dIscharges for June,July and August are approxImately two and one hal f tImes the annual mean.MId-channel vqlocltles are frequently In the range of 7 to 9~ft/sec.Clearly the malnstem Is unsuitable for chinook rearing during these months,although the fIsh use the margins for redIstributIon from the tributaries.Side channel flows typically mirror the maJnstem, and the amount of suitable rearing habitat with acceptable velocities for -22- juvenile chinook depends upon the channel geometry of the side channel and the proximal malnstem. Monthly Flow (cfs) Month Maximum Mean Minimum January 2,452 1,542 724 February 2,028 1,320 723 March 1,900 1,177 713 Apr II 2,650 1,436 745 May 21 ,890 13,420 3,745 June 50,580 27,520 15,500 July 34,400 24,310 16,100 August 37,870 21,905 8,879 September 21,240 13,340 5,093 October 8,212 5,907 3,124 November 4,192 2,605 1,215 December 3,264 1,844 866 Average 15,900 9,651 4,785 Table 6.Summary of monthly streamflow statistics for the Susltna River at Gold Creek.(Harza-Ebasco Susltna Joint Venture 1985b). At most ranges of discharge,those s I de channe I s that have a broad relatively flat bottom and a gradually sloping shoreline profile possess a greater degree of marginal area with more suitable velocities than channels with a relatively narrow and Incised cross section geometry.In addition, a reach of the malnstem that Is constricted wll I have a steeper stage/discharge relationship than one less confined.In such areas there Is an Increase In responsiveness of site flows In adjacent sIde channels to Incremental changes In malnstem discharge. -23- ~._-_._------------- Malnstem discharges during late July and August,when the highest densities of juvenile chinook are In the side channels,average 23,100 cfs.Flows are relatively stable,with occasional sudden Increases as the basin responds to the highly variable,and sometimes erratic,precipitation patterns.In August single day flood peaks have reached 60,000 cfs at the i Gold Creek gage.Extremes of flow are recognized to limit juvenile ~I_~..Y' ,~."v••"- production (Havey and Davis 1970;Smoker 1953).Spates may Induce the downstream displacement of Juvenile chinook or force them to seek refuge In pools,which may subsequently dewater on lowering discharges. I) Side sloughs are principally dependent on local surface runoff and groundwater upwelling and possess velocities typically less than 1 ft/sec.y~,(,t,'e! They are characterized by a series of clearwater pools connected by short /, l shallow riffles.Side slough velocities typically fall wIth malnst~!n/ dI sch arge reduct I on as the rate of upwe I I I ng becomes red uced.~-Because there are differences In the elevation of the head berms relative to the malnstem,the flows at which sloughs become overtopped varies considerably, aI though genera I IY I tis between 20,000 to 30,000 cfs.Some sloughs are only overtopped at high discharge levels.At these overtopping flows,the side sloughs convey turbid malnstem water and velocities Increase. Downstream displacement of rearing juvenile chinook may occur,but probably ~"r I IA.,r,-,I'"(,;~!II U.{i ','/"on Iy to a small extent.~J>.,/,i 'J!!,'"\rr C<.~;,-ZJ,J!•I.' i ~jCfe·....-.•.'.j'.<-, > Tributary flows are Independent of variations In malnstem discharges but may display sIgnificant fluctuations.Peaks typically occur In June fol lowing snowmelt and may be a factor In promoting redistribution of the juvenile chinook to other areas.Velocities In Indian River and Portage Creek can reach 3 to 4 ft/sec at these times.Velocities In tributary (:::--.,",r'"i,..,(-I- '"""r:..-4!'_' -24- mouths are typrcally margrnal for rearrng Juvenrle chrnook.Although the least favored by chinook of the possible rearrng areas,upland sloughs have surtable velocrtes and are only slrghtly affected by rncreases In malnstem drscharge. From November through Aprrl,low air temperatures cause surface water In the basrn to freeze and streamflow becomes markedly reduced.Groundwater rnflow and baseflow from headwater lakes marntarn malnstem streamflow.The slgnrfrcance of these low flows and the rnfluence of upwel Irng on the overwrnterrng survrval of Juvenrlechrnook will be discussed further rn Section 4.10. 4.4 Water Depth Water depth rs determrned by streamflow,channel form,and streambed materrals.Provldrng other factors are suitable,rearrng chrnook salmon use a wr de range of water depths.Burger et a I.(1983)observed j uven rIe ch r nook at depths rang I ng from 0.2 to 9.5 ft rn the Kena r Rrver,Alaska, whr Ie Everest and Chapman (1972)reported preferences for depths of 0.5 to 1.0 ft rn two I daho streams.Depth preferences from severa I stu d res are summarrzed rn Table 5.In the middle Susrtna Rrver,the greatest number of chrnook per cell were found at depths of 0.1 to 0.5 ft rn turbrd water and 1.1 to 1.5 ft In low turbrdrty waters (Suchanek et al.1984). Temporal depth fluctuatrons are usually most varrable wrthrn the side channels and trrbutarIes,whrle the sloughs,when rndependent of the marnstem,are generally more unrform.Typrcal depths found rn side -25- channels,side sloughs or tributaries are not considered to be a limiting factor for Juvenile chinook rearing in the middle Susitna River at the typical densities of fish presently found. 4.5 Cover Cover Is extremely Important to rearing anadromous salmonlds to avoid predation by other fish,birds,and terrestrial animals and to avoid unsuitable velocities.Predation can cause significant mortalities among rearing juveniles,particularly after emergence from the gravei (Ai len 1969).Cover requirements may vary diurnally,seasonally or by species and fish size (Reiser and BJornn 1979).Overhead cover can be In the form of overhanging riparian vegetation (Boussu 1954;Hartman 1965),turbulent or turbid water,large Instream organic debris,or undercut banks (Bjornn 1971;-Chapman and Bjornn 1969).SUbmerged cover Is prov I ded by cobb I es and boulders with s41table Interstitial spaces,logs and aquatic vegetation.Experiments have demonstrated that juvenile fish numbers Increase when art I tr c IaI cover Is added to a stream (Bustard and Narver 1975).In the middle Susltna River,Ice processes and flow variations are of such a nature that a well-developed riparian vegetation zone has generally not been able to become established along the edge of most slrle channels and side sloughs.Without the promotion of bank stabilization by the root I ng of herbaceous and woody vegetation,undercut banks have been unable to form.Large organic debris Is rare in side channels and is found only to a minor degree In side sloughs.Hence,riparian vegetation, undercut banks and I arge organ Ic debr Is are not forms of cover typ I ca I IY available for juvenile chinook In these habitats.These types of cover are -26- more prevalent In upland sloughs,although these areas contain relatively few juven II e ch Inook. Cover for juvenile chinook In the middle Susltna River Is more typically provided by suitably sized substrate and turbid water.Field observations and catch data from ADF&G Indicate that juvenile chinook salmon abundance differs In turbid water compared to clear water.Catch rates at turbidities greater than 30 NTU were significantly higher (p =<0.001) than at turbidities less than 30 NTU In cells without any type of object cover.Thus,In the absence of object cover,turbid water Is used for cover by rearing chinook salmon (Suchanek et al.1984).The utilization of turbidity as cover appears to be most prevalent during July and August, following redistribution from the tributaries.When a turbid side channel becomes non-breached and transforms to a clearwater slough,the number of juvenile chinook per cell typically decreases (Suchanek et al.1984).Some >?,- juvenile chinook In turbid pool habitat will ·school If the water clears and ---••'-<•__.~•.••-~ move up to riff I es near the upstream end of the site where they seek out object cover.Middle Susltna River turbidity levels at Gold Creek range from 1 to 1,000 NTU,with an average summer turb I dty of 200 NTU (E.Woody Trlhey and Associates and Woodward-Clyde Consultants 1985). The newly emergent fry In the tributaries are probably the most susceptible to predation.Indian River and Portage Creek afford little cover In the form of riparian vegetatlo~,undercut banks,large organic debris,or turbid water.>In Indian River and Portage Creek,substrate composition and the percentage of fine materials present affect the amount of cover ava II ab J e to J uven)'Ie ch Inook.Large q uant I ties of s II t and sand depos i ted In a channel may fill Intersltlal spaces,preventing access between and -27- under the gravel and stones.The amount of fine sediments tends to be greatest In the sIde sloughs and Is related to their velocities and breaching flows.Overtopping of side sloughs durIng early summer may flush fine sediments from the side sloughs,but In some Instances large amounts of sand are transported Into the slough,particularly the lower section. In addition,the backwater effects at the downstream-juncture of the malnstem and side sloughs may Increase the amount of sediment present. Consequently,object cover from substrate may be extremely variable withIn and between side sloughs.However,the turbidity associated with the overtopp I ng f low s I ncr eases the amount of cover ava II ab Ie.I ncreases In numbers of Juvenile chinook In these cases may not be attributable solely to Juvenile chinook seeking out turbid water for cover.It may also be a f,h. function of access tOftlgratlng downstream.However,juvenile chinook freely move upstream Into these sites,In response to sal mon eggs from spawners,and seek overwintering habitat,so access may not be a problem If a suitable stimulus Is present.Due to their higher velocities,side channels usually possess less fine sediment than side sloughs.Filamentous algae,where It Is able to develop,may act as cover and Is discussed In the next section on food availability. 4.6 Food Availability Fish food production Is probably the most Important of the biotic factors affecting Juvenile chinook.Chapman (1966)suggests that the density of juvenile anadromous salmonlds may be regulated by food availability.Young salmon can feed both off the bottom and on drifting foods (Keenleyslde -28- 1962),but In streams,browsing on benthos may be rare and organisms are essentially derived from drift (Elliott 1973;Mundie 1971>. Published data on the food habits and feeding of young chinooks are fragmentary.Everest and Ch apman (1972)observed a strong pos i t I ve correlation between the size of juvenile chinook and water velocity at a given feeding station,and they postUlated that the movement of the fish Into faster water as they grew was related to the availability of Insect drift food.Burger et al.(1981)reported that juvenile chinook fed predominantly on chironomlds In the Kenai River,Alaska,but they did not differentiate which life stage.Becker (1970)and Dauble,Gray,and Page (1980),In studies of juvenile chinook feeding In the Hanford reach of the Columbia River,found that over 95 percent of the diet was aquatic Insects, of which chlronomlds were the principal component.Fifty-five to 65 percent of these chlronomlds were sub-adults and few pupae were taken (Becker 1970).Terrestrial Insects comprised only 4 percent numerically of the total food organisms.The majority of insects Ingested were drifting or swimming when captured.Loftus and Lenon (1977)obtained similar results In their study of chinook salmon In the Salcha River,southeast of Fal rbanks,AI aska. Rlls and Friese (1978),In a preliminary study of sal monld food habits In the Susltna River,concluded that adult terrestrial Insects made the greatest contr I but I on vo I umetr I ca I IY to the stomach contents of ch I n"'ok. However,their classification of adult terrestrial Insects included those with Immature aquatic stages and they did not separate out chlronomlds.In 1982 ADF&G conducted Investigations of food habits of juvenile chinook at five side sloughs and two clear water tributaries of the middle Susitna -29- River during August and September.At all sites,chlronomlds were numerically most Important with a variable ratio of larvae compared to adults.Terrestrial Insects numerically averaged less than 15 percent of the total stomach contents.Electlvlty Indices comparing abundance of prey Items In juvenile chinook diets to drift samples Indicated a preference for chlronomld larvae over chlronomld adults.Location of drift nets were not always proximal to areas where fish were caught,so drift samples may have been different from that to which the fish were exposed.No Juvenile chinook were examined from side channels (Alaska Dept.of Fish and Game, Susltna Hydro Aquatic Studies 1983a). Terrestrial Insects usually enter the drift by faIling or being blown off riparian vegetation or washed In from channel side areas Inundated by rapid flow fluctuations (Mundie 1969;Fisher and LaVoy 1972).The relatively low Importance of terrestrial Insects In the diet of juvenile chinook In the middle Susltna River Is probably related to ,low numbers In the drift,as the malnstem,side channels and side sloughs,In most Instances,lack a close border of riparian vegetation. Chlronomlds are the most ubiquitous of freshwater macrolnvertebrates and are successful In a wide range of environmental conditions.Brundln (1967) suggests that plelslomorph Chlronomldae were Initially cold adapted, thereby accounting for their success In the arctic at temperatures often close to the limit of life.The availability of food Items for macrolnvertebrates has been recognized as one of the major factors regulating their abundance and distribution In streams (Cummins 1975; Eggllshaw 1969;Hynes 1970).Filamentous algae or moss on a streambed -30- provides food sources for chlronomlds,If not directly,then In the microfauna and flora they support.Algal filaments are also Important to chlronomlds In providing support and protection from the current and abrasive sediments.WhItton (1970)and Milner (1983)reported on the strong association of chlronomlds and filamentous algae In flowing streams. It has been wIdely documented that suspended sediment reduces prImary production (Cordone and Kelly 1961;PhIl I Ips 1971;PhInney 1959)It plays a domInant role In the levels of primary productIvity of the middle Susltna River.Primary productIvIty rates or quantitative assessments of algal growth have not been measured,but EWT&A and the University of AI aska's Arctic Environmental Information and Data Center (AEIDC)are presently addressIng this question.The Information available to date Is from field observations.A winter-spring transition algal bloom may occur at open leads along the margins of the malnstem and side channels and In side sloughs (E.Woody Trlhey and Associates and Woodward-Clyde Consultants 1985).Observations by EWT&A In late winter/early spring of 1985 In open lead areas Indicated that active algal growth was most evident where upwe I I I ng or bank seepage occurred.The most typ I ca I grow th was dlatomacous In nature and chlronomlds were observed In association with the algae present.Some of the benthic production that occurs during the winter-spring transition may be dislodged and swept downstream during sprIng breakup,with the rapid Increase In streamflow (E.Woody Trlhey and Associates and Woodward-Clyde Consultants 1985).At prevailing springtime turbidities (50 to 100 NTU),the malnstem margin and side channels apparently continue to support a low to moderate level of primary production wherever velocity Is not limiting.Ward et al.(1980)report upon the scouring of algae from stone surfaces by suspended sedIment and -31- ------------_._. unfavorable velocities,and Cummins (1974)reported that Vannote and co- .2 workers had shown In experimental stream channels that flow perturbations v'J-...I.JY'\.- /limited the growth of filamentous algae.The euphotic zone at this time Is-- est I mated to extend to an average depth of between 1.2 and 3.5 feet (Van NIeuwenhuyse 1984). In summer,malnstem flows are at their highest levels.The total surface area available for primary production Is J Imlted by high turbidities that reduce the depth of useful light penetration to less than 0.5 feet (Van Nleuwenhuyse 1984).Conditions are more favorable In the side sloughs for algal growth (stabler flows and greater light penetration),unless they are breached.However,the amount of sediment on the channel bed Is also an Important factor Influencing the degree of algal growth and Is extremely varlable.wlthln and between side sloughs.Sediment deposition on the streambed may bury suitable sites for algal colonization and reduce the ab III ty of f II amentous forms to obtai n firm attachment. Field observations by EWT&A suggest that some of the sediment carried through sloughs becomes part of an organ Ic matr Ix of unknow n compos It Ion (probably bacteria,fungi and other microbes),which Is colonized by a layer of pennate diatoms and filamentous algae,and covers streambed material greater than two-three Inches.This type of growth was also observed In a number of rna I nstem and s I de channe I hab I tats.Phos phorus assoc Iated with the sea I ment may enhance th Is growth (E.Woody Tr I hey and Associates and Woodward-Clyde Consultants 1985). -32- During late September and early October,1984,extensive algal blooms were observed In the malnstem,side channels and side sloughs dominated by mats of green f II amentous al gae.Th Is b loom was I nduced part Iy by moderatl ng streamflows but principally by a notable reduction In turbidity levels to less than 20 NT~The depth of the euphotic zone at turbidities of 20 NTU .( approximates five feet (Van Nleuwenhuyse 1984).Some of this production Is dislodged and swept downstream or frozen In situ at freeze-up.This type of bloom may be a characteristic annual feature of the system (E.Woody Trlhey and Associates and Woodward-Clyde Consultants 1985). Macrolnvertebrate populations are also dependent on other factors In addition to their requirement for food.High flows can directly dislodge Immature Insects by scouring action (Hynes 1968;Martin 1976). Catastrophic drift of benthic organisms may result (Elliott 1967;Waters 1972),and the fauna can perish from mechanical Injury (Needham 1928)or by being carried out of the system.Rapid changes In flow can cause stranding of Insects (Brusven,MacPhee,and Blggam 1974),particularly when the stream banks are gently sloping.Such events may Infl let substantial losses on the benthic populations (Ulfstrand 1968;Ulfstrand,Nilsson,and Stergar 1974;Maltl and 1966). Accumulations of fine streambed sediments,as occurs In side channels and sloughs,are widely reported to reduce benthic Invertebrate abundance (Cordone and Kelly 1961;DeMarch 1976;Garmon 1970;Koski 1972;Wagner 1959).In general,species diversity and density decrease progressively from cobble through gravel,sand and silt (Pennak and Van Gerpen 1974). Sediments may restrict access to the undersurface of cobbles (Brusven and Prather 1974),leaving only exposed surfaces for colonization (Phillips -33- -----------_._.~-~...~- 1971>.The undersurface of cob bI es of fers protect I on from predators and displacement by the current for many benthic Invertebrates. Conseq uent I y,macro I nvertebrate abundance,part I cu I ar I y ch I ronom I d populations,Is likely to be considerably higher In tributaries that have more suitable substrate and less sediment.However,drift of chlronomlds and other food organisms Is probably greater In the side channels and tr I b utar I es than the s I de sloughs.Sloughs,when they become breached, wll I probably have Increased drift through them.Juvenile chinook typically feed on dr I ft by sight (M und Ie 1974).The ab II I ty of fish to detect food Items In the turbid water of the side channels Is less and may explain the preference of juvenile chinook for shal lower depths and lower velocities to enhance feed I ng on the dr I ft I n these areas.Juven II e ch I nook have been observed enter I ng clearwater slou'ghs to feed on sal mon eggs,I eav I ng the cover of turbid water If the food stimulus Is sufficiently strong. The greatest densities of juvenile chinook occur In their natal tributaries,Indian River and Portage Creek.Indian River Is also one of the principal coho rearing areas,and chironomids were the dominant food fY~F" numerically In juvenll e coho stomach samples (Dug;n:-Sterr~t-I':''C .~~-.•.".y".._''- 1984).Lister and Genoe (1970)found that the habitat requirements of co- habiting chinook and coho fry were similar during the first three months of stream life.Thus,competition for food organisms could come Into 'play In these tributaries.The physical environment of the middle Susltna RIver exercises I Imitations on the chinook population In malnstem associated habitats that prevent chinook from attaining a level where density dependent mechanisms operate.The quantity of drifting food Items Is -34- r', .\.r:l~j"~-' "I"')"j -J Ii''._...rr \"'~'''i ..i ,,~.-,"-If'to 1'" \cY ,}\l;f widely variable at different sites and at dlffe~:~t .:I(esA:,~f .,tl~~j growing L~"J;f '\ season.Tab Ie 4 shows that J uven II e ch Inook In 4r Ibutary"hab Itat"dIsp I ayed J ./ greater grow th,In terms of I ength,than fish from s I de sloughs and s I~ l·~--·----­channels,even under a colder temperature regime (Figure 8).-Hence,food availability In the side channels and side sloughs Is likely to be a limiting factor to growth and thus overal I survival. 4.7 Predation The role of cover to avoid predation has been discussed In Section 4.5. b''.i, Fish predators Include rainbow trout,rearing coho,resident dolly varden, ?. and scu I pins.Juven II e ch I nook are most suscept IbIe to predation In the- tributaries due to the presence of higher numbers of fish predators compared to those Ins I de channel s or s I de sloughs.Mortality from fish predation Is reduced for Juvenile chinook that migrate to the side channels and obtain cover from the turbid water.J When juvenile fish are In the / shallower turbid water or clear water of the sloughs and tributaries,they maya I so be taken by pi sc I vorous birds,notab Iy kI ngf Ishers,dip pers and mergan\sers.Mortality from predation,In comparison to other factors,Is relatively minimal. 4.8 Space Requirements Juvenile chinook salmon have space requirements that are probably related to the abundance of food (Chapman 1966).The I nterre Iat Ionsh Ip between cover,food abundance and mlcrohabltal preferences of rearing salmonlds are not clearly understood,and thus the spatial needs are not adequately defined (Reiser and Bjornn 1979).Space requirements vary with size and -35- i1514---SimulatedTributaryTemperature130Mean'81/'82TemperatureatRM15012++l1ean'81/'82TemperatureatRM110..1 1-I0++++0i!i0+0.......100+0+u0+0'-"0~0fil9~~~8-.-';"----+---~.-.-...0~~./"'-~....~7/'......~./...~f-l...I6/...VI"~/,I/"5/,,/,4-f~"3-II/'~'\I"I24',,~,.,1~\l5\HJ$°1\JUNEIJULYIAUGUSTISEPTEMBERIOCTOBERFigure8.ComparisonbetweenaverageweeklystreamtemperaturesfortheSusltnaRiverandItstributaries.(UnIversltyofAIaska,ArcticEnvironmentalInformationanaDataCenter1984a). tIme of year.Studies In CalifornIa by Burns (1971>showed significant correlatIons between living space and salmonld biomass.JuvenIle chinook densities In the side channels and side sloughs do not appear high enough for space requirements to become a significant factor.However,In the natal tributaries,Indian River and Portage Creek,space requirements may regulate densities of emergent chinook fry,particularly with the presence of emergent coh~These factors,In association with competition for food and the high snowmelt streamflow,may account for the migration of significant numbers of Juvenile chinook from the tributarIes.Downstream migration may also occur as a function of Innate behavior. 4.9 Temperature Malnstem water temperatures normally range from 0 0 C during the November- to-April period to 11 0 C or 12 0 C from late June to mid July.Water temperatures In side channels are similar to those of the malnstem.Unless overtopped,surface water temperatures In side sloughs are Independent of the malnstem.Unbreached sloughs receive nearly al I of their clear water flow from local runoff and groundwater Inflow and display greater diurnal temperature fluctuations than other fish habitats.During the winter, slough flow Is primarIly maIntained by upwel ling groundwater with stable temperatures around 3 0 C.The temperature of the upwel ling groundwater significantly Influences surface water temperatures In the slough,often maintaining th~above 00 C throughout most of the winter. Salmonlds are cold water fish with wei I-defined temperature requirements during rearing.Water temperature Influences growth rate,activity and the abilIty to capture and use food.Brett (1952)lists the preferred -37- _. temperature range for juvenile chinook to be 7.3 to 14.6 0 C and noted that chinook underyearl ings displayed increasing percentage weight gains as temperature was increased from 10.0 0 to 15.7 0 C.When tem peratures fe I I below the preferred minimum,growth rates became reduced.However, juvenile chinook of Susltna stock may be better adapted genetically to sustained growth at lower temperatures than fish from rivers In Oregon and Washington. The principal growth period Is from May to September when temperatures are probab I yin the opt I mum range.Tab Ie 4 I nd I cates that there was on Iy a small Increase In length for Juvenile chinook In the side channels and side sloughs from early September to mid-October,1984,suggesting that the fal I algal bloom does not seem to promote substantial chinook growth at that time.Kenai River chinook fry grew from an average total length of 43 mm In ear Iy May to an average of 71 mm by the end of October.Burger et a I. (1983)consider this rate to be fairly typical for chinook growth at the end of the summer growing season in Alaskan drainages. With the onset of freeze-up and colder water temperatures,minimal feeding and little growth occur.The maximum Is likely to be a few millimeters. The average length of outmlgratlng 1+smolt from the middle Susltna River was 90 mm In both 1981 and 1982.Assuming the 1985 value Is likely tobe similar,it Indicates that significant growth may occur in the spring before outmlgration,as the average length In mid-October was 65.5 mm. Condition and length of outmlgratlng smolt are Important factors In ocean surv Ivai. -38- The effect of temperature on I ce processes wI II be dIscussed further In SectIon 4.10 on overwInterIng survIval. 4.10 OverwInterIng SurvIval OverwInterIng survIval Is a sIgnIfIcant factor In the production of JuvenIle rearing salmonlds (Hynes 1970).Studies In the middle Susltna RIver to date have been mInimal and the habItat requIrements for overwInterIng chinook have not been clearly defined.A study was - undertaken In the wInter of 1984/85 by ADF&G to examine thIs subject. Numbers of juvenile chinook Increase In the sIde sloughs during September and October,as groundwater upwellIng or sal mon eggs from spawners may attract overwintering fIsh.Tributaries,malnstem and sIde channels are also known to be used by juvenl'le fIsh as overwintering areas.A comparison between measured surface water temperatures In side sloughs~w~:o f\Dt CO \.r(.,I.((..\'?'\~t",2. durIng the wInter and sImulated malnstem temperatures Is gIven In Table 7. UpwellIng In sIde sloughs and sIde channels may result In open leads throughout the winter. Juvenile chinook become relatively Inactive at low water temperatures.As drift of food organIsms Is reduced at the associated low flows,feedIng activIty Is mInimal.Cover Is therefore an Important factor,and when water temperatures fal I below 60 C,juvenile chInook ha\'e been observed to move closer to cover (Burger et al.1983).Due to the lack of glacier melt In wInter,juvenile chInook no longer obtain cover from turbid water,and substrate becomes Important as a velocIty break and resting habitat. Burger et a I.(1983)observed that the su bstrate plays a key ro I e I n the -39- ------------_._-,-"'" 198219821983LocationRMFebMarAprAugSepOctNovDecJanFebMarAprMaylSlough8AMouth125.46.52.41.7a a0.41.3Slough8AUpper126.45.84.42.53.8 3.3Slough9128.78.95.92.33.84.7Slough11135.72.53.13.33.12.9 2.92.92.93.03.56.0Slough21141.81.61.93.12.21.10.8I~0IMainstemLRX29126.10.0 0.02.910.96.50.60.0 0.00.00.0 0.03.0LRX53140.20.0 0.02.510.86.40.60.00.00.00.00.02.6Note:Mainstemtemperaturesaresimulatedwithoutanicecoverandwarmearlierinthespringthanwhatnaturallyoccurs.ThustheAprilmainstemtemperaturesareprobablywarmerthanwhatwouldoccur.Table7.COmparisonbetweenmeasuredsurfacewatertemperatures(oC)Insidesloughsandsimulatedaveragemonthlymalnstemtemperatures.(AlaskaDept.ofFishandGame,SusltnaHydroAquaticStudies1983b). overwintering strategy of Juvenile chinook In the Kenai River. -"'.... Bjornn (1971>also considers substrate to be essential for winter cover.' Consequently,the quantity of deposited fine sediment In the channels may be an Important factor In determining suitable overwintering habitat. Remnants of the fal I algal bloom may also act as cover,particularly where maintenance has been possible In the warmer water of the open leads. Associated Immature Insect stages could provide a food source for the Juvenile chinook.Predation pressure on juvenile chinook Is probably much reduced during the winter,and the major mortality arises from unsuitable phys I ca I cond I tl ons.I ce processes dom I nate the hydro log I ca I and - biological characteristics of the middle Susltna River from November to April.The most Important factors affecting freeze-up of the Susltna River are air and water temperature,Instream hydraulics and channel morphology. When side sloughs are occasionally ov.ertopped by malnstem water during staging at freeze-up,the relatively warmer water Is replaced by large volumes of 00 water and slush Ice.If the overtopped condition persists, the warming Influence of the upwelling Is diminished and the slough becomes a less favorable overwintering hablta~ The formation and characteristics of the common types of Ice found In the middle reach of the Susltna River are summarized In the Instream Flow Relationships Report,Volume 1 (E.Woody Trlhey and Associates and Woodward-Clyde Consultants 1985).Stream Insects are wei I adapted to cold conditions and may survive In egg or dlapause stages.They may also bury deeper Into the substrate where water temperatures may be above freezing. In open water areas,anchor Ice may have a d~~~lng effect and divert water ,._~..:>.~"'""'" out of established channels.Juvenile flshffove Into the diverted channels and,should the flow be diverted sUddenly back to Its original channel, -41- ------------_. fish may be stranded and die.Needham and Jones (1959)report that Ice dams were a major source of mortality In juvenile trout In Sierra Nevada streams.Anchor Ice can encase the substrate,making It useless as cover to fish.However,the major source of mortality during the winter Is believed to be dewatering and freezing.Side channels and side sloughs without significant groundwater upwel ling may freeze completely.In severe cases,this may Include the subsurface flow down to the water table. Tributaries like Indian River and Portage Creek are less likely to freeze completely and will have some flowing water. Another problem caused by Ice processes for Juvenile chinook occurs during spr I ng breakup.The durat Ion of the breakup per lod depends on the Intensity of solar radiation,air temperature,and precipitation. Tributaries have usually broken out In their lower elevations by late April,and open water exists at their confluences with the Susltna River. Increased flows from the tributaries erode the Susltna River Ice cover for considerable distances downstream from their confluences.As water levels In the river begin to rise and fluctuate with spring snowmelt and precipitation,the Ice cover erodes.Ice becomes undercut and col lapses Into the open leads,drifting to their downstream ends and accumulating In sma I I Ice Jams.In th Is way,Ieads become stead IIY wider and longer. Major Ice jams generally occur In shall.ow reaches of the malnstem,with a narrow confining thalweg channel along one bank,or at sharp river bends. Major jams are commonly found aOjacent to side channels or sloughs. Breakup Ice jams commonly cause rapid,local stage Increases that continue rising until either the jam releases or the adjacent sloughs or side channels become flooded.While the jam holds,flow and large amounts of -42- -----------_..- Ice are diverted Into side channels or sloughs,rapidly eroding away sections of riverbank and often pushing Ice wei I up Into the trees. Generally,the final destruction of the Ice cover occurs In early to mid May when a series of Ice jams break In succession,adding their mass and momentum to the next Jam downstream.This continues untl I the river Is swept clean of Ice except for stranded Ice floes along shore.These events have detrimental effects on the blot~A substantial amount of the spring aI ga I growth Is dis lodged and carr I ed dow nstream.Benth I c macro- Invertebrate and 1+chinook may become similarly displaced.Juvenile fish could be forced Into refuge channels,which become cut off from the main channels as flows change with Ice movements.It Is difficult to estimate the mortality that arises from spring breakup,and It Is probably highly variable from year to year. -43- 5.0 EVALUAT ION OF WI~PROJECT CONDITIONS 5.1 I ntroduct Ion This section of the report subjectively evaluates with-project effects on the abiotic and biotic factors outlined In Section 4 and discusses the possible Implications for Juvenile chinook sal mon In the middle Susltna River.Tributary habitat should not be significantly altered under with- project conditions,and the factors discussed In Section 4.0 relating to this habitat will probably remain relatively unchanged.Therefore, tributary habitats are not discussed In detail In Section 5.0. 5.2 Flow Regime In November 1984,the AI aska Power Author Ity subm Itted a report (Harza- Ebasco Susltna Joint Venture 1985a)to the Federal Energy Regulatory Commission evaluating alternative flow requirements to the flow regime specified In the original Susltna Hydroelectric Project License Application.In their evaluation,APA selected one alternative,Case E-VI, as the preferred alternative flow regime.The primary reasons to refine the earlier flow scenario were threefold. 1.The need to consider the use of malnstem and side channels for rearing fish In establishing flow requirements.This rational was not used In establishing Case C flow requirements In the license application. 2.The requirement for seasonal flow control over the entire year in order to maintain overal I aquatic habitat values. -44- --------------.. 3.The necessity to have maximum flow constraints. Case E-VI flows have been developed for four different reservoir operation scenarios.Scenarios A and B assume operation of the Watana Reservoir only,with electrical energy demand forecasts for 1996 and 2001,while Case C and D assumes both Watana and Dev II Canyon reservol rs In operation and energy demand forecasts for 2002 and 2020.This subjective evaluation wll I focus on Case D,as It represents the long term scenar 10 and the greatest change In flow regime from preproJect conditions. 5.3 Discharge/Velocity A controlled flow regime under with-project conditions will result In a decrease In average discharge during the summer and an Increase In the winter In the middle Susltna River.Between June 3 and September 1,flow constra I nts prov I de for a min I mum discharge of 9,000 cfs (Harza-Ebasco Susltna Joint Venture 1985a)(Table 8).These lower flows,as compared to natural conditions,w II I result In a reduction of side channel surface area.For example,a 50 percent reduction of malnstem discharge from 20,000 to 10,000 cfs will result In an approximate 28 percent reduction In side channel surface area (Figure 9).The minimum flow constraint of 9,000 cfs under Case E-VI was selected to maintain 75 percent of existing side channel rearing habitat for chinook salmon (Harza-Ebasco Susltna Joint Venture 1985a).Williams (1985)carried out a comparison between natural and with-proJect hydraulic conditions (Case E-VI-D)In four large side channels of the middle Susltna River for the open water rearing period (May 20 to September 15).The results showed that the surface area of side channels where suitable velocities would be avaIlable for juvenile chinook -45- -----------_._---- WaterGoldCreekFlow(cfs)WaterGoldCreekFlow(cfs)WeekPeriodMinimumMaximumWeekPeriodMinimumMaximum---1431Dec.-06Jan.2,00016,0004001July-07July9,000*35,0001507Jan.-13Jan.2,00016,0004108July-14July9,000*35,0001614Jan.-20Jan.2,00016,0004215July-21July9,000*35,0001721Jan.-27Jan.2,00016,0004322July-28July9,000*35,0001828Jan.-03Feb.2,00016,0004429July-04Aug.9,000*35,0001904Feb.-10Feb.2,00016,0004505Aug.-11Aug.9,000*35,0002011Feb.-17Feb.2,00016,0004612Aug.-18Aug.9,000*35,0002118Feb.-24Feb.2,00016,0004719Aug.-25Aug.9,000*35,0002225Feb.-03Mar.2,00016,0004826Aug.-01Sep.9,000*',35,0002304Mar.-10Mar.2,00016,0004902Sep.-08Sep.-8,00035,0002411Mar.-17Mar.2,00016,0005009Sep.-15Sep.7,00035,000I2518Mar.-24Mar.2,00016,0005116Sep.-22Sep.6,00035,000".,2625Mar.-31Mar.2,00016,0005223Sep.-30.Sep.6,00035,00001I2701Apr.-07Apr.2,00016,000101Oct.-07Oct.6,00018,0002808Apr.-14Apr.2,00016,000208Oct.-14Oct.6,00017,0002915Apr.-21Apr.2,00016,000315Oct.-21Oct.5,00016,0003022Apr.-28Apr.2,00016,000422Oct.-28Oct.4,00016,0003129Apr.-05May2,00016,000529Oct.-04Nov.3,00016,0003206May-12May4,00016,000605Nov.-11Nov.3,00016,0003313May-19May6,00016,000712Nov.-18Nov.3,00016,0003420May-26May6,00016,000819Nov.-25Nov.3,00016,0003527May-02June6,00016,000926Nov.-02Dec.3,00016,0003603June-09June9,000*35,0001003Dec.-09Dec.2,00016,0003710June-16June9,000*35,0001110Dec.-16Dec.2,00016,0003817June-23June9,000*35,0001217Dec.-23Dec.2,00016,0003924June-30June9,000*35,0001324Dec.-30Dec.2,00016,000,*Minimumsummerflowsare9,000cfsexceptindryyearswhentheminimumwillbe8,000cfs.Adryyearisdefinedbytheone-in-tenyearlowflow.Table8.SusltnahydroelectricprojectflowconstraintsforenvironmentalflowrequirementCaseE-VI.(Harza-EbascoSusltnaJointVenture1985a). 2500 MAINSTEM 100 EXPOSED GRAVEL BARS SIDE CHANNEL__------0---=---.....:::::::::::::::=-----4'50 2000 ....--- 1500 1000 500 400 -i 0 300 --Dlen Cl:10 0.... U to~200 -- t':l N OJ ltl....0. <!(f) ell 5 cu.., cc c:i'-....() :l i1l (f)~ CI:l .., i1l.-Pol050l-- 40 :l '"- 30 TRIBUTARY MOUTH UPLAND SLOUGH 20 0.5 10 TRIBUTARY '------'_..-----!-_----'-_----'-_--l.-__----'-_.........._--'-_....L.-_....I..-_.l...-_.l...---l O.1 16 17 18 19 20 21 22 239101112 13 14 Mainstem Discharge at Gold Creek (xl0 3 ,cfs) Figure 9.Surface area responses to malnstem discharge In the Talkeetna-to- Devil Canyon reach of the Susltna River (RM 101 to 149).(Klinger and Tr Ihey 1984). -47- would In fact be larger and more persistent under wIth-project condItions. ThIs Is partIcularly evIdent In side channels wIth a broad relatIvely flat bottomed profile.SimIlarly,a reductIon In malnstem flow from 20,000 cfs to 10,000 cfs would cause an approxImate 138 percent Increase In side slough surface area.The side sloughs wll I become more Independent of the malnstem,as overtoppIng of the head berms wll I be less frequent. WIth-project conditions under a base load supply wIll provIde for dIscharge and velocity levels wIth greater stabIlIty and less fluctuations throughout the growing season of juvenile chInook.Flow varIatIons from year to year wIthin this period wll I also be less.Although the simulated 34-year record (1950-1983)IndIcates that hIgh flow events wIll reach 37,000 cfs, the frequency of these events dur Ing the grow Ing season wI I I be marked I y less,particularly In June and July (Figure 10).These flows wIll generally reduce the downstream displacement of juvenile chinook from the middle Susltna River and the mortality that can result If fish seek out refuge In Iateral pool s. 5.4 Water Depth In SectIon 4.3 water depth was considered unlikely to be a lImiting factor In juvenile chinook rearing In the mIddle Susltna River.The greater stab I I Ity of discharges under wIth-project conditions wll I result In less temporal depth varIatIons,particularly In the sIde ch~nnels. -48- ~-­.............---N=NATURALFLOWo=WITHPROJECTCASE0FLOW'-._.-.........../................-............-.--',/--.--,t----____,.--/",,......,........,"""','............/-----------"'"',','"','"O"IN)"""""-............."...............'""°50(0)- 'j.'--'---Ogo(O)--r'Ogo(N)/'40,00030,000en-CJUJCJ20,0000:Ict~:I:\00IenC10,000oNote:MAYJUNEJULYAUGUSTSEPTEMBEROCTOBERQl0Isthetypicalhighflow~Q50Isthetypicalmedianflow,andQ90Isthetypicallowflow.Figure10.Co~parlsonofthemiddleSusltnaRivernaturalandwith-proJect(CaseD)exceedanceflow(cfs)forthemonthsMaytoOctobercalculatedfromweeklystreamflow5forthewateryears1950-1983. 5.5 Cover Turbid water Is Important as cover for rearing juvenl Ie chinook In the mIddle Susltna RIver. The Watana and Devil Canyon reservoirs have been estimated to trap between 80 to 100 percent of the Incoming sediment (R &M Consultants,Inc.1982). Partl cIes sma IIer than 0.003 mm are IIke Iy to rema In In sus pens Ion In the water rei eased downstream.Peratrov Ich,Nottingham and Drage,Inc.(1982) estimate that turbidIty levels downstream of the Watana and Devil Canyon dams w II I range from 20 to 50 NTU In the summer and 10 to 20 NTU In the wInter months.A theoretical plot of turbidity against depth of lIght penetratIon to the compensation point (depth at whIch light Intensity Is one percent of that at the surface)Indicates that at 50 NTU,this depth Is over three feet (Figure 11).At typical preproject summer turbIditIes of 200 NTU,the compensation point Is approximately 1.2 feet.Although ADF&G (Suchanek et al.1984)found that juvenile chinook densItIes Increased at turbidItIes greater than 30 NTU,this result does not defIne the value of 40 to 50 NTU water as cover compared to 200 NTU.AI though II ght penetration Is greater at 40 to 50 NTU,the water may stll I be sufficIently turbId to provide significant cover for juvenIle chInook.However,water In the lower with-project range of 20 to 30 NTU has a compensation poInt of five feet or greater and Its cover value Is likely to be less. Presently,the amount of sedIment transport durIng the summer In the mIddle Susltna RIver Is extremely variable,wIth hIgh rates generally occurring durIng perIods of peak flow events.However,under wIth-project condItIons,vIrtually all sand sized (greater than 0.05 mm)and larger -50- TURBIDITY (NTU'S) 1200 r 1000 I SOO t 200o 400 600o+-----l -lIL..-__--L 2 3 E4 :r:t-Eb 5 CJ 6 7 9 Figure 11.Theoretical curve of turbidity versus depth of compensation point.(Reub,Trlhey,and Wilkinson 1985). ( -51- --------------_..-. particles wll I be removed by deposition In the reservoirs.A greater percentage of the sediment load released downstream of the dams wll I probably remain In suspension and be carried through the middle reach. Under with-project conditions,the principal source of the sediment transported through the middle Susltna River wll I be coarse material eroded from the banks downstream of the dam and materl al brought down from the tr I butar Ies.More energy shou Id be ava II ab Ie for transport I ng sed I ment than Is required to transport the available sediment supply;and hence,It has the potential to scour out and carry downstream fine sediments. Without the further deposition from high sediment loads,the availability of substrate as suitable cover will Increase In side channels with larger bed elements.Similar conditions may occur In a number of side sloughs If suitable flushing flows operate after dam construction. The reduced variation In discharge,the greater degree of light penetration,and the reduction In streambed sediment should enhance algal growth throughout the summer In side channels and a number of side sloughs. If this algal growth forms filamentous mats,as has been observed In localized areas of the middle Susltna River at certain times of the year, It could provide a source of cover for juvenile chinook.In addition,the reduction In streamflow variation wll I al Iowa more stable shoreline condition,thereby permitting a zone of riparian vegetation to potentially develop.This vegetation could reduce channel bank erosion and provide cover for juvenile fish.However,Ice processes,In association with the higher winter flows,may limit riparian vegetation development. In summary,turbidities In the lower range of anticipated with-project values wll I not provide the same amount of cover,but other types of cover -52- should become more available and adequately compensate.These trade-offs appear to favor wIth-project condItIons for cover when the positIve effects of lower turbIdIties on other sIgnIfIcant rearing habitat factors are consl dered. 5.6 Food Availability If,as discussed In Sect Ion 5.5,an overal I Increase In pr I mary product Ion may be postulated under with-project conditions,then a general promotIon of food organism production for Juvenile chinook will result. Ad di tiona II y,increased f Iow stab iII ty and a decrease in fI ne sed I ment on the streambed should directly enhance the numbers of benthic invertebrates, Incl ud Ing ch i ronom ids. Less high flow events wll I probably reduce catastrophic drift of organisms. However,the overal I rise In numbers of benthIc invertebrates Is I ikely to increase density dependent drift.Overal I,the quantity of drift in mainstem associated habitats should be higher and drift rates of food organisms wil I be more uniform and constant throughout the growing season. In addition to increased food availability,the ability of juvenile chinook to locate the drifting prey items wil I be Improved due to lower turbidity levels.(The amount of drift enterIng a number of side sloughs durIng the summer wil I,however,be reduced due to less overtopping events from lower average flows under with-project conditions.TerrestrIal insects associated with vegetation may become more significant in the diet of juveni Ie chinook if riparian zones are able to become established to any extent along the margins of side channels and side sloughs. -53- ---------------_..-.. - 5.7 Predation The predation of juvenile chinook by plsclvorous birds may Increase In side channels under with-project conditions as a result of their being more visible In the lower turbidity water.However,alternative types of cover should become available and overal I mortality from this source Is likely to remain comparatively negllble. 5.8 Space Requirements Downstream migration by juvenile chinook from the Indian River and Portage Creek tributaries may be related to competition for food and space. Densities of redistributed fish In side channels are low as conditions are relatively unfavorable for rearing fls~Under a with-project scenario of reduced f low var I atl on,less high f low events,and I ncr eased food avallabll Ity,fish that previously migrated from the middle Susltna River may remain In the more favorable rearing conditions of the side channels and densities should Increase.However,It Is unlikely that densities will attain levels where space requirements become significant.The retention of greater numbers of rearing juveniles and Improved rearing conditions shou Id enh ance surv I va I and may Iead to an overal I I mprovement In smo It production from the middle Susltna River.Competition for space may actually Intensify In the tributaries If seeded at higher le"'els as a consequence of Increases of numbers of returning spawners. -54- 5.9 Temperature Project operation wll I have a notable Influence on the temperature of water discharged below the dams.The reservol rs wIII store heat In the summer while releasing water with lower-than-natural temperatures between spring breakup and mid-summer.For the remal nder of the year,temperatures of the released water would be higher than under natural condItions (Table 9). Dev II Canyon Location Month Natural Dam (2020)Difference Portage Creek May 6.2 3.1 -3.1 (148.9)June 9.9 5.7 -4.2 July 10.4 7.6 -2.8 Aug 9.9 8.0 -1.9 Sept 5.9 8.5 +2.6 Oct 0.6 6.1 +5.5 Sherman May 6.2 3.8 -2.4 (130.8)June 9.8 6.5 -3.3 JUly 10.4 8.1 -2.3 Aug 10.0 8.3 -1.7 Sept 6.2 8.3 +2.1 Oct 0.6 5.3 +4.7 Whiskers Creek May 6.8 5.1 -1.7 (101.4)June 10.4 8.3 -2.1 July 11.0 9.6 -1.4 Aug 10.5 9.2 -1.3 Sept 6.4 8.3 +1.9 Oct 0.6 4.3 +3.7 Tab Ie 9.Simulated monthly mean temperatures (OC)for the malnstem Susltna RIver,DevIl Canyon to Talkeetna.<University of Alaska,Arctic Env I ronmental InformatIon and Data Center 1984). Water temperatures from May through October may potentl ally reduce the growth rates of juven I Ie ch I nook.AE IDC produced estl mates of seasonal fish growth as a function of water temperatures and body weight of the fish (University of Alaska,Arctic Environmental Information and Data Center -55- 1984a).The growth function used was observations on sockeye salmon.Results showed that for simulated malnstem temperatures at RM 130,juvenile fish would potentially have a 24 to 29 percent reduct Ion In body wei ght over the May to October grow I ng season. However,these predictions are based on studies In the laboratory and may have little relevance to Juvenile chinook of Susltna stock In the natural situation.Table 4 ibowed that juvenile chinook lD ·the tributaries under a >_._-_."--~-,.....-. co I der temperature r:.Q~me dI sp I ayed greater growth,In terms of length,- -'----.-..-hh--" over the May to October per I od than Juven II e fish from s I de channe I sand side sloughs.Greater food availability In the tributaries was probably the dom I nant factor accountl ng for I ncreased growth.Hence,under with- project conditions,If Increased food availability Is sustained,as previously discussed,then the potential detrimental effects of lower temperatures on growth rates,as compared to natural conditions,would be negated.With warmer temperatures extending through October,growth rates may Indeed be Improved over natural conditions In malnstem associated habitats and enhance the condition of fish entering the winter period. The colder spring with-project conditions could delay outmlgratlon of chinook smolt from the middle Susltna River until a water temperature of 70 C Is reached In late June.The delay of two to three weeks compared to natural conditions Is unlikely to have a detrimental effect on smolt I \ ........- survival. Average September to Apr II ma I nstem temperatures be low the Dev II Canyon dam under with-project conditions will range from 1.4 to 2.7 0 C just upstream of the Chulitna River confluence and 2.3 to 4.0 0 C near Portage Creek. These temperatures are respectively 0.4 to 1.4 0 C and 1.9 to 2.9 0 C warmer -56- than natural temperatures (University of Alaska,Arctic Environmental Information and Data Center 1984a).Consequently,a better malnstem Incubating habitat for salmonld embryos should exist under with-project scenarios,due to the warmer malnstem water temperatures during the winter Incubation period.This factor,In conjunction with stabler flows and less fine sediment on the streambed,may Induce chinook spawning In the malnstem and side channel habitats. 5.10 Overwintering Survival The operation of the hydroelectric project wll I have significant effects on the Ice processess of the Susltna River,due to changes In flows and water temperatures In the river below the dams.Generally,winter flows wll I be several times greater than under natural winter conditions.Fifty percent exceedance values for with-project conditions (Case E-VI-D)are on the order of six to eight times greater than flows under natural conditions for the months November through April (Figure 12). Upstream of the Ice front,staging levels wll I be lower due to lack of freeze-up,despite Increased winter flows,and groundwater upwel ling may be reduced In side sloughs.Anchor Ice may form In open water areas during cold periods,affecting flow distribution between channels and adversely Influencing overwintering fish.Downstream of the Ice front,the higher w Inter flows are likely to Increase upwelling rates and may lead to an Increase In the surface area of openwater,low velocity side channel and side slough habitat.However,the benefit of upwelling areas for overwintering chinook may be lessened If,due to the higher flows,side -57- ,ul'-0wCJIa:VIetCD:I:I0CJ)..~15,00010,0005,000oN=NATURALFLOWD=WITHPROJECTCASEDFLOW~-----------------~----~~0'0(0).050(0)_...--..._-------------~--------------------0'0(0)O,o(N),_,_°so(N)---=-----,_~_~----------------------------O,o(N)_ •_._-.=~-:'-.:='='-.---.-_..__.._......::..:=..::.~=.-=--:=--_.--:...:::NOVEMBERDECEMBERJANUARYFEBRUARYMARCHAPRILNote:Ql0Isthetypicalhighflow1Q50Isthetypicalmedianflow,andQ90Isthetypicallowflow.Figure12.COmparisonofthemiddleSusltnaRivernaturalandwith-proJect<CaseD)exceedanceflows<cfs)forthemonthsNovembertoAprilcalculatedfromaverageweeklystreamflowsforthewateryears1950-1983. sloughs and side channels become overtopped with near 0 0 C water more frequentl y. The reduction in fine sediment on the streambed wil I improve winter cover for juvenile chinook.A potentiai problem with regard to the effect of ice processes on overwintering chinook under with-project conditions Is the degree of dai Iy fluctuations in flow.If significant variations do take place,then local ized flooding and dewatering couid occur with detrimental effects and increase chinook mortal ity. Average temperatures for the November to Apr iI per iod wi II be 0.5 to 3.0 0 C warmer under with-project conditions (Table 10),although from December to March they will be near 0 0 C.With the warmer temperatures extending through the fa I I,freeze-up of th e river be low the dam wou Id be de I ayed (Table 11).Since the maximum upstream extent of the ice cover below the dams would be somewhere between RM 124 and RM 142,there would be no continuous ice cover between this area and the damsite,and consequently, no breakUp or meltout in that reach.With warmer and more stable flows,a slower meltout of ice cover in place wil I occur.This gradual spring meltout is predicted to be 7 to 8 weeks earl ier than normal with both dams in operation.With the slower meltout,extensive volumes of broken ice wou Id not be f I oati ng downstream and accumu I ati ng aga i nst unbroken ice cover,thereby lessening the incidence of ice jamming.This would substantially reduce river staging and local ized flooding In the spring. The overal I shorter winter period of extremely low temperatures and less severe spring breakup conditions has the potential to improve the overwintering survival of chinook. -59- -----------,--- 1971 -1972 Natural Dev II Canyon 2020 RM Range Mean Range Mean 150 o -6.8 0.7 0.6 -8.4 2.6 130 o -6.9 0.8 0 -8.3 2.0 100 o -7.1 0.8 0 -8.5 1.6 1974 -1975 Natural Dev I I Canyon 2020 RM Range Mean Range Mean 150 o -8.5 0.9 0.5 -10.0 3.0 130 o -8.6 1.0 0 -9.9 2.3 100 o -9.1 1.1 0 -10.3 1 .9 1981 -1982 Natural Dev II Canyon 2020 RM Range Mean Range Mean 150 o ~7.7 1.1 0.8 -8.6 3.9 130 0-7.9 1.1 0 -8.5 3.4 100 o -8.4 1.3 0 -9.0 2.7 1982 -1983 Natural Dev II Canyon 2020 RM Range Mean Range Mean 150 0-7.9 1.1 0.6 -9.1 3.2 130 o -8.0 1.2 0 -9.0 2.7 100 o-8.4 1.3 0 -9.3 2.1 Table 10.Susltna River temperature ranges (oC)for the period September through April under natural and with-project conditions (both dams -2020 demand).(University of Alaska,Arctic Environmental I nformatl on and Data Center 1984a). -60- Natural Conditions 1971 -72 1976 -77 1981 -82 1982 -83 Both Dams -2020 Demand 1971 -72 1982 -83 Startl ng Date at Chu Iitna Confluence Nov 5 Dec 8 Nov 18 Nov 5 Dec 5 Dec 14 Mel t-out Date May 10-15 May 10 Apr II 15 March 12 Maximum Upstream Extent (RM) 137 137 137 137 133 127 Table 11.Comparison of timing of freeze-up and Ice break-up In the middle Susltna River under natur~1 and with-project conditions (both dams -2020 demand).(Harza-Ebasco Susltna Joint Venture 1984). -61- REFERENCES Alaska Dep~of Fish and Game,Susltna Hydro Aquatic Studies.1981~ Phase I final draft report.Adult anadromous fisheries project. 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