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HomeMy WebLinkAboutSUS503IJ IJ • • • • • • • • • I • • ~ -- SUSITNA HYDROELECTRIC PROJECT FEDERAL ENERGY REGULATORY COMMISSION PROJECT No. 7114 A FRAMEWORK FOR THE ASSESSMENT OF CHINOOK SALMON REARING IN THE MIDDLE SUSITNA RIVER UNDER ALTERED FLOW, TEMPERATURE AND SEDIMENT REGIMES EWT&A UIID.II CONTRACT TO [}{]~[ffi~~=~[ID~®©@ SUSITNA JOINT VENTURE DRAFT REPORT APRIL 1985 DOCUMENT No. - ___ ALASKA POWER AUTHORITY _ ___. II II II · II Ill II II II -- II • II II ~ II SUSITNA HYDROELECTRIC PROJECT Docu•nt No. - Suaitna file No. 4.::1.1.3 A FRAMEWORK FOR TBE ASSESSMENT OF CHINOOK SALMON REARING IN TBE MIDDLE SUSITNA RIVER UNDER ALTEPED FLOW, TEMPERATURE AND SEDIMENT REGIMES Report by E. Woody Trihey & Associates Alexander H. Milner Under Contract to Harza-Ebasco Susitna Joint Venture Prepared for Alaska Power Authority Draft R1!port Apri 1 1984 TABLE OF CONTENTS 1 • I NTRODUCT I ON •••••••••••••••••••••••••••••••••••••••••••••• 2. OVERY I EW OF CHI NOO< SALM:>N ESCAPEMENT OF THE SUSITNA RIVER DRAINAGE •••••••••••••• ; ••••••••••••••••••••• 7 3. DISTRIBUTION OF REARING JlNENILE CHINOO< SALN:>N IN THE MIDDLE SUSITNA RIVER ••••••••••••••••••••••••••••••• 11 4. FACTORS THAT I NFLl£NCE J lN EN ILE REARING CHI NOO< 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 Introduction ............................. "' •••••••••••• 18 Flow Regime, •••• ,, ••••••••••••••••••••••••••••••••••••• 18 DIscharge/ V~! ac f ty ••••••••••••••••••••••••••••••••••• 20 Water Depth •••••••••••••••••••••••••••••••••••••••••• 25 Cover .....................•.•.....•.................. 26 Food Avallab I I tty ........•.•......•.................. 28 Predatl on .•.....•........................•........... 35 Space Requl rernents ••••••••••••••••••••••••••••••••••• 35 Temperature ............•..................•.......... 31 Overwintering Survlval ••••••••••••••••••••••••••••••• 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 ntroc:luct I on •........................................• 44 F I ow Reg I me •••••••••••••••••••••••••••••••••••••••••• 44 DIscharge/VelocIty ••••••••••••••••••••••••••••••••••• 45 Water Depth •••••••••••••••••••••••••••••••••••••••••• 48 Cover •••••••••.•••....•.•••..••..••••.••.•.••••.••••. 50 Food Ava II ab II I ty .................................... 53 Predatlon •••••••••••••••••••••••••••••••••••••••••••• 54 Space Req u I ranents ••••••••••••••••••••••••••••••••••• 54 Temperature •••••••••••••.•••••••••••••.••••••••.••.•• 55 OverwInterIng Surv Iva I ••••••••••••••••••••••••••••••• 57 6. REFERENCES •••••••••••••••••••••••••••••••••••••••••••••••• 62 Fl gure 1 Fl gure 2 Figure 3 Fl gure 4 Fl gure 5 Fl gure 6 Figure 7 Figure 8 Figure 9 FIgure 10 Fl gure 11 Figure 12 LIST OF FIGliRES 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 salmon by macrohabltat type on the Susltna River between the Chulitna River confluence and Devil Canyon, May through November 1983 Juven fie chI nook salmon mean catch per cell 15 at side sloughs and side channels ~Y sampl lng 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 complied 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 Talkeetna-to-Devil Canyon reach of the Susltna ·River (RM 101 to 149) Compariso n 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 point Comparison of the middle Susltna River 58 natural an~ with-project (Case D> exceedance flows (cfs) for the months November to April calcu la ted from average weekly streamflows for the water years 195Q-1983 Tab I e 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9 Table 10 Tab I e 11 LIST OF T,tBLES Susftna River annual chinook salmon escape-8 ment and tfmfng for 1983 by sub-basin Peak survey counts and percent dfstrfbutfon 10 of ch f nook sal mon f n streams above RM 98.6 f n 1981-84 Typical Juvenile chinook densftfes from other 13 studies Aver age I ength s of 0+ ch f nook sa I mon d ur I ng 16 1984 fn the middle Susftna River Depth and velocIty preferences for Juvenfl 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 <°C> In side sloughs and simulated average monthly malnste~ tanper~tures Sus f tna hydroelectrIc project f I ow con-46 strafnts for environmental flow requirement case E-VI Simulated monthly mean temperatures <°C) for 55 the mafnstem Susltna River, Devil Canyon to Talkeetna Susftna River temperature ranges <°C) for the 60 period September through Aprfl under natural and with-project conditions Comparison of tfmlng of freeze-up and fee 61 break-up In the middle Susftna River under natural and with-project conditions 1 • I NTR<DUCT I ON The Alaska Power Authority CAPA> 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 CRM> 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 hydt·oelectrlc project are given In the lnstream Flow Relationships Report, Volume 1, prepared by E. Woody Tr I hey and Assoc lates CEWT&A> and Woodward Clyde-Consultants (1985). As part of the environmental assessment studies for the proposed project, Investigations have been conducted s i nce 1974 to quantify fish resources and evaluate uti I lzatlon 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 CRM 98.6-152). This section o·t the river Is considered to be the most susceptible tow lth-project Im pacts. Anadromous salmon are usually prevented from moving upstream of Devil Canyon by high water velocity. Be low Talkeetna CRM 98.6) project Induced changes In streamflow; s t ream temperature and sediment concentration will be buffered by the Input of a number of large tributaries, notably the Ta I keetna, Chu I I tna and Yentna rIvers, whIch wIll be u nat fected by construction and operation of the project. ~ I Figure 1. Susltna River drainage basin with major tributaries and geographic featuers. (University of Alaska. Arctic Environmental Information and Data Center 1984b). W!thln the middle Susltna River. evaluation species have been selected for study. This procedure Is In accordance with Alaska Power Authority, Aleska Department of FIsh and Game, and U.S. FIsh and W II d I I fe ServIce guIde I I nes for studying habitats of greatest concern, which are those uti I lzed by commercially and recreational ly Important f:sh species that are most I lkely to be significantly Influenced by the project. Six principal aquatic habitat types. based on morphologic. hydrologic and hydraulic characteristics. have been Identified within the Talkeetna-to-Devil Canyon reach of the Susltna River. namely; malnstem. side channel. side slough, up I and slough, tributary. and tributary mouth. ThaT r character lstlcs are summarized In Figure 2. The habitats that respond most markedly to varl~tlons In malnstem discharge are the sIde channels and sIde s I oughs and thus are the most I Ike I y to be significantly altered In a with-project situation CKI Inger and Trlhey 1984). The prlmar·y species and life stages selected for eval uatlon were chum salmon (Oncorhynchus~) spa~nlng adults and their Incubating embryos and chinook salmon c.oa_ tshowytscbo) rearing juveniles <E. Woody Trlhey and Associates and Woodward-Clyde Consultants 1985>. which typically utilize the side channel and side slough habitats to the greatest extent <Dugan. Sterrltt. and Stratton 1984). Chinook salmon are Important to both the commercial and sport fishery. Coho ~ k!sytcb) fry principally rear In the trIbutarIes and up I and s I oughs w h II e sockeye CQ.. narka) make the most use ot 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 . .l ( ,····("1 ( '·c' ... ~( i. .... ··.. \..-( '·, . ·····\_ ••... ::.J, .. \ ·-·~ ··•·· .•.. ,.1 / ClNIIAl HAIITAT CATIGOIIIS or Til( SUSITNA 11\IU 1, Mllft1km H1bleal Con\h.l\ of thoioe pOthOn\ of lh~ Su\ttn.a tclvtr 1 .... U nmm~ly COO· vey llte~nlllow thtGu.hout tht yur. loth Una~ and mulhpW ch•nn(lr,·.-<h~ ••t lnclud~ in 1hi1 h.abilo11 c•lti'O'Y· Croundw•k'f 1ntJtr•hut.ary 1nftow .app~·.a•to lu:o In· :onu:qutnli•l conuibuiOt\ to aht uvrr~l dur.al..ll''''hU ol m.ait\•1~n1 h•LII.at. M.)Wuetm h,at,il,.l K typtully chliiUirtiud by h•Kh wo~trt vdoc11ht'' .,.,., ~•· ~rmorrd 1lrt~lJfl11. SuWr.attl ~ntr,.y consi\1 c.# boukJrr .and fOhh'e '''' m.altrio~h with lnlerslilill sp.Kt>S ftl~d with 1 aroul·hl..t mi.turt of tmaW gr.,vc~ .and a~citll tJnds. Slapende.-d ..diment conccnlto~hons .and turbit.lily .au: h•gh dunna 1ummer d~ to lhr inAut-nCt of aYcial mek·w•ter. ~~~~o~nojlo~ rrct"d,· '" c.uly f.al 1nd tht m.a.n,ltm du" 1pptrct11bly In Oclo~r. An 1ce cowr lo.nt~ on I he-••vtr in l•tt Novtmbtt or D.ecttnbtr. ll Sldo Chan...t thb~al conr.ioll ol thOM poniont of oho 5uw~• Rlv .. • 1h11 ~.,,.,,.ly cnn~y ,.,~imllow duMa the ope-n w1ter if.aW)u but bKonw IJIIWt:cWt~ dr.w.atrrrd durin¥ period• t.f &ow flow. Sidtchttnnrl h.aW~I nuytat\' tllhct in wei· dtointd ovctflowchanMI>, or lA pooliydrintd w1~rcou..o• Auwin•ohu>u¥h P••· li~ly lU~t.~l 1r.awJ b~" ind b~nch IIURIIht mJIICII1' of lht m.lll'hlt'ITI lt\'tl, S•l4t ch.anm .. Mu~~mbcd t'lev.alton• •~ 'YIMC.alt lo~..-• 1h1n the n~~n monthly WJit.'f surf.act t~v.alion• of the nw'n\km Su~nt11 Rtvff nbM"Ncd dunn111une, July, t11IMJ Au&u\1. SiJt Ch.1nnet Jubil•t• .,, ChM.Ck'fiH"'.J by Ut1llo'A"I dt•plh\, lo~r Yt:loCilllft). ~nd wtWicrr 'llt.ambed INietltlik th.an the ~t'Ct>Rt h.ahtt"l of lh~ m.ain~rm rivet. )) Side Sluuah H•Wt•l b loc•IH in 'Pfiha·Wd ovtrflt>VW ch•nnl"h betwten 1h~ rtllt: of the nuutJpl.a~t~ •nd th" m.ainu .. ·m .and ,MJt 'h•nnt•l, of I he Su~n• kivt'r .-n11u usu•l· ly sr,u••ltd fro1n lht m•in"tm 1nd 'idt ch•nnt:h hr ,...t'l·'-fKl't~lcd bw~r'\ An c•· poM.od .anuvWI bt"rm ofllf!n •rPM .lit:\ lht he.Kt of lht ~lc·u&h front m••"lt.·rn or ,Kf~ ch.ann~ floW\. The cunuolin.c ,ereMnbecthrr~o~mh.an~ t..·lt•\ll,lhon, .al lh•· ""~'t:"m end of thf! 'k.le \lou"t" ., .... .,,.:luty leu lh.m &he"""·''''' \url.u.t: ~"'""'""It\ uf the m~Jn R'WlniMy fto~M ol thr nwin\ol~m Su\•n.l NtYl'f uh~,... .. 'tl fur Jurw July, .1nd Aut~u\1. Atlht ~nltrnwd~le 1nd klw-flow pt'~toch. lht.• ud~ slou¥h\ ltrt•H:y ct.e•r w•k•r hum ~llribuwriel 1nd/or up'-Wiintet~rountJwJU.•t lA Of o\G I~ ll. 11Jftlb) . lhl"C ( k•11 w.aiCf inftu~ tlf(' ~uconlt.al conlttftuiOI\ In tlw t'IU\h..·tu.c ollho\ ho~h ... U lypc. lht' Woflttf lurfo~c..•l'lcv .. ltun of the Su • .an.a Ntvl't .,;t•rtt•to~ly c•u~·• ,tll.h'L"""''t..'' 10 r.trnd Ml up into lhtolou~h fronlilllo~rcnd 1•\Df 6G 1~81c. l'ld,bl h·tn thouah eht\ sut»co~ntt.ll lwckw•ler ea-.h, lhe \luu~lh lunc1.un hydro~ultt •• u., \llt.''Y much likt urul ilfl'Mn ''f"lt'nb iiRLI k'Yrr•l hun..Jw..J lt•4.1 nf lht' ,lou~h t hJnnt-4 often conwys, w.attr indciM.'Rtlt:nl of m.aimlrrn bJC~w.alcr fl~cl\. AI h•,.:h •luVi'\ tl.e wiWf surfue clcv.atton of lht nllin\olern tivH i' 'uffiC.enllo ovrttop lht· uvvc• end of lho •loullh tADr&G 1911c, 198lbl. S..tfact w•ocr oonop••••u••• on oht •.t• 1loutehs durin1 •umrnl'r mon&h' .art princip.Uy 1 lu"' ''''"of ~ir lctnt,t't.llure, wi.Ar r•tle..~llon, o~nd the •~'"l•~;alurc ollht' loco~f runol. 4) Upl•ttcl Sloullhii•IMI•I d~f•n from ohe side •luu.:h hJbOJtln th•t lht up>ll<lnoond of the ,&oush i' n01 intcfCOnnl<ltd wllh the surf.-fr w.alcr\ ol1he m•imh:m Su\ifnil l1ver Of il' \ide lhl!lnn.:h. lhe~e •lou&hl tllt' ,.h,uclctiud by lht> Jlh·wnc~ ol bt!•ver d•m\ •nLI 1n o~ccumul,tion ol silt covering lhe ,ub\lr.alc '~""'""• frorn lhl' •1·,\coce uf m<llin\lt:m ICOutin• floW\. Sl Tribullry H•bil•l con•i•U ol the ful compltiTk'nl of hr<fr•u•c 1nd mc.rvhuluK"= conc.J~ion' th•t occut in lht Uibutltiet. The-ir 'uwn•l wr•f'rllow, '~t~lll•rnl, •nd tht:lf1'\ll rt'Kim..•\ tt'n..-t.t the: inlt'K"Iinntrllht: hydrok1"'y, jit'(llno. •1\Cit luno~\l• o~ th~ tuhu'"'V u ... ~ .. "l'. Th .. ·••h'(\K .al .. unhuh.:' oftuhut.ary h .. IHI.tltlfl.' nul d··s .. · ul-..-nt ''" m.au•il~m corwltfl(lns. 61 TtibuUry Muuth tt.bUt eau~ncb ftom lhe uppttn'I0\1 potnl .,.. tht Uohuury .n· llurnced by mo~inMe.un Su\ltn,a IUvtf 01 'luu11h ll.w:kw''~' eth:' h IO lht dowMUr.am t'al~nl of lhl' tribut.lry plunw whic: h co'lt:ll\J• into lht.' "'"'"~h'!u Su\lln.a Rivtt or •luullh IADf&G 1911<, 1912hl. 1) Ul..t H•bie•t (&Hlillll of VMiuu' lcntic envifon~nb lh•l O((IJ( .;thin lh.r su .. tn• M•v~• tfro~inJa&t. 1~ h .. bico~u r.anp from '"'·'•· ,h .. n, ·"· i\O~trd ,,.._t', awrt.ht"'i on &h~ aundr.a 10 l.uyrf. ch..:pet L.ai.. .. -., wt.M:h connt'l"t lo &hL' INM'"''tn S~o~\•m• J::ivfl lhtouvh W\.'l·tJ~r.ntd lf1butlty 'Y'''""· lht: l.ake' tcceiv..-1htit w.tl~f lrum ,..,,,.,,, ,urf.u.:c.• tunoif • .lntflot uibut,ui~•. Figure 2. General habitat categories of the Susltna River. (Alaska Dept. of Fish and Game, Susltna Hydro Aquatic Studies 1983a). I VI I 6C 50 40 ~ z ..,30 0 Ill: w Q. 20 10 0 60 !)() ~40 z w 30 0 Ill: "' Q. 20 10 0 I &4.4 I 17.1 ~2.9 4.9 , TRIBUTARIES. Uf'l.AND SIDE SIDE SLOUGHS CHA~NElS SLOUGHS CHUM. RELATIVE ABUNDANCE OF JUVENILE et.-e SALMON e.e tl. 7 12 .I ,. I TRIBUTARIES. Uf'l.AND SIDE SIDE ., SLOUGHS CHANNElS SLOUGHS CHINOOK .-.. 60 50 I ~40 z ..,30 0 Dt., I Ill: "' Q. 20 II. I 10 -0 10.8 0.9 -1 TRIBUTARIE!i' Uf'l.AND SIDE SIDE ., SLOUGHS CHANNElS SLOUGHS COHO 60 50 I 1---, 40 ~ ... lr-. I z ..,30 0 41.7 a: "' Q. 20 41.3 10 o.a -0 I 8.& --I ~-~ RI&UTARIES. Uf'l.AND SIDE SIDE SLOUGHS CHANNElS SLOUGHS SOCKEYE Figure 3. Relative abundance and distribution of juvenile salmon within different habitat types of the middle Susltna River. <Schmidt et al. 1984). ..... The purpose of this preliminary draft report Is to provide a fr amework for evaluating chinook rearing In the middle Susltna River under with-proj ect conditions when further data become avai l able and appropriate analyses are completed. At present. this report contains an overview of juvenile chinook studies to date. a comparative evaluation of the s i gnificance 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 a I tered under wIth-project conditions. and the likely consequences for juvenile chinook. A future draft of this report wll I Include the tot lowing analyses presently underway by EWT&A. <a> Modeling of streamflow variability under w lth-project conditions and the potential effect on the quantity o r suitable rearing habitat. (b) Weighted Usable Area (WUA) forecasts tor juvenl le chinook rearing habitat as related to malnstem d i scharge. (c) An euphotic zone model assessing the effects of reduced turbidity on I lght penetration and the lmpl I cation for primary and secondary productivity levels. (d) Extrapolation of WUA forecasts for juvenile chinook to the entire middle Susltna River. A number of reports prepared by the Alaska Department of F i sh and Game <AD F&G> are Important to this analysis. Includ i ng the 1984 resident juvenll e anadromous fIsh study. the 1984 food avail ability study. and ~tie 1984/85 overw lnterlng stud y. -6- 2. OVERVIEW OF CHINOOK SALMON ESCAPEMENT AND SPAWNING OF THE SUSITNA RIVER DRAINAGE The Susltna River affords a migrational corridor and spawning and juvenile rearing areas for chinook, coho, chum, sockeye, and pink (.Q.. gorby:scba) salmon from Its mouth on Cook Inlet <RM 0) to Devil Canyon <RM 152). From 1981 to 1984, 95 percent of the co~merclal monetary value In the Upper Cook In I et fIshery was derIved from sockeye, chum, and coho catches. ChI nook salmon contribution In 1984 was 1.65 percent. Approximately 10 percent of the total commercial chinook catch I n 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 allow lng the majority of spawning chinook salmon to reach theIr natal streams. The r Jver bas In supports a comparatively larger annual chinook salmon sport catch, which 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 Susltna River In late May to early June. In 1983, the minimum total escapement was 125,600 fish. Subdralnage escapement and timing for 1983 are given In Table 1, In which estimate methods and their associated limitations were summarized by Jennings (1984). Approximately 80 percent of the chI nook salmon were est I mated to have returned to the Yentna sub-basin. Spawners In the middle river (Talkeetna-to-Devil Canyon reach) account for a smal I percentage of the remaining escapement. In 1983 th Is percentage was 3.5, or 3,800 fIsh. The majorIty of the spawnIng above -7- I I I I I I I I I I I I I I I I I I I Sl'b-Basln Numbers Tim lng Lower Susltna River (RM 0 to 56,300 Mid June 80), excluding Yentna River to mid July <RM 28) Yentna River (RM 28) 44,700 Talkeetna <RM 97 .1> and 16,100 (62,000) Chul ltna (RM 98.6) rivers, Including Susltna River from fi4 80 to 98.6 Talkeetna Station to Devil 8,500 (9,500) third week I n Canyon (RM 98.6 to 152) June to third week In July Total Susltna basin 125,600 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 estl mates. Table 1. Susltna River annual chinook salmon escapement and timing for 1983 by sub-basin. (Adapted from Jennings 1984}. -8- RM 80 occurs In t he lerger tributaries, notably the Talkeetne and Chul ltna rivers. In the past three yeers, an average of 34 chinook salmon have overcome th6 high velocities and spawned In tributaries abov~ Devil Ca nyon. In the middle Susltna River, chinook salmon spawn only In tributary stream hablta~ Portage Creek and Indian River account for over 90 percent of the ~pawners <Barrett, Thompson, end Wick 1984). Trlhey (1983) examined the hydraulic conditions In the mouths of these two tributaries and concluded thet passage of spewnlng fish Is not likely to be lmpelred at low malnstem discharge~. Peak spawner survey counts In the trlbutery streams Indicate an averege eiHPJal increa:.J of 87 percent between 1981 and 1984 <Table2>. Spawning peaks fell between July 24 and August 6 In each year (Alaska Dept. of Fish and Game, Susltna Hydro Aquatic Studies 1981a, 1982; Barrett, Thompson, and Wick 1984). The majorfty of chinook spawners aged 5 and 6 hed migrated to sea In their second year of II fe. The number of eggs per fsmele spawner has not been estimated for chinook sel mon, but Beauchamp, Snepe·rd, and Pauley (1983) put the typical renge as 3,000 to 6,000. No Information Is available on egg- to-fry survival, but Jennings (1984) summarized the factors effecting Incubation and their application to the middle Susltna River. -9- 198 1 1'36 2 1'383 1'313 4 Ri ver Peak ... Pect ic ... Peak \ Pe ak \ ~verag e St r eam Mil e Count Oi stri· C:l u nt OiH r i · Count Dis tr i· Count Di s t r i • .. 1/ but i on l / but i on 1/ but i on 1/ bu t i on Distribut ion Wh i sken Creek 101 .4 0 0 3 0.1 67 0.'3 0 .6 Ch ase Cr eek 106.'3 1 5 0.6 I S 0 .3 3 * 0.4 Lane Creek 113 .6 40 3 .6 47 1 .9 12 0 .3 23 0.3 0.8 5 t h of Ju l y Cr . 123.7 3 0 .1 0 0 17 0 .2 0.2 Sher,.,an Creek 130.8 3 0 .1 0 0 0 0 * 4th of Jul y Cr . 131 .I 56 2.3 6 0 .1 9 2 1 .3 I. 3 Cold Creek 136.7 21 0 .9 23 0 .5 23 0.3 0 .6 Ind i an Rive r 138 .6 422 l7 .6 I ,053 42 .6 1 . 1'33 26 .9 1,456 20.3 26 .8 Jack Lo ng Creek 144 .5 z 0.1 6 0 .1 7 0 .1 0.1 Portage Creek 148.9 659 58 .8 1 . 25 3 50 .7 3 ,140 70.9 5,4 46 75 .9 68 .3 .·· Cheechako Cr eek 152 .5 16 0.7 25 0 .6 29 0 .4 0.6 Ch i nocl< Creek 156.8 5 0 .2 8 0.2 15 0.2 0.2 Dev i l Creek 16 1 .0 0 0 • 0 0 * Fog Cr eek 176 .1 0 0 0 0 2 • • TOTALsY 1 ,12 1 ·100 .0\ 2 ,4 716 100 .2\ 4,43 2 100.0\ 7,180 99 .9\ 99.9\ 1/ Peak c oun t i ncl udes li ve p lus dead fi sh. 21 Percent d i stribution tota l s may not equal 100 due to r ound ing er r ors. • Trace Table 2 . Peak survey counts and percent d i stribution of chinook salmon In streams above RM 98.6 In 1981·84. <Alaska Dept. of Fish and Game, Susltna Hydro Aq~atlc Studies 1985). -1o- 3. DISTRIBUTION OF REARit«; JlNE_NILE CHINOOK SALMON IN THE MIDDLE RIVER As part of the Susftna Hydroelectric Aquatic Studies program, the Juvenile anadromous habitat stu dy was carried out by AOF&G. In 1981 and l982 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 distr i bution data was then used In 1983 and 1984 to select specific sites for more detailed Investigations regarding the suftabf I fty of selected habitat areas for juvenf·le chinook salmon, and for measuring rearing habitat response to changes In mafnstem 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-Devil Canyon sub-basin of the Susftna River (Alaska Dept. of Fish and Game, Susftna Hydro Aqu ~tlc Studies 1981b; Dugan, Sterrltt, and Stratton 1984). Juvenile chinook salmon In the Susftna 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 following 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 middle 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 feeding, rather than living, In distinct reaches of the river for extended periods of time (Beauchamp, Sneperd, and Pauley 1983). Redistribution of chinook fry In the middle Susltna River results In Increased utll lzatlon of side channels, side sloughs, and upla ,!H~ sloughs from July onwards. Highest densities are typically found In the side channels <Dugan, Sterrltt, and Stratton 1984). Side sloughs become more Important as rearIng areas In September and October. TrIbutarIes become less significant after November as low winter flows and Icing occu~ The malnstem, side channels, side sloughs, and tributari es are used by juvenile chinook as overwintering areas <Alaska Dept. of Fish and Game, Susltna Hydro Aquatic Studies 1981b; Dugan, Sterrltt, and Stratt·on 1984). Rlls and Friese (1978) concluded that juvenile chinook overwinter mainly In side channels , as opposed to sIde s I oughs, but theIr resu Its were based on a smal I s ample size and thus are probably Inaccurate. Population estimates of rearing juvenfle chinook by conventional methods have not been undertaken In the middle Susltna River. Indices of fish density In four macrohabltat types (side channels, side sloughs, upland sloughs, and tributaries) were obtained In 1983 using backpack elec·tro- flshlng units a nd 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 eel I (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 cell, or 0.88 fish per square meter <na2>. Conversely, averages of less than one fish per cell were found In some side and upland sloughs In May. Chinook fry (0+) densities Increased at mafnstem associated macrohabltats rn l~te July following red.fstrfbutfon from the tributaries. A comparison of slde slough and side channel densities for 1983 Is given In Figure 5. Tha 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/m2). Side slough densities In September and October may reach five tfmes the values for earl fer In the ye ar. Typical chinook fry dens!~l es from a number of other studies are given In Table 3. Age 0+ 0+ 0+ Flsh/Area (no/;z) 0.59 -1.35 0.44 - 1 .60 1 .90 Region Idaho Idaho Idaho Reference BJornn (1978) Sekul lch and BJornn (1977) BJornn et al. (1974) Table 3. Typical Juvenile chinook densities from other studies . -13 .. I -... I . EiQhl Sites Combined 4.0% Whiskers Creek Slouoh Side Channel Mainttem II 9. 3°/o O•bow Ont 8.2 ., • SIOUQh22 SIDE SLOUGHS~ five Tributaries Combined 10.4•1. Oabow One 10.7% SlOE CHANNELS Side Channel 10 ... 17.9% Twelve Situ Combined Slouoh 9 6 . .;:;:---___UPLAND SLOUGHS COM 8 IN ED MACROHABITAT TYPES FIgure 4. DensIty d I str I but I on of juven II e chI nook sal m.on by mecroheb I tat type on the Susltne River between the Chulitna River .confluence end Dev II Canyon, May through November 1983. Percentages ere based on mean catch per cell. (Dugan, Sterrltt, end Stratton 1984). ..J ..J ... u a: ... Q. X 0 ~ C( u z C( ... ::E ~0 4 .0 S) ~~8EiiAL,?~g~CITIONS mJ ~~O&ti TC:TA~~~~~I TIONS * NO (f'I'OAT • •CHI NOOK CATCH S E"T FIgure 5. Juven II e chI nook sa I mon mean catch per ce II at sIde s I oughs and side channels by sanpllng period, May through November 1983. (Dugan, Sterrltt, and Stratton 1984). -15- Average total lengths of 0+ chinook for lndlen River end melnstem essocleted hebltets during 1984 ere g i ven In Teble 4. No weight enelyses ere presently available to compare condition of Juvenile chinook from d I fferent heb I tats. Time of Yeer Lete May July 1st ~ 15th July 16th-31st August 1st -15th August 16th -31st Eerl y September October 1st-15th lndlen River 38 mm 49 111111 55mm 59 Rill 61 nvn 64 mm 65.5 mm Side Channels/ Side Sloughs 41 mm 48 mm 52 nim 52 Rill 56 mm 58 mm 61 mm Tebl e 4. Average totel lengths of 0+ chI nook sat mon In m Jill meters (mm> during 1984 In the middle Susltna River. <Roth and Stratton In press>. Outmfgratlon of the 1+ chinook smolts from the Talkeetna-t~Oevll Canyon sub-basin occurs principally In May and June and Is completed by September. Average srnolt length for 1981 and 1982 was 90 mm (Roth, Gray, end Schmidt 1984). Rising water temperatures may stimulate smolt outmlgratlon <Seno 1966). The crltlcel temperature Influencing this movement for chinook eppeers to be 7 degrees centigrade <OC>. When temperatures fell 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- migration (Godin 1980; Groot 1982). In 1983 numbers of outmlgratlng chinook smolt from the middle Susltna River were I nsignificantly correlated with mellnstem discharges <r2: 0.25) <Roth, Gray, and Schmidt 1984>. -17- 4. FACTORS THAT INFLUENCE JlNENILE REARI~ CHINOOK SALMON IN THE MIDDLE SUSITNA RIVER 4.1 Introduction Stream habitat parameters have a significant Influence on all stages of the salmonld I lfe 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, I Ike chinook, which spend an extended time rearing In freshwater, habitat quantity and quality determine the number of fish that survive to smoltlflcatlon; and hence, the productive capacity of the system. Figure 6 Is a conceptual flow chart l.)f the factors likely to Influence the production of rearing Juvenile chlnouk salmon In the middle Susltna River. Many of the factors are Interrelated, but nine of them are hlghl lghted for discussion. These factors and their Interrelationships will 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 lmpl lcatlons for rearing chinook. 4.2 Flow Regime Streamflow Is a major determinant of J uvenile 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- f-- 1----- t SUBSTRATE Si ze and Ex tent o f Glaci a l F ines in I nte rstit i al Spaces S USPEND ED SEDI MENT TURBI DITY PRIMARY PR OD UCTIVITY r INCIDENT LIGHT/DEPTH ,... .. ---I -0 • I ..... . ~ ..... ·--. ... _ ...... _ ..... '-.... -; c;, . Aih l TE MPE RATUR -I I WATER 'MPERATURE t ·- UPWELLING ICE PRO CESSES l v ~RWINTERING SURVIVAL ' i SUBSTRATE Size and Extent of Glacial Fines i n Interstitial Spaces SUSPENDED SEDIMENT TURBIDITY PR IMARY PRODUCTIVITY I NCIDENT LIGHT/DEPTH i L---------' ,.. ------. --· --"-........ • r ........ • r • ~ • o: TfS r:,_:.i -:;-.)l:~I T I';<J ~ ;v e:-. WATER DEPTH COVER RIPARIAN VEGETAT ION BEN T HIC INVERTEBRATES FLOY! REGIME ~-- ' VELOCITY ~------~--------/ REARING JUVENILE CHINOOK SALMON - FOOD AVAILABILITY -SPA REQUIRI ~~------~----~--t TERRESTFiiAL INVERTEBRATES \ -------- DRI FT INTERSPECIFIC & INTRASPECIFIC COMPETITION FLOWREGIME ~--------------------------------------------~ VELOCITY REARING JUVENILE CHINOOK SALMON •oo lBILITY SPACE REQUIREMENTS ] ORin 2J INTERSPECIFIC & INTRASPECIFIC COMPETITION UPWELLING OVERWINTERING SURVIVAL PREDATION al. (1974) showed that a reduction In stream pool area resulted In a loss of Juvenile sal monld rearing capacity, and Thompson <1972>, In developing streamf I ow optIma for rearIng habItat, recommended a 1:1 pool to rIff I e ratio. Diversity and streamflow Is Important to juvenile salmonlds. 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 veloci-ty. 4.3 Discharge/Velocity In a study of chinook salmon In the Kenai River, Alaska, young of the year (Ot 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, selecteJ 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. Age Depth (ft) 0+ 0.5 -1.0 0+ < 2.0 0+ 1.0-4.0 Velocity (ft/sec) < 0.5 0.3 0.2-0.75 Reference Everest and Chapman (1972) Stuehrenberg (1975) Thompson ( 1972 > Table 5. Depth and velocity preferences for juvenile chinook from other studies. -2o- 1.0 w t/) ;:) .. .8 0 > .6 t-::::; iii ~ .4 0 a: Q. .2 Number of fish examined (N) "' 163 Length range = 55-85 mm 0 N ~ ~ m ~ ~ ~ ~ ~ ~ N ~ ~ ~ ~ 0 0 0 0 -----N N N N N ~ WATER VELOCITY (f.p.s.) Figure 7. Fac ing-water velocity and probability of use for juvenile chinook complied 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 velocities and shallower depths are preferred by Juvenile chinook under turbid conditions as compared to clear water. The greatest number of ch lnook pe r 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 I ow turbIdIty waters I ess than 30 NTU. No adJustments for gear eft I c I ency dIfferences were ma c" .:t In cal cuI at I ng the mean number of chinook per eel I, as beach seines were used to capture fish tn turbid water, while In clear water electroflshlng was employed. Lorenz (1984) found that In smal I Alaskan streams, a hand held seine had a higher catch efficiency per unit effort than an electoshocke~ 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. As Is typical of unregulated northern glacier rivers, the Susltna River has high turbid water during 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 an annual mean of 9,650 cfs (Table 6). Average monthly discharges for June, July and August are approximately two and one half ·times the annual mean. Mid-channel velocities 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 tor red I str I but I on from the 1'r !butarles. Side channel flows typically mirror the malnstem, and the amount ot suitable rearing habitat with acceptable velocities tor -22- Juvenile chinook depends upon the channe l geometry of the side channe l and the proxIma I maIn stem. Monthly Flow (cfs) Mv nth. Maximum Mean Minimum January 2,452 1,542 724 February 2,028 1,320 723 March 1,900 1,177 713 April 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 side channels 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 w I th a rei at! ve I y narrow and Inc I sed cross sect I on geometry. In addI t Ion, a reach of t he malnstem tha~ Is constricted will have a steeper stage/discharge relationship than one less confined. In such areas there :-an Increase In responsiveness of site flows In adjacent side channels to Jnc r en. 1'\tal changes In malnstem discharge. -23- Malnstem discharges during late July and August, when the highest densities of j uvenl le 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 Gold Creek gage. Extremes of flow are recognized to I lmlt juvenl le fish production (Havey and Davis 1970; Smoker 1953). Spates may Induce the downstream displacement of Juvenile chinook or f~rc~ them to seek refuge In pools, which may subsequently dewater on lowering discharges. Side sloughs are principally dependent on local surface runoff and groundwater upwell lng and possess velocities typically less than 1 ft/sec. They are characterized by a series of clearwater pools connected by short shallow riffles. Side sloug~ velocities typically fal I with malnstem discharge reduction as the rate of upwel I lng becomes reduced. Because there are differences In the elevation of the head berms relative to the malnstem, the flows at which sloughs become overtopped varies considerably, although generally ft Is between 20,000 to 30,000 cfs. Some sloughs are only overtopped at high discharge levels. At these overtopping flows, the side sloughs convey turbrd malnstem water and velocities Increase. Downstream displacement of rearing Juvenile chinook may occur, but probably on I y to a small extent. TrIbutary flows are Independent of var I atl ons In ma I nstem dIscharges bu·'" may display significant fluctuations. Peaks typically occur In June following 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 -.'Z4- mouths are typically marginal for rearing juvenile chinoOk. Although the least favored by chinook of the possible rearing areas, upland sloughs have suitable velocltes and are only slightly affected by Increases In malnstem discharge. From November through April, low air temperatures cause surface water In the basin to freeze and streamflow becomes markedly reduced. Gr o undwater Inflow and baseflow from headwater lakes maintain malnstem streamflow. The slgnl ~Jcance of these low flows and the Influence of upwelling on the overwintering survival of Juvenile chinook will be discussed further In Section 4.10. 4.4 Water Depth Water depth Is determined by streamflow, channel form, and streambed materials. Prov i d i ng other factors are suitable, rearing chinook salmon use a w f de range of water depths. Burger et a I. ( 1983) observed J uven I I e chinook at depths ranging from 0.2 to 9.5 ft In the Kenai River, Alaska, w h II e Everest and Chapman (1972) reported preferences for depths of 0.5 to 1.0 ft In two Idaho streams. Depth preferences from sever a I studIes are summar i zed In Table 5. In the m:ddle Susltna River, the greatest number of chI nook per eel I were found at depths of 0.1 1 o 0.5 ft In turbId water and 1.1 to 1.5 ft In low turbidity waters <Suchanek et at. 1984). Temporal depth fluctuations are usually most variable within the side channels and tributaries, while the sloughs, when Independent of the malnstem, are generally more un i form. Typical depths found In side -25- channels. side sloughs or tributaries are not considered to be a limiting factor for Juvenile chinook rearing In the middle Susltna River at the typical densities of fish presently found. 4.5 Cover Cover Is extremely Important to rearing anadromous salmonlds t o avoid predation by other fish. birds. and terrestrial animals and to avoid unsuitable velocities. Predation can cause significant mortal ltles among rearing Juveniles. particularly after emergence from the gravel <Allen 1969). Cover requIrements may vary d I urna II y. seasonal I y 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 lnstream organic debris. or undercut banks (8jornn 1971; Chapman and Bjornn 1969). Submerged cover Is provided by cobbles and boulders with su:table Interstitial spaces, logs and aqutttlc vegetation. Experiments have demonstrated that Juvenile fish numbers Increase when artificial 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 side channels and side slough~ Without the promotion of bank stab II lzatlon by the root! ng of herbaceous and woody vegetatl on, undercut banks have been unable to form. Large organic debris Is rare In side ch~nnels and Is found only to a minor degree In side sloughs. Hence, riparian vegetation, undercut banks and I arge organIc debrIs are not forms of cover typ I ca II y available for juvenile chinook In these habitats. These types of cover are -26- more prevalent In upland sloughs, although these erees oonteln relatively few juven II e chI nook. Cover for juvenile chinook In the middle Susltne River Is more typically provided by suitably sized substrate end turbid water. Field observations end catch data from ADF&G Indicate that juvenile chinook salmon abundance differs In turbid water compared to clear water. Catch rates at turbidities greater then 30 NTU were significantly higher (p = < 0.001> than at turbidities less then 30 NTU In cells without eny type of object cover. Thus, In the absence of object cover, turbid water Is used for cover by rearing chinook salmon (Suchanek et el. 1984). The utilization of turbidity es 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 wll I school If the water clears and move up to r Itt I es near the upstream end of the sIte where they seek out object cover. Middle Susltna River turbidity ievels at Gold Creek range from 1 to 1 ,000 NTU , wIth en average summar turo I dty of 200 NTU <E. Woody Trlhey end Associates end Woodward-clyde Consultants 1985). The newly emergent try In the tributaries are probably the most susceptible to predation. Indian River and Portage Creek afford little cover In the form of riparian vegetation, undercut banks, la r ge organic debris, or turbid wate r. In Indian River and Portage Creek, subs t rate composition and the percentage of fine materials present affect the amount of cover available to juvenile chinook. Large quantities of s lit a nd sand deposited In a channel may fill lntersltlal 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 ~edlments 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 slda 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 associate d with the overtoppIng t I ow s I ncr eases the amount of cover ava II ab I e. I ncr eases In numbers of Juvenile chinook In these cases may not be attributable solely to Juvenile chi nook seeking out turbid water tor cover. It may also be a function of access to migrating downstream. However. Juvenile chinook freely move upstream Into these sites. In response to salmon 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 ava II ab Ill ty. 4.6 Food Availability Fish food production Is probably the most ~mportant of the biotic factors affecting Juvenile chinook. Chapman (1966) suggests that the density of Juvenile anadromous salmonlds may be regulated by food avallabll lty. Young salmon can feed both off the bottom and on drifting foods (Keenleyslde -28- 1962), but In streams, browsIn g on enthos may be rare and organIsms are essentially derived from drift (EII l ott 1973; Mundie 1971). Published data on the food habits and feeding of young chlnooks a r e fragmentary. Everest and Chapman ( 1972) observed a strong posItIve correlation between the size of Juveni le chinook and water velocity at a gIven feedIng stat I on, and they postu I ated that the movement of the fIsh Into faster water as they grew was relate d to the availability of Insect drIft food. Burger et a 1. ( 1981 ) reported that J uven II e chI nook fed predominantly on chlronomlds In the Kenai River, Alaska, but they did not differentiate which life stage. Becker (1970) and Cauble, Gray, and Page 0980), In studies of Juvenile chinook feeding In the Hanford reac h of the Columbia River, found t hat 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 on l y 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 FaIrbanks, 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 contrIbutIon vo I umetr I cal I y to the stomac h contents of chI nook. However, their classification of adult terrestrial Insects Included those with Immature aquatic stages and they did not separate out chlronomlds. In 1982 AOF&G conducted Investigations of food habits of Juvenile chinook at five side sloughs and two clear w<!ter tributaries of the middle Susltna -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 numer i cally 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 adult~ 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 chI nook were exam I ned from sIde channels <AI aska Dept. of FIsh and Game, Sus I tna Hydro Aq uatl c StudIes 1983 a). Terrestrial Insects usually enter the drift by falling or being blown off riparian vegetation or washed In from channel side areas Inundated by rapid flow fluctuat i ons (Mundie 1969; Fisher and LaVoy 1972).-The relatively low Importance of terrestrial Insects In the diet o f juvenile ch i nook I n 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 c I ose border of rIparIan vegetatl on. Chlronomlds are the most ubiquitous of freshwater macrolnvertebrates and are successful In a wide range of environmenta l conditions. Brundln (1967 ) suggests that plelslomorph Chlronomldae were Initially cold adapted, thereby accountIng for theI r su c cess In the arctl c at temperatures often close to the I lmlt of I lfe. The avallabll lty of food Items for macrolnve r tebrates h as been recogn i zed as one of the major factors r~gulatlng their abund a nce and d istribution In streams <Cummins 1975; E ggll s h ~w 1969; Hyne s 1970 ). Filamentous algae or moss on a str e ambed -3o- provides food sources for chlronomlds, If not directly, then In the microfauna and flora they suppor~ 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 !959) 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 ask a'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 upwelling or bank seepage occurred. The most typical gr o wth was d I atomacous In nature and chI .·onom Ids were observed In as soc I at I on w I th 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 I ncr ease In stream f I ow (E. Woody Tr I hey and Associates and Woodward-Clyde-Consultants 1985). At prevailing springtime tcrbldltles (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 li miting. 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- workers had shown In experimental stream channels that flow perturbations lim I ted the growth of f II amentous algae. The euphotic zone at th Is time Is estimated to extend to an average depth of between 1.2 and 3.5 feet <Van Nleuwenhuyse 1984). In summer, malnstem flows are at their highest levels. The total surface area available for primary production Is limited by high turbidities that reduce the depth of useful I lght 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 sedimen t on the channel bed Is also an Important factor Influencing the degree of algal growth and Is extremely variab l e within and between side sloughs. Sediment deposition on the streambed may bury suitable sites for algal colonization and reduce the abll lty of filamentous forms to obtain firm attachment. Field observations by EWT&A suggest that some of the sediment carried through sloughs becomes part of an organic matrix of unknown composition (probably bacteria, fungi and other microbes), which Is colonized by a layer of pennate diatoms a nd filamentous a l gae, and covers streambed materla .l greater than two-three Inches. This type of growth was also observed In a number of ma! nstem and sIde chan ne I habItats. Phosphorus assocIated w lth the sedIment may enhance thIs growth <E. Woody Tr I hey and Associates and Woodwa r d-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 filamentous algae. This bloom was Induced partly by moderating streamtlows but principally by a notable reduction In turbidity levels to less than 20 NT~ The depth of 1he 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-C l yde Consultants 1985). Macrolnvertebrate populations are also dependent o n other factors In addition to their requirement for food. High flows can directly dislodge Immature Insects by s couring 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 lnfl let substantial losses on the benthic populations (Uifstrand 1968; Ulfstrand, Nilsson, and Stergar 1974; Maitland 1966). Accumulations ot fine streambed sediments, as occurs In side channels and sloughs, are widely reported to reduce benthic Invertebrate abundance <Cordone and Kelly 1961; DeMarch 1976; Gammon 1970; Koski 1972; Wagner 1959). In general, species diversity and density decrease progressively from cobble through gravel, sand and slit (Pennak and Van Gerpen 1974). ·sediments may restrict access to the undersurface of cobbles <Brusven and Prather 1974), leaving only exposed surfaces for colon i zation (Phillips -33- 1971). The unders urface of cobbles offers protection from predators and displacement by the current for many benthic I nvertebrates. Consequently, macrolnvertebrate abundance, particularly chlronomld populations, Is I lkely 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 tributaries than the side sloughs. Sloughs, when they become breached, will probably have Increased drift through them. Juvenile chinook typically feed on drift by sight (Mundie 1974). The abll tty 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 shallower depths and lower velocities to enhance feedIng on the drIft In these areas. Juven II e chI nook have been observed enterIng c I earwater s I ougns to feed on sa I 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 tr lbutar les, I ndl an Rl ver and Portage Creek. Indian River Is also one of the pr Inc I pa I coho rearIng areas, and chI ron om Ids were the domInant food numerically In juvenile coho stomach samples <Dugan, Sterrltt, and Stratton i984). 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 I mitations 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- widely variable at different sites and at different times of the growing season. Table 4 shows that juvenile chinook In tributary habitat displayed greater growth, In terms of length, than fish from side sloughs and side channels, even under a colder temperature regime (figure 8). Hence, food availability In the side channels and side sloughs Is I Jkely to be a I lmltlng factor to growth and thus overal I survival. 4. 7 Predat Jon The role of cover to avoid predation has been discussed In Section 4.5. Fish predators Include rainbow trout, rearing coho, resident dolly varden, and sculplns. Juvenile chinook are most susceptible to predat i on In the tributaries due to the presence of higher numbers of fish preda tors compared to those In side channels or side sloughs. Mortality from fish predation Is reduced for juvenile chinook that migrate to the side channels and obtain cover from the turbid water. When juvenile fish are ln the shallower turbid water or c l ear water of the sloughs and tributaries, they may also be taken by plsclvorous birds , notably kingfishers, dippers and merganlsers. Mortality from predation, In comparison to other factors, Js rel ~tlvely 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 I at lonsh I p between cover, food abundance and mlcrohabltal preferences of rearing salmonlds are not clearly understood, and thus the spatial needs are not adequately def 'ned (Reiser and Bjornn 1979). Space requirements vary with size and -35- 15 14 ---Simulated Tributary Temperature 13 D Hean '81/'82 Temperature at RM 150 12 + + tiean '81/'82 Temperature at 0 RM 110 . 11 ~ + + + + 0 + 0 0 + 0 10 ~ 0 D + + u 0 0 0 0 ~ D I.) 9 ~ ::::> + ~ 8 -. -':"-------r'-. ,... ...... 0 l>l / -... ~ .... l"il 7 /' ...... i!i / ' 0 E-< ' I 6 / ' VI ' 01 / ' I 5-/ ,, / ' ' 4~ / ' , ., 3~ " o' I \ I ., I 2-f ' 0 ' ., 1 ~ ' 6 ,m $ I ' 0 I I I I I JUNE JULY AUGUST SEPTEMBER OCTOBER Figure 8. Comparison between average weekly stream temperatures for the Susltna River and Its trIbutarIes. (University of AI aska, Arctic Environmental Information ana Data Center 1984a). time of year. Studies In California by Burns (1971> showed significant correlations between living space and salmonld b i omass. Juvenile chinook densities In t he side channels and side sloughs do not appear high enough for space requirements to become a s i gnificant factor. However, In the natal tributaries, Indian River and Portage Creek, space requirements may regulate densities of emergent chinook fry, particularly with the presenc e 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° C during the November- to-April per iod to 110 Cor 12o C from late June to mid July. Water temperatures I n 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 all of their clear water flow from loca l runoff and groundwater Inflow and display greater diurnal temperature fluctuat l ons than other fish habitats. During the winter, slough flow Is primarily maintained by upwe t llng groundwater with c;table temperatures around 30 C. The tem perature of the upwelling groundwater significantly Influences surface water temperatures In the slough, often maintaining them above 0° C throughout most of the winter. Salmonlds are cold water f i sh wi th well-defined temperature requirements during r earing. Wa t er temperature Influences growth rate, acti v ity and the ab II I ty to capture and use food. Brett ( 1952) I I sts t he preferred -31- temperature range for juvenile chinook to be 7.3 to 14.6° C and noted that chinook underyearl lngs displayed Increasing percentage weight gains as temperature was Increased from 10.00 to 15.7° C. When temperatures fell below the preferred minimum, growth rates became reduced. Ho~ever, 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 y In the opt I mum range. Tab I e 4 IndIcates that there was on I y a smal I Increase In length for juvenile chinook In the side channels and side sloughs from early September to mid-October, 1984, suggesting that the fall alga I b I oom does not seem to promote substantIal chI nook growth at that tl me. KenaI R lver chI nook fry grew from an average total length of 43 mm In ear I y May to an average of 71 mm by the end of October. Burger et a 1. (1983) consider H is 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 was90 mm In both 1981 and 1982. Assumlngthe1985 value Is llkelytobe similar, It Indicates that significant growth may occur In the spring before outmlgratlon, 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 Ice processes wIll be d lscussed further In Section 4.10 on overwintering survival. 4.10 Overwintering Survival OverwInterIng surv Iva I Is a sIgnIfIcant factor In the product I on of Juvenile rearing sal~onlds (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 salmon eggs from spawners may attract overwintering fish. Tributaries, malnstem and side channels are a I so known to be used by juven II e fIsh as overwInterIng areas. A com par I son between measured surface water temperatures In sIde s I oughs during the winter and simulated malnstem temperatures Is given In Table 7. Upwell lng In side sloughs and side channels may result In open leads throughout the wInter. Juvenile chinook become relatively Inactive at tow 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 fall below 6° C, juvenile chinook have been observed to move closer to cover <Burger et at. 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 ve 1 oc I ty break and restI n g habitat. Burger et a I. ( 1983 > observed that the substrate pI ay s a key ro I e In the -39- I • 0 I 19S2 19S2 19S3 location RM Feb Mar Apr Aug Sep Oct Nov Dec Jan Feb Mar Apr t Slough SA Mouth 125.4 6.5 2.4 1.7 0 0 0.4 1.3 Slough SA Upper 126.4 5.S 4.4 2.5 3.S Slough 9 12S.7 S.9 5.9 2.3 3.S Slough 11 135.7 2.5 3.1 3.3 3.1 2.9 2.9 2.9 2.9 3.0 3.5 Slough 21 141.S 1.6 1.9 3.1 2.2 1.1 o.s Mainstem LRX 29 126.1 0.0 0.0 2.9 10.9 6.5 0.6 0.0 0.0 0.0 0.0 0.0 3.0 LRX 53 140.2 0.0 0.0 2.5 10.S 6.4 0.6 0.0 0.0 0.0 0.0 0.0 2.6 Note: Mainstem temperatures are simulated without an ice cover and warm earlier in the spring than what naturally occurs. Thus the April mainstem temperatures are probably wanmer than what would occur. Table 7. Comparison between measured surface water temperatures <OC> In side sloughs and simulated average monthly malnstem temperatures. (Alaska Dept. of Fish and Game, Susltna Hydro Aquatic Studies 1983b). May 3.3 4.7 6.0 overwintering strategy of juvenile chinook In the Kenai Rive~ Bjor nn (1971) also considers substrate to be esse:1tlal for winter cover. Consequently, the quantity of deposited fine sediment In the channels may be an Important factor In detsrmlnlng suitable overwintering hablt~t. Remnants of the fall algal bloom may also act as cover, particular ly 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 juven ile chinook Is probably much reduc~d during the winter, and the major mortality arises from unsuitable physical conaltlons. Ice processes dominate the hydrological and biological characteristics of the middle Susltna River from November to April. The most Important factors affecting freeze-up of the Susltna River are al r and water temperature, lnstream hydrau lies and channel morpho I ogy . When side sloughs are occasionally overtopped by malnstem water during staging at freeze-up, the relatively warmer water Is reptaced by large volumes of 0° 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 lnstream Flow Relati o nships Report, Volume I <E. Woody Trlhey and Associates and Woodward-Clyde Consultants 1985). Stream Insects are wei I adapted to cold cond I tlons and may surv lve In egg or d I apause 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 damming effect and divert water out of establ lshed channels. Juvenile fish move 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 use I ess as cover to fish. However, the major source of mortal tty during the winter Is believed to be dewatering and freezing. Side channels and side sloughs without significant groundwater upwelling may freeze completely. In severe cases, this may Include the subsurface flow down to the water table. Tributaries like Indian River and Portage Creek csre less likely to freeze completely and will have some flowing water. Another problem caused by Ice procas ses for juvenile chinook occurs during spring breakup. The duration of the breakup period depends on the Intensity of solar radiation, air temperature, and precipitation. Tributaries have 11sual ly broken out In their ~ower e t evatlons 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 I n the river begin to rise and fluctuate with spring snowmelt and precipitation, the Ice cover erodes. Ice becomes undercut and collapses Into the open leads, drifting to the i r dow~stream ends and accumulating In smal I Ice jams. In this way, leads become steadily wider and longer. Major ice jams generally occur In shallow reaches of the malnstem, with a narrow confining thalweg channel along one bank, or at sharp river bends. Major jams are commonly found adjacent to side channels or sloughs. Breakup Ice jams commonly cause rapid, local stage Increases that continue rising until either the j a m releases o-the adjacent sloughs or side channels becom (! 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 Jce well up Into the t r ees. 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 cont i nues until the river Is swept clean of Ice except for stranded Ice f l oes along shore. These events have detrimental effects on the blot& A substantial amount of the spr i ng algal growth Is dislodged and carried downstream. Benthic macro- Invertebrate and 1+ chinook may become similarly displaced. Juvenile fish could be force d 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 probab l y highly variable from year to year. -43- 5.0 EVALUATION OF WITH-PROJECT CONOITI ~N S 5.1 Introduction This section of tha report subjectl~ely evaluates with-project effects on the abiotic and biotic factors outl lned fn Section 4 and discusses the possible Implications tor juvenile chinook salmon In the middle Susltna River. Tributary habitat should not be significantly altered under wit~. 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 lty subm ltted a report (Harza- Ebasco Susltna Joint Venture 1985a) to the Federal Energy Regulatory Commission evaluating alternative flow requirements to the flow regime speclt!ed In the orig i nal Susltna Hydroelectric Project License Appl lcatlon. In their evaluation, APA selected one alternative, Case E-VI, as the preferred a I ternat lve t I ow reg I me. The prImary reasons to ret I ne the earl fer flow scenzwlo were threefold. 1. The need to consider the use of malnstem and side channels tor rearing fish In establ lshlng flow requirements. This rational was not used In establishing Case C flow requirements In t~e license application. 2. The requirement tor seasonal flow control over the entire year In order to maintain overall 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 0 assumes both Watana and Oev I I Canyon reservoirs In operation and energy demand forecasts for 2002 and 2020. This subjective evaluation wll I focus on Case o. as It represents the I ong term scenarIo and the· greatest change In flow regime from preproJect condition~ 5.3 Discharge/Velocity A controlled flow regime under w_lth-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 constraints provide for a minimum discharge of 9.000 cfs (Harza-Ebasco Susltna Joint Venture 1985a) <Table 8). These lo~·f1r flows. as compared to natur~l conditions. wll I result In a reduction of side channel surface area. For examp l e, 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 hydraul lc conditions (Case E-VI-0) 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- Water Gold Creek Flow (cfs) Water Gold Creek Flow (cfs) Week Period Minimum Maximum Week Period Minimum Maximum --14 31 Dec. -06 Jan. 2,900 16,000 40 01 July -07 July 9,000* 35,000 15 07 Jan. -13 Jan. 2,000 16,000 41 08 July -14 July 9,000* 35,000 16 14 Jan. -20 Jan. 2,000 16,000 42 15 July -21 July 9,000* 35,000 17 21 Jan. -27 Jan. 2,000 16,000 43 22 July -28 July 9,000* 35,000 18 28 Jan. -03 Feb. 2,000 16,000 44 29 July -04 Aug. 9,000* 35,000 19 04 Feb. -10 Feb. 2,000 16,000 45 05 Aug. -11 Aug. 9,000* 35,000 20 11 Feb. -17 Feb. 2,000 16,000 46 12 Aug. -18 Aug. 9,000* 35,000 21 18 Feb. -24 Feb. 2,000 16,000 47 19 Aug. -25 Aug. 9,000* 35,000 22 25 Feb. -03 Mar. 2,000 16,000 48 26 Aug. -01 Sep. 9 ,000* ·. 35,000 23 04 Mar. -10 Mar. 2,000 16,000 49 02 Sep. -08 Sep. -8,000 35,000 24 11 Mar. -17 Mar. 2,000 16,000 50 09 Sep. -15 Sep. 7,000 35,000 I 25 18 Mar. -24 Mar. 2,000 16,000 51 16 Sep. -22 Sep. 6,000 35,000 • 26 25 Mar. -31 Mar. 2,000 16,000 52 23 Sep. -30. Sep. 6,000 35,000 01 I 27 01 Apr. -07 Apr. 2,000 16,000 l 01 Oct. -07 Oct. 6,000 18,000 28 08 Apr. -14 Apr. 2,000 16,000 2 08 Oct. -14 Oct. 6,000 17,000 29 15 Apr. -21 Apr. 2,000 16,000 3 15 Oct. -21 Oct. 5,000 16,000 30 22 Apr. -28 Apr. 2,000 16,000 4 22 Oct. -28 Oct. 4,000 16,000 31 29 Apr. -05 May 2,000 16,000 5 29 Oct. -04 Nov. 3,000 16,000 32 06 May -12 May 4,000 16,000 6 05 Nov. -11 Nov. 3,000 16,000 33 13 May -19 May 6,000 16,000 7 12 Nov. -18 Nov. 3,000 16,000 34 20 May -26 May 6,000 16,000 8 19 Nov. -25 Nov. 3,000 16,000 35 27 May -02 June 6,000 16,000 9 26 Nov. -02 Dec. 3,000 16,000 36 03 June -09 June 9,000* 35,000 10 03 Dec. -09 Dec. 2,000 16,000 37 10 J~ne -16 June 9,000* 35,000 11 10 Dec. -16 Dec. 2,000 16,000 38 17 June-23 Jun~ 9,000* 35,000 12 17 Dec. -23 Dec. 2,000 16,000 39 24 June -30 June 9,000* 35,000 13 24 Dec. -30 Dec. 2,000 16,000 * Minimum summer flows are 9,000 cfs except in dry years when the minimum will be 8,000 cfs. A dry year is defined by the one-in-ten year low flow. Table 8. Susltna hydroelectric prcject flow constraints for environmental flow requirement Case E-VI. (Harza-Ebasco Susltna Joint Venture ~985a). 2500 - MAINSTEM 100 1500 1000 500 400 -i 0 300 -'ii) Ill Cll 10 Q ... u IC ~ 200 -- :'; N. Ill t:) ... c.. ~ C/) Ill 5 c u 100 :l r:: -Ill ... n ::J t:) C/) )> C'O .., t:) 0 so CJ 1-- 40 ::J ~ 30 UPLAND SLOUGH 20 0 .5 10 .____,_ _ __.__....__L.. _ _.L.. _ _.._ _ _.___..._____. _ __._ _ _.__..........__..___-J 0 . 1 9 1 0 11 12 13 14 15 16 17 18 19 20 21 22 23 Mainstem Discharge at Gold Creek (x1Ql, cfs) Figure 9. Surface area responses to malnstem discharge In the Talkeetna-to- Devil Canyon reach of the Susltna River CRM 101 to 149). (Klinger and Tr I hey 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 wIll 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. within this period wll I also be less. Flow variations from year to year Although the simulated 34-year record ( 1950-1983) IndIcates that hIgh f I ow events w II I reach 37,000 cfs, the frequency of these events during the growing season wll I be markedly less, particularly In June and July <Figure 10). These flows will generally reduce the downstream · displacement of juven~ le chinook f r om the middle Susltna River and the mortal lty that can result If fish seek out refuge In lateral pools. 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 stabll lty of discharges under with-project conditions wll I result In less temporal depth variations, particularly In the side channels. -48- I 4:. 10 I Note: Figure 10. 40,000 30,000 Cll -u w 0 20,000 a: < :J: 0 en 0 10,000 0 -"' " .. " ...... " .. " .... " ........ " .... " .. / .... , " ' " ,_-/ --O,o(N)" -----Oso(D)-, j.·--,--O,o(D) __, , ___.. a,o(N) ;· ', ', N = NATURAL FLOW D = WITH PROJECT CASE D FLOW ', ',, ', ' ' '',,,',,, -.............. ',, "~ ', ------........_---""·----.... MAY JUNE JULY AUGUST SEPTEMBER OCTOBER Q10 Is the typical high flow1 Q50 Is the typical median flow, and Qgo Is the typical low flow. Comparison of the middle Susltna River natural and with-project (Case 0) exceedance flow (cfs) for the months May to October calculated from weekly streamflows for the water years 1950-1983. 5.5 Cover Turbid w8ter Is lmport8nt 8S cover for re8rlng juvenile chinook In The middle Susltna River. The W8t8n8 8nd Devil C8nyon reservoirs have been estimated to trap between 80 to 100 percent of the Incoming sediment <R & M Consultants, Inc. 1982). Particles smaller than 0.003 mm are likely to remain In suspension In the water releesed downstream. Per8trovlch, Nottingham 8nd Drage, Inc. (1982) estimate that turbidity levels downstream of the W8tana 8nd Devil Canyon dams wIll range from 20 to 50 NTU In the summer 8nd 10 to 20 NTU In the winter months. A theoretical plot of turbidity 8galnst depth of I lght penetration to the compensation point (depth at which I lght Intensity Is one percent of that 8t 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 8ppr·oxlmately 1.2 feet. Although ADF&G (Suchanek et al. 1984) found th8t juvenile chinook densities lncre .~sed at turbidities greater than 30 NTU, t his result does not define the value of 40 to 50 NTU water as cover compared to 200 NTU. AI though I I ght penetratl on Is greater at 40 to 50 NTU, the water may stl I I be suf f lc I entl y turbid to provide significant cover for juvenile chinook. However, water In the I ower w lth-project range of 20 to 30 NTU has a compen58tl on pol nt of five feet or greater 8nd Its cover value Is likely to be Jess. Presently, the amount of sediment transport during the summer In the middle Suslt •• a River Is extremely varl8ble, with high rates generally occurring during periods of peak flow events. However, under with-project conditions, virtual Jy all sand sized (grea ~er than 0~5 mm> and larger -5o- i= !:: F= fh c Figure 11. 2 3 4 !I I 7 II 9 TURBIDITY (NTU 'S) Theoretical curve of turbidity versus depth of compensation poi nt . (Reub, Trlhey, and Wilkinson 1985). -!>1- particles wll I be removed by deposition In the reservoirs. A greater percentage of the sediment load released do~nstream 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 will be coarse material eroded from the banks downstream of the dam anC: materIal brought down from the trIbutarIes. More energy shou I d be ava i I ab Je for transportIng sedIment than Is required to transport the available sediment supply; and hence, It has the ~otentlal to scour out and carry downstream fine sediments. Without the further deposition from high sediment loads, the avallabll lty 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 I lght penetration, and the reduction In streambed sedIment shou I d 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 allow a more stable shorel lne condition, thereby permitting a zone of riparian vegetation to potentially develop. ThIs vegetatl on cou I d reduce channel bank eros I on and provIde cover for Juvenile fish. However, Ice processes, In association with the higher winter flows, may limit riparian vegetation davelopment. 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 ma-e available and adequate:Jy compensate. These trad&-offs appear to favor with-project conditions for cover when the positive effects of lower turbidities on other significant rearing habitat factors are cons I dertld. 5.6 Food Avallab!l lty If, as discussed In Section 5.5, an overall Increase In primary production may be postulated under with-project conditions, then a general promotion of food organIsm product I on for juven I I e chI nook w II I resu It. Additionally, Increased flow stability and a decrease In fine sediment on the streambed should directly enhance the numbers of benthic Invertebrates, Inc I ud lng ch lronom Ids. less high flow events wll I probably reduce catastrophic drift of organisms. However, the overall rise In numbers of benth ic lnvertebr·ates Is likely to Increase density dependent drift. Overal I, the quantity of drift In malnstem as sociated habitats should be higher and drift rates of food organIsms w I II be more ura I form and constant throughou t the growIng season. In addition to Increased food avallabll lty, the ab i lity of juvenile chinook to locate the drifting prey Items wll I be Improved due to lower turbidity levels. The amount of drift entering a number of side s l oughs during the summer will, however, be reduced due to Jess overtopping events from lower average f I ows under wIth-project condItIons. Terrestr I a I In sects associate d with vegetation may become more significant In the diet of j uven I I e chI nook If rIparIan zones are ab I e to become estab I I shed 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 avall~ble and overall mortality from this source Is likely to remain comparatively negllble. 5.8 Space Requirements Do~nstream 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 a!; conditions are relatively unfavorable for rearing fls~ Under a with-project scenario of reduced flow variation, less high flow events, and Increased food availability, fish that previously migrated from the middle Susltna River may remain In the more favorable rearing conditions of the side c hannels and densities should Increase. However, It Is unlikely that densities wIll attain levels where space r equirements become significant. The retention of greater numbers of rearing juveniles and Improved rearing condl ~lons should enhance survival and may lead to an overall Improvement In smolt production from the middle Susltna River. Competition for space may actually Intensify In the tributaries If seeded at h l gher levels as a consequence of Increases of numbers of returning spawner~ -54- 5.9 Temperature Project operation wll I have a notable Influence on the temperature of water dIscharged bel ow the dams. The reservol rs w I I I store heat In the summer while releasing water with lo~er-than-natural temperatures between spring breakup and mid-summer. For the remainder 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 ( 1 01 .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 Table 9. Simulated monthly mean temperatures (OC) for the malnstem Susltna River, Devil Canyon to Talkeetna. <University of Alaska, Arctic EnvIronmental Information and Data Center 1984). Water temperatures from May through October may potentIally reduce the growth rates of juvenile chinook. AEIDC produced estimates 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 derived by Brett (1974) from observations on sockeye salmon. Results showed that for simulated ma!nstem temperatures at RM 130, Juvenile fish would potentially have a 24 to 29 percent reduction In body weight over the May to October grow lng 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 showed that Juvenile chinook In the tributaries under a colder temperature regime displayed greater growth, In terms of length, over the May to October per I od than Juven II e fIsh from sIde channels and side sloughs. Greater food avallabll lty In the tributaries was probably the dominant factor accounting for Increased growth. Hence, under w i th- 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 o·t tls~. 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 7° C Is reached In late June. The delay of two to_ three weeks compared to natural conditions Is unl lkely to have a detrimental effect on smolt surv Ivai. Average September to Apr II mal nstem temperatures bel ow the Dev II Canyon dam under w lth-project condItIons w II I range from 1.4 to 2.7° C Just upstream of the Chul ltna River confluence and 2.3 to 4.oo C near Portage Creek. These temperatures are respective I y 0.4 to 1.4° C and 1.9 to 2.9° C warmer -56- than na t ural temperatures <University of Alaska. Arctic Env i ronmental Information and Data Center 1984a). Consequently. a better ma l nstem 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 sf de channel habItats. 5.10 Overwintering Survival The operation of the hydroelectr i c 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 th~ ord~r cf six to eight times greater than flows under natural co nditions for the months November through Apr II <F lgure 12). Upstream of the Ice front. staging levels wll I be lower du e to -lack of freeze-up. despite Increased winter flows. and groundwater upwel I lng may be reduced In side s l o ughs. Anchor Ice may form In open water areas during cold periods. affecting flow distribution between chann e ls and adversely Influencing overwinteri ng fish. Downstream of the Ice front. the higher winter flows are I l kely to Increase upwel I !ng rates and may lead to an Increase In the surface area of openwater. low velocity side channel and sIde s I ough habItat. However. the benet It of upwel II ng areas for overwintering chinook may be lessened If. due to the higher flows. side -57- I Ul «f' 15,000 N = NATURAL FLOW 0 = WITH PROJECT CASE 0 FLOW llf -10,000 -------------~ ~ QII(D) a .. (o) u UJ ~ a: c( :I:. 0 ----... __ _........__ _______ ---....____ ------------u .. (D) CJ) i5 5,000 .,___ ---------------a,o( ... ... ... ... _________ -::-:-:.:-::-:-:.:-:.::.::.:::::=:::==~==~= QH(N) ---.::.:..------------• -·-•-• • -·--·-·-· a.o(N)-·-·-·-·-·-0 NOVEMBER DECEMBER JANUARY FEBRUARY MARCH APRIL Note: Q10 Is the typical high flow1 Q50 Is the typical median flo~, and Q90 Is the typical ·low flow. Figure 12. Comparison of the middle Susltna River natural and with-project (Case 0) exceedance flows (cfs) for the months November to April calculated from average weekly streamflows for the water years 1950-1983. sloughs and side channels become overtopped with near 0° C water more frequent! y. The reduction In fine sediment on the streambed wll I Improve winter cover for juvenile chinook. A potential problem with regard to the effect of Ice processes on overwintering chinook under with-project conditions Is the degree of dally fluctuations In flow. If significant variations do take place, then local lzed flooding and dewatering could occur with detrimental effects and I ncr ease chI nook mort a II ty. Average temperatures for the November to Apr II period wIll be 0.5 to 3.0° C warmer under with-project conditions (Table 10), although from December to March they will be near 0° C. With the warmer temperatures extending through the fall, freeze-up of the river below the dam would be delayed <Tatlle 11>. Since the maximum upstream extent of the Ice cover below the dams would be som8where between RM 124 and RM 142, there would be no continuous Ice cover between this area and the damslte, and consequently, no breakup or meltout In that reach. With warmer and more stable flows, a slower meltout of Ice cover In place wll I occur. This gradual spring meltout Is predicted to be 7 to 8 weeks earlier than normal with both dams In operation. With the slower meltout, extensive volumes of broken Ice would not be floating downstream and accumulating against unbroken Ice ~ cover, thereby lessening the Incidence of Ice Jamming. This would substantially reduce river staging and localized flooding In the spring. The overal I shorter winter period of extremely low temperatures and less severe sprIng breakup condItIons has the potent! al to Improve the overwintering survival of chinook. -59- 1971 -1972 Neturel Oev II Canyon 2020 RM Renge Me en Renge Me en 150 0 -6.8 0.7 0.6 -8.4 2.6 130 0 -6.9 0.8 0 -8.3 2.0 100 0 -7.1 0.8 0 -8.5 1.6 1974 -1975 Neturel Dev II Cenyon 2020 RM Renge Meen Renge Meen 150 0 -8.5 0.9 0 .5-10.0 3.0 130 0 -8.6 1 .o (i -9.9 2.3 100 0 -9.1 1 • 1 0 -10.3 1 .9 1981 -1982 Neturel Dev II Cenyon 2020 RM Renge Me en Renge Me en 150 0-7.7 1.1 0.8 -8.6 3.9 130 0-7 .9 1 • 1 0 -8.5 3.4 100 0 -8.4 1 .3 0 -9.0 2.7 1982 -1983 Neturel Dev II Canyon 2020 RM Renge Me en Renge Me en 150 0-7.9 1.1 0.6-9.1 3.2 130 0 -8.0 1.2 0 -9.0 2.7 100 0 -8.4 1.3 0 -9.3 2.1 Table 10. Susltne River tempereture renges <°C> for the period September through April under neturel end with-project conditions (both dams -2020 demand). (University of Alaska, Arctic Environmental I nformatl on end Deta Center 1984a). -6o- Noturo! Qondltlons 1971 -72 1976 -77 1981 -82 1982 -83 Both Doms -2020 Oemond 1971 -72 1982 -83 StartIng Date at Chulitna Confluence Nov5 Dec 8 Nov 18 Nov 5 Dec 5 Dec 14 Mel-t-out Date May 1 D-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 natural and with-project conditions (both dams -2020 demand). <Harzo-Ebasco Susltna Joint Venture 1984). -61- REFERENCES Alaska Dept. of Fish and Game, Susltna Hydro Aquatic Studies. 1981a. Phase I final draft report. Adult anadromous fisheries project. Alaska Power Authority. Susltna Hydroelectric Project. Report for Acres American Inc., Buffalo, NY. 1 vol. --· 1981b. Phase I final draft report. Resident fish Investigations on the upper Susltna River. Alaska Power Authority. Susltna Hydroelectric Project. 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