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HomeMy WebLinkAboutAPA4013I I I I I ! I I iK lL/~5" ,$8 Ad-3 v\.o I '-t D\3 PRELIMINARY DRAFT IMPACT ASSESSMENT TECHNICAL MEMORANDUM SEDIMENT TRANSPORT Prepared By: Arctic Environmental Information and Data Center University of Alaska-Fairbanks 707 "A"Street Anchorage,Alaska 99501 Submitted to: Harza-Ebasco Susitna Joint Venture 711 "H"Street Anchorage,Alaska 99501 1985 ARLIS Alaska Resources LihrMy &Information Services lUlehorage.A1aska .J ~ ex:> Nr-... ~ ~ ooo LC) LC)r-... M M TABLE OF CONTENTS INTRODUCTION • PURPOSE STATEMENT OF THE PROBLEM • OVERVIEW OF ENVIRONMENTAL ASSESSMENT TECHNIQUES. METHODS AND PROCEDURES • FISH RESOURCE. IMPOUNDMENT ZONE • MIDDLE RIVER • LOWER RIVER SEDIMENT EFFECTS ON AQUATIC ORGANISMS. SEDIMENT TRANSPORT • OVERVIEW • SYNOPSIS OF RESULTS. ANALYSIS. ANTICIPATED NEGATIVE EFFECTS • Impoundment. Middle River • Lower River. POTENTIAL WITH-PROJECT BENEFICIAL EFFECTS SUMMARY REFERENCES • 1 1 3 5 10 12 13 19 29 32 35 35 44 46 46 46 49 55 57 59 63 ARLIS Alaska Resources Library &Information Services lUlchorage,Alaska INTRODUCTION ? PURPOSE This transport ftf~o7 document is a comprehensive assessment of f with-proj ect sediment on fish associated with the proposed upper Susitna River basin the Susitna Hydroelectric Proj ect. hydroelectric development.Impoundment of the upper Susitna River would cause a change in the natural pattern of stream discharge and,consequently,of suspended sediments,bedload,sedimentation,and river bed aggradation and degradation.Since suspended sediments and bedload are important variables Gt,ffecting habitat for Susitna River drainage fish,studies were initiated in the beginning phases of Susitna environmental investigations to identify potential adverse or beneficial with-project effects of the expected alteration. This report is one in a series on aquatic impact issues associated with These issues --instream temperature, 0€~r\vC«-,"",lP'r,v("' water quality,turbidity,instream ice,and ~d --are examined separately in five separate technical memoranda.Following review they will be integrated into a single draft impact assessment report.The Alaska Power Authority and Harza-Ebasco intends to utilize the final impact assessment technical memorandum to discuss issues with agencies and intervenors in the Susitna licensing process. Impact issues addressed in this series of reports were defined in the course of the Susitna licensing process.Following Federal Energy Regulatory Commission (FERC)review of the original license application,the Alaska Power Authority corrected noted deficiencies and provided supplemental information. The license application was subsequently ruled acceptable.FERC then proceeded with the preparation of an Environmental Impact Statement (EIS). 33RD4-005 - 1 - This decision set in motion a chain of events in accordance with Council on Environmental Quality mandates on EIS preparation (Vide 40 CFR 1500). Significant issues to be analyzed in depth in the EIS were identified during scoping meetings.Twelve fishery were identified to this process;of these, Issues F-1, F-2, F-4,F-5,and F-6 identified the effects of with-proj ect flows on salmon and resident fish habitats and populations as topics to be addressed. APA commissioned a series of environmental field investigations and analyses of existing published and unpublished information to provide accurate statements of expected impact of the Susitna project on sediment transport and river morphology,and subsequently,on fish resources.Over the years the data base and statements of anticipated effects have been scrutinized by agency and intervenor representatives in a series of workshops and discussions. This process has refined the data base and impact statements based on it. This document is intended to serve as a discussion document and as an aid to decision-making.It contains a presentation of the sediment transport issue, a brief synopsis of the relevant information base,the ramifications of altered sediment regimes to aquatic habitats and fish,and the projected effects on fish due to various modes of Susitna project operation.It does not contain voluminous data and analyses of sediment and river morphology. Statements of effect or of no effect and the confidence with which those statements are made are provided. 33RD4-005 - 2 - STATEMENT OF THE PROBLEM The proposed project is sited in the upper Susitna River drainage basin and consists of two dams to be constructed over a period of about 15 years. The first dam,known as the Watana Dam,would be completed near RM 184 at a site three miles upstream from Tsusena Creek.It would include an undergrou~d powerhouse and an 885 ft high earthfill dam and a reservoir approximately 50 miles in length.This reservoir would have a surface area of 38,000 acres and a usable storage capacity of 3.7 million acre-feet (ma£).The second dam, named Devil Canyon,would be built near RM 152 at a site 33 miles downstream of the Watana dam site.It would be 645 ft high and would impound a 26-mile-Iong reservoir,having a surface area of 7,800 acres and a usable storage capacity of 0.36 maf (Acres American,1983). Construction and subsequent operation of the two Susitna hydroelectric dams is expected to alter the normal sediment transport regime of the river, thereby influencing river bed morphology.With both dams on-line,the area between Devil Canyon (RM 152)and the Oshentna River (RM 235)would be converted from a lotic to a lentic system.After impoundment,these reservoirs would resemble naturally occurring,deep,glacial lakes (Acres 1983). Sediment trap efficiencies of the Watana Dam alone and of the Watana and Devil Canyon dams together have been estimated by modeling and by fitting data to two different reservoir sedimentation curves (Harza-Ebasco Susitna Joint Venture 1984a).Results indicate that the dams would trap between 78 to 100% of all sediment entering the reservoirs (Harza-Ebasco Susitna Joint Venture 1984a).This,coupled with regulated with-project flows,would noticeably affect instream environments downstream of the dams in several ways. 33RD4-005 - 3 - i I ( ! I ·l I I r 1 j I I i --.---.----.-..-----.--..----.----..-.-..---..----.-.-------.--....--.--..-----..--..-...-.-..-.---.-.-..--.---..-.-..--..---..--.-.--..--.---..-------.--..-.'.,I i ) .1 ,l l ) Suspended load and bedload would be markedly reduced from those seen naturally.This situation would preyail to a point downstream of the ")VTalkeetnaandChulitnariversrespectiveconfluenceswiththeSusitna. I'- Because of their very large sediment loads relative to the mainstem,input from the Talkeetna and Chulitna rivers with-project would dominate the Susitna's sediment load in a manner analogous to present (R&M 1982a; Harza-Ebasco ~Joint ve;t~~"~Partly as a consequence of reduced sediment load and partly because of the with-project flow regime,the main channel of the Susitna River above the confluence with the Talkeetna would have a tendency to narrow and,in spots,degrade (R&M 1982a;Harza-Ebasco Susitna Joint Venture 1985).Some sloughs and tributary streams would become perched and some mainstem habitats could become dewatered as a result (R&M 1982a;Harza-Ebasco Susitna Joint Venture 1985;R&M and EWT&A 1985).In time, the river bed would attain a new equilibrium with the with-project flows.The reservoirs would also dampen the effects of freshets,reducing instances of flood waters entering sloughs.These changes could fffect fish population I numbers. " '\"'J \j r."!"' ~.,. j (J}) ,oj 'J ";}I tJ"~ ~;J\ )~~I l.../ I \ '.~ c..Lu-1~7 ! \ ., .';," CJ -/1, U 33RD4-005 - 4 - :I ,/ '.I l ,j I \ I 'I J ,I :'! :I ( ----------------------~------~----------------------------------------.---.-----------------------------------------.---".-.----------------------~--------------~~-~------------'.1 II I I j :I :\ I OVERVIEW OF ENVIRONMENTAL ASSESSMENT TECHNIQUES Over the past 30 or so years,a variety of methods have been developed for use in evaluating environmental impacts.The impetus behind this effort was,and remains,federal resource management law.Prominent federal environmental acts (table 1)were reviewed to identify fish and wildlife· impact assessment requirements.Four broad areas of public interest form common themes in environmental law:species-populations,biological integrity,environmental values,and habitat.Common methods of addressing these themes are reviewed below,as is the methodology used in this analysis. The first class of environmental assessment techniques examined is that of species-populations.Notable federal acts calling for this approach include the Endangered Species Act,the Federal Nonnuclear Energy Research and Development Act,the Surface Mining Control and Reclamation Act,and the Federal Water Pollution Control Act (table 1).Many and diverse schemes exist for estimating population numbers and density.The simplest technique,and possibly the one in widest use by managers,is the index.Population assessment indices are of two distinctly different types.The first is a count of animals made in a manner which does not allow direct population estimation by application of sampling theory.This technique employs a sample survey in the absence of known sampling probabilities.Many ADF&G fish escapement surveys are of this type.The second kind of index is one based on complete counts of some known portion of a population,e.g.,salmon on redds in a given reach of river.This approach allows one to conduct a relatively intensive and statistically valid analysis by incoporating basic knowledge of a species life history with the count data.Multiple regression analysis is the most frequently used tool in this regard. 33RD4-005 - 5 - i ) I Table 1.Federal acts which independently and collectively establish minimum standards for environment impact assessment. Archeological and Historic Preservation Act,16 U.S.C.469,et seq. Clean Air Act,as amended,42 U.S.C.7401,et seq. Coastal Zone Management Act,16 U.S.C.1451-,-et seq. Endangered Species Act,16 u.S.C 1531,et seq.--- Estuary Protection Act,16 U.S.C.1221,e~seq. Federal Land Policy and Management Act,43 U.S.C.1701,et seq. Federal Nonnuclear Energy Research and Development Act,42 U.S.C.5901 et ~. Federal Water Pollution Control Act,33 U.S.C.1251,~~. Federal Water Project Recreation Act,16 U.S.C.460-1(12),et seq. Fish and Wildlife Coordination Act,16 U.S.C.661,et seq.----- Forest and Rangeland Renewable Resources Planning Act,-r6 U.S.C.1601,et seq. Land and Water Conservation Fund Act,16 U.S.C.4601 -4601-11,et seq.----- Marine Protection,Research and Sanctuary Act,33 U.S.C.1401,et seq. National Environmental Policy Act,42 U.S.C.4321m et seq, National Historic Preservation Act,16 U.S.C.470a,et seq. National Forest Management Act,16 U.S.C.472,et seq. Rivers and Harbors Act,33 U.S.C.403,et seq. Soil and Water Resources Conservation Act,-r6 U.S.C.2001,~~. Surface Mining Control and Reclamation Act,30 U.S.C.1201,et ~. Water Resources Planning Act,42 U.S.C.1962,et ~.. Watershed Protection and Flood Prevention Act,16 U.S.C.1001,et ~. 33RD4-005 - 6 - I j I More involved methods of population assessment include direct counts and variants of the mark,release,and subsequent recapture technique.Direct counts are best in terms of validity,but naturally turbid conditions in the Susitna drainage hamper its use there.Over the last decade,the ADF&G and the USFWS have expended much effort in improving electronic fish counters for use in turbid conditions.This work has greatly influenced census work in many glacially-moderated systems. Mark-recapture techniques have a relatively long history of use in the United States.While widely used and under continual evolution,none of them produce overly satisfying results in a statistical sense.This is because all mark-recapture techniques rely on a range of assumptions which are difficult to meet in the wild (e.g.,one common assumption is that there exists a well defined population of animals;another is that the average probability of observing a marked animal is equal to the average probability of observing an unmarked animal). The chief pieces of legislation calling for its use are the Federal Water Pollution Control Act and the National Environmental Policy Act (table 1).If fully applied,such an approach would document energy flow through the system allowing one to precisely predict overall effects of change.In practice this is never done because it is very labor intensive and,thus too costly. Instead,it is common for a few representative species and/or relationships to be singled out for study,thereby narrowing its scope.Field study is typically undertaken to document seasonal numbers of target species in the study (often without regard to their relationship to local or regional populations),their habits (e.g.,special use areas),and food resources. Biologically based on assessments have increasingly made use of models (some 33RD4-005 - 7 - elaborate,some not)to predict with-project effects.Two factors limit the veracity of conclusions reached by this approach.First,a given model's ability to predict the future depends heavily on whether it is multidimensional or not and the assumptions used.Most models used are one dimensional limiting their utility.Second,conclusions reached in this I I \ approach are subjectively applied ad hoc to the system as a whole. Consideration of economic and environmental values (the third of the four areas of public interest addressed by federal law)is the essence of the National Environmental Policy Act.This approach to impact assessment usually entails estimating the monetary and nonmonetary values of the resources to be affected.Implementation of a values approach to impact assessment is (and will continue to be)limited by the difficulty (some would say the impossibility)of setting values on often intangible environmental components such as aesthetics. The fourth approach to environmental impact assessment recognized by federal law is habitat analysis.The principal laws legitimizing this approach are the Federal Land Policy and Management Act,the Fish and Wildlife Coordination Act,the Forest and Rangeland Renewable Resources Planning Act, the Endangered Species Act,and the Surface Mining Control and Reclamation Act (table 1).Various techniques are available for characterizing habitat quality.For example,species diversity is often used as an index of habitat quality.This type of index accounts for both numbers of species and numbers of individuals of each species in each habitat type.The approach has been challenged on a number of grounds.For example Wiens (1978)points out that it is insensitive to which species are present (Le.,it treats rare and common species alike),while Inhaber (1976)notes the absence of a standard of comparison (a problem of all biological indices). 33RD4-005 - 8 - Another habitat based impact assessment approach is the U.S.Fish and Wildlife Services Habitat Evaluation Procedures (HEP).HEP is a species-habitat approach;habitat quality being denoted through use of an index derived by evaluating the ability of key habitat components to supply the life requisites of the subject species.Its chief limitation is that predictions made are applicable only for the species being evaluated,i.e.,it does not directly relate that species to other ecosystem components. The U.S.Fish and Wildlife Service's Instream Flow Incremental Methodology (IFIM),another habitat based approach,is closely related to HEP in logic.It too focuses on target species relationships with their habitat, defined as Weighted Usable Area (WUA).Water depth,velocity,and substrate data are coupled with habitat suitability curves to compute WUA.The chief limitation of this approach is that it fails to take into account the effects of with-project change on factors such as growth,competition,mortality,and movement.These limitations are at the heart of a recent benchmark judicial ruling (Energy Management 1984)against use of the IFIM and in favor of a less rigorous,more qualitative,approach. 33RD4-005 -9 - METHODS AND PROCEDURES The existing Susitna River Information base consists of a mix of quantitative and qualitative data and model results:some is compatible,some is not.It is strongly biased towards habitat descriptors.Natural and qualitative with-project environmental parameters are well known,as are the likely responses of aquatic organisms to changes of the types predicted.Given this, a habitat based impact assessment is the logical technique of choice for the Susitna River study. This analysis was accomplished by comparing predictions of the with-project environment with information on fish distribution,abundance,and habits and on known fish and invertebrate response to perturbations of the types predicted.Professional judgement was used as necessary to interpret the relationship between various data base components,Le.,the relative comparability and utility of quantitative information vs. information vs.model runs. To assess effects of with-project changes in sediment transport on instream biota,AEIDC first reviewed the information base on how suspended sediments affect aquatic organisms.Ideally,information used in an effects analysis is specific to the water body in question.Pertinent Susitna River specific information (i.e.,data on sediment effects on the biota)is not broad in scope,consisting only of preliminary primary production data and ocular estimates of the appearance of in-slough spawning gravels following floods.Where necessary,information from other areas and latitudes was used to aid in the analysis.This factor imposed no constraint on conclusions reached because organisms respond to sediments in similar ways worldwide. Next,information on Susitna River fish stocks was assembled and synthesized. 33RD4-005 -10 - Following this,estimates of with-project environmental changes (and the information and procedures used in deriving them)were reviewed.Both the information base on fish stocks and that on the with-project sediment transport regime are adequate for use in an effects analysis.These three steps (determining how various life forms are affected by sediments,compiling information on the fish resource,and reviewing project sediment transport studies)provided the basis for predicting effects of the with-project sediment transport regime on aquatic organisms. Available information is sufficient to address with-project sediment transport effects on 13 of the 19 fish species present in the project area. These are all five salmon species,eulachon,Bering cisco,burbot,round and humpback whitefish,rainbow trout,Arctic grayling,and lake trout. Tables 11,12,and 13 summarize predicted with-project negative sediment transport-related effects on fish.Collectively,they provide an overview of anticipated negative effects by species,location,and time of year for both the Watana Dam and Watana and Devil Canyon dams together.A dimensionless ordinal scale identifies the relative severity of anticipated effects.Its values range from: o -given predictions of the with-project sediment transport regime and available knowledge of the fish species in question,no negative effects are likely. 1 -the with-project sediment transport regime ·could negatively influ- ence a species life stage,but the effects should be relatively minor. 33RD4-005 -11 - burbot,little is known of the life histories of resident fish at this season. A synopsis of available fish resource information follows. IMPOUNDMENT ZONE The principal source of information on fish distribution,abundance, habitat use,and life history in the impoundment zone is ADF&G 1981a and 1983d.Impoundment study area investigations were conducted in 1981 and 1982 by ADF&G Su-Hydro during the open water field season (May-October).These studies concentrated on Arctic grayling,making data on this species the most complete.Data on overwintering activities in this area is particularly scarce for all species.The major objectives of this study were to: 1)determine the seasonal distribution and abundance of fish populations in the proposed impoundment area;2)identify spawning and rearing areas;and 3)determine the physical and chemical characteristics of these habitats (ADF&G 1981a,1983d).More specific tasks dealt with determining the distribution,abundance,and migratory habits of Arctic grayling;determining the distribution and relative abundance of selected resident fish species; determining the abundance of lake trout and Arctic grayling in Sally Lake; recording biological information on selected resident fish populations to provide information on survival and growth;and identifying Arctic grayling spawning and rearing locations within and adjacent to the with-project impoundment areas (ADF&G 1983d). Prior to initiation of the 1981 ADF&G Su-Hydro studies,fish resource data for this area were collected by the U.S.Fish &Wildlife Service (1952, 1954,1957,1959a,1959b,1960,1965)and ADF&G (1978).These studies were preliminary Susitna environmental assessments designed primarily to define species composition.They also highlighted selected habitat locations of 33RD4-005 -13 - 2 -given available information,the with-project sediment transport regime would negatively affect fish productivity. 3 -available information indicates that the with-project sediment transport regime may negatively affect a species productivity,but more data are needed to so state with certainty. The veracity of conclusions reached varies by species and by river reach in consequence of differences in available information quantity and type. FISH RESOURCE Judged against criteria for EIS preparation (40 CFR 1500),existing information on Susitna River fish resources is generally adequate for an assessment of with-project effects.(An EIS is simply an accounting tool whose chief purpose is to ensure that all elements deemed significant by.the scoping process are considered in decision making.)Available information on open water season salmon-life stage activities (distribution,abundance, spawning timing and location,rearing,and migration)is quite complete;the overwinter salmon data base is much less so.Nonetheless,it is sufficient for the purposes used.Tables 2 and 3 respectively provide an overview of basinwide salmon escapements and the time of occurrence of their maj or life phases.As with salmon,information on resident species is much more complete for the open water season than it is for winter.Unlike salmon,however,it is heavily weighted towards selected species.It,too,is sufficient for EIS preparation purposes.Information on rainbow trout,burbot,and Arctic grayling in the open water season is more complete than for other residents. With the exception of limited winter radio-tagging data for rainbow trout and 33RD4-005 -12 - I I I Table 2.Susitna River Salmon Escapement Estimates,1981-1984. Year Chinook Sockeye 1 Pink Chum Coho 2Total 1981 272,500 85,600 282,700 36,800 677,600 1982 265,200 890,500 458,200 79,800 1,693,700 1983 176,200 101,300 276,800 24,100 578,400 1984 250,000 605,800 3,629,900 812,700 190,100 5,488,500 1 Second run sockeye only. 2 The 1984 drainage wide escapement estimates.Escapement counts for 1981 through 1983 do not include chinooks or any escapements into tributaries downstream of RM 77,with the exception of those into the Yentna River. Source:ADF&G 1983a;Barrett,Thompson,and Wick 1984,1985. 33RD4-005 -14 - Table 3.Susitna River Salmon Phenology. DATE HABITAT RANGE PEAK CHINOOK (KING)SALMON Adult Inmigration Cook Inlet -Talkeetna May 25 -Aug 18 Jun 18 -Jun 30 Talkeetna -D.C.Jun 07 -Aug 20 Jun 24 -Jul 04 Middle River Tributaries Jul 01 -Aug 06 Juvenile Migration Middle River 1&3May18-Oct 03 Spa~ming Middle River Tributaries Jul 01 -Aug 26 Jul 20 -Jul 27 Lower River Tributaries Jul 07 -Aug 20 Jul 20 -Jul 27 COHO (SILVER)SALMON I-' lJ1 Adult Inmigration Cook Inlet -Talkeetna Jul 07 -Sep 28 Jul 27 -Aug 20 Talkeetna -D.C.Jul 18 -Sep 19 Aug 12 -Aug 26 Middle River Tributaries Aug 08 -Sep 27 Middle River 1&3 May 28 -Aug 21JuvenileMigrationHay18-Oct 12 Spawning Middle River Tributaries Sep 01 -Oct 08 Sep 05 -Sep 24 Lower River Tributaries Aug 08 -Oct 01 CHUM (DOG)SALMON Adult Inmigration Cook Inlet -Talkeetna Jun 24 -Sep 28 Jul 27 -Aug 02 Talkeetna -D.C.JulIO -Sep 15 Aug 01 -Aug 17 Middle River Tributaries Jul 27 -Sep 06 Hiddle River Sloughs Aug 06 -Sep 05 3 May 28 -Jul 17JuvenileHigrationMiddleRiverHay18-Aug 20 33RCl/007h Table 3.Susitna River Salmon Phenology. (cont'd) DATE HABITAT RANGE PEAK Spawning Middle River Tributaries Jul 27 -Oct 01 Aug 05 -Sep 10 Middle River Sloughs Aug 05 -Oct 11 Aug 20 -Sep 25 Middle River Mainstem Sep 02 -Sep 19 Lower River Tributaries Jul 27 -Sep 09 Aug 06 -Aug 14 SOCKEYE (RED)SALMON 2 Adult Inmigration Cook Inlet -Talkeetna Jul 04 -Aug 08 Jul 18 -Jul 27 Talkeetna -D.C.Jul 16 -Sep 18 Jul 31 -Aug 05 Juvenile Migration Niddle River 1&3 Jun 22 -Jul 17Nay18-Oct 11 ......Spawning Middle River Sloughs Aug 05 -Oct 11 Aug 25 -Sep 25 0' PINK (HU}WBACK)SALMON Adult Inmigration Cook Inlet -Talkeetna Jun 28 -Sep 10 Jul 26 -Aug 03 Talkeetna -D.C.JulIO -Aug 30 Aug 01 -Aug 08 Middle River Tributaries Jul 27 -Aug 23 Middle River Sloughs Aug 04 -Aug 17 3 May 29 -Jun 08JuvenileMigrationMiddleRiverMay18-Jul 24 Spawning Niddle River Tributaries Jul 27 -Aug 30 Aug 10 -Aug 25 Middle River Sloughs Aug 04 -Aug 30 Aug 15 -Aug 30 Lower River Tributaries Jul 27 -Sep 09 Aug 06 -Aug 09 ~All migration (includes migration to and between habitat,not just outmigration). 3 Second run sockeye only. No data available for pre-breakup movement;earlier date of given range refers to initiation of outmigrant trap operation. Source:Barrett,Thompson and Wick 1984,1985;Schmidt et al.1984;ADF&G 1983a,c. 33RCl/007h/2 particular interest.Additional information on the fish resource in this area is found in the transmission corridor studies of Schmidt et ale 1984c. The natural environment between Devil Canyon and the upstream end of the proposed Watana Reservoir provides habitats for nine fish species (ADF&G 1983d);eight are year-round residents and one (chinook salmon)is anadromous (Figure 1).Within Devil Canyon,Fog Creek (RM 176.7)marks the upstream limit of salmon migration in the mainstem Susitna River.Only three streams, in the canyon had salmon observed in them during 1984.These streams, (Cheechako,Chinook,and Fog creeks)had,in total,fewer than 100 chinook salmon observed using them for spawning (Barrett,Thompson and Wick 1985). Arctic grayling are the most widely distributed and abundant species utilizing habitats above the canyon.The total 1982 Arctic grayling population above 15 cm in length in eight of the impoundment zone streams was estimated to be over 16,000 (ADF&G 1983b).Mainstem areas above the canyon provide essential overwintering habitat for Arctic grayling,which move .into tributaries to spawn following breakup in late Mayor early June (ADF&G 1983d).Arctic grayling migrate out of natal tributaries in September as I water levels and temperatures begin to drop.They overwinter in mainstem environments which become less turbid following freeze-up (ADF&G 1983d). Except for documentation of their presence,little is known of the relative abundance of other species resident in the environments of the proposed impoundment zone.Based on limited capture data,it seems that both burbot and longnose sucker are relatively common there (ADF&G 1983d). Elsewhere in the Susitna River,burbot spawn under the ice in tributaries (such as the Deshka River)over gravel substrates from January to February, and radio tagged fish data suggests they also spawn in the mainstem (ADF&G 1983b).During the rest of the year,they apparently distribute themselves 33RD4-005 -17 - Figure 1. l-- Fish uf the irnpound~ent zone. I-' 00 SUSITNA RIVER DRAINAGE BASIN Fish Species P,esent lower Rivor:(20)Arctic grayling,Arctic lamprey,Boring cisco,bUlbol,chinook sillmon,chum salmon,coho salmon,Dolly Varden,oulachon, humpb;:Jck whilcflsh,lake Iroul,1000005c sucker,northern pike, pHlk salmon,rainbow troul,round whllcfi!Jh,slimy sculpin, sockeyo salmon.1I110espino sllckleback.and nlnosplno sllckleback. Mlddlo Rivor:(161 A,cUc grayling,Arctic lamprey.burbol,chinook salmon.chum salmon,coho salmon.Dolly Varden,humpback whllellsh.lake trout,100g0050 suckor,pink salmon,rainbow Iroul,round while fish.slimy sculpin,sockoyo salmon,and Ihroosplno slickleback. Impoundmont Zone;(9)Arcllc grayling,burbol.Dolly Varden.humpback whllelish.lake troul,longnose sucker.round whlle"sh,slimy SCUlpin,and chinook salmon. I I I I, II , III I II I] II throughout the deeper portions of aquatic environments.Susitna River long- nose sucker are spring spawners which move from overwinter habitats in the mainstem to tributary natal areas from late May to early June (ADF&G 1983d). Small numbers of round and humpback whitefish have been captured (at two loca- tions)within the impoundment areas,but there are no estimates of their rela- tive abundances (ADF&G 1983d).If they behave similarly to lower river and middle river whitefish,they also overwinter in mainstem environments.AI- though available information is scant,it appears that these two white fish species spawn in early October in clearwater tributary streams. Although not currently present in mainstem areas,some lake trout might gain access to the reservoirs as a result of the project.Sally Lake,which supports a lake trout population of undetermined number,would be inundated by the Watana Reservoir (ADF&G 1983d).Lake trout generally spawn from August through December and require stable lake shore gravel substrates for reproduction.High lake (located immediately north of Devil Canyon)is a tributary system to Devil Creek which has a resident population of rainbow trout.Should the proj ect be completed,it is possible that some rainbows might gain access to the Devil Canyon reservoir by outmigrating down Devil Creek.Elsewhere in the basin,rainbow trout typically overwinter in lakes and mainstem habitats,returning in the spring following breakup to spawn in tributary streams.Most rainbow trout spawn in clearwater streams whose beds are covered with relatively small cobbles and have relatively moderate velocities (ADF&G 1983b). MIDDLE RIVER Fish and aquatic habitat investigations have been conducted on the Susitna River since the 1950's to evaluate the proposed hydroelectric project 33RD4-005 -19 - I I II u (U.S.Fish and Wildlife Service 1952, 1954,1957,1959a,1959b,1960,1965; Barrett 1974;ADF&G 1976, 1978,1981a,1983a,1983b,1983c,1985b;Barrett, Thompson,and Wick 1984,1985;Riis 1977;Schmidt et al.1984a,1984b;and Wangaard and Burger 1983).In 1980,the Susitna Hydroelectric Aquatic Studies Program was initiated to collect data on the fish and aquatic habitat resources of the basin. Extant Susitna River basin data on fish distribution,abundance,and habitat use focuses on salmon and are temporally and spatially limited.The studies,and therefore the information available,is more complete for the open water season and for the area upstream of the Chulitna River confluence. A summary of ADF&G's Su-Hydro studies of the fish resources downstream of Devil Canyon is available in a report by Woodward Clyde Consultants and Entrix (1985).ADF&G's Su-Hydro studies have documented migration timing of salmon runs in the Susitna River;estimated the population size and relative abundance of salmon in various sub-basins of the Susitna River;estimated the total salmon escapements into sloughs and tributaries upstream of RM 98.6; quantified selected biological characteristics of Susitna River salmon stocks (e.g.,sex ratio,fecundity,length at age);identified important spawning areas for some resident species;documented timing and estimated the relative utilization of macrohabitat types by juvenile and adult salmon and some resident species;developed habitat suitability criteria for adult and juvenile salmon,eulachon,Bering cisco,and some resident species;estimated population size and survival for juvenile chum and sockeye;documented outmigration timing of juvenile salmon;collected baseline physical and chemical water quality data in identified macrohabitat types;developed understanding of site-specific habitat responses to various mainstem discharges;evaluated the capability of adult salmon to pass into selected 33RD4-005 -20 - sloughs;and confirmed the importance of groundwater upwelling for salmon spawning in sloughs. Above the Chulitna River confluence (RM 98.5)salmon spawn in a variety of tributaries,sloughs,and a few mainstem sites.In this river reach,coho and chinook have only been found to spawn in tributary stream environments; pink salmon primarily in tributary streams (with a small number utilizing slough habitats);chum salmon in tributary,slough,and mainstem environ- ments;and sockeye almost exclusively in sloughs (Barrett,Thompson and Wick 1985).Over 90%of salmon spawning in this reach occurs in tributaries I :II (Barrett,Thompson &Wick 1985). At least eighteen tributary streams in the middle river provide salmon spawning habitats (table 4).Over 96%of the total chinook escapement above the Chulitna confluence spawn in tl-lO streams;Portage Creek (RM 148.9)and Indian River (RM 138.6)(table 4).In 1984,these two streams had a combined escapement of over 13,000 fish which represented a little over 5%of·the basin's total chinook resource (Barrett,Thompson and Wick 1985).Only about 10%of Susitna River coho salmon spawn above the Chulitna confluence;they apparently spawn only in tributaries in .this reach (Barrett,Thompson and Wick 1985).Indian River (RM 138.6)is the most important tributary for coho, providing a little over 30%of the reproductive habitat available here (table 5).Portage and 4th of July (RM 131.1)creeks and Indian River provide reproductive habitats for over 80%of middle river pink salmon;this repre- sents about 1%of the total Susitna escapement for pink salmon (Barrett, Thompson &Wick 1985).The same three streams provide over 98%of tributary spawning habitat for chum salmon in this reach (Barrett,Thompson and Wick 1985).In 1984,these tributaries accounted for about 1%of the total Susitna chum salmon escapement. 33RD4-005 -21 - -_._.----,~--.~~ Table 4.Peak Salmon Survey Counts Above Talkeetna for Susitna River Tributary Streams. 5D'ITVEY STREAN ~Coho Chinook 1974 1976 1981 1982 1983 1984 1975 1976 1977 1978 1979 1981 1982 1983 1984 Whiskers 0.25 27 70 176 115 301 22 8 3 67 Creek (1m 101.4) Chase 0.25 40 80 36 12 239 15 3 Creek (RN 106.9) Slash 0.75 6 2 5 Creek (RI1 111.2) Gash 1.0 141 74 19 234 Creek (RI1 111.6) Lane 0.5 3 5 2 24 40 47 12 23 Creek (RN 113.6) Lower 1.5 56 133 18 24 NcKenzie (RN 116.2) McKenzie 0.25 Creek (RN 116.7) Little 0.25 8 Portage (RI1 117.7) Fifth 0.25 3 17 N of July (RI1 123.7)N Skull 0.25 Creek (RI1 124.7) Sherman 0.25 3 Creek (RN 130.8) Fourth 0.25 26 17 1 4 3 8 1 14 56 6 92 of July (RN 131.0).. Gold 0.25 1 21 23 23 Creek (RN 136.7) Indian 15.0 64 30 85 101 53 465 10 537 393 114 285 422 1,053 1,193 1,456 River (RI1 138.6) Jack 0.25 1 1 6 2 6 7 Long (RN 144.5) Portage 15.0 150 100 22 88 15 128 29 702 374 140 140 659 1,253 3,140 5,446 Creek (RI1 148.9) Cheechako 3.0 16 25 29 Creek (RN 152.5) Chinook 2.0 4 8 15 Creek (RN 156.8) --- TOTAL 307 147 458 633 240 1,434 62 1,261 767 254 425 1,121 2,473 4,416 7,178 33RCl/005a/l -L- Table 4.Peak Salmon Survey Counts Above Talkeetna for Susitna River Tributary Streams. (cont'd) SURVEY STREAH ~Chum Sockeye ----1974 1975 1976 1977 1981 1982 1983 1984 1974 1975 1976 1977 1981 1982 1983 1984 Whiskers 0.25 1 Creek (RH 101.4) Chase 0.25 1 1 Creek (R1'1 106.9) Slasb 0.75 Creek (RH 111.2) Gash 1.0 Creek (R1'1 111.6) Lane 0.5 3 2 76 11 31 Creek (R1'1 113.6) Lower 1.5 14 1 23 1 HcKenzie (RH 116.2) HcKenzie 0.25 46 Creek (R1'1 116.7) Little 0.25 31 18 Portage (RH 117.7) Fifth 0.25 6 2 N of July (R1'1 123.7)w Skull 0.25 10 1 4 Creek (R1'1 124.7) Sherman 0.25 9 6 Creek (R1'1 130.8) Fourth 0.25 594 78 11 90 191 148 193 1 of July (R1'1 131.0) Gold 0.25 Creek (R1'1 136.7) Indian 15.0 531 70 134 776 40 1,346 811 2,247 1 2 1 1 1 River (RH 138.6) Jack 0.25 3 2 4 Long (RH 144.5) Portage 15.0 276 300 153 526 1,285 12 Creek (RH 148.9) Cheechako 3.0 Creek (RH 152.5) Chinook 2.0 Creek (RH 156.8) ---- TOTAL 1,401 73 512 789 241 1,736 1,494 3,814 48 2 1 1 1 13 33RCl/005a/2 ~~-~-~~---'---..~~ Table 4.Peak Salmon Survey Counts Above Talkeetna for Susitna River Tributary Streams. (cont'd) SURVEY STREAH ~Pink ----1974 1975 1976 1977 1981 1982 1983 1984 Whiskers 0.25 75 1 138 293 Creek Om 101.4) Chase Creek (RH 106.9)0.25 50 38 107 6 438 Slash Creek (RM 111.2)0.75 3 Gash Creek (RH 111.6)1.0 6 Lane Creek (RH 113.6)0.5 82 106 1,103 291 640 28 1,184 Haggot Creek (RH 115.6)0.25 107 Lower 1.5 23 17 585 HcKenzie (RH 116.2) HcKenzie 0.25 17 11 Creek (RH 116.7) Little 0.25 140 7 162 Portage (RH 117.7) Deadhorse 0.25 337 '"Creek (RH 120.8) .t:- Fifth 0.25 2 113 9 411 of July (RH 123.7) Skull Creek (RH 124.7)0.25 8 12 1 121. Sherman Creek (RH 130.8)0.25 6 24 48 Fourth 0.25 159 148 4,000 612 29 702 78 1,842 of July (Rfl 131.0) Gold Creek (Rfl 136.7)0.25 32 11 7 82 Indian River (Rfl 138.6)15.0 577 321 5,000 1,611 2 738 886 9,066 Jack Long (RH 144.5)0.25 1 5 14 Portage 15.0 218 3,000 169 285 2,707 Creek (RH 148.9) Cheechako 3.0 21 Creek (RH 152.5) Chinook 2.0 Creek (RH 156.8) ---- TOTAL 1,036 575 12,157 3,326 378 2,855 1,329 17 ,417 Source:Barrett 1974;Barrett,Thompson and Wick 1984,1985;Riis 1977;ADF&G 1976,1978,1981,1983a. 33RC1!005a!3 [1 u [J in the last four years,the majority (>88%)of chum salmon spawners counted were in 10 of the 34 (tables 5 and 6).Three of these 10 (8A,II,21)have added significance in that they also accommodated over 90%of all sockeye spawning in the middle river (table 5). Relatively few salmon spawn in mainstem nonslough habitats;of those which do,chum salmon predominate.Generally,spawning habitats within the mainstem proper are small areally and widely distributed.In 1984,ADF&G made a concerted effort to identify mainstem middle river spawning habitats;they identified 36 spawning sites.Numbers of fish counted at each of these sites varied from one to 131 with an average of 35 (Barrett,Thompson,and Wick 1985).The estimated total mainstem escapement was approximately 3,000 chum salmon (Barrett,Thompson and Wick 1985).This is less than 0.5%of the total Susitna escapement. Four of the five salmon species (all but pink)use middle river waters for rearing purposes (Schmidt et al.1984b).At this time insufficient information exists to characterize the relative importance of mainstem rearing habitats relative to each other.From May to September juvenile chinook rear in tributary and side channel environments,coho mostly rear in tributary and upland sloughs,and sockeye move from noted side sloughs to upland sloughs for rearing.From May to July rearing chum juveniles are distributed throughout side slough and tributary stream environments (Dugan,Sterritt,and Stratton 1984). Based on escapement counts for 1984,34 middle river sloughs collectively provided habitat for approximately 5.5%of all salmon migrating above Talkeetna station (Barrett,Thompson and Wick 1985).These sloughs are of particular importance to middle river chum and sockeye salmon.About 50%of the chum and almost all of the sockeye spawning above the Chulitna confluence 33RD4-005 -25 - , 33RC1!007b Table 6.Chum Salmon Escapement for the Ten Most Productive Sloughs Above RM 98.6,1981-84. Percent River 4-Year of Total Slough Mile 1981 1982 1983 1984 Average Escapement 8 113.7 695 0 0 217 228 3.4 8B 122.2 0 99 261 860 305 4.5 Moose 123.5 222 59 86 284 163 2.4 I AI 124.6 200 0 155 217 143 2.1 8A 125.1 480 1,062 112 2,383 1,009 14.9 9 128.3 368 603 430 304 426 6.3 9A 133.8 140 86 231 528 246 3.6 I j 11 135.3 1,119 1,078 674 3,418 1,572 23.2 II 17 138.9 135 23 166 204 132 1.9 21 141.1 657 1,737 481 4,245 1,780 26.2 Source:Barrett,Thompson,and Wick,1984,1985. 33RD4-005 -27 - II I i\.. occurs in sloughs.This represents about 2%of all chum and less than 0.5%of all sockeye spawning in the Susitna drainage (Barrett,Thompson and Hick 1985).Spawning habitat quality apparently varies greatly between sloughs as, Of the five salmon species present,only chinook and coho were captured in the middle river during the 1981-82 winter field season (ADF&G 1983c). Preliminary studies indicate that significant numbers (perhaps 25 to 50%)of chinook and coho juveniles reared in this zone overwinter in side slough and tributary stream environments (ADF&G 1985a).Provisional capture data for the 1984-85 winter field season show that a few sockeye are also overwintering in this area of the river (Crawford 1985).Preliminary evidence indicates that few juvenile salmon utilize the mainstem proper for overwintering purposes (ADF&G 1985a). Of the 11 resident middle river fish species (figure 1),capture data indicate that rainbow trout,Arctic grayling,round whitefish,longnose sucker,and slimy sculpin are common (ADF&G 1983c).Dolly Varden,burbot, humpback whitefish,threespine stickleback,and Arctic lamprey also occur,but all appear to be more abundant in the lower river (Sundet and Wenger 1984). Lake trout are found only in surrounding area lakes,none of which would be influenced by the project. Less is known about most resident fish species in the middle river than about salmon.Rough population estimates made in 1983 showed there to be about 4,000 adult rainbow trout in the middle river.Catch data from 1981-84 in the middle river show round whitefish to be the most abundant species and that Arctic grayling and longnose sucker are more abundant than rainbow trout which are more common than burbot (Sundet and Wenger 1984).Lakes in the Portage Creek and Fourth of July drainages where rainbow trout are abundant probably contribute heavily to middle river rainbow populations (Crawford, Hale,and Schmidt 1985). 33RD4-005 -28 - Given the naturally reduced winter flow regimes of tributary streams,the majority of resident fish (with the exception of lake trout)probably overwinter somewhere in the mainstem.It is generally believed that most 11 II resident fish which migrate to tributaries in the summer overwinter downstream of their natal tributaries in the mainstem (Sundet and Wenger 1984).Of the most common resident species,three (round whitefish,longnose sucker,and slimy sculpin)can occur year-round in the mainstem.Rainbow trout and Arctic grayling migrate out of tributaries by early October and most overwinter in the mainstem slightly downstream of these tributaries (Crawford,Hale,and Schmidt 1985). LOIVER RIVER At least 17 tributary streams and six sloughs provide salmon reproductive habitats downstream of the Chulitna confluence.Tributary systems in this reach support more than 99%of all spawning salmon.To date,no chinook, sockeye,or pink salmon have been observed spawning in lower river mainstem waters;all apparently use tributary streams exclusively for this purpose (Barrett,Thompson and Wick 1985).Small numbers of chum and coho salmon have been seen spawning in 13 separate mainstem sites and six side sloughs;most members of these two species also spawn in tributary environments.ADF&G estimates that,in aggregate,the number of chum salmon spawning within mainstem environments in this reach represents roughly 0.3%of the 1984 basinwide escapement.The estimated number of spawning coho in the mainstem represents roughly 0.2%of the 1984 escapement (Barrett,Thompson and WickI .J 1985).Chum salmon were the principal users of side slough spa~vning environments,being present in five of the six sloughs used.Their estimated numbers represent roughly 0.1%of the total 1984 escapement.Only six coho 33RD4-005 -29 - were seen spawning in sloughs in 1984;all were in one slough (Barrett, Thompson and Wick 1985).Thus,lower river sloughs are less important than middle river sloughs for spawning purposes. Less is known of salmon rearing and overwintering habitats in lower river mainstem environments than in the middle river.Coho,chinook,chum and sockeye juveniles primarily rear in tributaries;chinook,chum,and sockeye juveniles also make use of side channels.Sloughs are limited in occurrence and are not used heavily by any salmon species (Crawford,Hale,and Schmidt 1985).A few coho and chinook have been captured during winter in mainstem environments in this river reach (ADF&G 1983c). Several million eulachon spawn in late May to early June in the lower 50 miles of the mainstem Susitna River.Most of these fish spawn below RM 29 in main channel habitats near cut banks over loose sand and gravel substrates (Barrett,Thompson and Wick 1984).Bering cisco return to the Susitna River in late August and spawning takes place from September through October.In 1981 and 1982,spawning activity peaked in the second week of October.Bering cisco are known to spawn only in main channel environments;the majority of spawning apparently takes place between RM 75 and RM 85 (Barrett,Thompson and Wick 1984). Little is known about most resident fish life histories in the lower river.The 13 resident fish species found in the lower river,with the exception of lake trout,northern pike,and ninespine stickleback,are generally believed to be common (Sundet and Wenger 1984).As elsewhere in the drainage rainbow trout,Arctic grayling,and Dolly Varden spend most of the open water season in tributaries,using the mainstem principally for migration and overwintering (ADF&G 1983b).These species move into tributaries to spawn in the spring after breakup.Rainbow trout and Arctic grayling outmigrate 33RD4-005 -30 - from most eastside tributaries in September (Crawford,Hale,and Schmidt 1985).Burbot,whitefish,longnose sucker,sculpin,stickleback,and Arctic lamprey are found in both the mainstem and tributaries during the open water season.All of these species are believed to overwinter in the mainstem,but only rainbow trout,burbot,and slimy sculpin were captured there during 1982 winter sampling (ADF&G 1983b).Round whitefish are believed to spawn in October at either mainstem,tributary mouth,or tributary locations (Schmidt, et al.1984b).Burbot spawning generally occurs between January and March under the ice in areas influenced by the mainstem or in tributaries like the Deshka. Based on ongoing radio telemetry studies,it appears that favored mainstem overwinter habitats for adult rainbow trout and burbot differ principally by depth and location (Crawford 1985).Tagged rainbows are most frequently relocated in mainstem side channels,near tributaries,in waters generally less than five feet in depth.Tagged burbot are frequently located in winter in mainstem pools greater than six feet deep along river bends. However,most of the tagged burbot were found in the Deshka River.Both species seem to favor low velocity environments. 33RD4-005 -31 - SEDIMENT EFFECTS ON AQUATIC ORGANISMS The literature was searched for information describing the ways in which suspended sediment affects aquatic life to aid in evaluating the effects of the with-project sediement regime on them.A negative correlation exists between turbidity level and instream primary productivity (McCart and DeGraaf 1974).Turbid conditions reduce penetration of incident solar radiation and can limit growth of aquatic plants that are important food for stream invertebrates which in turn,are food for fish (Cordone and Kelly 1961). Deposition of sediment can,overtime,reduce available habitat for stream invertebrates (Giger 1973).As sediment accumulates,the character of the substrate can change from being relatively diverse to one being relativelyI1 II homogeneous.Hany invertebrate species which are important salmonid food II 11 items are adapted to life on relatively stable gravel and rubble bottoms;they cannot inhabit relatively unstable areas of shifting sand and silt (McCart and deGraaf 1974). Benthic macroinvertebrate numbers in reservoirs may be limited by a range of variables,of which siltation is one (Isom 1971).Accumulated silt can clog intragravel interstices reducing water flow and,hence,oxygen availability.This may negatively affect invertebrates also,(Ziebell 1960) especially those which respire through gills,such as caddisfly,mayfly,and stonefly larvae (McCart and deGraaf 1974),all of which are important fishufooditems.Silt may injure aquatic insect gills or membranes,thereby interfering with respiration (Usinger 1956).In silty environments,epifauna are often replaced by those more tolerant of low dissolved oxygen levels,such as dipterans and aquatic worms (Eustis and Hillen 1954),some of of which 33RD4-005 -32 - I ! I burrow into bottom sediments and offer reduced availability to fish (Phillips . 1971)• Given extremely high concentrations over a prolonged time,suspended silt can accumulate in fish gill filaments,reducing oxygen exchange and eventually causing death (Cordone and Kelly 1961).However,this seldom happens I I I I II I : I I II [I naturally.Highly turbid waters may reduce forging efficiency and hence, survival rates in sight feeders,such as sa1monids (Phillips 1971).Because suspended sediments eventually settle,major changes in bottom habitats might result from increased sediment deposition.Fine material accumulates on the stream bottom filling up spaces between stones and boulders.This decreases the permeability of the substrate resulting in decreased intragravel flow. Various authors have reported that increased sediment deposition can be detrimental to the survival of salmonid eggs and alev{ns,the most sensitive stages in the life cycle.Reduction in survival of salmon eggs and a1evins is roughly in proportion to the reduction of water flow through the gravel,which in turn varies with the concentration of sediment--the greater the sediment concentration the greater the reduction in permeability.When permeability is reduced,eggs and fry are likely to suffer from oxygen deprivation and poisoning from waste metabolites which are not removed.Hall and Lantz (1969) found that a five percent increase of material smaller than 0.03 in (0.8 mm) in diameter in spawning substrate caused a decrease in survival of emergent coho fry.Sediment can also form a barrier to fry emergence by blocking interstitial gravel spaces through which fry move.Survival of fry after emergence can also be reduced by loss of escape cover if cracks and spaces fill with sediment.McCart and de Graaf (1974)noted that _,if sedimentation is of short duration,streams can recover quickly without any long-term consequences for the aquatic ecosystem.The rate of reinvasion of stream 33RD4-005 -33 - I i I ! habitats is usually most rapid when short sections of stream rather than entire drainages are affected,adequate reservoirs of new organisms exist,and the degree of sediment deposition is slight. 33RD4-005 -34 - I I i I [I I ' I I 1....J SEDIMENT TRANSPORT OVERVIEW Sediment transport data pertaining to Sus'itna Basin waters have been collected and analyzed by the U.S.Geological Survey (USGS),the Alaska Department of Fish and Game (ADF&G),R&M Consultants,Inc.(R&M),Harza-Ebasco Susitna Joint Venture (H-E),Peratovich,Nottingham,and Drage Inc.,and E.Woody Trihey and Associates (EWT&A).USGS information useful in addressing the sediment transport issue includes over 30 years of stream discharge data and some site-specific,systematically gathered,sediment and hydraulic data for the October 1981 to February 1984 period.The latter include suspended sediment concentration,bedload discharge,particle size distribution,and mainstem cross-sectional dimensions (Knott and Lipscomb 1983,1985). USGS field stations for the 1981-84 study were located on the Talkeetna and Chulitna rivers (near their respective confluences with the Susitna)and on the Susitna River (one station was just upstream of the Talkeetna River confluence,another was located near Sunshine,the last was near the mouth of Gold Creek).This study found that from November through March,suspended sediment concentrations at all stations were similar to each other,generally less than 10 mg/L (Knott and Lipscomb 1983,1985).Suspended sediment concentrations rose rapidly in May of 1982 in concert with breakup;recorded concentrations were again somewhat similar in that all were in the low hundreds of mg/L (Knott and Lipscomb 1983,1985).Great differences in suspended sediment concentrations were noted between sampling stations in July and August,the time of maximum glacial meltwater flow.Concentrations in this time period ranged from 90 to 768 mg/L for the Talkeetna and Susitna rivers (measured at the two stations located near the town of Talkeetna)and from 766 to 1270 mg/L for the Chulitna.River (Knott and Lipscomb 1983,1985). 33RD4-005 -35 - At Sunshine (below the confluences of the Talkeetna and Chulitna rivers)the USGS found suspended sediment concentrations in the July -August timeframe to be between 424 to 1430 mg/L (Knott and Lipscomb 1983,1985). The USGS documented the fact that the Chulitna River was the major contributor of both suspended sediment and bedload to the mainstem Susitna below Talkeetna (Knott and Lipscomb 1983).For example,bedload discharges from the Susitna River (near Talkeetna)ranged from 106 to 2840 tons per day during the 1982 water year (October 1981 to September 1982);bedload at the Chulitna River site ranged from 2560 to 18,300 tons per day during the same interval (Knott and Lipscomb 1983).Between June and September 1982,the total bedload discharge at the USGS sample site upstream of Sunshine was two to five times greater than that at Sunshine (Knott and Lipscomb 1983), providing indirect evidence of aggradation in the mainstem.The same data also indicate that material deposited above Sunshine is transported under natural conditions by periodic high flows. The USGS graphed water discharge against both suspended sediment and bedload concentrations and found a positive correlation to exist,i.e., sediment transport volumes increased with increasing water flow (Knott and Lipscomb 1983,1985).However,the correlation was not directly proportional; Susitna River sediment transport rates increase exponentially above a point for each incremental change in water discharge (Knott and Lipscomb 1983, 1985).USGS sediment yield estimates for the 1982 water year are presented in table 7. R&M (1982a)combined existing USGS stream discharge and suspended sediment data with aerial photographs of the Susitna River,information on bed material size,and cross-sectional transects of stream morphology to calibrate a water surface profile model (R&M 1982a).They concluded that the mainstem 33RD4-005 -36 - Table 7.Estimated and recorded sediment yield. Drainage Water Station Name Area Discharge Total Sediment (tons) and Number (mi 2 )Period (acre-ft)Silt-Clay Sand Gravel Totalb Susitna River near 6,320 May 920,000a 170,000 100,000 1,100 270,000 Talkeetna (15292100)June 1,700,000a 430,000 330,000 5,300 770,000 July 1,500,000a 680,000 220,000 1,900 900,000 August 1,000,000a 310,000 52,000 100 360,000 September 1,100,000a 330,000 140,000 900 480,000 May -Sep 6,200,000a 1,900,000 840,000 9,300 2,800,000 I Chulitna River near 2,570 May 386,700 88,000 73,000 48,000 210,000 Talkeetna (15292400)June 1,092,000 880,000 610,000 230,000 1,700,000 July 1,575,000 1,900,000 910,000 190,000 3,000,000 August 1,252,000 1,000,000 510,000 150,000 1,700,000 September 1,085,000 1,200,000 350,000 66,000 1,600,000 May -Sep 2,670,000 600,000 810,000 110,000 1,500,000 Susitna River at 11,100 May 1,633,000 280,000 260,000 15,000 550,000 Sunshine (15292780)June 3,738,000 1,500,000 1,200,000 130,000 2,900,000 July 3,876,000 2,800,000 1,400,000 75,000 4,300,000 August 2,083,000 1,800,000 660,000 14,000 2,500,000 September 2,906,000 1,900,000 880,000 46,000 2,800,000 May -Sep 14,236,000 8,300,000 4,400,000 280,000 13,000,000 Source:Knott and Lipscomb 1983 a -Estimated b -Rounded lJ 33RD4-005 -37 Susitna River channel between Devil Canyon and the Chulitna River confluence would tend to narrow and become more defined under with-project conditions (R&H 1982a).Downstream of the Susitna-Chulitna confluence the river would stabilize with-project;there would be fewer subchannels and increased vegetation cover (as plants colonized barren bars now subj ect to periodic flooding).Specific with-project changes predicted in river morphology by R&M (1982a)are summarized in table 8. R&M (1982b)also calculated reservoir sedimentation rates using assumed trap efficiencies (table 9).They note that the estimated deposit in Devil Canyon reservoir (assuming 100%trap efficiency of Watana Reservoir)(table 8) appears too low (R&M 1982b).Given knowledge of sediment size distribution and flow volumes,R&M (1982b)believes that the reservoir(s)would noticeably affect downstream environments;with-proj ect summer turbidity between Devil Canyon and the Talkeetna River confluence would sharply decrease because of reservoir sediment trapping (R&M 1982b).Winter with-project turbidities are predicted to be near natural as in-reservoir near surface suspended sediments are likely to settle rapidly,especially following free~e-up (R&M 1982b). R&M (1982c)and R&M and EWT&A (1985)also collected and analyzed streamflow and sediment transport mechanism data for 19 tributary stream mouths.The outlets of Jack Long,Sherman,and Deadhorse creeks are predicted to aggrade sufficiently to restrict fish access (R&M 1982c),while tributary mouths at Ili'l 127.3 and RM 1l0.1,as well as Skull Creek,are predicted to significantly degrade (thereby threatening the railroad bridges there).The remaining 13 tributaries evaluated are predicted to either aggrade or degrade with-project,but without effects on fish access or other resources. 33RD4-005 -38 - Table 8.Predicted morphologic change with-project. RM 149 to 144 RM 144 to 139 RH 139 to 129.5 RH 129.5 to 119 R.H 119 to 104 RM 104 to 95 RM 95 to 61 RM 61 to 42 RN 42 to 0 Mainstem N/C Less erosion of valley walls;distributaries may become inactive;channel will be more uniformly sinuous;less reworking of streambed deposits. Less erosion of valley walls;channel will be more univormly sinuous. Less erosion of valley walls;channel will be more uniformly sinuous;river will continue to hug west bank. N/C Chulitna will extend alluvial deposits across mainstem Susitna;east bank of the Susitna could erode; Talkeetna River flow will maintain channel along east bank of the Susitna. Hain channel of the Susitna River will stabilize. N/C N/C Slough Some sloughs could be dewatered. Side channels and sloughs may become perched. N/C Tributary Portage Creek will degrade with-project;it will not be perched. Tributary at RM 144 could become perched. Fourth of July Creek and Indian River will grade their beds to match regulated flows;Gold Creek will become perched. N/C N/C =No Change Source:R&M 1982a 33RD4-005 39 Table 9.Reservoir sedimentation. 50-Year 100-Year I III Watana 100 percent trap efficiency 240,000 af 472,500 af 70 percent trap efficiency 170,000 af 334,000 af Devil Canyon with 70 percent trap efficiency of loJatana 100 percent trap efficiency 79,000 af 155,000 af 70 percent trap efficiency 55,000 af 109,000 af Devil Canyon with 100 percent trap efficiency of l-Jatana 100 percent trap efficiency 8,600 af 16,800 af 70 percent trap efficiency 6,100 af Souce:R&M 1982b 33RD4-005 -40 - The firm of Peratrovich,Nottingham &Drage,Inc.undertook an analysis of turbidity levels in the Watana Reservoir.Using a model (DEPOSITS)to compute turbidity at various depths,they concluded that particles less than three to four microns (about 20%of summer sediment input)would remain suspended (Peratrovich,Nottingham &Drage 1982).They predicted maximum outlet turbidity levels to be around 50 NTUs (roughly 200 to 400 mg/L); predicted minimum turbidity levels are around 10 NTUs (roughly 30 to 70 mg/L). Peratrovich,Nottingham &Drage (1982)predict that wind mixing in the ice-free season would keep sediments sized 12 microns or less in suspension, at least in the upper 50 ft of the water column.Resuspension of nearshore sediments are predicted to occur during storm intervals producing short-term higher than ambient turbidity levels (Peratrovich,Nottingham &Drage 1982). Trihey (1982)analyzed field data collected by others on the mouths of Indian River and Portage Creek.His calculations (made for mainstem discharges of 8,000,13,400,21,500,and 34,500 cfs)indicate that both stream mouths would degrade with-project providing fish passage.He also analyzed with-proj ect effects on salmon access to middle river sloughs.He focused analysis on Slough 9 arguing that it'is a reasonable index of entrance conditions in all middle river sloughs.Trihey (1982)reports that access to Slough 9 would not appear to be restricted by flows at or above 18,000 cfs; access becomes increasingly difficult as flows decrease.At 12,000 cfs, Trihey (1982)reports that acute access problems would occur. Harza-Ebasco Susitna Joint Venture used sediment discharge data for the Susitna River taken near Cantwell to estimate sediment inflow to the proposed reservoirs.Using the sediment rating-flow duration curve method and assuming 100%reservoir trap efficiency,they estimated that 6,730,000 tons of sediment 33RD4-005 -41 - would be trapped per year in the Watana Reservoir;the 100-year sediment de- posit would be about 7%of the dead storage volume (Harza-Ebasco Susitna Joint Venture 1984a).Without Watana Reservoir,Harza-Ebasco Susitna Joint Venture (1984a)estimates sediment deposit in the Devil Canyon Reservoir would be about 7,240,000 tons per year;the 100-year deposit would be about 60%of the dead storage volume.With both dams on-line,sediment deposit in the Devil Canyon Reservoir is estimated to be about 515,000 tons per year;the 100-year deposit would be about 4%of dead storage capacity.Reduced sediment load below the dams would result in some mainstem degradation downstream to the vicinity of the Chulitna and Talkeetna confluences with the Susitna River (Harza-Ebasco Susitna Joint Venture 1984a). Estimates of with-project mainstem degradation are provided in table 10. At certain mainstem sites,with-project bed degradation is predicted to vary from 1-1~ft under a dominant discharge of about 30,000 cfs (Harza-Ebasco Susitna Joint Venture 1985).Flows of this volume are expected in the early years of Watana and Devil Canyon reservoirs (Harza-Ebasco Susitna Joint Ven- ture 1984a).Predicted degradation of side channel and sloughs varies between o to 0.3 ft (Harza-Ebasco Susitna Joint Venture 1985;R&M and mJT&A 1985). Because of channel degradation,higher than natural flows would be required to overtop slough berms.Using an assumed one-foot channel degradation as a bench mark,with-project flows necessary to overtop slough berms would need to be 4,000 to 12,000 cfs greater than natural (Harza-Ebasco Susitna Joint Venture 1985).Harza-Ebasco Susitna Joint Venture (1985) predict that if slough berms were overtopped,water velocity would be sufficient to carry out fines ~.004 mm.However,coarser silt and fine sand entrained by overtopping water would settle in their stead (Harza-Ebasco Susitna Joint Venture 1985). 33RD4-005 -42 - Table 10.Potential degradation at selected sloughs,side channels and mainstem sites. Discharge at Gold Creek (cfs) 5000 7000 10000 15000 20000 25000 30000 35000 iQ.QQQ ~55000----Location Estimated Degradation (ft) *Main Channel near Cross Section 4 0.1 0.2 0.3 0.6 0.8 1.1 1.3 1.5 1.7 1.9 2.4 Main Channel between Cross Sections 12 &13 0.1 0.2 0.3 0.4 0.6 0.8 1.1 1.3 1.8 2.4 3.7 Main Channel upstream from Lane Creek 0.2 0.2 0.3 0.4 0.6 0.8 1.0 1.2 1.5 1.8 2.5 Mainstem 2 Side Channel at Cross Section 18.2 Main Channel 0 0 0 0 0 0.1 0.2 0.3 0.5 0.7 1.2 Northeast Fork 0 0 0 0 0 0 0 0.1 0.1 0.2 0.2 Northwest Fork 0 0 0 0 0 0 0 0.1 0.1 0.2 0.2 Slough 8A 0 0 0 0 0 0 0 0 0 0 0 Slough 9 0 0 0 0 0 0 0 0.1 0.2 0.3 0.5 Main Channel upstream from Fourth of July II Creek 0.3 0.3 0.4 0.6 0.8 1.1 1.3 1.5 1.7 2.0 2.5 I J 0 0.1 0.2 0.4 0.6 1.0 2.0SideChannel100 0 0 0 Lower Side Channel 11 0 0 0 0.1 0.2 0.3 0.5 0.7 1.0 1.3 2.1 Slough 11 0 0 0 0 0 0 0 0 0 0 0.1 Upper Side Channel 11 0 0 0 0 0 0.1 0.2 0.3 0.6 0.9 1.8 Main Channel between Cross Sections 46 &48 0.3 0.4 0.6 0.9 1.2 1.4 1.7 1.9 2.1 2.4 2.8 Side Channel 21 0 0 0 0 0 0 0.1 0.1 0.2 0.2 0.3 IJ Slough 21 0 0 0 0 0 0 0 0 0.1 0.2 0.5 Source:Harza-Ebasco Susitna Joint Venture 1985 *Locations are defined on pages 7 to 11 in Harza-Ebasco Susitna Joint Venture 1985. 33RD4-005 -43 AEIDC (1985)analyzed natural geomorphic change in the Susitna River between Devil Canyon and the Chulitna confluence by comparing aerial photographs taken over the last 36 years.AEIDC (1985)concluded that the reach in question is slowly degrading its bed under natural flows as it has ice age.Sloughs were found to be transitory in nature,being continually created and destroyed by natural sediment transport mechanisms (AEIDC 1985). SYNOPSIS OF RESULTS The Watana and Devil Canyon reservoirs are predicted to trap most sediment reaching them.The consequences of this are varied.First,the reservoir environments would be characterized as highly turbid (-50 NTUs)with relatively high sedimentation rates.Second,reduction in sediment load II, I\, downstream of the Devil Canyon Dam would induce some channel degradation to about the confluences of the Talkeetna and Chulitna rivers with the Susitna. Channel degradation coupled with regulated with-project flows would reduce the incidenceAof floods which overtopped slough berms.Floodwaters,while still capable of resuspending intragravel fines,would deposit significant amounts of sand and silt in their place.Some naturally occurring patterns of stream aggradation near the Talkeetna and Chulitna confluences with the Susitna River could be enhanced,but natural discharges from the Talkeetna River should be sufficient to keep a channel open. Predictions of the with-project environment (based on the studies outlined above)are sufficiently detailed and verifiable to allow an evaluation of the with-project sediment transport regime on fish.The chief limiting factor confronting all investigators is the apparent hysteresis between sediment load and water discharge,a problem common to glacial meltwater streams (R&M 1982;Knott and Lipscomb 1983,1985).The net result 33RD4-005 -44 - II,J u of this is to make long-term predictions relatively more accurate than those for the short-term.This condition,while potentially troubling to engineers, is of small importance to the effects analysis which,of necessity,has a long-term focus. 33RD4-005 -45 - ,j ANALYSIS ANTICIPATED NEGATIVE EFFECTS IMPOUNDMENT ZONE The following discussion explains predictions summarized in table 11. Predicted with-proj ect sedimentation and suspended sediment levels in the. impoundments would negatively influence to varying degrees all fish species present.Anticipated with-project suspended sediment loads in the reservoirs vary seasonally from a summer high of between 200 to 400 mg/L (50 NTU's)to a winter low of between 30 to 70 mg/L (10 NTU's)(Peratovich,Nottingham,and Drage 1982).Summer levels could occasionally be higher than this,especially nearshore,as storm runoff is expected to re-entrain sediment deposited during winter dra'vdown (Peratovich,Nottingham and Drage 1982).Following extensive review of sediment effects on North American benthic and planktonic communities and on population,reproduction,and species composition of fish, Newport and Moyer (1974)concluded that water bodies having suspended sediment concentrations above 100 mg/L year round were unlikely to support a viable sport fishery.The reasons for this are many but chiefly concern the effects of sediment on aquatic organism respiration efficiency.Suspended inorganic sediment can mechanically damage and interfere with oxygen transport across membranes (McCart and DeGraaf 1974;Cordone and Kelley 1961). 33RD4-005 -46 - Table 11.Anticipated relative negative with-project sediment transport effects on impoundment zone fish. Devil Canyon OperationWatanaOperation Effects 1 Fish Species Scale Date Chinook salmon Arctic Grayling adult migration 0 spawning 0 incubation 0 rearing 1 Oct-Apr Lake Trout adult migration 0 spawning 2 Aug-Dec incubation 2 rearing 1 Oct-Apr Whitefish 3 adult migration 0 spawning 0 incubation 0 rearing 1 Oct-Apr Rainbow Trout adult migration 0 spawning 0 incubation 0 rearing 1 Oct-Apr Burbot adult migration 0 spawning 1 Jan-Feb Incubation 3 rearing 1 Longnose Sucker adult migration 0 spawning 0 incubation 0 rearing 1 Oct-Apr 1 a -no concern 1 -low 2 -moderate to severe 3 -possible Effects Scale o a a 1 o 2 2 1 o o o 1 o o a 1 a 1 3 1 o o o 1 Date Oct-Apr Aug-Dec Oct-Apr Oct-Apr Oct-Apr Jan-Feb Oct-Apr 2 The Devil Canyon dam would block upstream passage of chinook salmon,a few of which spawn in Cheechako Creek (RM 152.5)and Chinook Creek (RM 156.8); with-project sediment transport would not negatively influence habitats there. 3 This table is applicable to both humpback and round whitefish. 33RD4-005 -47 - The with-project sediment transport regime would most affect lake trout and burbot,the only two impoundment zone species which naturally reproduce in lake environments.Lake trout normally spawn in fall over the gravel substrates of clearwater lakes.The combined effects of lake drawdown and winter sedimentation would generally limit in-reservoir reproduction rates by this species.Embryos which were not dehydrated by receding reservoir water levels in winter (i.e.,those spawned below the lower low water level)would face the consequences of sediment build-up on natal beds (i.e.,oxygen deprivation).Burbot spawn in winter under the ice and over gravel in either lakes or streams.This species population could be held in check by the anticipated pattern of winter sedimentation also,but too little is known of the precise pattern of sedimentation to allow an accurate assessment of the degree,or magnitude,of its effects on burbot embyros.Burbot are broadcast spawners and can spa\vn in a wide range of depths.It may be that some embryos in some areas might find favorable conditions for reproduction and growth (e.g.local hydraulic conditions might produce eddies where sedimentation rates were relatively low). Reservoir rearing habitat quality for all species would be low (table 11).Given the predicted reservoir environment in winter,it is likely that invertebrate populations there would become dominated by infauna capable of living in low oxygenated environments (see p.32 of this report),rather than by epifaunal fish foods such as caddis fly larvae.This would translate into lowered food availability for fish.Sedimentation would also reduce IJ available cover afforded by cobbles and boulders making fry somewhat more susceptible to predation. 33RD4-005 -48 - I ! I I i MIDDLE RIVER ZONE Tables 12 and 13 summarize anticipated with-project negative sediment transport effects on middle river zone anadromous and resident fish.These effects can be placed into one of two categories;those centered on the mainstem proper and those centered on slough spawning habitats.Immediately after project startup and regardless of whether one or two dams are on-line, the mains tern between Devil Canyon and its confluence with both the Talkeetna and Chulitna rivers would begin to degrade (R&M,Woodward-Clyde Consultants, and Harza Ebasco Susitna Joint Venture 1985).Mainstem degradation would continue until the bed adjusted to the new (regulated)flow volume.The river's channel would narrow as it entrenched (R&M 1982;Harza-Ebasco Susitna Joint Venture 1985).With-project mainstem degradation (coupled with regulated flows)would accelerate the natural process of slough senescence noted by AEIDC (1985).Sloughs in the natural (i.e.,unregulated)environment are continually created and destroyed over time as a consequence of the slow but continuous process of river bed degradation.In its essence,the process of slough senescence begins with the perching of slough mouths by the degrading river (AEIDC 1985).In time the slough is left behind by the river and eventually it evolves into dry land (AEIDC 1985).Under natural 1 conditions new sloughs are constantly and coincidentally created as entrained bed material is redeposited (AEIDC 1985). Unlike natural,with-project sloughs would not complete their life cycle, nor would new sloughs be created.With-project,the effect of freshets neces- sary to entrain bed material for slough building would be greatly diminished. Once the bed achieved equilibrium with with-project flows,the process of slough perching would cease (Harza-Ebasco Susitna Joint Venture 1985).With- project sloughs,following a period of environmental adjustment delimited by 33RD4-005 -49 - I I the period of mainstem degradation,would superficially appear to be in stasis with the environment,i.e.,they would not gradually make the transition to dry land.Change would be occurring,however.The dams would reduce the I I I I III I II I I I IIJ I j incidence of freshet-induced overtopping of slough berms (Harza-Ebasco Susitna Joint Venture 1984a).This would lead to a build-up of fines and coarser bed material (Harza-Ebasco Susitna Joint Venture 1984a;Blakely et al.,1985). Immediately downstream of the Chulitna confluence with the mainstem,a zone of with-project aggradation is predicted to occur (R&M 1982,Harza-Ebasco Susi~na Joint Venture 1984a).Aggradation here is likely to be significant and it may have consequence to the built as well as natural environment (R&M 1982).However,natural flow from the Talkeetna River is believed sufficient to maintain a distinct channel through this zone (R&M 1982;Harza-Ebasco Susitna Joint Venture 1984a). The chief sediment transport problem concerns degradation of traditional slough spawning habitats for chum,pink,and sockeye salmon (table 12).,As indicated above,the with-project rate of flood-induced overtopping of slough berms would be greatly diminished over natural conditions.This is predicted to result in both a buildup of intragravel fines (floods are necessary to re-entrain deposited fines thereby rehabilitating spawning beds)and a buildup of larger,coarser material deposited during each flood event (Harza-Ebasco Susitna Joint Venture 1984a,1985).Unless mitigated,this process would eventually destroy all in-slough salmon spawning habitats by filling in gravel interstices and by altering the character of spawning substrates.Since no new sloughs would be created under the with-project sediment transport regime, this means that unless mitigated,the annual average drainagewide escapements would in time be reduced by as many as 20,000 adult chum (eight-year average 33RD4-005 -50 - Table 12.Anticipated relative negative with-project sediment transport effects on middle river zone anadromous fish. Date Devil Canyon Operation i 1 Fish Species Watana Operation Effects 1 Scale Location Effects Scale Location Date sloughs year-round sloughs year-round sloughs Aug-Sept sloughs Sept-May sloughs year-round I I I I I I II IIIJ Chinook salmon adult inmigration spawning incubation rearing/smolting outmigration Chum salmon adult inmigration spawning incubation rearing/smolting outmigration Pink salmon adult inmigration spawning incubation rearing/smolting outmigration Coho salmon adult inmigration spawning incubation rearing/smolting outmigration Sockeye salmon adult inmigration spawning incubation rearing/smolting outmigration o o o 1 o o 1 2 1 o o 1 2 o o o o o 1 o o 1 2 1 o sloughs sloughs sloughs sloughs sloughs Aug-Sept Sept-Nay Nay-June Aug Sept-May o o 1 o o 1 2 1 o o 1 2 o o o o o 1 o o 1 2 1 o sloughs sloughs sloughs sloughs sloughs sloughs sloughs sloughs sloughs sloughs year-round Aug-Sept Sept-May May-June Sept-May year-round Aug-Sept Sept-Nay year-round I I I J 1 0 1 2 3 -no concern -low -moderate -possible 11 See text for a complete description of the effects scale. 33RD4-005 -51 - from table 5),500 adult sockeye (eight-year average from table 5),and 270 adult pink salmon (six-year average from table 5)unless mitigated.These numbers represent 2.4%,.08%,and .007%respectively of all chum,sockeye,and pink salmon spawning in the Susitna drainage basin in 1984. Stream degradation at the mouths of all major middle river salmon spawning sloughs is predicted to be slight (table 10).Taken by itself,this can be interpreted to mean that there would be no with-project access problems for salmon.However,comparison of existing information on minimum mainstem flows necessary to allow passage of adult spawners into natal habitats (Blakely et al.,1985;Sautner,Vining,and Rundquist 1984)and knowledge of the ability of salmon to traverse stream reaches under given flows (Blakely et al.,1985;Sautner,Vining,and Rundquist 1984;Trihey 1982)to predictions of Case E-VI flows (Harza-Ebasco Susitna Joint Venture 1984b)and with-project mainstem degradation patterns (Harza-Ebasco Susitna Joint Venture 1985)leads to the conclusion that in some years some pink,chum,and sockeye salmon would not be able to reach traditional natal slough environments (table 12).With present information,it is impossible to accurately predict ~.,hich sloughs would be most affected,and hence,the number of fish affected.Additional study is not likely to improve this situation.Variables affecting flow estimates (e.g.,climate and energy demand)and the lack of a clear relationship between flow volume and sediment transport,make it unlikely that materially greater predictive precision is achievable,regardless of whether additional study effort is expended. Predicted with-project aggradation at the mouths of Deadhorse (RM 120.8), Sherman (RM 130.8),and Jack Long (RM 144.5)creeks would likely restrict access to spawning habitats for some salmon (R&M 1982a,1985).Escapement counts made to evolve indices of abundance indicate that relatively few salmon 33RD4-005 -52 - spawn in these streams (table 4).Based on the 1984 count (the highest on record),399 adult pink,10 chum,6 coho,and 7 chinook salmon could be displaced from traditional natal grounds as a result of with-project aggradation.This represents .01%,.001%, .003%,and .003%respectively of all pink,chum,coho,and chinook salmon spawning in the Susitna River basin in 1984.These counts are not direct censuses,so numbers reported under-estimate salmon use to some extent.However,as table 4 shows, relatively few salmon of any species have been tallied over the years in any of the subject streams. Unless mitigated,slough rearing habitat quality for chinook,chum, sockeye,and coho salmon would diminish as a result of the with-proj ect sediment transport regime (table 12).Reduction in the number of yearly floods would result in a change in character of in-slough substrates.The change would be away from heterogeneity,as irregularly sized gravel and cobble material,was gradually covered by fines and sand.The net result would be a diminishment in cover (EWT&A and Milner 1985)and,ultimately,food availability (the invertebrate fauna would predictably shift towards one dominated by infauna see p.32 of this report).Again,existing I I lJ II information does not permit an estimate of how many fish would be affected or of their ultimate fates. The with-project sediment transport regime would pose no problems to any of the resident middle river fish species (table 13),because with-project sediment loads would be lower than natural (cf.Knott and Lipscomb 1983 to the predictions of Harza-Ebasco Susitna Joint Venture 1984a,1985).This would be true even in the early years of project operation when scouring of the mainstem is predicted to occur.Potential with-project beneficial effects are discussed on pp.57 to 58 of this report. 33RD4-005 -53 - Table 13.Anticipated relative negative with-project sediment transport effects on middle river zone resident fish species. Date Date I iI, Fish Species Burbot adult migration spawning incubation rearing Whitefish 2 adult migration Rainbow trout adult migration spawning incubation rearing Arctic grayling adult migration spawning incubation rearing Watana Operation Effects 1 Scale Location o o o o o o o o o o o o o Devil Canyon Operation Effects 1 Scale Location o o o o o o o o o o o o o 1 o -no concern 1 -low 2 -moderate 3 -possible See text for a complete description of the effects scale 2 This table is applicable to both broad and humpback whitefish. 33RD4-005 -54 - I i (] I) (1 LOWER RIVER ZONE With-project sediment transport effects in the lower river are more difficult to predict than elsewhere in the study area.This is due to the braided nature of the mainstem (braided streams are difficult to model)and to the fact that relatively little study effort has been directed there.Project team members believe that more data are required to define with-project effects on the lower river (Bredthauer 1985).Prominent data gaps are listed in table 14. Based on USGS data (Knott and Lipscomb 1983,1985)the with-project sediment transport regime would be moderated below RM 97 by tributary input, especially those from the Talkeetna,Chulitna,and Yentna rivers (R&M and EWT&A 1985).As indicated earlier (see p.44),a significant zone of aggradation is predicted to occur near the Chulitna River's confluence with the mainstem «Harza-Ebasco Susitna Joint Venture 1984a).Downstream of that point,little else is known of with-project effects on sediment transport,and hence,its effect on fish. R&M and EWT&A (1985)believe that tributary mouths in this reach should become more stable as a result of with-project regulated flows.R&M and EWT&A (1985)estimate that with-project summer flows of around 25,000 to 30,000 cfs would be sufficient to allow passage into all lower river tributaries. However,they note that the mouths of Rolly (RM 39.0),Caswell (RM 64.0), Goose (RM 72.0),Montana (ID1 77.0),Rabiduex (RM 83.1)and Trapper (RM 91.5) creeks have possible inherent access problems which might become manifest under some with-project flows (R&M and EWT&A 1985).They further note that due to the braided nature of the mainstem in this reach,quantification of change would be difficult (R&M and EWT&A 1985).Salmon index counts were made by ADF&G in these streams in 1984;around 3,000 chinook,300 sockeye,900 33RD4-005 -55 - Table 14.Prominent data gaps in the lower Susitna River information base. Sediment aggradation/morphology Backwater effects at tributary mouths Turbidity regime (local,plumes) Relationship of flow and fish access to streams,sloughs,side-channels Survey of mainstream spawning sites found in 1984 Timing and magnitude of ice staging and relationship to upwelling Timing of flows -'increased spawning area,later dewatering Relate flows to rearing areas,spawning areas,access consideration Fish abundance,rearing curves Fisheries use of tributaries Effect of with-project flows on salt-water intrusion Source:Bredthauer 1985 33RD4-005 -56 - pink,590 chum,and 700 coho were counted (Barrett,Thompson,and Wick 1985). Although these counts do not indicate total escapement,they do provide some measure of the relative importance of each stream to each species.From this perspectiv~,Montana Creek is the most important of the six streams for chi- nook (total count of 2,309)and pink (total count of 469)salmon,Trapper Creek is the most important of the group for sockeye salmon (total count of 200),Goose Creek is the most important of the six for chum salmon (total count of 383),and Rabideux Creek is the most important of the group for coho (total count of 480)(Barrett,Thompson,and Wick 1985). The with-project sediment transport regime probably would not negatively affect any species spawning or overwintering in the mainstem lower river proper.This conclusion is based on the fact that overall sediment loads would be diminished with-project (although only slightly)from natural, thereby somewhat enhancing the quality of the environment.A discussion of the with-project beneficial effects is found in the next section. POTENTIAL WITH-PROJECT BENEFICIAL EFFECTS The with-project in-reservoir sediment transport process would not convey or otherwise impart any beneficial effects to fish or their food organisms. However,with-project sediment transport in the middle river might lead to an increase in primary productivity.Once the bed restabilized,sediment load in this reach would be less than natural (see pp.35 to 45 of this report).An increase in aquatic primary production could lead 'to an increase in consumers which,in turn,might equate with an incremental gain in fish habitat quality. Existing information is insufficient to gauge or even to characterize the magnitude of this effect.With-project turbidity in the middle river would still be substantial due to suspended glacial flour (the reservoirs could not 33RD4-005 -57 - trap all sizes of fines,some of which are present as colloids).(This topic is addressed in length in the Turbidity Memorandum,another rpeort of this series).Also unknown is whether natural invertebrate numbers and kinds limit present fish numbers.This latter point is central to a determination of whether there would be a gain in fish habitat quality.An ongoing AEIDC study seeks to understand natural primary rates of production in this reach;its results may shed light on the question of with-project primary productivity, but not necessarily on its effect on fish. The with-project reduction in sediment load could lead to an increase in available mainstem salmon spawning habitats.The with-project sediment transport regime is predicted to keep the bed downstream of Devil Canyon relatively free of fines.This effect would diminish with distance downstream as tributaries added their sediment loads to the mainstem.It would not be noticeable below the Talkeetna and Chulitna confluence with the mainstem due to their moderating influence.Present information does not allow estimation of the magnitude of this. No major (i.e.,demonstrable)beneficial gains in primary production are likely to occur as a result of the with-project sediment regime in the lower river.This is due to the moderating influence of sediment inputs from the Talkeetna,Chulitna,and Yentna rivers (see pp.35 to 45 of this report). Existing information is insufficient to assess whether any other sediment transport associated beneficial effects could occur in the lower river. However,the slight reduction in suspended load and bed load caused by the dams might improve fish habitat quality somewhat. 33RD4-005 -58 - SUMMARY This report presents the results of an analysis of existing information of the effects of the with-project sediment transport regime on fish.It is based on a comparison of predictions of the with-project environment ''lith information on fish instream flow needs and their response to sedimentation. Based on existing data (sediment transport calculations and model runs and life history information)and professional judgement,with-project sediment transport phenomena (unless mitigated)would limit fish numbers in the impoundment zone and in the middle river.Reservoir sedimentation (coupled with winter drawdown)would limit reproduction by lake trout and possibly burbot.In the middle river,with-proj ect reduction of the number and intensity of floods would eventually diminish slough spawning habitats for salmon.Un~ess action was periodically taken to clean slough spawning beds, sedimentation attendant to periodic floods would eventually lead to a loss of these habitats.Comparison of estimates of released water flow variability and estimates of with-project mainstem degradation to salmon life history data and information on minimum water depth necessary at slough mouths to provide salmon access,leads to the conclusion that in some years some sloughs would be blocked to salmon.However,given the relatively small amount of with-project channel degradation predicted for the mouths of the principal spawning sloughs,this should not be a major problem.Potential with-project beneficial effects in the middle river are limited to a possible increase in primary production and an increase in salmon spawning habitat.An ongoing study may shed light on the primary production question.With-project sediment loads below the Devil Canyon dam would be markedly reduced over those occuring naturally.Following bed stabilization,it is possible that portions 33RD4-005 -59 - of the mainstem could function as salmon spawning habitat (the bed should be swept relatively clean of fines).Present information does not allow a prediction of the degree of this type of change,so no estimate of effected fish numbers is possible.Information is also too scant to allow an accurate appraisal of the effects of the lower river with-project sediment regime on fish.It is generally believed by APA's contractors that regulated with-project flows should help stabilize stream mouths in this reach. Although unquantifiable,the slight reduction over natural conditions of with-project mainstem sediment loads should improve habitat quality for fish somewhat;natural suspended sediment loads generally exceed the limits thought minimally acceptable for maintenance of vigorous resident fish populations. 33RD4-005 -60 - REFERENCES Acres American,Inc.1983.Application for license for major project, Susitna Hydroelectric Project,before the Federal Energy Regulatory Commission.Vol.5A.Exhibit E,Chaps.1 and 2.Alaska Power Authority.Susitna Hydroelectric Project.1 vol. Alaska Dept.of Fish &Game.1976.Fish and wildlife studies related to the Corps of Engineers Devil Canyon,Watana Reservoir Hydroelectric Project. Anchorage,AK.Report for U.S.Fish &Wildlife Service.1 vol. 1978.Preliminary environmental assessment of hydroelectric development on the Susitna River.Anchorage,AK.Report for U.S.Fish & Wildlife Service.1 vol. 1981.Resident fish investigation on the upper Susitna River. 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Studies. 1983c.Susitna hydro aquatic studies,phase 2 baseline data Vol.4.Aquatic habitat and instream flow studies,1982.Final Anchorage,AK.Alaska Power Authority.Susitna Hydro Aquatic Report for Acres American,Inc.3 vols. 1983d.Susitna hydro aquatic studies,phase 2 basic data Vol.5.Upper Susitna River impoundment studies,1982.Final Anchorage,AK.Alaska Power Authority.Susitna Hydro Aquatic Report for Acres American,Inc.150 pp. 1985a.Proposed Task Statement for FY86 Su-Hydro Scope of Work. 1985b.An evaluation of the incubation life phase of chum salmon in the middle Susitna River.Draft.Anchorage,AK.Susitna Hydro Aquatic Studies Winter Aquatic Investigations,September 1983 -May 1984.1985 Report 5.Vol.1.Report for Alaska Power Authority. 157 pp. 33RD4-005 -61 - Alaska,University of,Arctic Environmental Information and Data Center. 1985.Geomorphic change in the middle Susitna River since 1949.Second Draft.Report for Harza-Ebasco Susitna Joint Venture.Anchorage,AK. 1 vol. 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