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HomeMy WebLinkAboutAPA2828TECHNICAL REPORT No.2 _.__Alaska Power Aqthority FINAL REPORT JUNE 1985 DOCUMENT No.2828 M CONSULTANTS.INC.& OWARD-CLYDE CONSULTANTS wa?£~=~[ID~@©@ ITNA JOINT VENTURE ER CONTRACT TO TREAM FLOW RELATIONSHIPS REPORT SERIES PHYSICAL PROCESSES OF THE MIDDLE SUSITNA RIVER FEDERAL ENERGY-REGULATORY COMMISSION PROJECT Mo.7114 SUSITNA HYDROELECTRIC PROJECT ~ I Document No.2828 Susitna File No.4.2.2.1 TK 14J5 .S'fl F4:tl- (lO,;;tv...~ SUSITNA HYDROELECTRIC PROJECT INSTREAM FLOW RELATIONSHIPS REPORT SERIES PHYSICAL PROCESSES OF THE MIDDLE SUSITNA RIVER TECHNICAL REPORT NO.2 Report by R&M Consultants,Inc. Woodward-Clyde Consultants,Inc. and Harza-Ebasco Susitna Joint Venture Under Contract to Harza-Ebasco Susitna Joint Venture Prepared for Alaska Power Authority ,..... Final Report June 1985 - ,.... i """' - NOTICE ANY QUESTIONS OR COMMENTS CONCERNING THIS REPORT SHOULD BE DIRECTED TO THE ALASKA POWER AUTHORITY SUSITNA PROJECT OFFICE R24/3 2 "'"TABLE OF CONTENTSI Section/Title Page """ List of Tables iii List of Figu res vi Acknowledgments ix Preface x 1.INTRODUCTION 1.1 Pu rpose 1-1 1.2 Organization 1-2 1.3 Impacts Downstream of Other Projects 1-2 1.4 Data Sou rces 1-6 1.4.1 Streamflow 1-6 1.4.2 Suspended Sediment 1-6 1.4.3 Bedload and Bed Material 1-7 1.4.4 River Cross-Sections 1-7 2.RESERVOIR SEDIMENTATION 2.1 Factors Affecti ng Reservoi r Sedimentation 2-1 2.2 Reservoi r Sedimentation 2-4 2.2.1 General Approach 2-4 2.2.2 Sediment Load 2-4 2.2.3 Reservoi r Sediment Inflow 2-5 ~2.2.4 Sediment Trap Efficiency 2-7 2.2.5 Sediment Deposition 2-7 3.CHANNEL STABILITY 3.1 Introduction 3-1 3.2 Factors Affecting Channel Stability 3-3 .-3.3 General Analytical Approach 3-6 I""'-3.3.1 Deg radation 3-70.- ""'"3.3.2 Aggradation 3-9 ""'"0 3.3.3 Stability of Tributary Mouths 3-90 0 3.4 Analysis of Natural Conditions 3-10LO LO I""'-3.5 With-Project Conditions 3-11M M ~, R24/3 3 TABLE OF CONTENTS (Continued) Section/Title - - - ...... 4. 5. 6. 3.5.1 River Morphology 3.5.2 Channel Stability 3.5.3 Intrusion of Fine Sediments 3.5.4 Tributary Stability SLOUGH HYDROLOGY 4.1 Introduction 4.2 Factors Affecting Upwelling 4.2.1 Sources of Groundwater 4.2.2 Aquifer Conditions 4.3 Local Surface Runoff 4.4 Field Studies 4.4.1 Study Sloughs 4.4.2 Field Investigations 4.4.3 Results 4.4.3.1 Slough 8A 4.4.3.2 Slough 9 4.4.3.3 Slough 11 4.4.3.4 Slough 21 4.5 With -Project Changes SUMMARY REFERENCES ii 3-11 3-12 3-14 3-15 4-1 4-1 4-1 4-2 4-5 4-6 4-6 4-7 4-9 4-10 4-12 4-14 4-16 4-17 5-1 6-1 R24/3 4 LIST OF TABLES Number/Title Page ..- ,-_...~--- 1.1 1.2 1.3 2.1 2.2 2.3 2.4 3.1 3.2 3.3 3.4 3.5 3.6 Streamflow and sediment data,Susitna River basin. Mean flows and floods,Susitna River basin. Size distribution of bedload and bed material, 1982 data. Comparison of trap efficiencies estimated by Brune's curves,Churchill's curve,and sedimentation model. Reservoir trap efficiency by Brune's curves. Reservoi r trap efficiency by Chu rchi II's curves. Particle size distribution of suspended sediment. Cha racteristics of study sites on Middle Susitna River. Hydraulic parameters for mainstem sites. Hydraulic parameters for side channels and sloughs. Representative bed material size distribution for selected sloughs,side channel and mainstem sites. Armoring bed material sizes in selected sloughs, side channels and mainstem sites. Potential degradation at selected sloughs,side channels and mainstem sites . iii 1-8 1-9 1-10 2-9 2-10 2-11 2-12 3-16 3-17 3-18 3-20 3-21 3-22 R24/3 5 LIST OF TABLES (Continued) Number/Title Page 3.7 Natural and with-project average weekly flows of Susitna River at Gold Creek (1950-1983). 3-23 -- - 3.8 Maximum natural and with-project weekly flows of Susitna River at Gold Creek. 3.9 Susitna tributary stability analysis,summary of semi -quantitative assessment. 4.1 Regression equations for slough discharge vs.mainstem discharge (1982-1984). 4.2 Linear regression equations for slough discharge vs. mainstem stage (1982-19S4). 4.3 Rating tables,mainstem near study sloughs. 4.4 Falling head test results,Slough 9 -boreholes. 4.5 Regression equations for seepage rate vs. mainstem discharge. 3-24 3-25 4-19 4-20 4-21 4-22 4-23 4.6 4.7 4.S 4.9 Storm runoff analyses,Slough 9 tributary. 19S4 monthly water balances,Sloughs SA and 11. 19S4 month Iy water balance,Slough 9,Tributa ry 9B. Precipitation coefficients for transfer of recorded data. iv 4-24 4-25 4-26 4-27 R24/3 6 Number/Title LIST OF TABLES (Continued) Page 4.10 Estimated daily runoff,Slough SA,high rainfall 4-2S pattern. r-1 4.11 Estimated daily runoff,Slough SA,moderate rainfall 4-29 pattern. 4.12 Estimated dai Iy runoff,Slough SA,low rainfall 4-30 pattern. 4.13 Estimated daily runoff,Slough 9,moderate 4-31 rainfall pattern. 4.14 Estimated daily runoff,Slough 9,low rainfall 4-32 pattern. - ,~ v R24/3 7 LIST OF FIGURES Number/Title 1.1 Susitna River streamgage locations. 1.2 Typical river bed material. 2.1 Iso-turbidity vs.time,Eklutna Lake at Station 9, 1984. Page 1-11 1-12 2-13 2.2 2.3 Suspended sediment rating cu rve,Susitna River near Cantwell (Vee Canyon). Annual flow duration curves,Susitna River near Cantwell (Vee Canyon). 2-14 2-15 2.4 Suspended sediment rating cu rve,Susitna River at Gold Creek. 2.5 Seasonal flow duration curves,Susitna River at Gold Creek. 2-16 2-17 - 4.1 4.2 Approximate locations of slough study sites and data collection poi nts -stage recorders and seepage meters. Slough 8A upwelling/seepage,1982. 4-33 4-35 4.3 Slough 9 upwelling/seepage,1982. 4.4 Slough 11 upwelling/seepage,1982. 4-36 4-37 4.5 Slough 21 upwelling/seepage,1982. vi 4-38 R24/3 8 LIST OF FIGURES (Continued) Number/Title 4.6 Groundwater contou rs,Susitna River at Slough 8A (QGC =24,000 cfs). 4.7 Groundwater contours,Susitna River at Slough 8A (QGC =8,300 cfs). 4.8 Groundwater contours,Susitna River at Slough 8A (ice-covered mai nstem). Page 4-39 4-40 4-41 4.9 G rou ndwater contou rs,Susitna River at Slough 9 (QGC =25,000 cfs). 4-42 .-. .- """ 4.10 Groundwater contours,Susitna River at Slough 9 (Q GC =8,480 cfs). 4.11 Groundwater contours,Susitna River at Slough 9 (ice-covered mainstem). 4.12 Slough 8A water temperatures,1983. 4.1:3 Mean daily surface and intragravel water temperatures recorded at Lower Slough 8A -Site 3 (RM 125.6)and Upper Slough 8A -Site 3 (RM 126.6)during 1983-84 winter season . 4.14 Slough 9 water temperatures,1983. 4.1:5 Mean daily surface and intragravel water temperatures recorded at Slough 9 -Site 3 (RM 128.6)during the 1983-84 winter season. vii 4-43 4-44 4-45 4-46 4-47 4-48 R24/3 9 LIST OF FIGURES (Continued) ..... ""'" Number/Title 4.1 16 Slough 9 water temperatures,1983. 4.17 Slough 11 water temperatures,1983. 4.11S Upper Slough 21 water temperatures,1983. 4.19 Lower Slough 21 water temperatures,1983. 4.20 Response of Susitna River and Sloughs 8A,9 and 11 to September 1983 storm. 4.21 Response of Susitna River and Tributary 98 to August 1984 storm. 4.22 Response of Susitna River and Tributary 98 to to September 1984 storm. viii Page 4-49 4-50 4-51 4-52 4-53 4-54 4-55 ,---_._---------------,--------_._.~------------ """ - -- - R24/3 10 ACKNOWLEDGMENTS This report was prepared by Jeff Coffin and Stephen Bredthauer of R&M Consultant~and Howard Teas of Woodward-Clyde Consultants.Guidance and review were provided by Wayne Dyok of Ha rza-Ebasco Susitna Joint Venture and by Woody Trihey of E.Woody Trihey and Associates. ix -- - - ..... - ..... R24/3 11 PREFACE This is the second technical report of the Instream Flow Relationships Study technical report series prepared for the Susitna Hydroelectric Project.The primary purpose of the Instream Flow Relationships Report and its associated technical report series is to present technical information and data to facilitate the settlement process.These reports are specifically intended to identify the relative importance of interactions among the primary physical and biological components of aquatic habitat. The,presentation is primari ty limited to the Middle Susitna River,the reach from the mouth of Devil Canyon downstream to the confl uence with the Chulitna River.This section of the river is also referred to herein as "thE~middle reach".It encompasses river miles (RM)151 to 99,the downstream section of river in which the aquatic habitat will be most affe,cted by construction and operation of the Susitna Hydroelectric Proj- ect.Discussion is also presented for sedimentation that would occur in the Watana and Devil Canyon Reservoirs.The two reservoirs constitute the impoundment zone and extend from RM 151 to RM 230. The I nstream Flow Relationsh ips Report and its associated tech nical report series are not intended to be an impact assessment.However,these reports present a variety of natural and with-project relationships that provide a quantitative basis to compa re alternative streamflow regimes, conduct impact analyses,and prepare mitigation plans . The technical report series is based on the data and findings presented in a variety of baseline data reports.The tnstream Flow Relationships Re- port and its associated technical report series provide the methodology and appropriate technical information for use by those deciding how best to operate the proposed Susitna Hydroelectric Project for the benefit of both power production and downstream fish resources.The technical report series is described below . x R24/3 12 Technical Report No 1.Fish Resources and Habitats in the Middle Susitna River.This report consolidates information on the fish resources and habitats in the Talkeetna-to-Devil Canyon reach of the Susitna basin available through June 1984 that is currently dispersed throughout n urnerous reports. Technical Report No 2.Physical Processes Report. natlUrally occurring physical processes within the yon river reach pertinent to evaluating project habitat. This report describes Talkeetna-to-Devil Can- effects on riverine fish ,~ - Tech nical Report No 3.Water Quality/Limnology Report.Th is report consolidates existing information on water quality in the Susitna basin and provides technical discussions of the potential for with-project bioclccumulation of mercury,influences on nitrogen gas supersaturation, changes in downstream nutrients and changes in turbidity and suspended sediments.This report is based principally on data and information that are available through June 1984. Technical Report No 4.Instream Temperature Report.This report consists of three principal components:(1)reservoir and instream tem- perature modelling;(2)selection of temperature criteria for Susitna River fish stocks by species and life stage;and (3)evaluation of the influences of with-project stream temperatu res on existing fish habitats and natu ral ice processes. Technical Report No 5.Aquatic Habitat Report.This report describes the availability of various types of aquatic habitat in the Talkeetna-to-Devil Canyon river reach as a function of mainstem discharge. Tech nical Report No.6,Ice Processes Report.This report describes the natlU rally-occu rring ice processes in the middle river,a nticipated changes in those processes due to project construction and operation,and xi - ..... - - - - - R24/3 13 disc:usses effects of natu rally occu rring and with-project ice conditions on fish habitat . xii R24/3 14 1.0 INTRODUCTION -I 1. 1 Purpose ~ I This report was designed to bring together the available information on sedimentation,stream channel stability and slough hydrology that has been collected in the Middle Reach of the Susitna River,and to discuss the changes Ii kely to occu r due to construction and operation of the Susitna Hydroelectric Project.The Middle Reach encompasses the river from Talkeetna,at river mile (RM)99,to the outlet of Devil Canyon at RM 151. This is the section of the river downstream of the impoundments that will be most affected by the construction and operation of the Susitna Hydroelectric Project.Also included in this report is discussion of reservoi r sedimentation within Watana and Devi I Canyon Reservoi rs,which extend from RM 230 to RM 151. The with-project conditions discussed in this report are based on analyses conducted for a two-dam,two-stage development.Watana Dam was to be constructed first,followed by construction of Devil Canyon Dam. However,in April 1985,the APA proposed that the Susitna Hydroelectric Projlect be changed from the two-dam,two-stage development to a two-dam, three-stage development (APA 1985).Under the proposal,a 705-foot high material-fill dam will be built during Stage 1 development at Watana (RM 184).Stage 2 includes the construction of a 646-foot concrete-arch dam,with a fill saddle dam at Devi I Cany<?n (RM 152).Stage 3 development will raise the Stage 1 Watana dam 180 feet to a crest height of 885 feet.Stage 2 and 3 developments will result in the "two-dam system described in the FERC license application (APA 1983a). Until the Stage 3 development is completed,with-project conditions will differ from those under the two-stage development,primarily due to the smaller capacity of the Stage 1 Watana Reservoi r.The Stage 1 Watana Dam will be large enough so that reservoir sedimentation estimates will be very similar.However,reservoir releases will be greater in late summer since 1-1 R24/3 15 the reservoir will tend to fill earlier in the year.The higher flows may have some effect on channel stability and slough hydrology. While these differences are not explicitly stated in this report,they may be ,astimated from the information presented. 1 .2 Organization Following a brief review of environmental effects downstream of other large hydropower projects in the Introduction,the next three sections of the report review pertinent Susitna Hydroelectric Project studies to date on specific types of physical processes.They discuss the effects of those processes on the aquatic habitat in the Susitna River.Section 2 addresses sedimentation processes in the reservoir,Section 3 deals with stability of channels in the Middle Reach downstream of the project,and Section 4 disGusses g rou ndwater upwelling and local su rface runoff as related to aquatic habitat in sloughs downstream of the project.Section 5 presents a summary of the three types of processes and the specific project effects. Ref,erences are listed in Section 6. 1.3 Impacts Downstream of Other Projects Construction of dams at Watana and Devil Canyon would affect the terr'estrial and aquatic habitat downstream of Devil Canyon,with possible effects on fish,riparian vegetation,and wildlife.The effects on the physical processes of sedimentation (reservoir and stream channel)and groundwater upwellings are the focus of this report.The following descriptions of environmental impacts downstream of similar projects introduce the subject of downstream effects of dams on these processes. Kellerhals and'Gill (1973),Petts (1977),Taylor (1978)and Baxter and Glaude (1980)have summa rized chan nel response to flow regu lation. Operation of reservoi rs sign ificantly alters the flow regime.There is often an increase in the diurnal variation of flow due to the variation in the 1-2 - ..- .- R24/3 16 amount of water passing the turbines in order to follow the load demand. Annual peak discharges are reduced not only due to storage,which allows no overflow over the spillway,but also due to the su rcharge storage provided by the rise in water level above the spillway crest.Routing th rough a reservoi r with no available storage may reduce some flood peaks by over 50%(Moore,1969),depending on the characteristics of the spillway,reservoir,and flood hydrograph ..The magnitude of the mean annual flood of the Colorado River below Hoover Dam has been reduced by 60%(Dolan,Howard,and Gallenson,1974).The total volume of flow may be reduced due to the increase in time during whkh seepage and evapo- ration losses may occur.Base flow tends to be increased due to seepage and to minimum releases to the channel below the dam. Reservoi rs with a la rge storage capacity may trap and store over 95%of the sediment load transported by the river (Leopold,Woiman,and Miller, 1964).Although reservoir shape,reservoir operation,and sediment characteristics have some influence (Gottschalk,1964),the actual percentage depends primarily on the storage capacity-inflow ratio (Brune, 19·53). The:effect of dams on the sediment load must be considered in relation to changes in river sediment transport capacity,flow regime,chan nel morphometry,and tributary inflow.Tributaries which transport large quantities of sediment into a regulated stream with reduced capacity to flush away sediments may stimulate mainstem aggradation,an increase in bed slope of the tributa ry,and trench ing of the deposit to form a channel that is in quasi-equilibrium with the flow regime (King,1961;Kellerhals, Church and Davies,1977).A reduced water-surface elevation in the mainstem also produces an increased hydraulic gradient at the tributary mouth.The increased gradient results in increased velocities,ban k instability,possible major changes in the geomorphic character of the tributary stream,and increased local scour (Simons and Senturk,1976). 1-3 ..... ..... R2~f/3 17 All of the bedload entering a reservoir is deposited in the reservoir.This reduction in sediment supply is usually greater than the reduction in sedi- ment-transport capacity.This deficit in sediment transport generally results in erosion downstream of the dam,except where an armor layer or an outcrop of bedrock occurs (Petts,1977).Degradation will occur where the regu lated flow has sufficient tractive force to initiate sediment movement in the channel (Gottschalk,1964).Once the channel bed has been stabilized,either by armoring or by the exposure of bedrock,then the banks,which usually consist of finer material than the bed,begin to fail and the channel will widen.Where armoring or bedrock occu r across the width of the'channel,a simple adjustment will occur where streamflow is accommodated in the existing channel. The sediment load plays an important role in the process of meander migration across alluvial plains by forming point bars from bed load depo- sition on the inside bank.These point bars are then aggraded to flood- plain·levels due to the deposition of suspended sediment in the emerging vegetation during peak flows.The reduction in sediment load may disrupt this process,with at least local ecological changes.Widening of channels at meander bends and lateral instability may also be expected (Kellerhals and Gill,1973). Maximum degradation normally occurs in the tailwater of the dam,but may ext,end downstream.Rates of degradation up to 15 cm per year have been observed in sand-bed rivers,both in the United States (Leopold,Wolman, and Miller,1964)and in Europe (Shulits,1934).Channel adjustment to bed degradation and the associated reduction in slope was observed for nearly 250 km below Elephant Butte Dam (Stabler,1925),also involving silt and sand size bed material.When an armored condition occu rs where the river is unable to recharge itself to capacity,the river may pick up additional material downstream,as was observed on the Colorado River below Hoover Dam (Stanley,1951). 1-4 - R24/3 18 The channel properties of gravel-bed rivers such as the mainstem of the Peace River in Alberta appea r to be controlled by floods with a recu rrence intelrval of 1.5 to 2 years (Bray,1972).Regulation reduces these flows, effelctively reducing the size of the gravel-bed river without immediately changing the channel,but certain channel properties will adjust to the chan nel regime over a longer period of time.On the Peace River,the entrenched layer of the channel,the proximity of bedrock,and the resis- tant bed material preclude significant changes in width and depth relation- ships or in the slope (except near tributary junctions),but deep scour hoh~s at bends will fill to some degree,and gravel bars exposed above the new high water mark will have emerging vegetation (Kellerhals and Gill, 1973). Vegletation encroachment on the higher elevations of the gravel bars down- stream of a dam can be expected due to the reduced summer streamflows and the lower flood peaks,and in time could encroach on present high water channels (Tutt,1979;Kellerhals,Church and Davies,1977).The effE!ct of the additional vegetation would be to increase the channel rough- ness,thus decreasing the channel water conveyance.The channel size and capacity could gradually decrease due to vegetation encroachment, deposition of suspended load in the newly vegetated areas,accumulation of material from the valley walls and deposition of sediment brought in by the tributaries.During periods of high flow,higher river stages could be expected. ThE!W.A.C.Bennett Dam on the Peace River had a dramatic unplan ned impact on the Peace-Athabasca Delta (Baxter and Glaude,1980).The delta is a series of marshes interspersed with lakes and ponds of various sizE!s.Before the dam was built,the delta was maintained in this state due to almost annual flooding,which prevented vegetation typical of drier g round from being able to establish itself.The hyd rological situation itself was complex.The Peace River,passing to the north of the delta, contributed little to the actual flooding,but its flood waters blocked the exit of the Athabasca River,which entered from the south and caused the 1-5 .~ R24/3 19 actual flooding.After construction of Ben nett Dam,the delta sta rted drying up,with dry-ground vegetation establishing itself.The effect of the dam was initially obscured due to lower than normal precipitation for some years previously,but it was eventually concluded that the dam was at least a contributing factor,as flood levels on the Peace River were lowered,resulting in the Peace River no longer blocking the exit of the Athabasca River. 1.4 Data Sources 1.4.1 Streamflow Streamflow records a re available from the U.S.Geological Su rvey (U.S.G.S.)for va rious stations on the river and its tributa ries.The periods of available records are shown in Table 1.1.The stream gaging locations are shown in Figure 1.1.The mean annual and seasonal flows and floods of selected recu rrence intervals a re shown in Table 1.2. 1.4.2 Suspended Sediment Suspended sediment data are available from the USGS at ten sampling stations and are also shown in Table 1.1. The mean annu~1 suspended loads are about 5,660,000 tons,7,260,000 tons and 16,714,000 tons,respectively,for the Susitna River near Cantwell,at Gold Creek and at Sunshine,7,412,000 tons for the Chulitna River near Talkeetna and 1,642,000 tons for the Talkeetna River near Talkeetna. The suspended sediment concentration for the Susitna River upstream from the confluence with the Chulitna River ranges from essentially zero milligrams per liter (mg/l)in winter to nearly 1,000 mg/I during 1-6 R24/3 20 summer floods.The Chulitna River,with 27 percent of its basin covered by glaciers,has recorded suspended concentrations up to 4,690 mg/I (Knott and Lipscomb,1985). 1.4.3 Bedload and Bed Material Limited bed load discharge data are available,from the U.S.G.S.as are also shown in Table 1.1.Typical size distributions of the bedload are shown in Table 1.3. A total of 48 bed material samples were collected from the mainstem and side channels of the Susitna River between the mouth of Devil Canyon (RM 150)and the confluence between the Susitna and Chulitna Rivers (RM 98.6)(Harza-Ebasco,1984c).These samples were used to determi ne the size distributions by sieve analysis.Bed material size distribution had also been estimated in an earlier study (R&M Consultants,Inc.1982b)by grid sampling techniques.Figures 1.2a and 1.2b show some examples of typical bed material.Average size distributions are shown in Table 1.3. 1.4.4 River Cross Sections Cross sections of the Susitna River have been surveyed at 106 locations between RM 84.0 near Talkeetna and RM 150.2,about 1.3 miles upstream from the confluence with Portage Creek (R&M,1981a; 1982c,1984a).Cross sections at 23 locations also are available between RM 162.1 at Devil Creek and RM 186.8 at Deadman Creek (R&M,1981a),all 23 of which are in the impoundment zone. - 1-7 -_._.--,----,......._----------------------------,.,.,;..,---------- TABLE 1.1 -STREAMFLOW AND SEDIMENT DATA, SUSITNA RIVER BASIN Suspended Sediment Bedload Drainage 2 Streamflow Number Period Number Period USGS Area,~mi Period of of of of of Gaging Station Gage No.(km 1.Record Samples Record Samples Record Susitna River ~near Cantwell 15291500 4,140 5/61-9/72 43 62-72,82 (l0,720)5/80-Pres. ~at Gold Creek 15292000 6,160 8/49-Pres.375 49,51-58,62 3 7/81-9/81 (15,950)67-68,74-83 near Talkeetna 15292100 27 6/82-10/83 29 6/82-2/84 right channel below Chuli tna 15292439 5 5/83-10/83 7 5/83-2/84 t;\"'"'R.near Talkeetna left channel 15292440 5 5/83-10/83 7 5/83-2/84 below Chuli tna R. near Talkeetna at Sunshine 15292780 11,100 5/81-Pres.53 7l,n,R1-M 34 7/81-2/84 (28,750) at Susi tna 15294350 19,400 10/74-Pres.44 -75-83,.....(50,250)I Chulitna River 15292400 2,570 2/58-9/72 ,53 58-59,67-72,18 7/81-9/82 .....,near Talkeetna (6.656)5 /BO-Pres.80-83 bel,ow canyon 15292410 13 83 15 3/83-2/84 near Talkeetna,-I I Talkeetna River 15292700 2.006 10/74-Pres.133 66:-83 33 7/81-2/84 near Talkeetna (5,196 ) SOURCE:Table reproduced from 'Wang,Bredthauer,and Marchegiani (1985)____, 1-8 ...... - ,""" TABLE 1.2 -MEAN FWWS AND FLOODS SUSITNA RIVER BASIN ~ Periods of 3 3 ~rec ord s used Mean F19ws,cfs 2y m Isec)Max.Floods,cfs (m Isec) Gaging Station in analysis Summer-Winter-Annual 2-year 10-year 50-year -Susitna River 1962-72 11,900 1,000 6,400 32,000 54,000 65,000 near Cantwell 81-83 (337 )(28 )(181 )(906)(1530)(1840 ) at Gold Creek 1950-83 17,800 1,600 9,720 48,000 73,700 97,700 (504)(45 )(275 )(1,360)(2,090)(2,770) at Sunshine 1982-83 45,600 4,500 25,100 142,000 182,000 212,000 (1,290)(127)(710)(4,020) (5,150)(6,000) Chulitna River 1959-72 16,200 1,400 8,800 42,000 62,000 87,000 ~near Talkeetna 81-83 (459)(40)(249 )(1,190)(1,760 )(2,460 ) Talkeetna River 1965-83 7,300 700 4,000 27,500 49,000 61,000 near Talkeetna (207)(20)(113)(780)(1390 )(1730) II Hay through October 21 November through April - ?OoBCE:Wang,Bredthauer,and Marchegiani (1985) 1-9 - ..- - ~, I - TABLE 1.3 -SIZE DISTRIBUTION OF BEDLOAD AND BED MATERIAL,1982 DATA Size Distribution of Particles % Bedload Bed Haterial Gage Sand Gravel Cobble Sand Gravel Cobble Susitna River near Talkeetna 78 16 6 0 30 70 Chulitna River near Talkeetna 41 58 1 26 64 10 Talkeetna River near Talkeetna 75 23 2 5 52 43 Susitna River at Sunshine 56 42 2 5 66 29 Source:Knott and Lipscomb (1983) Harza-Ebasco Susitna Joint Venture (1984) (Table reproduced from:Wang,Bredthauer,and Marchegiani (1985) 1-10 1 I .... I.... I-' l -I , ~ l ;/cou~ 1 /7 )J --1 1 SOURCE:Modified from (EWT &A and WCC,1985) •Proposed Dams i te o Streamgage (a 11 USGS except Watana, which is R &M) f 10 RI\llHmile Incr.menls Scole ,.":16mil., LOCATI ON MAP l } SUSI'INA RIVER S'!'REAr4;AGE LC>2ATIONS PREPARED BY: -l;Z~.!o========== I=l &M CONSULTANTS.INC. ENGlIl'Jl!rinB titldLtl~I(JT.HvonCLCClIBTd flURVISVORB FIGURE 1.1. PREPARED FOR: [}{]&~~&0 ~[ID&~©@ SUSITNA JOIt,n VENTURE - - (a)On a gravel bar near the Confluence of the Susitna and Chulitna Rivers (b)The Susitna River near Talkeetna River bed under 1 ft.(O.3m)of water Fig.1.2 -Typical River Bed Material SOURCE:wang,Bredthauer,and Marchegiani (1985) -PREPARED BY; -f~~f'~I1=====,===-===:::== !=I&M CONSUL.TANTS,INC. PREPARED FOR: G:f)&~~&c [g[ID&®©@ SUSITNA JOINT VENTURE 1-12 R24/3 22 2.0 RESERVOIR SEDIMENTATION ..- I, - - - f"-" I J - 2.1 Factors Affecting Reservoir Sedimentation ThB effect of the project on sediment transport in the Susitna River is of concern as it relates to aquatic habitat.This section briefly describes the processes of reservoir sedimentation and details the factors which affect trap efficiency.Trap efficiency is the percentage of incoming sediment which is retained in the reservoir.Section 3 discusses downstream project effE~cts on channel stability,which are derived from changes to the flow and sediment regimes of the river.Changes to the sediment regime result from trapping all the bedload sediment and a large proportion of the suspended sediment which enters the reservoir,thus substantially reducing the sediment supply downstream.Sediment effects on water quality are addressed in Report Number 3,the Water Quality/Limnology Report. Trap efficiency of a reservoi r depends on the sediment pa rticle fall velocity and on residence time of the sediment within the reservoir.Fall velocity is determined by a number of factors,including particle size and shape,pa rticle density,sediment chemical composition,water temperatu re, water viscosity and sediment concentration (R&M 1982d;PN &D and Hutchison 1982;Jokela,Bredthauer and Coffin 1983).The chemical composition may cause electrochemical interactions which lead to particle agg regation or dispersion.Small pa rticles may agg regate into clusters which have settling properties similar to larger particles and fall more rapidly (R&M 1982d).A review of data from glacial lakes (R&M 1982d) indiicated that particle sizes of 2 microns (0.002 mm)and less would pass through the reservoir. Another report (PN&D and Hutchison,1982)concluded that particles smaller than 3 to 4 microns would likely remain in suspension and be carded through the reservoir.Wind mixing would be significant enough to retain particles of diameter 12-microns and less in suspension above the 2-1 R24/3 23 - 50-foot depth.Strong windstorms would cause re-entrainment of sediment, resulting in short-term increases in suspended sediment at the reservoir edges. Data collected at Ekl utna La ke (R&M 1982a,1985b),approximately 100 mi les south of the Watana damsite,indicate that the mean particle size of sediment carried through the lake is 3 to 4 microns equivalent diameter, with la rger particles bei ng deposited most rapidly and forming a delta. ..- i r - I .1 Residence time of sediment within the reservoir is determined by the capacity-inflow ratio,by the reservoir geometry (plan shape and depth), and by size and location of reservoir outlets.Capacity-inflow ratio is the major factor,~ut it may be modified by "short-circuiting"of sediment- ladEm inflow to the outlet if little mixing occurs.Shallow,open lakes are more conducive to formation of internal currents (due to winds)than are deep,confined lakes.These internal currents slow down the settling processes,especi.atly for fine,slowly-falling particles.Deep reservoirs with large surface areas are almost continuously subjected to mixing processes generated by climatic influences (wind and su rface energy transfer)and by inflowing and outflowing currents.This mixing creates a substantial amount of turbulence which tends to keep the fine sediments in suspension (PN&D and Hutchison 1982).Location and size of reservoir outlets also affect trap efficiency,with bottom outlets more effective in removing the higher sediment concentrations near the bottom (R&M 1982d). Short-ci rcuiting of inflow may occu r if hydraulic conditions in the reser- voir are such that the inflow plume travels to the dam outlet and is dis- charged with little interaction having taken place with the ambient water. The~plume may travel th rough the reservoir as overflow,underflow or inte,rflow,depending on whether it follows atop,bottom,or middle layer in the reservoir depth.The flow depth is determined by the relative den- sities of the stream water and the lake water,the equilibrium depth being that where densities of the two are the same.Density is primarily a fundion of temperature and suspended-sediment concentration and to some 2-2 -._----_._-'---_._--.--------------, - - R24/3 24 extent of dissolved-solids concentration.Frequency,duration,and intensity of underflows and interflows have also been attributed to lake bathymetry,especially near the stream mouth (R&M 1982d).Illustrations of the variation of turbidity (and thus of suspended sediment concentration)versus depth and time are shown for Eklutna Lake for 1984 in Figure 2.1.An example of interflow is seen during mid-August in Figure 2.1. Another process which can affect sediment levels in a reservoir is slope failure and deposition from the surrounding banks.Soil stability is reduced by the reservoir raising the ground water table,especially when it also acts to thaw permafrost that had been bi ndi ng the soil.The primary types of slope failure and subsequent erosion that are expected in the Watana Reservoir are shallow rotational slides and other shallow slides, mainly skin and bimodal flows (Acres American 1982).Devil Canyon Reservoir slopes are expected to be stable after impounding due to shallow overburden materials and stable bedrock. Rotational slides are landslides with well-defined,curved shear surfaces, concave upward in cross-section.Skin flows are detachments of a thin veneer of vegetation and mineral soil,with subsequent movement over a plana r,inclined su rface.In the reservoi r impou ndment area,this usually indicates thawing of fine-grained overburden over permafrost.Bimodal flows along the reservoir shore are slides that consist of steep headwalls containing ice or ice-rich sediment.The ice-rich sediment retreats' retl~ogressively through melting to form a debris flow which slides down the face of the headwall to its base (Acres American 1982). ThEl Alaska Power Authority (1983)made quantitative estimates of the increases in suspended sediments expected from skin slides,bimodal flows, and shallow rotational slides in the two reservoirs,including where they wer'e likely to occur.A "worst case"scenario was assumed,in which 2x108 cubic meters of unconsolidated materials would slide into the res,ervoirs.It was assumed that all particles less than or equal to 10 2-3 R24/3 25 microns would become suspended in the water.This resulted in an estimate of 35 percent (by dry weight)of the material being suspended. Seventy-five percent of this suspended material was assumed to be trapped in the reservoir.This reduced to an estimated maximum yield of 33 million metric tons of suspended particulates which could pass through the reslervoirs and on downstream.Most of this activity would probably occur during the first five years of reservoir operation. 2.2 Reservoi r Sed imentation 2.2.1 General Approach Bedloads were estimated as percentages of suspended sediment loads using available data at the Gold Creek,Talkeetna,and Sunshine gages on the Susitna River.All bedloads were assumed to be trapped by the reservoirs.Bedloads at Devil Canyon Reservoir were computed for with-and without-Watana Reservoi r conditions. - - - Churchill curves (Harza-Ebasco,1984c). Canyon Reservoi r were estimated for Reservoir conditions. Sediment deposits in Devil with -and without-Watana - - - 2.2 ..2 Sediment Load Sediment discharges at the Cantwell (Vee Canyon)and Gold Creek gages were computed by the sediment rating flow du ration cu rves method.Suspended sediment discharges and the corresponding water discharges for the Cantwell (Vee Canyon)gage are shown in Figure 2.2.The data for the Cantwell (Vee Canyon)gage were grouped into three groups,each corresponding to the period from June to October, 2-4 - - - - - - ..- R24/3 26 November to April,and May,in order to estimate sediment discharge during the summer,winter,and breakup periods.Only one sample was available for the November-April period and two samples for the May period.These data were insufficient to develop separate curves. Therefore,one sediment rating curve was fitted visually to all data points.Using this suspended sediment rating cu rve and the flow-duration curve for Vee Canyon on Figure 2.3,the mean annual suspended sediment discha rge at the Cantwell (Vee Canyon)gage was computed to be about 5,660,000 tons/year. Suspended sediment discharges and the corresponding water discharges for the Gold Creek gage are shown on Figure 2.4.The data for the Gold Creek gage,collected in the period from 1949 to 1982,were divided into three groups corresponding to June-October, November-April,and May periods.The points for the June-October and May periods indicated separate trend lines and were fitted with two curves.Limited data points were available for the low-flow period of November-April.These points appeared to be fitting the lower part of the May curve.Therefore,the May curve was used for the November-April period.The daily flow duration curves for the Gold Creek gage for the June-October and November-May periods were derived using the 1950-1982 flow data and are shown on Figure 2.5.The mean annual suspended sediment discharge at the Gold Creek gage was computed to be about 7,260,000 tons/year. 2.2.3 Reservoir Sediment Inflow Suspended-sediment inflows to Watana and Devil Canyon Reservoir were computed by transposing sediment discharges at the Cantwell (Vee Canyon)and Gold Creek gages,whose locations bracket the two reservoirs.Sediment discharges at the two gages were assumed to follow the following exponential relationship (Vanoni;1975): 2-5 --R24/3 27 - - - - - - - In which: qs1 =sediment discharge per unit drainage area (unit sediment discharge)at point 1 qs2 =unit sediment discharge at point 2 A 1 =drainage area for point 1 A2 =drainage area for point 2 n =exponent U~ing the unit sediment discharges at the Cantwell (Vee Canyon)and Gold Creek gages,exponent "n"in the above equation was computed to be -0.376.Thus,suspended-sediment discharge at the Watana damsite was computed to be 6,530,000 tons/year for the drainage area of 5,180 square miles.Assuming no Watana Reservoir,the suspended-sediment discharge at the Devil Canyon was computed to be 7,030,000 tons/year using a drainage area of 5,810 square miles. Bedload discharge was estimated to be three percent of suspended-sediment discha rge,based on the following analysis. Bedload and suspended sediment discharges for the Susitna River near Talkeetna were estimated to be 43,400 and 2,610,000 tons/year, respectively,for water year 1982.Thus,the bedload discharge is about 1.6 percent of suspended sediment discharge.For the Sunshine gage,bedload discharge is about 3.2 percent of suspended sediment discharge,based on the bedload and suspended sediment discharges of 423,000 and 13,330,000 tons/year,respectively for water year 1982.A value of 3 percent was used in the analysis. 2-6 -I ..... R24/3 28 2.2.4 Sediment Trap Efficiency 7~~0 c? Sediment trap efficiencies of Watana and Devil Canyon Reservoirs were estimated by the Brune's and Churchill's curves (U.S.Bureau of Reclamation,1977).The trap efficiency of Watana was also estimated by PN &D and Hutchison (1982)using a sedimentation model.Similar modeling is not available for Devil Canyon Reservoir. A comparison of the trap efficiencies of Watana and Devil Canyon Reservoirs estimated by the three methods IS shown in Table 2.1. The Watana trap efficiency ra nges from 96 to 100 percent based on B ru ne's cu rves.The trap efficiency is about 100 percent based on the Churchill's curves for local silt.The trap efficiency computed by a reservoir sedimentation model,DEPOSITS,ranges from 78 to 96 percent depending on reservoir mixing and dead storage volume. The trap efficiency of Devil Canyon Reservoir ranges from 86 to 98 percent based on the B ru ne'S'cu rves.The trap efficiency estimated with the Churchill's curves is 95 percent for local silt and 88 percent for fine silt,the latter case being for sediment discharged from an upstream reservoir.Tables 2.2 and 2.3 show the estimation of the trap efficiencies by Brune's curves and Churchill's curves. 2.2.5 Sed iment Depos ition Based on the estimated trap efficiencies shown in Table 2.1,Watana Reservoir was assumed conservatively to trap all sediment inflow to the reservoi r.The resu Iti ng sediment deposition over a 50-and 100-year period will be about 210,000 and 410,000 acre-feet.The gross reservoir volume is about 9,470;000 acre-feet at a normal maximum pool elevation of 2,185 feet,of which 5,730,000 acre-feet is the dead storage CAPA,1983a).The 100-year sediment deposit is only about 7 percent of the dead storage volume. 2-7 - - - - R24/3 29 Without Watana Reservoi r,the 50-and 100-yea r sediment deposits in Devil Canyon Reservoir would be about 226,000 and 442,000 acre-feet, respectively,also assuming a trap efficiency of 100 percent.The gross reservoir volume of Devil Canyon Reservoir is about 1,090,000 acre-feet at a normal maximum pool elevation of 1,455 feet,of which about 740,000 acre-feet is dead storage.The 100-year sediment deposit is about 60 percent of the dead storage volume. With Watana Reservoir,the 50-and 100-year sediment deposits in Devil Canyon Reservoir would be abut 16,100 and 31,400 acre-feet, respectively,or about 2 and 4 percent,respectively,of the dead storage volume,assuming 100 percent trap efficiency for sediments from the intervening drai nage a rea.Any fine suspended sediment passed through Watana Reservoir was assumed to also pass through Devil Canyon Reservoir. The sediment volumes presented above were computed using the procedures of the U.S.Bureau of Reclannation(1977).Percentages of clay,silt,and sand of the incoming suspended sediment were estimated to be 20,38 and 42,respectively,using sediment data for the Cantwell (Vee Canyon)and Gold Creek gages (Table 2.4).Using unit weights for clay,silt and sand of 26,70 and 97 Ib/fe, respectively,the u nit weights of the sediment deposits after 50 and 100 years were estimated to be about 80 and 82 Ibs/ft3,respectively. The unit weight of bedload was estimated to be 120 Ib/ft 3 . 2-8 ,-------~-----------'1"--~---- - - TABLE 2.1 COMPARISON OF TRAP EFFICIENCIES ESTIMATED BY BRUNE'S CURVES,CHURCHILL'S CURVE,AND SEDIMENTATION HODEL Method Trap Efficiency,% Wa:tana Devil Canyon Brune's Curves Coarse Sediment Median Curve Fine Sediment Churchill's CurVe Local Silt Fine Silt DEPOSITS l10del Quiescent Minimum Mixing t1aximum Mixing 100 99 96 100 94 to 96* 86 to 93* 78 to 90* 98 94 86 95 88 *Corresponding to dead storage volumes from 5,340,000 acre-feet to 900,000 acre-feet (reservoir capacity =9,470,000 acre-feet at normal 'maximum pool). SODbCE:Harza-Ebasco (1984c) ~I 2-9-.,----........----_.......-"I""'""-----~~-"-----_......._--~--_.~------------------ !""", TABLE 2.2 RESERVOIR TRAP EFFICIENCY BY BRUNE'S CURVES Reservoir Storage Capacity af Average Annual Inflow af Capacity -:-Inflow Trap Efficiency Max.Median Min. Watana Devil Canyon 9,47o,ooai/5,780,ooodl 1.64 1,090,OOol/6,580,OOo!!0.17 100 98 99 94 96 86 ,."., - lJ y At normal maximum pool elevaton 2185 feet -above mean sea level.From License Application,Exhibit E,Chapter 2, page E-2-55 (11). At normal maximum pool elevation 1455 feet above mean sea level.From License Application,Exhibit E,Chapter 2, page E-2-55 (11). Converted from average annual flo\'I of 7990 cfs at Watana,as shown in License Application,Exhibi1:E,Chapter 2, Table E.2.4 (11). Converted from average annual flow of 9080 cfs,as shown in License Application,Exhibit E,Chapter 2,Table E.2.4 (11). SODT-CE:Harza-Ebasco (1984c) 2-10 I 1 ))1 ))J )J ,]J }J j J )Jf TABLE 2..3 RESERVOIR TlUP EFFICIENCY BY CHURCHILL'S CURVES (1)(2)(3)(4) (5) (6)(7)(8)(9)(10) Average'1J Cross-Retention %of Trap Storage l/Average1J RetentionlJ Reservoirif Sectional MeanW Pe riod -:-Silt Effi- Reservoir Capacity Inflow Period Length Area Velocity Velocity Passing'ciency ft 3 cfs sec ft ft 2 ft/sec sec 2 /ft % Watana 4.13x10 11 7990 5.l1x107 2.75x105 1.50x106 0.53x10-2 9.70xl09 <0.1 100 to I i--'Devil Canyonf-l (local silt)O.4/ixlO ll 9080 O.52x107 1.69x10S O.28xlO6 3.23xlO-2 O.16xl09 .5 ~5 Devil Canyon (fine silt)12 88 l/ 11 )J if 2J Y At normal maximum pool elevation 2185 ft for Watana and 1455 ft for Devil Canyon. From License Application,Exhibit E,Chapter 2,page E-2-55. FroID License Application,Exhibit E,Chapter 2,Table E.2.4. Col.(2)-:-CoL (3). Converted froID 52 reservoir miles for Watana and 32 reservoir miles for Devil Canyon. Col.(2)-:-Col.(5). Col.(3)-:-Col.(6). SOuRCE:Harza-Ebasco (1984c) I J )-J })1 )._]J ..--]'~))]]J J 1j •I TABLE 2.4 PARTICLE SIZE DISTRIBUTION OF SUSPENDED SEDIMENT No.Particle Size (mm) Stream Gaging of 11 .002 .004 .008 .016 .03-i--.062 .125 .250 .500 1.000-------percent Finer ThanVStationSam~ Susitna River 34 12 16 23 31 41 53 64 81 96 100 nr.Denali Susitna River 27 12 18 25 3]43 54 67 86 97 100 nr.Cantwell Susitna River 24 15 19 27 35 47 61 75 86 98 100 at Gold Creek Susitna River 13 29 35 53 72 79 90 100 nr.Talkeetna IV Chul1 tna River 36 21 31 37 46 55 62 72 85 99 100 I nr.Talkeetnat-' IV Talkeetna River 16 9 16 22 41 53 65 85 99 10031 nr.Talkeetna Susitna River 17 22 JJ 43 53 62 67 79 90 100 at Sunshine Susitna River 9 16 23 JJ 43 52 60 82 94 100 at Susitna Station 1/Samples for which full range of size distributions were analyzed. 2/The percentages given are the median values from a range of oberved percentages for various sizes. SOtJR::E:Harza-Ebasco (1984d) })1 --1 1 J 1 ]1 1 -)))j 850 19 5 4 I 2 ,. 3 3 (SAMPLE FREQUENCY~TYP.IJ22 50 60.,...,.._.....__ aoo I I I I 1,0 II \I J 1/\I 111'1 1;'0 \ \ . \\I I 40... E-i.oj 5 NTU ~\\\)r~i I ~"o:10~I J '"<l> 20-1 \ \\\\/1 \L~,I I I ! I I \1-700 I 10 o I I I111II1 I I 111111 II!!II I I JAN I FEB i MARCH •APRIL I MAY 'JUNE 'JULY'AUG I SEPT j OCT i NOV I DEC i --T t ISO-'IURBIDITY vs.TIl.\1E}EKIlJ'INA LAKE @ STATION 9 (1984) Source:Figure reproduced fram (R &M 1985b) PREPARED BY; [~Ji\\J;l=.!-.._~'V [========== R &M CONSULTANTS.INC. IiNQINIlIiJ:10 DUCLCGoIDTD HvonDLlI;:JalHTIl RUnVIIVCRO FIGURE 2.1 PREPARED FOR: G{]&~~&CJ ~[ID&~©@ SUSITNA JOINT VENTUriE 1 '})1 )}]-')1 J J J ) ">'"7 t>':- /./- ",-"'- /;- / , I "/ ,----r----r-:~:yL_----T----- &~~ ,A./'-~ ~~.0~,~-~-_._----_._~. ,fJJ i !:"1 I •.Ju~;'Ocr :/1'''j'I'-T:'!~::Y~.'1P/<i ---:': '.1 I Frl"~!>O/',!/cCDNP)I?~Z ~)97t.. .j .'X~j,r/l'" / "/"._-- ./ I·i v L+-l.I.___;.,'--'.',I.-~-j-.I -'I Ii!•.,,I 1 .",:I I :~•~rl"",,/1 /!"I'.'9 .. .L I .!... -~"""'-I-'-L-I"".'I'!I.i\t:;~~I·.il'l ri _~__L..c/""'-./t 1 '1 ..1 ,.·..·..1 [.__J_..,_.'.-I I'.,:III '--"'I Iv,.i'/lll'--'----'I·"I-I·.j-..---,·-{I·I.·"·r···1 ·1:I.I .1L_./:.._:'1 ../'.1 I'i ..'.'1 /I.I····+-W .,~.,"'~..i :II;Ii i<~LJ-J~J-'J -+!_.:._....L_ ..._____'__J~l=~~~_... '~' -II I .. Il i~i~:" -V -_.. ~.~~••1 1 '.__ I ~:I"':'," ',~__,--_.1 __-_.,.j .. It •.~.•.i ,ii i'~I ooo,L ..•.•:'.,-lid 1 I:.l:I~'-~-~-'-1 ~';j 10,000 '-- N I I-' ,/::> i 1 i :-;--~--:-;'-'c-T~-'-,-,------.. '-~rc :.:-:-1 , f"'I.~I~~IJ11n+.•.:.jCtc~~!~·ii]j ":*z:i"I "i :, :I!!I I I !I!,--...i....-L~_~...,,~O...u ,,, SOURCE:Harza-Ebasco (1984c)Suspended Sediment Rating Curve Susitna River near Cantwell (Vee Canyon) PREPARED BY: ~ R &M CONSULTANTS.INC. BNtJIN_EJR8 C1eCLCGIBTD t4YD~CL.QUlIB'T1II BURV.VCRa FIGURE 2.2 PREPARED FOR: [g]&OO~&0 ~[ID&~©@ SUSITNA JOINT VENTURE - ...... - 1- --++++tttll'--++~H,1 H,+i ,t.I!1 f'.l l :++--1-,--...1 f,-L 100 om 0.05 0.1 0.2 0.5 1 10 20 3IJ 4<l 50 60 70 90 95 98 99 99.8 99.9 99.99 'ANNUAL FIDW DURATION CURVE, SUSITNA RIVER NEAR 'CANTWELL (VEE CANYON) ..... PREPt.REO BY; ~1<3i\\.l1l ""__r'c'~·.:.J'\:.JI========== R&M CONSULTANTS,INC.FIGURE 2.3 2-15 PREPARED FOR; [}{)&~g&co @:[ID&~©@ SUSlTNA JOINT VENTURE PREPARED BY: -.-J~~~..!========~= R&M CONSULTANTS,INC.FIGlJ I 2 2 2IIjI I rr d I!Ii I rim :3 456789 1 I Iii I 2345678912 ·1r '1 ill 2:3 4 1 516178~111 2 3 1 i 5 f j81~:I,I I I ,I 1,_'"I !:1 ~2 ~~~6 7 8 ~i PREPARED FOR: SUSITNA JOINT VENTURE - 20,OO~_'J-!t 1ft ecf: HI ~h ANNUAL FLOW DURATION aJRVES, SUSI'INA RIVER at GOLD CREEK 10 9 8 PRloPARED BY; --5~~~~=========== I=lE~M CONSULTANTS,INC.FIGURE 2.5 2-17 PREPARED FOR; SUSITNA JOINT VENTUHE .... ..... ""'": I R24/3 30 3.0 CHANNEL STABILITY 3.1 Introduction The middle reach of the Susitna River alternates between single-channel and split-channel configu rations.A number of ba rren gravel ba rs or vegletated islands exist in the river.The mid-channel gravel bars appear to be mobile during moderate to high floods (R&M,1982e).A number of tributaries,including Portage Creek,Indian River,4th of July Creek,and Lane Creek,join the main river in this reach.Almost every tributary has built an alluvial fan into the river valley.Due to relatively steep gradients of some of these tributaries,the deposited material is somewhat coarser than that normally carried by the Susitna River. Vegetated islands generally separate the main channel from side channels and sloughs.These sloughs and side channels exist on one ban k of the rivt~r at locations where the main river channel is confined towards the opposite bank.The flows enter into these sloughs and side channels, depending upon the elevations of the berms at their heads relative to the mainstem river stages (Table 3.1).Coarser bed materials are generally found at the heads of sloughs and side channels,as the flow entering these sloughs and side channels is from the upper layer of the flow in the main channel and does not carry coarse material.This relatively sediment- frel~flow picks up finer bed material at the heads,thereby leaving coarser material. Evaduation of morphological changes between 1949-1951 and 1977-1980 (AEIDC,1984)indicates that some sloughs have come into existence since 194'9-51,some have changed character and/or type significantly,and others have not yet changed enough to be noticeable.Many sloughs have evolved from side channels to side sloughs or from side sloughs to upland sloughs (definitions of slough types and other habitat types may be found in (EWT&A and WCC,1985)).Thus,they are now higher in elevation relative to the water surface in the mainstem at a given discharge.The 3-1 ..... ..... - R24/3 31 per'ching of the sloughs and increased exposure of gravel bars above the water su rface are indicative of river degradation over the 35-year period. However,the photographs presented in the report also show significant increase in the number and/or size of barren gravel bars,which indicates that localized sediment depositions have also occurred.Therefore,both deSlradation and localized deposition can be expected to occur in the Susitna River under natural conditions,depending upon the flows and sediment loads. Under with-project conditions,the flow regime of the Susitna River will be modified,and the reservoi rs will trap most sediment except the smaller particle sizes of fine silt and clay size material.The river will strive to adjust itself to a new equilibrium.The main channel will have the tendency to be more confined with a narrower channel.This may cause the main channel to recede from the heads of some sloughs and side channels. Of major concern are potential aggradation or degradation in the sloughs and side channels at their entrances,and at sites in the main channel. Also of concern.are intrusion of fine sediment into the gravel bed and its subsequent entrapment.In case of fine sediment deposition on the gravel bed,appropriate measures may be necessary to flush out the sediments so that the bed can be kept clean. Another concern is the potential change in hydraulic conditions at the mouths of tributa ries due to lower mai nstem water levels.Of special inte~rest are I ndian River and Portage Creek,wh ich receive the majority of the escapement of chinook and chum salmon entering tributaries upstream of the Chulitna River confluence.Potential perching of these and other tributaries above the mainstem,the decrease or elimination of the backwater area at the mouth,and increased velocities could restrict fish access to spawning areas CTrihey,1983).Conversely,excessive degradation at some tributaries could potentially cause maintenance problems at stream crossings of the Alaska Railroad (R&M,1982f). 3-2 - - - R24/3 32 This segment of the report discusses the analyses of sedimentation processes conducted by Ha rza-Ebasco (1985),R&M (1982e,f)and Tri hey (1983)in order to evaluate stream channel stability under natural and with-project conditions for study sites in the mainstem,in selected sloughs and side channels,and in significant tributaries.For these analyses,a stable channel means that its shape,slope and bed material size distribution do not change significantly with time.Thus,these physical parameters are relatively constant,although there may actually be exchange of soil particles in the bed from time to time.Major items discussed in this section are: - 1. 2. 3. 4. 5. Evaluation of sedimentation processes under natural conditions; Eval uation of potential deg radation or aggradation under with-project conditions; Determination of discharge rates at which the mainstem flows are likely to overtop the entrances of the sloughs and side channels under natural and with-project conditions; Estimation of discharge rates for the sloughs and side channels at which their beds will be unstable,and also estimation of the rates required to flush out fine sediment deposits;and Estimation of changes in tributary mouth conditions at significant tributa ries. ....., 3.2 Factors Affecting Channel Stability To provide some background for analyzing the specific problems under study,a brief description of sediment transport in a river is given below. Sediment particles are transported by the flow as bedload and suspended load.The suspended load consists of wash load and bed-material load.In large rivers,the amount of bedload generally varies between about 3 and 25 percent of the suspended load (Harza-Ebasco,1985).Although the amount of bedload is generally small compared to the suspended load,it is important because it shapes the bed and affects the channel stability. 3-3 ,~ - ..- - R24/3 33 The amount of material transported or deposited in a stream under a given set of conditions depends upon the interaction between variables representing the characteristics of the sediment being transported and the capacity of the stream to transport the sediment.A list of these variables is 9iven below (Simons,Li and Associates,1982). Sediment Characteristics: Quality:Size,settling velocity,specific gravity,shape,resistance to wear,state of dispersion and cohesiveness. Quantity:Geology and topography of watershed;magnitude,intensity, du ration,distribution and season of rainfall;soil condition; vegetal cover;cultivation and grazing;surface erosion;and bank cutting. Capacity of Stream: Geometric shape:Depth,width,form and alignment. Hydraulic Properties:Slope,roughness,hydraulic radius, discha rge,velocity,velocity distribution,tu rbu lence, tractive force,fluid properties and uniformity of discha rge. The above variables are not independent,and in some cases the effect of a variable is not definitely known.However,the responses of channel pattern and longitudinal gradient to variation of the variables have been studied by various investigators,including Lane (1955),Leopold and Maddock (1953),Schumm (1971)and Santos-Cayudo and Simons (1972). ThE!studies by these investigators support the following general relationships (Simons and Senturk,1977): 3-4 };'}~~ 'Zll (i) , ~(i i) (i ii) (iv) (v) (vi) - - ..- R24/3 34 depth of flow is directly proportional to the cube root of water discharge; channel width is directly proportional to sediment discharge and to the square root of water discharge; channel shape expressed as width to depth ratio is directly related to sediment discharge; channel slope is inversely proportional to water discharge and directly proportional to both sediment discharge and grain size; sinuosity is directly proportional to valley slope and inversely proportional to sediment discharge;and transport of bed material is di rectly related to streampower (defined as product of bed shear and cross-sectional average velocity),and to concentration of fine material,and inversely related to bed material sizes. Because of the complexity of interaction between various variables,the river response to natural or man-made changes is generally studied by (i)qualitative analysis,involving morphological concepts;(ii)quantitative ancdysis involving application of morphological concepts and various empirical or experimental relationships;and (iii)quantitative analysis using mathematical models.The insight to the problems obtained th rough the qualitative approach provides u nderstandi ng of the methods requ i red to qucmtify the changes in.the system.Mathematical modeling can help to study many factors simultaneously.Work by Simons and Li (1978)and others indicate that physical process-computer modeling provides a reliable methodology for analyzing the impacts and developing solutions to complex problems of aggradation,degradation and river response to engineering activities. For'river channels of non-cohesive sediment,qualitative predictions of river response have been made using Lane's relationship (Lane,1955): QSr:vGsd s 3-5 R24/3 35 in which Q =stream discha rge S :=longitudinal slope of stream channel G =bed material discharges d s =particle size of bed material,generally represented by d 50 (median diameter) ThE!use of the above relationship to predict potential responses of the Susitna River under natural and with-project conditions is discussed in S ec:t ion 3.5.1. Pre~dictjon of quantitative changes in a river system requires geomorphic and hydraulic data or information wh ich a re generally not readi Iy avai lable. Considerable effort,time and money are required to collect such information.The data of primary needs include hydrological and topographic maps and charts,large scale aerial and other photos of the river and surrounding terrain,existing river conditions (roughness coefficient,aggradation,degradation,local scour near structures), discharge and stage data (under natural and with-project conditions), existing channel geometry (main channel,side channels,islands),sediment data (suspended load and bed-load,size distribution of bank and bed material and suspended sediment),and size and operation of anticipated reservoir(s)on the river system. Because the available data did not usi ng computer tech niques,the relationships were used to predict the study sites. 3.3 General Analytical Approach permit meaningful mathematical modeling morphological concepts and empi rical potential agg radation or degradation at Hal~za-Ebasco (1985)evaluated the sedimentation processes of degradation and aggradation under natural and with-project conditions in the Susitna 3-6 - - R24/3 36 River at the study sites (Table 3.1),using the approaches discussed below. 3.3.1 Degradation Generally,river bed degradation occurs downstream of newly constructed diversion and storage structu res.The rate of degradation is rapid at the beginning,but is checked by either the development of a stable channel slope or by the formation of an armor layer if sufficient coarse sediment particles are available in the bed. The important variables affecting the degradation process are: 1.Characteristics of the flow released from the reservoir; 2.Sediment concentration of the flow released from the reservoir; 3.Characteristics of the bed material; 4.I rregularities in the river bed; 5.Geometric and hydraulic characteristics of the river channel;and 6.Existence and location of controls in the downstream channel. The assumptions used in the analysis of degradation include: 1.Bedload is completely trapped by the reservoir,but suspended sediment particles of .004 mm and less in diameter will remain in suspension and pass through the reservoir (PN&D,1982).The sediment passi ng th rough the reservoi r would be about 18 percent of the sediment inflow (Harza-Ebasco,1984d); 2.Irregularities in the river and channel configurations remain unchanged; 3-7 - - - - - .-, R24/3 37 3.Sediment supply due to bank erosion is negligible; 4.Sediment eroded from the river bed is carried downstream as bedload; 5.Sediment injections by tributaries are carried downstream without significant deposition; 6.Size distribution of bed material is constant th roughout the depth at each study site;and 7.Sufficient coarse material exists in the river bed to form an armoring layer which prevents further degradation. The size of armoring bed material was estimated using (i)the competent bottom velocity concept of Mavis and Laushey (1948)and U.S.Bureau of Reclamation (1977);(ii)·the tractive force versus transportable size relationship derived by Lane (1953);(iii)the Meyer-Peter,Muller formula (U.S.Bureau of Reclamation,1977); (iv)the Schoklitsch formula (U.S.Bureau of Reclamation,1977);and (v)Shields criteria (Simons,and Li and Associates,1982). The depth of degradation or the depth from original streambed to top of the armoring layer was computed by the following relationship given in (U.S.Bureau of Reclamation,1977): _ 1y - y (--1)d a Wp in which: ,.,.. y =d y =a depth of deg radation,feet thickness of armoring layer,assumed as 3 times transportable size or 0.5 feet,whichever is smaller 3-8 .... - - - - R24/3 38 wp =decimal percentage of material la rger than the size The transportable size for a given discharge was the average of the five sizes estimated by using the five methods mentioned above. 3.3.2 Aggradation Potential aggradation at the entrances of sloughs and side channels was estimated by comparing the transportable size for the flow in the mainstem before diversion into the slough or side channel and the transportable size for the remaining flow in the main channel after diversion into side channel or slough.If the two sizes were significantly different,it was concluded that some of the bedload being transported would be deposited near the entrance. 3.3.3 Stab i Iity of Trib utary Mouths The regulation of floods by reservoi r operation resu Its in a decrease in stage during the mean annual flood of from 3.2 to 7.6 feet at the mouths of tributaries between Devil Canyon and the Chulitna River confluence.Similarly,the decrease in average summer flows results in average reductions in water levels of 1-4 feet.A smaller proportion of the material transported to the tributaries'mouths will be transported downstream.Consequently,alluvial fans will increase In size at the mouth of affected tributaries.Also,the reduced summer water levels may result in headcutting and scour by the tributa ries th rough thei r delta materials. Field data were collected at nineteen tributaries.A qualitative analysis was conducted to determine if the above problems were likely to occur.A semi-quantitative analysis (R&M,1982f)was done on six creeks,and considered channel slope,the sediment discharge rate, the bed material size distribution and the decrease in stage expected at the tributary mouth.Due to their importance to chinook and chum salmon spawning,Indian River and Portage Creek were analyzed in 3-9 R24/3·39 more detail for changes operation,including bed 1983). in hydraulic changes and conditions due to project average velocities (Trihey, .- - 3.4 Analysis of Natural Conditions The~basic data used in this study were taken from various reports prepared for Alaska Power Authority by the Alaska Department of Fish and Game,Susitna Hyd ro Aquatic Studies Team (ADF&G);R&M Consu ltants, Inc.(R&M);and Harza-Ebasco Susitna Joint Venture (H-E).Discharge and sediment data also were taken from the publications of the U.S. Geological Survey,Water Resources Division (USGS),prepared in co-()peration with the Alas ka Power Authority (Knott and Lipscomb,1983, 198:5). Hydraulic parameters such as stage-discharge relationships,channel widths,average channel depths,measured velocities and bed slopes of sele~cted side channels and sloughs,were taken from various reports of R&M (R&M,1982 b,c,f,g)and ADF&G (ADF&G,1983b,1984b).The hydraulic parameters for the main channel reaches were derived from the data given in (Harza-Ebasco,1984b).Some unpublished data were obtained from USGS,R&M and ADF&G th rough correspondence.The site characteristics and hydraulic parameters for study sites in the mainstem, sidE~channels and sloughs are shown in Tables 3.1,3.2 and 3.3. The~Manning's roughness coefficients for various main chan nel reaches,-sidB channels and sloughs (Table 3.1)were estimated based on field rec()n naissances made in 1983 and 1984 and on the analysis presented by- - Harza-Ebasco (1984b). The~representative bed material size distribution for each site was derived from the analysis of the bed material samples collected by Harza-Ebasco. In the mainstem of the Susitna River,the surface material is generally coa rser than the sub-su rface material.The bed material samples collected 3-10 - - - - R24/3 40 in the sloughs and side channels,however,did not show any distinct difference between the su rface and sub-su rface materials.'The su rface and sub-su rface samples at a given site were combi ned to determine;,the r ~':' SiZEl distribution.The adopted size distributions are given in Tablet:~.,4. "(i"", ThElse are considered only indicative of the.bed material at the specifjc site~s because many additional samples would be required to determine a representative size distribution for the whole length of the study reach. ThEl sizes of armoring bed material corresponding to a selected range of discha rges (Table 3.5)were estimated as the average of the five sizes computed using the methods of competent bottom velocity;tractive force; Meyer-Peter,Mu Iler formu la;Schoklitsch formu la;and Shields criteria.A compa rison of median bed material size and the a rmori ng size.at each site indicated that under natural conditions,most of the selected sites are subject to temporary scour and/or deposition,depending upon the maSlnitude and characteristics of the sediment load and high flows caused by floods or breaching of ice jams. About 96 percent of the suspended sediment load carried by the river at Gold Creek under natural conditions is finer than 0.5 millimeter (medium to finE~sand,silt and clay).This fine sediment has been observed to deposit in side channels and sloughs.However,many of these deposits are re-suspended and removed du ring high flows,probably because of distu rbances of the su rface bed material layer. 3.5 With -Project Conditions 3.5.1 River Morphology The construction of the Susitna Hydroelectric Project will change the streamflow pattern and sediment regime.The essentially sediment- free flows from the reservoirs will have the tendency to pick up bed material and cause degradation.The modified discharges downstream from the dams,however,will have reduced competence to transport 3-11 - - - - - R24/3 41 sediment,especially that brought by the tributa ries.These two factors tend to compensate each other,resulting in the overall effects discussed below. The Lane relationship discussed in Section 3.2 is based on an equilibrium concept,that is,if any change occurs in one or two parameters of the water and sediment discharge relationships,the river will strive to compensate the other pa rameters so that a new equilibrium is attained.In the case of the Susitna River,both water discharge and bed load discharge will be modified by the reservoirs. Therefore,adjustments will occur in the slope of the river channel and in the particle sizes of the bed material.A number of studies (Hey,et al 1982)have indicated that the new median diameter under with-project conditions may correspond to the 0 90 or 0 95 of the original bed material. The potential morphological changes of the Susitna River also were addressed qualitatively by R&M (1982e).It was argued that the Susitna River between Devil Canyon and the confluence of the Susitna and Chulitna Rivers would tend to become more defined with a narrower channel.The main channeL river pattern will strive for a tighter,better defined meander pattern within the existing banks. A trend of channel width reduction by encroachment of vegetation and sediment deposition nea r the ban ks wou Id be expected. 3.5.2 Channel Stability Potential degradation at the selected sites was estimated for various discha rges using the discussed procedu reo The potential deg radation at each site estimated from these relationsh ips is listed in Table 3.6. These estimates are based on the assumptions that there would not be a significant supply of coarse sediments by the tributaries and that there would not be redeposition of bed material eroded from the upstream channel. 3-12 - R24/3 42 Table 3.7 shows average weekly flows at Gold Creek for four project operation scenarios and for natural conditions (Harza-Ebasco,1985). These data indicate about 50 percent reduction in flows during the' May through September period and about 3 to 4 times increase in flows during the October through April period.Table 3.8 shows annual maximum weekly flow at Gold Creek for natural and with-project conditions.Under with-project conditions,the maximum weekly flows occur under 2002 load conditions for almost every year. Using the average of these annual maximum weekly flows as the dominant discharge (about 30,000 cfs),the potential local degradation at the main channel sites would be in the range of about 1.0 to 1.5 feet.In the sloughs and side channels,the local degradation would be about 0 to 0.5 feet.These estimates,however,are based on the assumptions that there will not be significant injection of bedload by the tributa ries and that there wou ld not be redeposition of sediment eroded from the upstream channel.In actual situations,there will be sediments carried down by the tributaries,of which some will be deposited in the main river.Redeposition of some sediment eroded from the upstream channel will also occur.Therefore,actual degradation at the main channel sites would be less than that estimated. An accurate estimate of the actual degradation is difficult because of many unquantifiable parameters,such as bed material transport from tributaries and bank erosion,the degree of armoring by the present bed,and the actual streamflows and floods which would occur during the early years of project operation.However,based on available data and using empirical relationships,the above estimated degradation values are considered to be reasonable.The larger degradation would occur immediately downstream of the Devil Canyon Dam,and would decrease with distance downstream. Table 3.3 shows that bifurcation of flow at the heads of the sloughs and side channels would not significantly reduce the discharge rates 3-13 ,- ..... - .-. R24/3 43 in the main channel.Therefore,the competence of flow to transport bed material will not be affected due to bifurcation of flow and little aggradation should be expected in the main channel near the entrances to the sloughs and side channels. When the system energy demand increases (as in 2010),and less flow is discharged in July and August,the armoring layer developed earlier would be stable,more so than under natural conditions. However,infrequent high flood events would not be controlled to as great an extent as the smaller floods.These floods wou ld have the ability to disturb the armor layer and may cause bed degradation. Reservoi r operation studies indicate that floods up to the 50-yea r event will be reduced by about 50 percent at Gold Creek for project energy demands in 2020.Control of infrequent flood events will also be improved as energy demand increases,and the potential for fu rther bed deg radation wou Id therefore be reduced. Because of anticipated degradation in the mainstem,discharges higher than those under natural conditions would be required to overtop the berms at the heads of the sloughs and side channels.Assuming that the river bed at the entrances would be lowered by about one foot due to degradation,the with -project discharges that wou Id overtop the sloughs and side ~hannels were estimated to range between 4,000 and 12,000 cfs higher than those under natu ral conditions. 3.5.3 Intrusion of Fine Sediments The reservoir would trap all sediment except for particles sizes of .004 mm and less,which constitute about 18 percent of the suspended load.The velocities at the study sites (Tables 3.2 and 3.3)would be sufficiently high to carry these fine particles in suspension,and the substrate would generally be cleaner.However,some coarse silt and fine sand might be picked up from the river bed,especially during the early years of project operation.These fine materials would have 3-14 R24/3 44 the tendency to settle out in pools and backwater areas.Therefore, some deposition of such silt and sand in the sloughs and side chan nels is possible. 3.5A Tributary Stability The semi-quantitative assessment of the nineteen tributaries (R&M, 1982f)indicated that three creeks (Jack Long,Sherman and Deadhorse)are likely to have perched stream mouths,due to the streams not having the capability to downcut through their delta after the water level drops.The tributaries at RM 127.3,RM 110.1,and Skull Creek are estimated to degrade and to possibly affect the railroad bridges.The other tributaries studied will either degrade or aggrade,but without anticipated effects on fish access or rail road. The assessment is summarized in Table 3.9. The analysis of hydraulic conditions at Portage Creek and Indian River indicates that fish access has not been a problem and is unlikely to be a problem under with-project conditions (Trihey, 1983).These creeks will adjust their streambed gradients and will re-establish entrance conditions similar to those under natural conditions. - 3-15 --------~---------------""'._--------------------- TABLE 3.1 CHARACTERISTICS OF STUDY SITES ON MIDDLE SUSITNA RIVER.!.' .~Approx.Overall Overall Observed Estimated Estimated River Slope of Slope of Ove rtopping Bed Elev.~.anning's Miles Study Reach ~lain River Dischargel.J at Bead P.oughness Main Channel Nr.River 99.0 to .0017 .0017 NAlI NA .030 Cross Section 4 100.0 Main Channel Between 108.5 to .0012 .0012 NA NA .035 River Cross Sec-110.0 tions 12 and 13 Main Channel Upstream 113.6 to .0017 .0017 NA NA .035 from Lane Creek 114.2 (i!'-'Mainstem 2 Side Channels .0030 .0017 12,000 476.3 .035 at River Cross Section 18.2 NW Channel 114.4 .0020 .0017 12,000 476.3 .035 NE Channel 115 .5 .0024 .0017 23,000 484.6 .035 Slough 8A (main channel).0024 .0017 26,000 .032 NW Channel 126.2 .0024 .0017 26,000 .032-NE Channel 126.7 .0024 .0017 33,000 576.5 .032 Slough 9 128.3 .0026 .0016 16,000 604.6 .032 Main Channel Upstream From 131.2 to .0015 .0015 NA NA .035 the 4th of July Creek 132.2 Side Channel 10 134.2 .0039 .1017 19,000 656.6 .035 ~ Lower Side Channel 11 135.0 .0024 .0020 5,000 ..035 Slough 11 135.4 .0029 .0020 42,000 684.6 .032 ,~ Upper Side Channel 11 136.2 .0045 .0020 13,000 684.3 .035 l1ain Channel Between 136.9 to .0017 .0017 NA NA .035 ,,p:lIlRllJ,Cross Sections 46 and 48 137.4 Side Channel 21 .0030 .0032 Downstream from AS 140.6 12,000 .030 I""""Upstream from AS 141.9 20,000 .030 Slough 21 .0043 .0023 .03 a NW Channel 142.2 23,000 753.8I"""NE Channel 142.3 26,000 756.9 1/Data taken from various reports of n-E;ADF&G and R&M. 2/D:l,scharges at Gold Creek Station 3/Not applicable. ~SOURCE:Harza-Ebasco (1985) - 3-16 TABLE 3.2 HYDRAULIC PARAMETtRS FOR MAINSTEM SIIES 1.ocation Gold Creek Discharge (ds)-3,000 5,000 7,000 9,700 13 ,400 17 ,000 23 ,400 34 ,500 52,000 Near River Cross Section 4 Disi~harge,cfs 3,090 5,150 7,210 9,990 13,800 17,500 24,100 35,500 53,600-Width,ft 650 750 860 1,010 1,200 1,380 1,640 2,060 2,680 Depth,ft 2.9 3.4 3.9 4.6 5.5 6.3 7.3 8.9 10.6 Vel()cit.y,ft/sec 2.7 3.4 3.8 4.4 4.4 4.3 4.2 4.6 4.9 Between River Cross Sections 12 and 13 D1 s;~harge,cfs 3,090 5,150 7,210 9,990 13,800 17,500 24,100 35,500 53,600 Widl:h,ft 380 410 425 445 460 473 495 518 545 ~Depth,ft 5.6 6.6 7.6 8.0 9.2 9.9 11.2 13.1 16.0 Velc)city,ft/sec 2.3 3.0 3.4 4.2 4.7 5.3 6.1 7.0 7.7 upstream from Lane Creek Dis,~harge,cfs 3,090 5,150 7,210 9,990 13,800 17,500 24,100 35,500 53,600 Widl:h,ft 850 960 1,020 1,110 1,350 1,680 1,790 1,860 1,900 Depth,ft 5.9 6.8 7.4 8.2 8.5 9.3 10.0 11.a 12.9 Velc)city,ft/sec 1.7 2.2 2.6 3.1 4.1 4.3 5.2 6.7 7.5 upstream from 4th of July:Creek Dis,~harge,cfs 3,000 5,000 7,000 9,700 13,400 17,000 23,400 34,500 52,000 Wid'th,ft 250 340 430 580 800 970 1,150 1,250 1,380 Depth,ft 6.3 7.2 7.7 8.3 9.0 9.3 10.1 10.6 11.6 Vell)city,ft/sec 2.1 2.7 3.3 4.0 4.9 5.8 6.2 7.4 8.8 Between River Cross Sections 46 and 48 Di s~harge,cf s 3,000 5,000 7,000 9,700 13,400 17,000 23,400 34,500 52,000-Widlth,ft 305 385 465 545 600 650 710 800 920 Depth,ft 5.1 6.2 6.9 8.1 9.0 9.7 10.6 12.0 14.1 Vell)city,ft/sec 3.6 4.1 4.6 4.9 5.7 6.4 6.8 8.2 9.4 ~ SOURCE:Harza-Ebasco (1985) ~ - 3-17 ,--~---------------~---------------- -TABLE 3.3 HYDRAULIC PARAMETERS FOR SIDE CHANNELS AND SLOUGHS Slough/Side Gold Creek Channel Slough/Side Channel-Location Discharge Discharge Width Depth Velocity (ds)(It)Tft)(ft!sec)(1)-(2)(3)(4)(5)(6) Mainstel11 2 Side Channel Northwest Channel 17,000 150 112 LO 1.39 23,400 940 117 1.9 2.78 34,500 2,940 228 2.5 5.20 52,000 6,700 264 2.9 8.75 Northeast Channel 34,500 650 111 3.4 1.71.-52,000 2,900 124 3.8 6.09 Main Channel Below Confluence 17,000 150 128 0.5 2.31,...,.23,400 940 250 1.4 3.78 34,500 3,590 341 2.7 3.89 52,000 9,600 366 4.4 6.00 Slough 8A Northwest Channel 30,000 19 45 0.7 0.6235,000 47 45 0.9 1.18~- 40,000 98 45 1.0 2.2145,000 183 45 1.1 3.75 52,000 383 46 1.3 6.58 Northeast Channel 30,000 17 70 1.0 .4235,000 26 71 1.1 .5140,000 37 73 1.2-.59 ~45,000 51 75 1.4 .67 52,000 74 78 1.6 .77 Main Channel Below-Conflu",nce 30,000 36 62 0.8 .72 35,000 73 66 1.0 1.1440,000 135 70 1.1 1.74 45,000 234 72 1.2 2.68 r-52,000 457 78 1.5 3.96 Slough 9 23,400 80 73 1.3 0.8234,500 580 151 2.2 2.34-45,000 1,600 156 3.0 4.0352,000 2,650 160 3.2 5.30 -- 3-18 SOURCE:Harza-Ebasco (1985) I""", - 3-19 _.~.=------------------------------------------------- TABLE 3.4 REPRESENTATIVE BED MATERIAL SIZE DISTRIBUTION FOR SELECTED SLOUGHS,SIDE CR&~NEL AND MAINSTEH SITES ~in Channel near .062 .125 .250 Particle Size,mm .500 1.00 2.00 4.00 8.00 16.0 --Percent Finer Than Bed Material 32.0 64.0 Sizes \=):or Given Percentage D1e Dsc DgO - - CrOEIS Section 4.1.1 ~in Channel between Cross Sections 12 and 11£1 Main Cbannel upstream from L:ne Creekl./ !".ainstem 2 Side Channels at Cro,;s Section 18.2.-:!.1 Slough W' Slough 92.1 ~.ain Cbannel upstream from 4th of July Creek..U Side (bannel 10].1 Lower Side Channel II,down- stream from Slough lU' Slough 10.Q 1 Upperside Channel 11,up- scn,am from Slough 11.1...2.' :-'.ain Channel between Cross Section 46 and 48..L!.' Side (~annel 21,downstreac from Slough 21.1.1-' Slough 2L!1.1 2 2 3 2 1 o o 3 2 3 5 3 2 4 3 2 2 2 2 o o 7 3 7 6 7 6 6 5 5 5 3 10 5 7 10 10 15 8 12 7 8 8 7 4 4 13 8 9 13 12 18 11 17 10 12 12 10 6 6 16 12 10 17 13 20 14 20 14 15 15 13 8 8 22 18 14 22 15 23 20 25 19 20 20 17 12 12 29 24 21 29 18 30 27 34 30 27 27 24 17 17 42 32 32 37 28 41 36 44 41 35 35 33 23 23 70 50 48 53 47 63 55 62 58 50 50 53 40 40 89 77 77 73 83 93 78 82 84 68 68 72 62 62 1.7 3.0 5.0 1.7 4.3 0.5 2.5 0.8 2.6 2.2 2.2 3.3 7.5 7.5 20 34 35 30 35 22 28 2-0 32 30 46 46 65 78 84 110 70 58 85 80 72 100 100 100 96 96 - ~I &Lsed on 6 samples taken at three locations near cross section 4. lJ Based on 2 samples taken near river miles 109.3. 2.1 Eased on 2 samples taken in main channel upstream from Lane Creek. ~I Based on 4 samples taken in the !".ainstem 2 side channel,at four locations. 51 Based on 6 samples taken near the slough in the main channel at ~!125.6. '§'I Eased on 5 samples taken near the slough in the main channel at ~l 128.7- 2 1 &lsed on 3 samples taken in the main and side channels near o ~th af July Creek • .>1.1 Jj,;lsea on 2 samples taken in Slough 10. 91 &,sed on 2 samples taken in Side Channel 11,downstream from Slough 11. -U1.'&lsed on one sample taken in Slough 11. l ...Y Based on 2 samples taken bet..een cross sections 46 and 48. 1..Y &IBed on one sample taken near the upstream end of side channeL SOu-FLE:Harza-Ebasco (1985) .... ~ TABLE 3.5 ARMORING BED MATERIAL SIZES IN SELECTED ~SLOUGHS,SIDE CHANNELS AND MAINSTEM SITES Location Discharge at Gold Creek (cfs) 5,000 7,000 10,000 15 ,000 20,000 25 ,000 )J ,000 35,000 4D ,000 45,000 ~ Armoring Bed Material Size (rom) Ma:in Channel near 18 21 24 29 33 36 38 41 43 44 48 Cross Section 4 HaL in Channel between Cross Sections 12 &13 21 25 28 37 44 48 53 57 60 65 76 M.!lin Channel upstream 25 28 32 37 44 48 52 56 60 64 72 from Lane Cr eek H..ainstem 2 Side Channel at Cross Section 18.2 Main Channel 6 11 18 25 31 37 43 56 Nort~east Fork 5 9 13 16 18 21 24 29.-.North-"est Fork 5 9 13 16 17 19 21 24 Slough 8A 4 6 8 9 12 Slough 9 9 13 17 20 24 31 ~lin Channel upstream 27 31 35 40 45 50 54 57 61 64 71 from 4th of July Creek -.S:Lde Channel 10 5 13 22 29 37 45 60 L'Jwer Side Channel 11 5 16 22 28 34 39 45 50 61 Slough 11 5 17 U'pper Side Channel 11 7 13 20 30 44 57 84 Main Channel between 30 35 41 49 56 62 68 73 79 84 94 1""'"Cross Sections 46 and 48 Side Channel 21 6 10 15 18 22 25 28 31 37 ("- Slough 21 3 5 9 14 21 30 58 f'~ SOli'PeE:Harza-Ebasco (1985) iF_ -_._-------3-21 TABLE 3.6 POTENTIAL DEGRADATION AT SELECTED SLOUGHS, SIDE CHANNELS AND MAINSTEH SITES ' Location Discharge at Gold Creek (cfs)----5,000 7,000 10,000 15 ,000 20 ,000 2S ,000 30 ,000 35,000 40 ,000 45,000 55,000 Estimated Degradation,ft Main Channel near 0.1 0.2 0.3 0.6 0.8 1.1 1.3 1.5 1.7 1.9 2.4 Cross Section .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 Chs,nnel upstream 0.2 0.2 0.3 0.4 0.6 0.8 l.0 1.2 1.5 1.8 2.5 from I.ane Creek Mainstenl 2 Side_.Chann;~l at Cross Sec tion 18.2 Ma:ln Channel 0 0 0 0 0 0.1 0.2 0.3 0.5 0.7 1.2 No'rth-east Fork.0 0 0 0 0 0 0 0.1 0.1 0.2 0.2 NOlrth_est Fork °0 0 0 0 0 0 0.1 0.1 0.2 0.2 Slough BA 0 0 0 0 0 0 0 0 0 0 0 Slough 9 °0 0 0 0 a 0 0.1 0.2 0.3 0.5 Main Channel upstream 0.3 0.3 0.4 0.6 0.8 1.1 1.3 1.5 1.7 2.0 2.5 from 4th of July Creek ~~Side Channel 10 0 0 0 0 0 0.1 0.2 0.4 0.6 1.0 2.0 Lower Side Channel 11 °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 a 0 0 0 0 0.1 Upper Side Channel 11 °0 0 0 0 0.1 0.2 0.3 0.6 0.9 1.8 ~'-""Main Channel between 0.3 0.4 0.6 0.9 1.2 1.4 1.7 1.9 2.1 (\~~~/)2.8 Cros,;Sections 46 and 48 Side Channel 21 0 0 0 0 0 0 0.1 0.1 0.2 0.2 0.3 Slough 21 0 0 0 0 0 0 0 0 0.1 0.2 0.5 SOtJFCE::Harza-Ebasco (1985) 3-22 TABLE 3.7 NATURAL AND WITH-PROJECT AVERAGE WEEKLY FLNS OF SUSITNA RIVER AT GOLD CREEK (1950-1983) Wit.h-Project Flows1.J 1996 2001 2002 2020 Natural Load Load Load Load Week"Y Flow Conditions.lJ Conditions].'Condi t i ons~1 Cond1tions~1(T)(2)(3)(4)(5)(6)-1 1607 9552 9695 7027 103232155495409679699710300 3 1512 9526 9655 6965 10285414949537966669361020151427951896396897102256135495619789690310262713009603977568511014181258950296696802100829120493579521670999571011528711897163769448111149833884866167911712115779538093595987811311677715785258408581-14 1216 7593 7682 5832 8500151240726073035670824516140870287028554380001716676765676555347644-18 3654 6912 6875 5481 7532197914744975595910793220134668886900167809067211871.5 10440 10521 7434 9896222355611910119538115107822327284113671143890141025224293691167911741896010452252786011415115391022710322262631310974111421177310112272398710006101611395193172824491101241025416950938329247081015310275197979460302403110013102042091593553125294110021110322285961332233201047010629218109415332238711770110722122410756342041112367121772047811875..- 35 18377 12280 11929 18366 11281361562112685120881575611772371403911783111001403010998381287111269107901279010211-39 10663 10304 10033 10750 9649408102899087268297881241678283848266725886954253488543837464438557-43 4303 8636 8456 6531 8514443332844083456620846145286187928691682489084625629215916570329554~47 2358 9727 9698 7255 10122482204101961019574761060349197810892110257775111085018861116211312791811474 ~51 1785 10796 10915 7675 111625217391008010142726310590 -1/First week is the first week of month of January. 2/Based on environmental constraints,E-6. 3/Wacana Operation. 4/Watana -Devil Canyon operation. SOtJRCB:Harza-Ebasco (1985)3-23 - TABLE 3.8 MAXIMUM NATURAL AND WITH-PROJECT WEEKLY FLOWS OF SUSITNA RIVER AT GOLD CREEK ~1996 2001 2002 2020 Natural Load Load Load Load Year Flow Conditions Conditions Conditions Conditions-1950 26171 10092 11534 21157 10327 51 30057 15024 11374 30057 11856 52 38114 14216 14216 37243 12721 53 35114 14356 15779 25643 11771 54 31143 13975 13975 31143 12664 55 37243 22402 19671 35236 18572-56 43543 25394 22429 32000 26000 57 37443 20071 19275 25943 13414 58 38686 12426 12426 37485 11817 59 44171 28700 16498 41415 14829 60 32043 13342 13914 28943 12203 61 38714 15622 15622 26000 13787 62 58743 26057 26057 35557 23571 63 40257 19900 19543 38549 22106 64 75029 18410 18410 29834 14941 65 33643 21913 21913 28514 19812..-66 47686 17098 17098 28014 14719 67 54871 41459 29071 41589 30600 68 37343 14439 15125 29429 12551 69 18114 9861 8000 8000 10228 70 26429 9211 ,9409 8126 10226 71 47186 22857 22857 37427 22857 72 44243 18029 19488 33149 18029 73 36443 11756 11756 23171 10293 74 31357 11846 11846 16614 10828 75 36400 19886 18629 29900 19886 76 29843 11965 11965 25844 11530 77 46300 15438 15438 25514 14420 78 22786 11800 11921 20214 11685 79 32457 12955 13558 32457 12927 80 33557 13106 13264 33557 13304 81 46729 37029 37029 39966 37029 ......82 28857 12141 12145 27500 11895 83 27343 12683 13481 26586 12875 -.SOUROE::Harza-Ebasco (1985) 3-24 B J })J 1 J J J J 1 1 J J ) TABLE 3.9 SUSITNA TRIBUTARY STABILITY ANALYSIS SUMMARY OF SEMI-QUANTITATIVE ASSESSMENT ,.,.., ".". R24/3 45 4.a SLOUGH HYDROLOGY 4.1 Introduction Flow into side-channel and upland sloughs comes from overtopping of upstream berms by mainstem flow,from local surface tributaries,and from groundwater upwelling.Slough discharges and hydraulic conditions when the upstream berms are overtopped are dominated by mainstem flow.The rel~ltionship between mainstem flow and slough flow for overtopped conditions has been previously shown in Table 3.3.Under with-project conditions,the upstream berms will be overtopped much less frequently. Consequently,groundwater upwelling and local surface runoff will control slough hydrology.This section of the report describes these two aspects of slough hydrology. OUI"ing non-overtopped conditions,sufficient local runoff and upwelling are required to provide sufficient flow to allow access to spawning areas in the sid4~sloughs for chum and sockeye salmon (AOF~G 1983a).Upwelling also provides water which both keeps incubating embryos from freezing and supplies them with oxygen.Much of this upwelling water is at 2°to 4°C throughout the winter.This warmer water keeps developing embryos alive dur'ing early incubation and maintains development at a level elevated above that which would occur in the mainstem at aoc (Wangaard and SUI"ger,1983). 4.2 Factors Affecting Upwelling 4.2.1 Sources of Groundwater G rou ndwater sou rces for the Middle Reach can be sepa rated into mainstem and local upland sources.The origin of all groundwater is at the su rface,ultimately coming from precipitation.Sou rces controlled by the mainstem originate at undefined points upstream of the upwelling location.Du ring the summer,upstream precipitation 4-1 ,~ - - R24/3 46 events and glacial melt supply the su rface water,which percolates into the groundwater.Much of the winter flow is maintained by water stored during the summer in the broad gravel floodplains below -the glaciers at the headwaters of the basin.Water from alluvial fans at the bases of upstream slopes and tributaries add to the flow.This is considered to be the basic sou rce of grou ndwater in the system (Acres American 1983). The upland component of groundwater upwelling comes from precipitation falling on the slopes above the river.After reaching the earth's surface,precipitation and/or snowmelt move as surface runoff or go into soil storage or groundwater.Recent precipitation and snowmelt history determine the amou nts of each wh ich occu r. Large precipitation events are usually required to contribute much water into the groundwater system.Upland sou rces are independent of mainstem discha rge levels,since local events drive the system. These local events also are unpredictable.The effects of upland sources on upwelling are most pronounced for steeper,higher and closer valley walls. 4.2.2 Aquifer Conditions An aquifer is generally considered to be a geological formation that is porous enough to hold significant quantities of water and also permeable enough to readily transmit it horizontally.The material of the floodplain aquifer in the Middle Reach typically consists of a thin layer of topsoil overlying 2 to 6 feet of sandy silt.Below this is a heterogeneous alluvium of silt,sand,gravel,cobbles,and boulders. Non-stationary streambed deposition is believed to be responsible for the heterogeneous pattern.The heterogeneous natu re of the material resu Its invariable hyd rau lic conductivities,both laterally and vertically (Acres American 1983).Depth through this material to bedrock is approximately 100 feet at the abutments to the Alaska Railroad bridge at Gold Creek (Prince 1964). 4-2 ..... - - - - ,.... R24/3 47 Groundwater flow through an aquifer may be confined or unconfined, depending on the location.Unconfined aquifers are similar to u nderg round lakes in porous materials.There is no restricti ng material at the top of the aquifer,so the groundwater levels are free to rise and fall.The top of the unconfined aquifer is the water table.Below the water table the aquifer is saturated,while above the water table it is only partially saturated.Much of the sand, gravel and cobble alluvium underlying the Susitna River's bed is an unconfined aquifer.This unconfined aquifer is bounded by bedrock on the sides and bottom.Groundwater flow through the system is downhill,running parallel to the valley walls and following the general cou rse of the su rface river,but at a much slower rate. Conditions In unconfined aquifers are such that changes in mainstem stage have a delayed and mi nimal effect on water table elevation. This is caused by the large volume of aguifer that must be filled to raise the water table by a given amount. A confined aquifer is a layer of saturated,porous material located between two layers of much less permeable material.If these confining layers are essentially impermeable,they are called aquicludes.If the layers are permeable enough to transmit water vertically to or from the con~ined aquifer,but not permeable enough to laterally transport water as an aquifer,they are called aquitards. A confined aquifer bounded by one or two aquitards is called a leaky or semiconfined aquifer.Aquitards consisting of layers of fine silt often bou nd the high Iy permeable sand and g ravel all uvium,creating piping zones where groundwater is easily transmitted.Along the Susitna River,such piping zones are believed to be sources of shallow lateral flow to the upwelling areas.These piping zones would be most likely to rapidly respond to changes in mainstem stage, because such changes would be transmitted into the aquifer as pressure effects rather than by filling or draining the pore space of the aquifer.A regional confined aquifer may be providing water to 4-3 - -. R24/3 48 the sloughs and mainstem.However,the preponderance of near-surface bedrock along the valley walls and nearby mountains minimizes the likelihood of a confined regional aquifer being a significant water source,although some local springs and seeps may occur at faults in the bedrock.According to APA (1984b),neither regional flow from the valley walls into the alluvium nor downriver flow through the alluvium appears to be sufficient to provide all of the apparent groundwater upwelling to the side sloughs . .Ice processes have a dramatic effect on lateral flow during the win- ter.As an ice cover forms on the river,the effective water su dace level (WSL)in the mainstem rises dramatically.Flow becomes confined by the ice at the water su rface.Friction caused by movement against the stationary ice cover reduces the velocity of the river water.Water level rises as the velocity drops.The ice cover also acts directly to increase the WSL by floating on the surface. The increased pressu re supplied by the floating ice increases the effective WSL to near the top of the ice cover.In the Middle Reach, confined 2,OOO-cfs flow may have the same effective WSL as 20,000 cfs with no ice cover present.The result of this increase in stage is a much higher hydraulic head,increasing lateral flow from the mainstem into the groundwater system and,presumably,resulting in increased upwelling in the side channels and sloughs. G rou ndwater temperatu res are buffered from seasonal climatic variations by the heat storage in the aquifer.As groundwater moves th rough the system,it adds to or removes heat from the su rrou ndi ng material.Heat transfer during groundwater movement can occur by both conduction and convection.The groundwater temperatu re approaches that of the surrounding material,and remains stable through the year.The net energy balance is such that groundwater temperature in the Middle Reach stabilizes at about 2-4°C, approximating the mean annual (time-weighted)mainstem temperature. 4-4 R24/3 49 The temperature of the groundwater is a function of time.This becomes important when considering groundwater temperatures in areas of confined flow.The response of flow under confined conditions can be very rapid since the changes are caused by pressu re waves.However,actual time of flow is much greater. Therefore,fluctuations of groundwater temperatures in these areas are similar to those in areas of unconfined flow.The distance through the alluvium that is travelled is much more important on the moderating effect on the temperatu re of the groundwater than the presence or absence of a confining layer. 4.3 Loca I Surface Runoff - RUlloff from a drainage basin is influenced both by climatic factors and physiographic factors (Chow,1964).Climatic factors include the forms and types of precipitation,interception,evaporation,and transpiration,all of which exhibit seasonal variations.Physiographic factors are further classified into basin characteristics and channel characteristics.Basin characteristics include such factors as size,shape,and slope of drainage areas,permeability and capacity of groundwater formations,presence of lak'es and wetlands in the basin,and land use.Channel characteristics are primarily related to the hydraulic properties of the channel which govern the movement of streamflows and determine channel storage capacity. Many of the above factors are interdependent to a certain extent,and can be highly variable in nearby basins.The general basin characteristics of each of the study sloughs are described in the following section. 4-5 R24/3 50 4.4 Field Studies 4.4.1 Study Sloughs Four sloughs have been chosen for intensive sampling.These four, 8A,9,11 and 21,were chosen because they are the most important side sloughs for salmon spawning and incubation (ADF&G 1984c). They also encompass a wide range of physical variables,allowing a better understanding of the general upwelling conditions in the Middle Reach.The relative locations of each of the study sloughs a re shown i n Fig u re 4.1. Slough 8A,located between RM 125 and RM 127,is a side slough on the east side of the river.The two-mile long slough is relatively straight with two upstream channels connecting it to the mainstem (Figure 4.2).Overtopping of the northwest channel at RM 126.2 occurs at about 26,000 cfs,while overtopping of the northeast channel at RM 126.7 occurs at 33,000 cfs.The substrate in the upper slough is primarily cobble and boulders,and in the lower slough is gravel and cobble.At present,several beaver dams,some of them armored with cobble,are located along the slough.Surface water input is supplied by 6 to 8 streams coming down from steep slopes adjacent to the slough with shallow or exposed bedrock. Slough 9 is a 1.2 mile-long S-shaped side slough on the east side of the river between RM 128 and RM 129.3 (Figure 4.3).The upper slough has a fairly steep slope and cobble/boulder substrate.The lower slough has a low gradient and smaller substrate consisting of gravel/cobble.Overtopping discharge of the berm at the upper end of the slough is about 16,000 cfs.A major water source during non-overtopped conditions is slough 98 (Figure 4.3).This small slough drains a marshy area near the head of the slough.A small tributary (Tributary 98)with a drainage area of about 1.5 square miles enters the slough further down. 4-6 ..... - R24/3 51 Slough 11,located between RM 135 and RM 136.5,is another side slough on the east bank of the river.This mile-long slough was formed in 1976 as an overflow channel when an ice jam blocked the river during breakup.The upper slough has a cobble/boulder substrate while the lower slough is less steep and has a mostly gravel/cobble substrate.The slough overtops at approximately 42,000 cfs.There are no tributaries into the slough.Non -overtopped flow in the slough comes from seepage and upwelling in the lower two-thirds of the slough (Figure 4.4). Slough 21 is located at about RM 142,on the east side of the river, and is about one-half mile long.The upper one-half of the slough is divided into two channels,with overtopping flows of 23,000 and 26,000 cfs.There are no tributa riesconveyi ng su rface ru noff to th is slough.Groundwater upwelling is very obvious,as large areas of strong upwelling and springs occu r th roughout the slough (Figu re 4.5).A large upland area may provide considerable input into the local groundwater. 4.4.2 Field Investigations In order to explain the relationship between the mainstem and upwelling in the sloughs,several studies,described in the following section,were conducted in the study sloughs.The data are described in this section,while the resu Its from the data are discussed in the followi ng section. Slough discharges were recorded in Sloughs SA,9,11 and 21.Daily mainstem flow or stage measurements have been compared with slough flow using linear regression analysis,with slough flow as the dependent variable (Table 4.1)(R&M 1982,1985a;Acres American 1983;APA 1984b;Beaver,1985).Analysis was complicated by frequent overtopping of the upstream berms in Sloughs 8A and 9 during much of the summer.Data collected in 1984 were particularly 4-7-------_._-------------------------------------------- - - .- .- R24/3 52 useful in investigating groundwater upwelling to the sloughs because a significant portion of the 1984 open-water data are for very low mainstem discharge rates,thus minimizing complicating effects such as su rface runoff and overtopping of berms.Correlations between slough discharge and mainstem stage are given on Table 4.2. Correlations for 1982 and 1983 are for daily data,while data for 1984 are for average weekly data.Correlation with mainstem stage,rather than mainstem discharge,makes it easier to estimate groundwater upwelling for various with-project scenarios,particularly winter conditions when ice stagi ng effects have been simulated.Simila rly, the use of weekly rather than daily averages makes it easier to apply the results of with-project simulations,which are generally expressed as weekly average mainstem stage or discharge values.Rating tables for the mainstem locations are given in Table 4.3. Additional data were obtained by monitoring groundwater surface levels in shallow wells dug in the vicinities of sloughs 8A and 9 (R&M 1982g,APA 1984b).The data allow groundwater flow direction to be determined in the areas immediately around sloughs 8A and 9. Comparison of the plots for different dates and mainstem flows shows the temporal va riability of flow patterns in the groundwater system (Figu res 4.6-4.11). In order to better estimate aquifer permeability,pump tests were attempted at several existing wells near Slough 9.However,the pump tests were unsuccessful in providing usable data. Consequently,falling head tests were conducted to provide estimates of aquifer transmissivity.The results are shown in Table 4.4 . - Mainstem,groundwater, have been continuously These data show the (Figures 4.12 -4.19). intragravel and slough water temperatures recorded (ADF&G 1983a,b;1984 b,c,d). range in variations for different locations 4-8 R24/3 53 Seepage meter data were obtained at upwelling sites in several sloughs (APA 1984b).The data serve as another indicator of flow rate through the groundwater system.Relationships between mainstem discharge and upwelling rates are tabulated in Table 4.5. In 1984, 1985a). slo' flol disch e the .Ich of 'as also other investigated (R&M put into ributary monthly spatial wasinthesloughsthewaterbalance Studies focused on I .. s loca A var inVI wa1 4.4.3 Res - - - -. ,.... I the '__~TT'OO--rrYUTdUTfc-a-n-a---thermal behavior of each-slou-gh--is substantially different from that of the other sloughs studied.The discha rge at Slough 11 seems to correlate very well with mainstem discharge,while the discharge at Slough 9 is largely controlled by mainstem overtopping of the berm.The discharge at Slough SA may be complicated by factors such as surface runoff and groundwater underflow from sources other than the mainstem of the Susitna River.However,where it has been possible to remove the effects of some of these complicating factors and isolate attention on only the groundwater upwelling contribution to slough discharge, fai rly good correlations between slough discha rge and mai nstem discha rge have been observed.In very general terms,based on available information,it appears that variations in the groundwater contribution to slough discharge at Sloughs 8A,9,and 11 might be reasonably represented by 0.0001 to 0.00035 of corresponding variations in mainstem discharge at Gold Creek (APA,1984b). 4-9 -- .-. - - - R24/3 54 Regardless of the complicating factors affecting discharge from each slough,the available data suggest that the temperature of upwelling groundwater remains fairly constant throughout the year,at a temperature approximately equal to the mean annual (time-weighted, not discharge-weighted)mainstem temperature.Heat exchange between groundwater and soil materials,and mechanical dispersion during groundwater transport through the aquifer,are reasonable mechanisms to account for the observed groundwater temperatures. Since a general model can not be formulated to describe each slough, ~results from the individual sloughs are described below. 4.4.3.1 Slough 8A Slough discharge at Slough 8A is moderately well correlated to mainstem discharge and stage (Tables 4.1,4.2).Local runoff from the adjacent steep,rocky hillslopes causes some disruption of the relationship.The data for the period September October 20,1984,when little precipitation fell,yielded the best relationship between slough discharge and mainstem discharge. The complicating effects of local ru noff and groundwater are further illustrated by seepage investigations.Seepage data collected at an upwelling site (meter 8-2)near the upstream berm f'n Slough 8A had a poorer correlation to mainstem discharge (R 2 =0.38)than did a site (meter 8-1)located in a small channel adjacent to a steep bank (R 2 =0.81)(Table 4.5) Water surface elevation data collected in 1983 from wells and boreholes indicate the general downvalley movement of groundwater in the vegetated island separating Slough 8A from the mainstem.Data collected with an ice cover on the mainstem (Figure 4.8)show a definite trend of groundwater flow down valley and from the mainstem towards the side-channel.The trend was also evident during the open-water period (Figure 4-10 - - R24/3 55 4.6).When streamflow is dropping,groundwater levels in the island may be higher than the water surface in either the slough or the mainstem (Figure 4.7). Intragravel water temperature in the slough rose from o.ooe during the winter (ADF&G 1983a)to 5.5°e in August (ADF&G 1984a)of 1983.During the open water season mainstem surface water ranged from 0.2°e in May to 15.8°e in July (ADF&G 1984a)(Figures 4.12-4.13).Temperatures in the middle of the slough are generally higher than those in the upper end of the slough,except in the latter half of July.The intragrave! temperatures generally appear to be subdued reflections of the surface water temperatures at corresponding points.However, surface water temperatures for the middle of the slough exhibit greater variations.The high temperatures recorded in the surface water at the middle of the slough can probably be attributed to solar heating,rather than to surface water discha rge as a result of overtopping. A monthly water balance study of Slough 8A conducted in 1984 (R&M,1985a)determined that 62%-73%of available precipitation falling on the Slough 8A watershed ran off as surface water (Table 4.7).Higher percentages of ru noff may occu r with fa rge storms,as the soil layer on the slopes above the river is relatively thin. Analysis of local precipitation data for 27 September to 7 October 1983 (Bredthauer 1984)shows an immediate response in slough discharge to a major rainstorm (Figure 4.20).The event occurred after a fairly long dry period (over one month).It was an intense storm,with 1.12 inches of rain falling in Talkeetna on 29 September.This amount of precipitation apparently was sufficient to raise the groundwater table and produce a rapid response. 4-11 ~' R24/3 56 The daily surface runoff pattern into Slough 8A was estimated for high,moderate,and low monthly precipitation (Tables 4.10, 4.11,4.12).The recorded slough discharges for August 1984 (high precipitation),September 1983 (moderate precipitation), and September 1984 (low precipitation)were separated into surface runoff and groundwater flow.Groundwater flow was estimated using the regression equation for slough discharge shown on the tables and the average daily flows for the Susitna River at Gold Creek.The estimated groundwater flow was then subtracted from the recorded value.(When the groundwater flow estimate from the regression equation exceeded the recorded value,groundwater flow was reduced to the recorded value.) Surface runoff was assumed to be the difference between the recorded discharge and the estimated groundwater flow. Although the estimates for surface runoff are not precise,Tables 4.10 through 4.12 do indicate that ther~are long periods when little surface runoff is contributed to Slough 8A,even in months when precipitation is well above average.The data in Table 4.10 also indicate that the runoff period extends for several days after a major precipitation event.Apparently,there is sufficient shallow subsurface flow on the valley slopes to maintain the flow for several days. 4.4.3.2 Slough 9 Due to the relatively low flow (16,000 cfs)required to II ~ertop the upstream berm,hydraulic conditions in Slough \/ 9 are dominated by mainstem flow for much of the summer.J/Upwelling occurs in the slough (Figure 4.3).contributing flow throug~out the year.Linear regression equations for mainstem and slough discharge data collected in 1983 and 1984 during periods of non-overtopping are shown in Table 4.1..The slopes of the equations for both the 1983 and the 1984 data are very similar.Table 4.2 gives the linear 4-12 - - - - R24/3 57 regression equations for the apparent mainstem related component of groundwater upwelling as a function of mainstem stage.Rating tables for the mainstem stage vs. flow at Gold Creek are shown in Table 4.3. Results of groundwater surface elevation measurements (Figures 4.9 -4.11)show movement from the side channel upstream of the slough toward the upper reach of Slough 9 between its head and Tributary 98 (APA 1984).A subdued response was often seen even at well 9-3,on the upland side of the slough.An analysis of lateral flow to the slough based on curves derived from an analytical solution to the flow problem showed slough flow to be much less than expected (APA 1984b).Major variations in the results of falling head tests performed in 1984 (R&M 1985a)indicate semiconfined aquifer conditions (Table 4.4).Data from seepage meters in 1983 showed a higher correlation at the downstream end of the slough than in a marshy area near the head of the slough (Table 4.5)(APA 1984).The poor correlation in the marshy area is likely due to water seeping into the groundwater system from Tributary 98. I ntrag ravel water temperatu res were very stable th roughout the study,at just over 3°C (Figures 4.14 and 4.15). Groundwater temperatu res from boreholes 9-1 A and 9-5 show a limited rise from 2°C in April to 4°C in September of 1983 (Figure 4.16)(APA 1984).Temperature data from borehole 9-3 show no variation related to the mainstem. There appears to be a strong inverse relationship between variations in temperatu re of the groundwater and distance from the mainstem.Figures 4.14 and 4.16 also show mai nstem temperatu re for compa rative pu rposes. 4-13 - R24/3 58 Tributary 9B was gaged at 2 locations in 1984:(1)at the base of the slope and (2)above its confluence with Slough 9.The intervening area between these 2 gages is an alluvial fan with meadows and beaver ponds.A sign ificant portion of the water measured at the base of the slope infiltrates into the ground before reaching the slough.The data indicate that the amount of infiltration loss is controlled by the water table level,which in turn is controlled by the stage in the mainstem (R&M,1985a). This is illustrated by the runoff analyses for two storm events in 1984,shown in Table 4.6.In the August 1984 storm,the downstream gage had about triple the peak flow of the upstream gage.This is in marked contrast to the flow patterns of the Septmber 1984 storm,in which streamflow at the downstream gage barely responded to the precipitation,and was about 1 cfs less than at the upstream gage.This pattern of water loss likely explains the delayed response of Slough 9 to the September 1983 storm (Figu re 4.20).Ru noff percentages for the 2 sites for the months of August-October 1984 are shown in Table 4.8. The daily surface runoff pattern into Slough 9 was estimated for moderate and low monthly precipitation (Tables 4.13 and 4.14)in the same manner as for Slough 8A.(An estimate could not be made for high precipitation,since the upstream berm was breached in these cases.)This analysis indicated that su rface flow occu rred more frequently than at Slough 8A.This is likely due to Tributary 9B originating from a small lake. 4 .4 .3.3 S Iou 9h 11 Slough 11 is the simplest of the sloughs studied,with no direct su rface tributa ries.Since its upstream berm is overtopped on Iy 4-14 R24/3 59 at relatively high flows (42,000 cfs),no surface water contributes to slough discharge for most of the year. Consequently,streamflow is maintained by ban k seepage and upwelling throughout the year (Figure 4.4). The relationship between slough flow and the mainstem is shown in Tables 4.1 and 4.2.Seepage meters,used to get an index of intragravel flow on the slough banks,also showed a strong relationsh ip to the mainstem at both the lower (R 2 =0.94)and upper (R 2 =0.83)sites (Table 4.5)(APA 1984). There was little effect on slough discha rge from precipitation events.The analysis of the data from the September 1983 storm event (Figure 4.20)showed no immediate respo~se in slough discharge,and only a minimal response to the mainstem level. The lack of response is in keeping with the lack of tributary input and small drainage a rea for the slough.This is fu rther illustrated in the monthly water balances (Table 4.7).Flow was stable th rough the summer,despite high precipitation in Ju Iy and August. I ntrag ravel water temperatu res in the slough were very stable year-round at about 3.GOC.Surface water temperatu res were less constant and did not show a pattern similar to that for intrag ravel temperatures.Su rface water temperatu res were also dissimil~r to mainstem temperatures (Figure 4.17). All of the above relationships tend to confirm that Slough "flow is derived from mainstem recharge to the local groundwater aquifer.Responses to changes in the mainstem are minimized and delayed.The delays and buffering also account for a very 4-15 - - R24/3 60 stable intragravel temperature and minimal response to the September 1983 storm. 4.4.3.4 Slougn 21 Upwelling and seepage locations at Slough 21 are shown on Figure 4.5.The relationship between mainstem discharge and slough discharge appears to be different at Slough 21 than at other·study sloughs (Table 4.5).Seepage appears to be negatively correlated to mainstem flow at one site,with seepage increasing as mainstem flow decreases,while no correlation existed between seepage and mainstem flow at a second site. The regression relationships between slough discharge and mainstem discharge (Table 4.1)were poor when all data were used,but had a very good relationship for data obtained late in 1982 (September 22 October 22),when little precipitation occu rred.Similar relationships were obtained for correlation with mainstem water surface elevations (Table 4.2). Water temperature patterns were fairly complex (Figure 4.18 and 4.19).The intragravel water temperature in the upper slough ranged from a winter low of 2.aoc in October to a high of 8.GOC during much of the summer (ADF&G 1984a).Higher temperatures of.up to 13.1°C were also recorded during overtopping for short periods.Su rface water temperatu re at the same location ranged from a.7°to 9.2°C (with the same overtopping exception).Generally,i ntragravel temperatures closely mirrored surface water temperatures throughout the year. In the lower slough,intragravel temperatures were about 3.3°C in March (ADF&G 1984a). - The geologic structure of the area explai n the data.Above the east side bench of old alluvial material at least 4-16 around the slough may of the slough there is a i-mile wide.This bench R2~1/3 61 may act as a large groundwater reservoir.It is a possible reason for the constant intragravel water temperature in the lower slough.The measu rements from the seepage meters may also be a function of local upland flow.The intragravel and surface water temperatures from the upper slough,on the other hand,seem to be more closely related to mainstem temperatu res. Slough 21 may show the effects of different sources at different points along the slough. 4.5 With-Project Changes Detailed projections can not be made of the slough discharge or temperature variations which might result from changes in mainstem conditions as a result of project operation.Because of the substantial differences among the sloughs in their hydraulic and thermal behavior,it wOLlld be necessary to construct mathematical models of each individual slough in order to make detailed predictions of the effects on the sloughs of changes in mainstem conditions.The different responses of Sloughs BA,9,and"to the same storm event are illustrated in Figure 4.20.The mainstem discharge in Figure 4.20 is in the range of summer with-project flows,with none of the sloughs upstream berms overtopped. Some sloughs,such as Slough 11,will probably respond fairly directly to changes in mainstem discharge.Slough 11 is generally characterized by a lack of tributary streams and rare overtopping of its upstream berm. Sloughs with similar environmental features might be expected to respond similarly to changes in mainstem discharge.Any such relationship for Slough 11 could be approximated by the regression equation in Table 4.1. Some sloughs,such as Slough 9,are overtopped during much of the time as a result of high river stage or ice staging.During such periods,such sloughs might be effectively considered as side channels of the river, rather than sloughs.If the overtopping flows for these sloughs are known,it can be estimated how often such sloughs will carry 4-17 I" ! R24/3 62 predominantly mainstem flow (at mainstem temperatures),rather than groundwater discharge.With-project flows will be less than normal summer flows,so the frequency of overtopping will be reduced.Slough 9 discharge under with-project conditions might be estimated from correlations of slough discharge to mainstem discharge during periods when the upstream berm is overtopped,and by the best-fit regression equation in Table 4.1 during periods when the berm is not overtopped.Flow from local tributaries would increase this last·estimate during snow melt and precipitation events. Most sloughs will probably be similar to slough 8A in that it will not be possible to separately determine each factor contributing to the discharge of the slough without conducting additional field investigations at each slough.Slough upwelli ng will be reduced due to the reduction in mai nstem discharge,but the sloughs will have similar contributions of flow·due to upland grou ndwater and local su rface ru noff. Temperatures of groundwater discharge to the sloughs appear to be reasonably approximated by the mean annual (time-weighted)river temperature.It is likely that any variations in mean annual river temperature as a result of project operation will also result in a similar change in the temperature of groundwater upwelling to the sloughs,to the extent that such upwelling is derived from the mainstem (e.g.I as IS probably the case at Slough 11).Any changes in water temperatu re of mainstem flow which is diverted down sloughs during overtopping could have some influence on the average temperatu re of grou ndwater. However,as noted above,overtopping will be much less frequent during project operation than under present conditions. 4-18 )) M19149 1 2 1 ))1 1 J ),J J J ]) TABLE 4.1 LINEAR REGRESSION EQUATIONS FOR SLOUGH D!SCHARGE VS.MAINSTEM D!SCHAHGE (1982-84) If>, I I--' ~ S IOLIgh 8A 9 11 21 Yea r 1984(1) 1983(2) 1984(1) 1983(2) 1984(1) 1983(2) 1982 (2) 1982(2) Reqression Equation Q8 =-0.08 +0.00017 G log Q8 =-5.0 +1.29 log G Q8 =-0.67 +0.00025 G log Q8 =-7.13 +1.85 log G Q8 =-3.83 +0.000526 G Q8 =5.10 +0.0000377 G Q8 =0.155 +0.000117 G Q8 =-0.627 +0.000128 G Q9 =-0.62 +0.00039 G log Q9 =-4.1 +1.15 log G Q9 =-149.7 +0.010008 G Q9 =2.94 +0.000307 G Q9 =1.97 +0.000351 G Qll =1.3 +0.000072 G log Qll =-1.5 +0.45 log G Qll =1.51 +0.000102 G Qll =2.15 +0.000104 G Q21 =-7.62 +0.00105 G Q21 =-0.570 +0.000445 G Q21 =-2.71 +0.000803 G ~ 0.53 0.79 0.73 0.91 0.103 0.001 0.086 0.631 0.82 0.84 0.264 0.089 0.805 0.68 0.76 0.766 0.504 0.543 0.l105 0.916 Comments 7/3 -10/30 (excl 8/23-8/28);Flow rate (2,200-27,900 cfs) 9/1 -10/20;Flow range (2,200-12,500 cfs) All values. Exc I ud i ng ave rtopp i ng flows,G:>30,000 6/6 -8/1 on Iy;exc I ud i ng G)30,000 6/6 -8/1 on Iy;exc I ud i ng G>30,000,Q8 >3 9/8 -10/30;Flow range (2,200-11,400 cfs) AI I va lues. Excluding overtoppinq flows,G)16,000 Exc I ud i ng G)16,000,Q9>8 6/1 -10/30;Flow range (2,200-40,600 cfs) All values. All va lues. AI I va lues. Excluding overtopping flows,G>24,700 September 22 -October 22 only;excluding G)24,700 Notes:Q8 =Slough 8A discharge,cfs;G =Mainstem discharge at Gold Creek,cfs (1)Source:R&M (1985a) (2)Source Beaver (1984) ~19/~9 }1 1 1 j 1 )1 ))l )I 1 j 1 )J SlougJ]Year 8A 1984(1) 1983(2) 9 1984(1) 1983(2) 11 1984 (1) 1983(2) 1982(2) 01:>-21 1982(2) I I\J 0 TABLE 4.2 LINEAR REGRESSION EQUATIONS FOR SLOUGH DISCHARGE VS.MAINSTEM STAGE (1982-84) Regression Equation ~Comments Q8 =-368.21 +0.6356 W1 0.78 Average weekly values,discharge and stage Q8 =-2149.8 +3.698 W1 0.065 All va lues Q8 =-92.3 +0.1683 W1 0.000 Excluding overtopping floWS,G)30,000 Q8 =-740.96 +1,2737 W1 0.626 June 6 -August 7 only;excludingG:>30,000,Q8>3 Q9 =-171.88 +0.28892 W2 0.84 Average weekly values,discharge and stage Q9 =-32801 +54.380 W2 0.228 All va lues Q9 =-769.1 +1.2871 W2 0.085 Excluding overtopping flows,G)16,000 Q9 =-877.21 +1.4658 W2 0.755 Excluding G>16,000,Q9)8 Q11 =-335.39 +0.49209 W3 0.96 Average weekly values,discharge and stage Q11 =-367.04 +0.54004 W3 0.783 AI I va lues Q11 =-327.05 +0.48278 W3 0.531 All va lues Q21 =-4400.2 +5.8554 W4 0.491 All va lues Q21 =-1810.6 +2.4130 W4 0.391 Excluding overtopping flows,G)o24,700 Q21 =-3244.1 +4.3212 W4 0.938 September 22 -October 22 only;excluding G>24,700 NOTES:Q8 =Slough 8A discharge,cfSj Q9 =Slough 9 discharge,cfsj Q11 Q21 =Slough 21 discharge,cfs. G =Mainstem discharge at Gold Creek,cfs W1=Mainstem stage at RM 127.1,ft. Slough 11 discharge,cfsj (1) (2) Source: C'.,ource: Beaver (1985). Beaver (1984). )1 M19/49 ~l t }D ))1 J 'I ')]._-))] TABLE 4.3 RATING TABLES,MAINSTEM NEAR STUDY SLOUGHS Discharge,Susitna Elevation.Feet Above Mean Sea Level River at Gold Creek RM RM RM RM (cfs)127.1 1£2......1 136.68 142.2 5,000 580.6 600.6 682.2 750.8 10,000 581.9 602.2 684.0 752.0 15,000 582.7 603.3 685.3 752.9 20,000 583.2 604.2 686.4 753.7 25,000 583.8 605.0 687.2 754.5 30,000 584.2 605.6 687.9 755.2 40,000 584.9 606.8 689.1 756.6 50,000 585.5 607.8 690.1 757.8 ,j:>. I N I-' Source:Harza-Ebasco Susitna Joint Venture.1984b.Middle and Lower Susitna River,Water Surface Profiles and Discharge Rating Curves,Volumes I and I I Draft Report.Susitna Hydroelectric Project Document No.481. Prepared for Alaska Power Authority.January. 1}19/?~)1 1 )-,1 )J ]1 D -p J I 1 J TABLE 4.4 FALLING HEAD TEST RESULTS SLOUGH 9 -BOREHOLES Depth of Well I.D.Screen Date Transm iss ivi ty Borehole (ft )1ft)of Test Ft 2 /Day Comments 9-1 0.146 24-27 07/17 /84 3.5 Good cu rve fit 9-1 0.146 24-27 07/31/84 5.4 Good cu rve fit,retest 9-1 0.146 24-27 08/15/84 3.4 Good cu rve fit,retest 9-1 0.063 9.4-10.7 08/15/84 0.2 Good curve fit 9-1 0.063 9.4-10.7 08/29/84 0.2 Good curve fit,retest 9-2 0.146 7-10 08/13/84 50 Sparse data,poor curve fit 9-2 0.146 7-10 08/15/84 92 Sparse data,poor curve fit,retest 9-2 0.146 7-10 08/29/84 12 Poor curve fit,retest 9-2 0.063 10.7-12.1 08/15/84 --No curve fit 9-2 0.063 10.7-12.1 08/25/84 2.6 Poor curve fit,retest 9-3 0.146 37-40 07/31/84 3.4 Good curve fit Ii::>9-3 0.146 37-40 08/14/84 3.6 Retest I 9-3 0.146 37-40 08/14/84 2.4 Retest after surging wei I.Value I\.)probably affected by previous I\.)testing. 9-4 0.063 11.7-13.1 08/13/84 --No useable data 9-4 0.063 11,7-13.1 08/13/84 --No useable data,retest Source:R&M (1985a) --rl19j~~-J 1 ")}J l J ". 1 ]-J -J '.1 TABLE 4.5 REGRESSiON EQUATiONS FOR SEEPAGE RATE VS.MAINSTEM DISCHARGE 5,300 -31,900 5,300 -31,900 Mainstem Flow Ranqe (cfs) 5,300 -24,500 5,300 -31,900 5,300 -31,900 Location 300 feet downstream of berm. Adjacent to bank. Downstream end on right bank. Downstream meter of 2.Marshy area feeding Tributary 98. Upstream meter of 2.Marshy area feeding Tributary 98. Streamgage site. 100 feet upstream of streamgage. Right bank,lower slough. Left bank,lower slough. 24,500 5,300 -31,900 9,300 -31,900 5,300 -22,000 5,300 R 2 0.81 0.38 0.62 0.19 0.94 0.83 Seepaqe Meter Reqression Equation 8-1 S =0.00691 G -50.20 8-2 S =0.00255 G +33.76 9-1 S =0.0067 G +77.3 9-2 No Correlation 9-3 S =0.00227 G +66.1 11-1 S =0.0042 G +30.18 11-2 S =0.001 G +32.95 21-1 No correlation 21-2 No co r re Iat i onoj::> I N W Notes:S G Seepage rate,mljmin Mainstem discharge at Gold Creek,cfs '''15/1<:':1 )")))})l l 1 -,-; TABLE 4.6 STORM RUNOFF ANALYSES SLOUGH 9 TRIBUTARY Slough 9 Tributary, Upper Site Slough 9,Tributary Lower Site 11>0 I N 11>0 Precipitation Period (1984) Runoff Pe r i od Total Precipitation (Inches) Max.Oai Iy Precipitation (Inches) Total Precipitation Volume (mi I I ion cubic feet) Total Runoff Volume (mi II ion cUbic feet) Baseflow Volume (mi II ion cubic feet) Storm Runoff Volume (mi I I ion cubic feet) %Runoff Groundwater Level, We II 9-3 Maximum Dai Iy Flow Susitna River at Gold Creek 08/17-08/25 08/17-09/06 6.46 2.05 10.96 6.468 1.034 5.434 50% 09/15-09/20 09/15-09/28 1.40 0.61 2.37 1.081 0.798 0.283 12% 08/17-08/25 08/17-09/06 6.46 2.05 21.91 12.181 0.272 11.909 54% 606.8 31,700 09/15-09/20 09/15-09/28 1.40 0.61 4.75 0.149 0.073 0.076 1.6% 604.8 11,400 Source:Table reproduced from R&M (1985a). 115/~,~-J )i t J )l })J ]"j ) TABLE 4.7 ..nn .......r\..ITIII \.J'"'".,..r-no ,...."1 ......-...........17U~1~IVI'lnL'nMILn DMLMI'~L~ SLOUGHS 8A AND 11 June Jill.:i AUQust Slou~ FI OW',Q (cfs)2.98 9.19 (mi II ion cu.ft.)7.46 (3-31)24.62 P rec i pita t ion,P (j nches)5.46 8.16 (million cu.ft.)19.14 28.61 Evaporat ion,E (i nches)2.02 2.49 (million cu.ft.)7.07 (3-31)8.72 (P-E)12.07 19.89 Q/(P-E)0.62 1.24(1) "'"Slough 11I tv Ln FI oW',Q (c f s )3.17 2.82 2.75 (million cu.ft.)8.21 7.58 7.35 Prec ip i tat ion,P (inches)1.49 4.72 6.78 (mi II ion cu.ft.)3.93 18.55 26.60 Evaporation,E (inches)5.66 2.21 2.49 (mi II ion cu.ft.)22.14 8.68 9.76 (P-E)(million cu.ft.)-18.21 9.87 16.84 Q/(P-E)-0.17 0.77 0.44 (1)Slough 8A I ikely overtopped in late August. Source:Table reproduced from R&M (1985a). September October 1.70 0.63 4.41 1.69 2.52 0.78 8.85 2.72 0.80 0 2.80 0 6.05 2.72 0.73 0.62 2.44 1.45 6.32 3.75 2.15 0.65 8.44 2.56 0.80 0 3.13 0 5.31 2.56 1.19 1.47 ~15/I~,1 -1 1 }.~I } Table 4.8 1 .-j )-J )]•$ 0I>- I tv 0"1 Slough 9 Tributary {Uppe r Site 1 Flow,Q (cfs) (million cu.ft.) Precipitation,P (inches) (million cu.ft.) Evaporation,E (inches) (million cu.ft.) P-E,Precipitation-Evaporation Q/(P-E) Slough 9 Tributary (lQwer Site} J!l!.:t .,noJ,"''''''''''''-'11 \.1 LI .......rn nAI ..............1;:70 ......·1VIl I nL I YtM I Lr\D1"\LM.I'f\.l~ SLOUGH 9,TRIBUTARY 9B August 2.62 7.02 7.44 12.62 2.49 4.21 8.41 0.83 Septembl;lr 0.91 (1) 2.54 2." 3.58 0.80 1.35 2.19 1.16 (1) October 0.50 1.34 0.87 1.48 o 1.48 0.91 Flow,Q (cfs)1.21 (mi II ion cu.ft.)3.23 Precipitation,P (inches)5.25 (million cu.ft.)17.81 Evaporation,E (inches)2.21 (million cu.ft.)7.50 (P-E),Precipitation-Evaporation 10.31 Q/(P-E)0.31 (1)Affl;lcted by runoff from storm in late August. Source:Table reproduced from R&M (1985a). 4.97 13.31 7.44 25.24 2.49 8.43 16.81 0.79 0.30 0.78 2." 7.16 0.80 2.71 4.45 0.18 0.07 0.19 0.87 2.95 o o 2.95 0.06 - - R23/3 47 TABLE 4.9 PRECIPITATION COEFFICIENTS FOR TRANSFER OF RECORDED DATA SitE! Continuous Station Talkeetna Sherman Devil Canyon Curry Slough 8A Siolugh 9 (Sherman ) Gold Creek 1.5 1.3 1.2 1.07 1.2 1.07 1.0 0.9 1.7 1.5 1.4 1.3 -. - To obtain precipitation estimate for above sites,multiply precipitation at the continuous station by the appropriate multiplier. Source:Table reproduced from R&M (1985a). 4-27 ~19/~,a ]3 I )~)) ~~J ~}))J 1 1 1} Da i Iy Precipitation(2) Date (inches) ,J:>. I l\.) ill 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 0.4 .51 .55 0.7 1.35 .58 .31 .06 .64 .37 2.19 1.33 TABLE 4.10 ESTIMATED DAILY RUNOFF,SLOUGH 8A HIGH RAINFALL PATTERN(1) Estimated Estimated Estimated Wi th-Project Estimated Measured Groundwa te r Surface Groundwater With-Project F I owe 3)Flow(4)Runoff Flow(5)Slough Flow (cfS)(cfs)(cfs)(cfs)(cfs) 5.9 5.1 0.8 1.6 2.4 5.6 4.7 0.9 1.6 2.5 5.2 4.3 0.9 1.6 2.5 4.8 4.2 0.6 1.6 2.2 4.8 4.5 0.3 1.6 1.9 4.4 4.4(6)0 1.6 1.6 4.1 4.1(6)0 1.6 1.6 3.8 3.8(6)0 1.6 1.6 4.4 4.4(6)0 1.6 1.6 4.1 4.1(6)0 1.6 1.6 3.6 3.6(6)0 1.6 1.6 3.2 3.2(6)0 1.6 1.6 2.6 2.6(6)0 1.6 1.6 2.4 2.4(6)0 1.6 1.6 2.2 2.2(6)0 1.6 1.6 2.0 2.0(6)0 1.6 1.6 1.7 1.7(6)0 1.6 1.6 2.6 2.6(6)0 1.6 1.6 4.1 3.6 0.5 1.6 2.1 4.8 3.8 1.0 1.6 2.6 5.2 4.2 1.0 1.6 2.6 5.9 4.0 1.9 1.6 3.5 8.0 3.8 4.2 1.6 5.8 34 5.0 29 1.6 3.1 65 6.9 58 1.6 6.0 44 7.3 37 1.6 34 17 6.3 11 1.6 13 11 4.7 6.3 1.6 7.9 8.0 3.7 4.3 1.6 5.9 5.9 3.3 2.6 1.6 4.2 4.8 2.7 2.1 1.6 3.7 ( 1 ) (2) ( 3 ) (4) (5 ) (6 ) 20%exceedance probabi I ity August 1984 precipitation.Data are from Talkeetna through day 21,from Sherman after day 21. AI I data are adjusted to Slough 8A. August 1984 Q8 =-0.67 +0.00025 G Assumes flow at Gold Creek is 9,000 cfs Estimated groundwater flow exceeded measured surface flow,so reduced groundwater floW to measured flow. ~19/?5-a}4 1 ~J -l J )1 }J ))1 TABLE 4.11 ESTIMATED DAILY RUNOFF,SLOUGH 8A MODERATE RAINFALL PATTERN(l) Estimated Estimated Estimated Wi th-Project Estimated Groundwater Surface Groundwater With-Project FloW(4)Runoff Flow(5)Slough Flow (cfs)(cfs)(cfs)(cfs) 5.7 2.0 1.6 3.6 5.7 15.1 1.6 16.7 5.2 11.8 1.6 13.4 4.6 10.7 1.6 12.3 3.9 7.7 1.6 9.3 3.3 6.0 1.6 9.6 3.0 4.7 1.6 6.3 2.8 3.6 1.6 5.2 2.6 3.4 1.6 5.0 2.5 2.8 1.6 4.4 2.4 2.2 1.6 3.8 2.2 1.8 1.6 3.4 2.1 1.2 1.6 2.8 2.0 1.3 1.6 2.9 2.0 1.0 1.6 2.6 2.0 0.8 1.6 2.4 1.8 0.6 1.6 2.2 1.7 0.5 1.6 2.1 1.6 0.5 1.6 2.1 1.7 0.5 1.6 2.1 2.0 0.8 1.6 2.4 2.7 1.1 1.6 2.7 3.5(6)0 1.6 1.6 2.1(6)0 1,6 1.6 1.6(6)0 1.6 1.6 1.5(6)0 1.6 1.6 1.7 2.1 1.6 3.7 1.6 18.2 1,6 19.8 1.7 23.6 1.6 25.2 2.2 17 .6 1.6 19.2 adjusted to Slough 8A. 7.7 20.8 17 .0 15.3 11.6 9.3 7.7 6.4 6.0 5.3 4.6 4.0 3.3 3.3 3.0 2.8 2.4 2.2 2.1 2.2 2.8 3.8 3.5 2.1 1.6 1.5 3.8 19.8 25.3 19.8 Measured Flow(3) (cfs) .08 0.7 .39 .07 .39 .74 .04 .30 .13 .21 1.46 .42 Da i ly P rec i pita t i on (2 ) (inches) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Date (1)61%exceedance probabi I ity. (2)September 1983 Talkeetna precipitation (3)September 1983 (4)Q8 =-0.67 +0.00025 G (5)Assumes flow at Gold Creek is 9,000 cfs. (6)Estimated groundwater flow exceeded measured surface flOW,so reduced groundwater flow to measured flow. .... I N 1.0 1 ,J M19!55a 5 1 ~~-l )]l '1 1 i D ))1 TABLE 4.12 ESTIMATED DAILY RUNOFF,SLOUGH 8A LOW·RAINFALL PATTERN(1) Estimated Estimated Estimated With-Project Estimated Groundwater Surface Groundwater With-Project FloW(4)Runoff Flow(5)Slough Flow (cfs)(cfs)(cfs)(cfs) 2.5 1.6 1.6 3.2 2.3 0.9 1.6 2.5 2.1 0.5 1.6 2.1 1.9 0.1 1.6 1.7 1.7(6)0 1.6 1.6 1.5(6)0 1.6 1.6 1.4(6)0 1.6 1.6 1.2(6)0 1.6 1.6 1.2(6)0 1.6 1.6 1.0(6)0 1.6 1.6 1.O(6)0 1.6 1.6 1.O(6)0 1.6 1.6 0.9(6)0 1.6 1.6 0.8(6)0 1.6 1.6 0.9(6)0 1.6 1.6 0.9(6)0 1.6 1.6 1 .2(6)0 1.6 1.6 1.7(6)0 1.6 1.6 1.9 0.3 1.6 1.9 2.2(6)0 1.6 1.6 1.9 0.3 1.6 1.9 1.6 0.6 1.6 2.1 1.4 0.6 1.6 2.2 1.3 0.7 1.6 2.3 1.2 0.5 1.6 2.1 1.2 0.3 1.6 1.9 1.1 0.4 1.6 2.0 1. 1 0.3 1.6 1.9 1.2 0.2 1.6 1.8 adjusted to Slough 8A 4.1 3.2 2.6 2.0 1.7 1.5 1.4 1.2 1.2 1.0 1.0 1.0 0.9 0.8 0.9 0.9 1.2 1.7 2.2 2.2 2.2 2.2 2.0 2.0 1.7 1.5 1.5 1.4 1.4 Measured F lowe 3) Lgfs) .n .02 .05 .13 .24 .18 .02 .12 .04 .61 .65 .05 Da i ly Precipitation(2) (inches) 1 2 3 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Date (1)93%exceedance probabi I ity (2)September 198L~Sherman precipitation, (3)September 1984 (4)Q8 ~-0.67 +0.00025 G (5)Assumes flow at Gold creek is 9,000 cfs (6)Estimated groundwater flow exceeded measured surface flow,so reduced groundwater flow to measured flow. tI:>o I wo -1 --1 M19/55a 6 'I 1 i J i )1 J l »<iI j J ]1 J 1 TABLE 4.13 ESTIMATED DAILY RUNOFF,SLOUGH 9 MODERATE RAINFALL PATTERN(l) Estimated Estimated Estimated Wi th-Project Estimated Da i Iy Mea su red Groundwa te r Surface Groundwa te r With-Project Prec ip i tation(2)FloW(3)Flow(4)Runoff Flow(5)Slough FI ow Date (inches)(cfs)(cfs )(cfs)(cfs)(cfsj 1 .07 2 3 4 5 6 8.3 5.6 2.7 2.9 5.6 7 7.8 5.2 2.6 2.9 5.5 8 7.1 4.7 2.4 3.9 5.3 9 .65 6.8 4.5 2.3 2.9 5.2 10 .36 6.4 4.3 2.1 2.9 5.0 11 .06 6.1 4.1 2.0 2.9 4.9 12 5.7 3.9 1.8 2.9 4.7 13 5.5 3.7 1.8 2.9 4.7 14 .36 5.3 3.6 1.7 2.9 4.6 Il::o 15 .68 5.5 3.5 2.0 2.9 4.9 I 16 5.3 3.5 1.8 2.9 4.7 w 17 5.3 3.3 2.0 2.9 4.9 /-'18 5.1 3.0 1.9 2.9 4.8 19 5.1 2.9 2.2 2.9 5.1 20 5.5 3.0 2.5 2.9 5.4 21 .04 5.7 3.5 2.2 2.9 5.1 22 .28 6.1 4.7 1.4 2.9 4.3 23 .12 6.6 6.2 0.4 2.9 3.3 24 7.3 5.3 2.0 2.9 4.4 25 6.1 4.1 2.0 2.9 4.9 26 5.9 3.5 2.1 2.9 5.3 27 5.7 3.1 2.6 2.9 5.5 28 .19 5.7 2.9 2.8 2.9 5.7 29 1.35 8.1 3.0 5.1 2.9 8.0 30 .39 14.2 3.9 10.3 2.9 13.2 (1)61%exceedance probabi I ity (2)September 1983 Talkeetna precipitation,adjusted to Slough 9 (3)September 1983 (4)Q9 =-0.62 +0.00039 G (5)Assumes flow at Gold Creek is 9,000 cfs c_Jl 9/55a-1 --»1 J 1 '1 1 ])1 »J Da i Iy P ree i pita t ion (2 ) Date (inches) ol:> I W !'U 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 .10 .22 .17 .02 .11 .04 .57 .61 .05 .12 .02 0.5 TABLE 4.14 ESTIMATED DAILY RUNOff,SLOUGH 9 LOW RAINfALL PATTERN(1) Estimated Estimated Estimated With-Project Estimated Measured Groundwater Surface Groundwa te r Wi th-Project Flow(3)Flow(4)Runoff flow(5)Slough Flow (cfs)(cfs)(cfs)(cfs)(cfs) "3.7 7.3 2.9 10.2 9.5 3.6 5.9 2.9 8.8 7.1 3.4 3.7 2.9 6.6 5.6 3.4 2.2 2.9 5.1 4.8 3.5 1.3 2.9 4.2 4.2 3.6 0.6 2.9 3.5 3.6 3.5 0.1 2.9 3.0 3.2 3.2 0 2.9 2.9 3.8 3.0 0.8 2.9 2.9 2.4 2.4(6)0 2.9 2.9 2.4 2.4(6)0 2.9 2.9 2.1 2.1(6)0 2.9 2.9 2.1 2.1(6)0 2.9 2.9 2.1 2.1(6)0 2.9 2.9 2.1 2.1(6)0 2.9 2.9 2.7 2.6 0.1 2.9 3.0 3.2 3.0 0.2 2.9 3.1 3.6 3.4 0.2 2.9 3.1 4.2 3.8 0.4 2.9 3.3 3.6 3.4 0.2 2.9 3.1 3.2 2.9 0.3 2.9 3.2 2.8 2.6 0.2 2.9 3.1 3.3 2.5 0.8 2.9 3.7 3.3 2.4 0.9 2.9 3.8 2.8 2.3 0.5 2.9 3.4 2.4 2.2 0.2 2.9 3.1 2.4 2.2 0.2 2.9 3.1 2.1 2.1(6)0 2.9 2.9 (1)93%exceedance probabi I ity (2)September 1984 Sherman precipitation (3)September 1984 (4)Q9 =-0.62 +0.00039 G (5)Assumes flow at Gold Creek is 9,000 cfs (6)Estimated groundwater flow exceeded measured surface flow,so reduced groundwater flow to measured flow. 1 j 1 1 1 J 1 -1 '"1 J )J J )1 } ;1', Jl l<l 13 .~)-CJ i I I "-"---~I I 13 ?~, 1"S~l ".·n--- ,l'ji ~"'I ' i t!' G 2(, 2J 14 -::) I !I ,],,/I[ I 'r, !I""'-f-:-=~-.:l--J~"!----, ,_I \?I ,?1 j)! J4 •Seepage Meter •Stage Recorder 22 ' C>• Ll \i' 9 15 /~.',..----~L ,,'"II., ;'v'-"!27 /{ o <(),'::) ..;I '1"\"I I /-(j .,?7f W1--'!~t'--._I ,I',I ,,(,(i ))1."../,i>-'I~71T/"'--'~u,,---,,-,- ..,....L 1----------- I I /)'0 ~y~~>_.:/ bUGH'SA 29 '''4,,-trj /----;;r"'" (1~-?""/)•fJ;:/~v' /"./-I,:p, i7 (./--e;o all~~G'..-cJ[~/I /1 .,J 'L-/" c?::> 12 .) i\:<0....u ~.&.'.."./ ,I \...,(---'~.'-;IIC':,~"~/"',,-'(I r -> ,/~6 14 \ , L' s~~~~~ ~~~"'~~~~~ ~25({j ~~I!~~: ~~ E3~~~25;'l (J")~fTlcr:.::;-'"D~t:;"Ql ~ -<c:::;'"z ~o l>"TI L ~oar:.::;-';uz0." ~lMJ~§] C!~ ;grIiJ © @ ~DILI"D~aJ Jm ;u~I.-,.-,I'Tl ;~I~~~ol~l 0!~II I~ l C~[j ~p t 2 ~-t i ..(I) (-~2:!1 'T1-~I G') c ::Dm ~•....-m- -I APPROXIMATE LCCATIONS OF SLCUGH S'IUDY SITES AND DATA COLLECTION POINTS,STAGE RECORDERS Ai."m SEEPAGE METERS •Stage Recorder •See a e Meter PREPARED BY; ~~/~ --1",.':.<.1 V 1========== 1=1 &M CONSULTANTS,INC. .NQ........·•0_0..OQ,.8T_"''''l::IlIOl.D-O'.T••UAV....O •• FIGURE 4.1 (b) 4-34 PREPARED FOR: SUSITNA JOINT VENTUflE 1 )1 ~1 --~~1 .1 -)-1 )j ))]J j 1 I 1 R ~/I/c~-,._ ~ I W 11l SlElPAGE Source:ADF &G(1983b) Slough 8A upwelling/seepage,1982. / ··-""jY6:r.(·;I.~.;,_~. "8M 8-1 SLOUGH 8A UPWELLINGI SEEPAGE o 2000 a I FEET IAPPflOIII,SCAU) •UPWElLING I 1 .]1 B .··-1 J )1 I ]1 1 1 .~D J •-UPWELLING SLOUGH 9 o 1000 I I fEET I APPRO)!SCAUI UPWELLINGI SEEPAGE 8M 9-3 0 o 8M 9-2 sus/rNA R/VER-- RM lDlU/ oj::>. Iw 0"1 Source:ADF &G(1983b) Slough 9 upwelling/seepage,1982. PREPARED 81. [.=)~.~Ji\V11=L~~,~..l~_L-_~ R &M CONSULTANTS.INC. EI\ll:iINl!finB Oc:dLOc.;.UlTB HYCROLOGlI6T'9 "UR~I5.YORQ FIGURE 4.3 PREPARED FOR: [i{]&OO(6&0 [g[ID&~©@ SUSITNA JOINT VENTUI1E J 1 j }j .1 1 1 -j --J 1 1 I ,p,. I w -..J / I ~ sus,r NA ,I/£flR . ~i;<. :1" SLOUGH II UPWELLING/SEEPAGE o 1000 I I FEET IAPPRO•.ICALf I •UPWELLING Source:ADF &G(1983b) PREPARED BY: =J~Jf01,====== R &M CONSULTANTS.INC. I.1NCiINlEllirlS DL!OLUc.ilIGTS HvcnOLDal6TS tlIURV8VOAB Slough 11 upwelling/seepage,1982. FIGURE 4.4 PREPARED FOR: [}{]&OO~&0 ~lli~&~©@ SUSITNA JOINT VENTURE 1 j 1 ·--1 j i ].]··1 1 .~]J ] • -UPW[Ll.I~G SLOUGH 2\ o 1000 I I fUT U ..,IlOX.leu!) UPWELLINGI SEEPAGE t ,.'JI.\~.:.~.••..>,:~:",.!._.....~L""'-'''''··'''''· RM 61142 .I.:",,,,,,.~.,:...-.. ,.•;,1-,-·d·....:..··'· RIV£R--- l'.~,_:,,'-'-l..·...f:;''''' ,~~:;:.-~.;.: 8M 21-2 ___SUSI rNA / .~;Jo:::...~-i·1 Source:ADF &G(1983b) SLOUGH 21 COMPlEX of:>. I w CJJ Slough 21 upwelling/seepage,1982. PREPARED BY; [:=J)j~ri'M1 !-c.c::.J V l R&M CONSULTANTS.INC. IiNQtNUfinB oeOLOUIDT&HyonOl.OQIBTB tiUAVISVOAB FIGURE 4.5 PREPARED FOR: [}{]&lru~&0 ~[ID&~©@ SUSITNAJOINT VENTURE 1 J 1 •1 j J 1 J »j J J ]I 1 J / •observation well "600"groundwater elevation Susitna water surface elevation Date:9-20-82 QGC:24.000 cfs QGC _(cfs) 20,200 28,200 32,500 32,000 26,800 24,100 24,000 8.9 12.2 8.6 5.4 7.9 7.7 7.5 -Temperature (Oe) Pred p i tat ion (mm) 19.0 29.8 11.2 9.4 10.0 18.6 6.0 .. Climatic Summary for Preceding 7-Day Period Sherman Cl imate Station Date 9-14 9-15 9-16 9-17 9-18 9·19 9-20 .J:> I W 1.0 .,FIG~4.EtSource:R&M (l982g) PREPARED BY: l5l>E?ff\\!;1 =L:1",.J 1.============= R &M CONSULTANTS.INC. tiNQINlI!lil=lU OL!OLUuID't1I HvDROLOQISYS "U"~."'iOAU GROUNDWATER CONTOURS SUSITNA RIVER'AT SLOUGH 8A PREPARED FOR: (M]&OO~&0 [g[ID&~©@ SUSITNA JOINT VENTURE --1 J 1 1 1 J ~1 -.)J ])1 t Ii>-o .:::'-:'~."':..:);~':.";'~'::"::_:" ~..~:; .<;.:..,...;:::.:; Climatic Summary for Preceding 7-Day Period Sherman CI imate Station Precipitation Temperature QGC Date (mIn)(Or),r \,~,-\cLS..,L 9-29 7.4 6.0 12,400 9-30 8.4 4.9 12,500 10-1 N/A 2.2 12,400 10-2 N/A 3.3 11,700 10-3 N/A 2.8 11 ,000 10-4 N/A 1.3 10,500 10-5 N/A 0.1 9,800 rv;,\-Not Available Source:R&M (1982q) / ·':··;':::·:.::.f'-::.;l.',;:~...; Legend •ob'servation well "600"groundwater elevation .Susitna water surface elevation Date:10-5-82 QGC:8,300 ·ds FIG~4.7 PREPARED BY; ~JKJl========== R&M CONSULTANTS.INC. ENOINa:6RB O~OLOuIBTa HvpnOLCQIBTB tJURYilVOAd ~ROUNDWATER CONTOURS SUSITNA RIVER'A..T SL~UGH8A PREPARED FOR: [}(]&OO~&D~(ID&~©@ SUSITNA JOINT VENTURE J -)]1 )1 -1 1 ~1 )]1 .~] .';- / ,:;":.";':":,:::::,',0 ~:""':':\!;:" ~ 4-20 7.0 1.7 1750 (ice)"600"groundwater elevation4-21 0.0 1.5 1800 (i ce) 4-22 0.0 1.2 '900 (Ice)Date:4-26-82 4-23 0.0 0.1 2000 (ice) QGC;4-24 1.6 1.1 ~IOO (ice)2300 cfs,ice Cover on 4-25 0.0 4.4 2200 (Ice)mainstem 4-26 0.0 1.0 2300 (ice) ...... "'"I "'"I-' Source:R&M (1982g}FIG.'4.8 PREPARED BY: =f~~~:rI~{} R&M CONSULTANTS.INC. "NGIN~lUnQ,Ol:!OLtJulllYIilI HVDnOLDQISYB .Ufl~IIV(.lAS GROUNDWATER CONTOURS SUSITNA RIVER '~.T SL.OUGH 8A PREPARED FOR: rrD&~~&0 ~[ID&®©@ SUSITNA JOINT VENTUliE )~~1 J 1 I 1 J ')}]J 1 1 1 J ,j::> I ,j::> to Climatic Summary for Preceding 7-Day Period Sherman Climate Station QGCPrecipitationTemperature ~(mm)(DC)(cfs) 6-25 2.0 16.5 27,000 6-26 0.0 15.9 28,000 6-27 0.0 14.9 29.000 6-28 0.8 12.7 30,000 6-29 0.0 13.0 29,000 6-30 9.2 13.6 27.000 7-1 1.6 10.1 25,000 Source R&M (1982g) Legend •observation well "600"groundwater elevation Date:7-1-82 QGC:25,000 cfs FIG ..4.9 PREPARED BY: l5lJ~)r~=c"}"~~L~J1========= R&M CDNSULTANTSJ INC. IiNGINB'liflD ULJQL.tJ(j,IO'f1ito HVOFlOLDUI8TB IiIURVIIIVDRo. GROUNDWATER CONTOURS SUSITNA RIVER ..AT ~LOUGH 9 PREPARED FOR: [}{]&OOC6&0 ~[ID&~©@ SUSITNA JOINT VENTUHE ))-~i 1 I J 1 l -I )1 1 1 J ] ..". I ..". W Legend Temperature QGC II observation well Date (mm)(Oe)_(cfs)"600"groundwater elevation 10-1 N/A 2.2 12,400 Date:10-7-8210-2 .~Ufl.3.3 11,700 10-3 iliA 2.8 11,000 Qc;<.:-8,480 cfs10-4 ;~/A 1.3 10,500 10-5 N/A 0.1 9,800 10-6 N/A 2.3 8,960 10-7 N/A 0.5 8,480 N/A -Not Available Source R&M (1982 FIG.:4.10 PREPARED BY: =J~~~.!========== R &M CON5ULTANTS~INC. E.NGINI!IlRO OL!OLOwIUT8 HVO~OLDaIBTIiI DUAVIIIVCRti GROUNDW ATER CONTOURS SUSITNA R.IVER AT SLOUGH 9 PREPARED FOR: [}:O&OO~&C1 ~[ID&~©@ SUSlTNA JOINT VENTURE I I I B 1 I I 1 J 1 I »)J )1 J J I -)~.~ .t:> I ol'> J::> #' _..'!.;;:.°0 ':.:!;;:~i';':'~'"i-:~,::.,".;, ::; Date 12-16 12-17 12-18 12-19 12-20 12-21 12-22 N/A -not Available ource:R&M (1982g) Temperature _eC) -4.6 -8.5 -16.2 -12.8 -I J.4 -18.8 -23.3 QGC (cfs) 2,300 (ice) 2,300 (ice) 2,300 (ice) 2,300 (ice) 2,300 (ice) 2,300 (ice) 2,300 (ice) "::'.:t. :~:._..~.:.... ...~.,.>~. ".~. legend •~bservation well "600"groundwater elevation Date:12'-22-82 QGC:2,~00 cfs,ice cover on malnstem ,, FIG."4.11" PREPARED BY: ~~:nw/l=l,_=--_L'Q:J R &M CONSULTANTS.INC. tiNGIINdOflO (H.!CLOGoIOTIl HVcnCLCCiIOT'a tiURVI!lVCHHJ GROUNDWATER CONTOURS SUSITNA RIVER AT SLOUGH 9 PREPARED FOR: [}{]&OO~&0 ~[ID&®©@ SUSITNA JOINT VENTURE -1 1 J -)1 J i "J .~)J ]-j ]J ))] JAN FEB HAR APR MAY JlJN JUL AUG SEP OCT NOV DEC ~SLOUGH 8A UPPER,SURFACE WATER LEGEND o MAINSTEM LRX 29,SURFACE WATER •SLOUGH 8A UPPER,INTRAGRAVEL o~ ..d/J~Jr .V;NIV\~ 14 6 B 12 10 o °c t t;; I I I I I L I I I I \I J,\N FEB ,lAB APR SEP OCT NOV DEC SOURCES:ADF&G (1983b) ADF&G PROVISIONAL 1983 ..,:....-.;,..:...:.-.-------~...;.--.;;....:....:-;...-._......I ~.:;.~---~... ~-.l:'Bl.PA RJ-ll BY;===========~g~~:2.lli!1 _" n &N1 CO(\JSLlL.:rANTS,INC. liNf';IN£URQ (..I(lC;LOClflTlJ H ......onOl..OOI6TB tJURVlSVOAOi FIGURE 4.12 SLOUGH 8A WATER TEMPERATURES,1983 ...,"j PREPARED FOR; (j{]&OO~&0 ~[ID&~©@ SUSIHJA JOIr'JT VnnUI1E ]!]))1 J 1 )j »-}).---))j ] .. ;\.:}/t f \.,.....\.J?i"'~.\ ... :\'~tP i~J :~:....:'.f lP '.. .I ..•,,"-,_,0 "of~.----II''"III 1'-,,_.1ft ""....~:-f'~~.-~•,-"I'':/.. :.""L.• t I··...J1';V·..;A;"..;~:;==-';'..A.......o'''-W MEAN DAILY SURfACE WATn !ENPERATU8£ -----UPPER SLOUGH 8A-SIT£3 (RM 126.6) ..........LOWER SLOUGH 8A-SITE 3 (RN liG.6) MEAN DAILY INTRAGfUVEI-WATER TEMPERATURE UPPER SLOUGH 8A-SITE 3 (RN 126.6) -"-"-LOWER SLOUGH 8A~SITE 3 (RM 125.6) 15 - 14 - 13 - 12 - -II - u 0 10 -- w 9- 0::8- :::>.-1- et 0::6- W a..5- ~I :e I 4- ~ W Q'\ .-3- 0::2- W.-l-et ~0- -I - -2 - -3 - -4 - :.\:;,; \f \I'~:i A ~1\y\~,~~ .,,~\. :."'..)~ 1 Source:ADF &G(198s) I I I I SEP OCT NOV DEC I JAN TfEB 1MAR 1APR , MAY JUN Mean daily surface and intragravel water temperatures recorded at Lower Slough 8A -Site 3 (RM 125.6)and Upper Slough 8A - Site 3 (RM 126.6)during the 1983-84 winter season . .."';~,_..._...~~.~_._..~i '--'-i .1 PREPARED BY; =J~~~f\j1=== R &rvl COI\ISULTANTS.INC. liN4IIN&tina OUOLlJLoIOTti HVOnOLOQIO ....O IH.JAVdYORB FIGURE 4.13 PREPARED FOR; [}{]&OO~&r:J ~[ID&®©@ SUSITNA JOINT VENTUI1E ))-j ])1 »}]1 J j J j )) JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC I~ 12 10 8'- °c It::> l.I 6 -....I o f'..-1-.~"....!'Iv J '"L-. LEGEND o MAIN STEM.LRX 29.SURFACE HATER o SLOUGH 9,SURFACE WATER •SLOUGH 9,INTRAGRAVEL .L NAYAPRMARfEB.JAN J !!I !I ----..L-I I I I I I JUN JUL AUG SEP OCT ~OV DEC SUSITNA JOINT VENTUI1E [}{]&[g1~&0 ~[ID&®©@FIGURE4.14 1 SLOUGH 9 WATERSOURCES:ADF&G (1983b)as presented in APA (1983b)TEM~ERATURESl 1983 ADF&G PROVISI()l\IAf'..c}983 DATA -.PREPARED FOR;~-----i PREPARED BY: IlNOINl!linO Ol:OI..O[iolUTB HVOnoI..OIlIQ.TO PURVdyQn., =J~~~ I="t&M CONSUL:rANTS.INC. )]J J !1 1 )J I -'J ) MfAN DAilY SURfACE WATER UNP£RATURI: -----SLOUGH 9.SITE :5 CRN 128.6) MEAN DAILY INTRAGRAVEL WATER TEMPERATURE SLOUGH 9.SITE :5 (RN 128.6) .. ".. ", I -'~:.:':- I ,..: • I"••"11\,'" I."" •~~.:}J"t.).,..I!~,•...,.~,'1 '....~ J 't ••/"8 ~.,~.•'fI'"" \"~\d"\J ._-,,__,"..".-•'. I JUN !..fa,. 0 1 I'.I.. I •I "., I MAY I APR ~"..'"a -,.",.'.,'e ,."l'I •,,',~:::... ••:t,',~"' ,.,\--- ,. T MAR T fEB T JAN T DEC Source:ADf &G(198s) t 1-'SEP OCT NOV ~I',I'II'/,t,t, ~,., I,,, •I I• 15- 14 - 13- 12 - -11- 0 10-0-9-w a::8- :J.....7- <t a::6- wa.S- ~4-~I w I ~.....3- OJ a::2- W .....1- <t ~0- -1- -2- -3- -4- - Mean daily surface and intragravel water temperatures recorded at Slough 9 -Site 3 (RM 128.6)during the 1983-84 winter season. ,,''-~c~~.__,~,,=~'-c,_~~,.r--'_C-'"f', PREPARED BY:-[=JJ5<::'~n.;~---===========J=},-S"=['l~_ Fl&M CONSULT.l\NTS.INC. ."",CiI,,,,l:liUfl l:U!CL.OG.I£ITa uVonOLO[]!UTS rJU'~VBVOl=l[) FIGURE 4.15 PREPARED FOR: O={]&~~&0 ~[ID&~©@ SUSITNA JOlt-H VENTURE J ]1 J -J )J J 1 1 J )J J 1 -] ,---..-I JAN FEB MAR APR HAY JUN JUL AUG SEP OCT NOV DEC I I I I '--I 14 12 10 .- B °c .t:> I .t:>I 6 l.O 41~~~ 'Vvl'......Ilo--~\ ~ o LEGEND o }~INSTEM LRX 29,SURFACE WATER •BOREHOLE 9-1A o BOREHOLE 9-3 ~BOREHOLE 9-5 ~ --_0 'GI ~..r-- DECNOV I J_._ OCT SUSITNA JOINT VENTURE [X]&~~&Cl~[ID&~@@ SEP ,I I I I I I I J I::N01Nafinil O[!Ol..l.1[OIUTD HYOnal<Oo.IIlTIi tiUFlIVB'{PrtEl .JMl FEn HAft APR MAY JUN JUL AUG SOURCES:ADF&G (1983b) ADF&G PROVISIONAL 1983 DATA ]as presented in APA (1984b)SLOUGH 9 WAT~~ .,~._,.~~.~.,~~.•,~_.~!:L£;ONSULTA1.'rS~PRQY.-IS.IQNAL 1983 DATA,_TEMPERATURES,1983, PREPARED BY:-,PREPARED FOR: [~)~c.:,1[f,\1;1 .=cI-l,_~~_"d'_L --_I FIG URE 4.16 r-~&IVI CONSULTANTSJ Ir\Jc. 1 J '1 J I J E 1 1 )'1 J J j OCT ~ SEP'AUGJULJUNMAY r.G APR SLOUGH 11,INTRA GRAVEL MAR o o SLOUGH 11,SURFACE WATER LEGEND £;.MAINSTEM AT SLOUGH 11,SURFACE ~'ATER FEB r"-v---""~~"~ JAN 8 N-I'-. 2 0_ o+~~ 14 f----,----I-----T----T-=---,-~~-,-~~--,-~~-~=~~=:=~~==I I I I I I I I I I 10 12 DC ._,,---,.I tl::o I lJlo I L I I I I I JAN FEB MAR APR W,Y JUN JUL AUG SEP OCT SOURCES;ADF&G (1983b)1 ADF&G PROVISIONAL 1983 DATA as presented in APA (1983b SLOUGH 11 UA'rER TEMPERATURES,1983 _:....::.:.:.~-=....-.....u.;..:;;;.:...;,.=;;;~_._.__.;;OO';I -'._~- PREPARED BY: l =-:i1f c::~;rI\V;1=!.:.~,=-_l~:;l. J:l&/VI CONSULTANTS.INC. IiNDll'Jtlfl'flO 0l1DLULilUT8 H .....OI'lOLOOIUyS rlUAVdVORB FIGURE 4.17 PREPARED FOR: G{]&OO~&0 ~[ID&~©@ SUSITf'.JA JOINT VENTURE f 1 )i 1 -1 1 1 1 1 1 ]J ~;l4 6 B 16 I I I I I I I n I I LEGEND 14,)\r V"IJ \ 0 ~INSTEM LRX 57,INTRAGRAVEL •SLOUGH 21 UPPER,SURFACE ~ATER I t>SLOUGH 21 UPPER,INTRAGRAVEL 12 I , I 10 DC,J:>, I U1 I-' l L____ _ I I I I I I I I L_I JI\N FEU ~L\R APR HAY JUN JUL AUG SEP nCT NOV DEC SUSITNA JOINT VENTUFlEIiNOlNllt01UoeOLO~IOT8 HY0l101.00lBTO lH..IR\laYORO SOURCES:ADF&G (1983b)a t d in APA (1984b)UPPER SLOUGH 21,=~..~~"_...ADF&G PROVISIONAL 1983 DATA s presen €W It 'tr MPE 8 PREPARE D BY;r .PREPARED FOR: -:::;Irc')f'r;;--,,''.A.~".Il'j'iii)Ii',"..c.__,,->L:.,~J~-.-,VII,,,','-';.,'t~"L_~'ff m ',_''''"£F::1:-',~,""""",,gi,_.;,~t,_,S=rL=G'~Y1 FIGURE 4.18 HARZA EBASCO R &M CONSULTANTS.INC. 1 1 )1 J -I -)J )1 1 1 ]i ] ,L ~vi~0 "--"-tl 2 ,.- 10 16 l~I I I I I I l~l I I Q LEGEND 14 1 )\'I ltV 11 \•MAINSTEH LRX 57,SURfACE I·IATER 0 MAINSTEH LRX 57,INTRAGRAVEL 12 ~ 0 SLOUGH 21 MOUTH,SURFACE WATER )\/ 0 SLOUGH 21 MOUTH,INTRAGRAVEL 8 ,°c 1-.-.t:> I (Jl IV I 6 I I I I I I DECNOV SUSITNA JOINT VENTURE OCTSEPAUGJULJUN FIGURE 4.19 HARFEBJAN IiNGINe-t:irlQ (J(!OI.ULolflTR HVPI1.0LD~IBTa tJUt=liVIIYORB PREPARED BY; l~~~fl\:vq-'=~:,~.",'.'::._J \].=.========= I=1&M CONSULTANTS.INC. APR HAY SOURCES:ADF&G (1983b)].LOWER SLOUGH 21 WATER,.==c~~~~=,~~ADF&G PROVISlqNA~-=1~JP DATA as presented ~n APA (1984b)TEMPERATURES,1~83 I i PREPARED FOR: [g]&~~&0 ~[ID&®©@ 'iii'9/261!0 E-<~ ~ 9/27 9/28, I I 9/29 9/30 10/1 10/2 10/3 10/4 10/5 10/6 10/7 10/8 10/9 -I:I I •I .:~-§r-"'-, I·I .-+-,, J t3,---j !-----l- I--J- -+-r--j-I-I-- L __;_+ - FIGURE 4.20 PREPARED BY; ---.:3l('--~/I~(~""..J'-'£.!'("1,=_==============~&M CONSULTANTS,INC. RESPONSE OF SUSITNA RIVER AND SLOUGHS SA,9 AND 11 TO SEP'IEMBER 1983 STORM PREPARED FOR; [}{]&~{b&0 ~[ID&~©@ SUSITNA JOINT VENTUi-lE __....,.;;;:4=-..£5..J.3 ---_ ~:o 8/17 8/18 8/19 8/20 8/21 8/22 "§•!+• ~r ---1-ti""'"I11 f--- ~2=t,- .... 8/23 EI/24 8/25 8/26 8/27 B/28 8/29 B/30 :E ...~L 1--=1= --r------+--- +--+- ~__l --r-----....-+-- I 1----- FIGURE 4.21 ..... PREPARED BY: --c:=J1.(c:Tr\\.'~~'::-J '(/1_:.=:-:::::,:========== R&M CONSULTANTS,INC. .NQ.N.....1;1.0 ...0£1'......M..,g ..O...,ag,••",..·U,""•.,Q•• RESPONSE OF SUSITNA RIVER AND TRIBUTARY 9B TO AUGUST 1984 STORM 4-54 PREPARED FOR: [}{]&ffi1~&C@[ID&®©@ SUSITNA JOINT VENTUF1E til~9/14 ~ 9/15 9/16 9/17 i L.' 9/18 9/19 9/20 9/21 9/22 I i-- _.~ 9/23 9/24 9/25 9/26 9/27 9/28F+==--------;-:-' . -f----. f---- I t- ----±::--~!-. ---~---~-=+=_._--.---·1 ==::::;=====+======t=::::::;==t::~===~====+==+==:=:r:-:-----:-----=-' =•.-__L=_....-....·=-~t -<---_.,------.-.., --I 1 -- --- -L .. ~_c-- ____....i , i I ,_. ~L §~ ~~ Cl - 9/14 9/15 9/16 9/17 9/18 9/19 9/20 9/21 9/22 9/23 9/24 9/25 9/26 9/27 9/28 DATE (l984) FIGURE 4.22 PREPARED BY: --r=i((~;rr\\/A~'~.'-:"..J~'-'-,=-l====::=,=======:=======:= R&MCONSULTANTS,INC. RESPONSE OF SUS1TNA RIVER AND TRIBUTARY 9B TO SEPTEMBER 1984 STORM PREPARED FOR: [}D&Im~&c ~[ID&~©@ SUSITNA JOINT VENTUCiE 4-55 - - - R24/3 63 5.0 SUMMARY Construction and operation of the Susitna Hydroelectric Project will affect several of the physical processes which produce and regu late the aquatic habitats in the Middle Susitna River.Changes will occur in the river sedimentation processes,in the channel stability,and in the groundwater upwelling processes.The specific project effec:ts a re reviewed below. The river sedimentation processes will change from strictly river-type to combined lake-type and river-type.A large proportion of the sediment reaching the impoundment zone from upstream will be trapped in the reservoirs,with only the fine suspended particles (smaller than about 3-4 microns)passing through to the river downstream.This will have some direct effects on the stability of the river chanlnel below the project. The reservoir releases will be transporting Iless sediment than comparable flows under natu rat conditions,and wi II consequently have capacity to transport additional sediment.The flows will thus have a tendency to pick up finer particles from the riverbed.However,with-project flows will also be smaller than natu rally-occu rring summer flows,with reduced ability to transport sediment.The net result of projE~ct construction and operation is that local areas of the mainstem in the Middle Reach are expected to degrade from zero to 1 foot.The median size of particles In the mainstem is likely to increase,making the channel more stable.The beds of sloughs and side channels may locally degrade hom zero to 0.5 foot. Local deposition in the mainstem,primarily due to bifurcation of the streamflow between the mainstem and other channels,is not expected to be significant.Due to possible degradation of the main river,the side channels and sloughs may require larger mainstem flows to overtop them, on the order of 8,000 cfs higher than under natural conditions.Fine sediments picked up from the river bed downstream of the dams may continue to intrude into the gravel beds of sloughs and side channels in pools and backwater areas.Jack Long,Sherma n,and Oeadhorse Creeks, 5-1 r R24/3 64 three tributaries used by salmon,may be unable to downcut through their delta deposits,but other tributaries shou Id not have simila r problems. Project effects on slough hydrology relate to likely changes in flow levels and water temperatu res.There is considerable variation between sloughs as to the nature of their dependence on the mainstem.Sloughs similar to Slough 11,whose flows are strongly related to the mainstem water level, are likely to experience a decrease in groundwater upwelling under with-project conditions.Other sloughs which derive significant inflow from upland sources or from local surface flow will be affected to a lesser extent.Temperatures of .groundwater upwelling to the sloughs are reasonably approximated by the mean annual (time-weighted)river temperature.Any variations in mean annual river temperature due to project operation will likely result in a similar change to the temperatu re of the slough upwelling derived from the mainstem. 5-2 R24/3 65 6.0 REFERENCES Aaserude,B.1985.Transmittal of Prelimina ry Data on Overtoppi ng Flows for Sloughs and Side Channels.E.W.Trihey &Associates, Anchorage,Alas ka.April. Acres·American,Inc.1982.Reservoir Slope Stability.Appendix K in 1980-81 Geotechnical Report by Acres American,I nco Prepared for Alas ka Power Authority. Hydrogeology Report. Anchorage,Alaska. Acres American,Inc.1983.Susitna Prepared H'ydroelectric Project,Slough for'Alaska Power Authority, Alaska Department of Fish and Game (ADF&G).1983a.Susitna Hydro I!1JlPi'lt Aquatic Studies·Phase 11 Data Report:Winter Aquatic Studies (October 1982 -May 1983).Prepared for Alaska Power Authority. Alaska Department Fish and Game Susitna Hydro Aquatic Studies, Anchorage,Alaska. Alaska Department of Fish and Game.1983b.Susitna Hydro Aquatic Studies Phase II Basic Data Report.Volume 4 (3 parts):Aquatic Habitat and I nstream Flow Studies,1982.Prepa red for Alaska Power Authority.Alaska Department of Fish and Game,Susitna Hydro Aquatic Studies,Anchorage,Alaska. Alaska Department of Fish and Game.1984a.Susitna Hydro Aquatic Studies,Report.No.3,Aquatic Habitat and Instream Flow Inves- tigations (May-October 1983):Chapter 3.Continuous Water Temper""' ature Investigations.Prepared for Alaska Power Authority.Alaska Department of Fish and Game,Susitna Hydro Aquatic Studies, Anchorage,Alaska. R24/3 66 Alaska Department of Fish and Game.1984b.Susitna Hydro Aquatic Studies,Report No.3,Aquatic Habitat and I nstream Flow I nves- tigations (May-October 1983):Chapter 1.Stage and Discha rge Mea- surements.Prepared for Alaska Power Authority.Alaska Department of Fish and Game,Susitna Hydro Aquatic Studies,Anchorage, Alaska. Alaska Department of Fish and Game.Hl84c.Susitna Hydro Aquatic Studies,Report No.1;Adu It Anad romous Fish Investigations (May-October 1983).Prepared for Alaska Power Authority.Alaska Department of Fish and Game,Susitna Hyd ro Aquatic Studies, Anchorage,Alas ka. Alaska Department of Fish and Game.1984d. Studies,Report No.2;Resident and I nvestigations (May -October 1983). Authority.Alaska Department of Fish Aquatic Studies,Anchorage,Alas ka. Susitna Hydro Aquatic Team Juvenile Anadromous Fish Prepared for Alaska Power and Game,Susitna Hydro Alaska Department of Fish and Game.1H85.Susitna Hydro Aquatic Studies,Report No.5,Wi nter Aquatic I nvestigations (September 1983 -May 1984),Volume 2,Appendix F:Winter Temperature Data. Prepared for Alaska Power Authority.Alaska Department of Fish and Game,Susitna Hyd ro Aquatic Studies,Anchorage,Alas ka. Alaska Power Authority (APA).1983a.Application for license for major project,Susitna Hydroelectric Project,before the FERC.Exhibit E, Chapter 1-3.Prepared by Acres-American,Inc.February. Alas ka Power Authority.1983b.Supplemental response 2-31,in response to the FERC April 12,1983 request for'supplemental information on the proposed Susitna Hydroelectric Project license application,project number 7114-000,filed with FERC on July 11,1983. 6-2 - R24/3 67 Alaska Power Authority.1984a.Evaluation of Alternative Flow Requirements.Prepared by Harza-Ebasco Susitna Joint Venture for Alaska Power Authority.November. Alas ka Power Authority.1984b.Alas ka Power Authority Comments on the Federal Energy Regulatory Commission Draft Envi ron mental Impact Statement of May 1984.Vol.9,Appendix VII -Slough Geohydrology Studies.Alaska Power Authority,Anchorage,Alaska.August. Alaska Power Authority.1985.Board of Directors Meeting. I nformation on Licensing Review and Consideration Staging of Construction of Susitna Hydroelectric Project. Supplemental of Proposed May 3. Arctic Envi ronmental I nformation and Data Center (AEI DC).1984. Geomorphic Change in the Devil Canyon to Talkeetna Reach of the Susitna River since 1949.Draft.Submitted to Harza-Ebasco Susitna Joint Ventu re for Alaska Power Authority.May. Baxter,R.M.and Glaude,P.1980.Envi ron mental Effects of Dams and Impoundments in Canada,Experience and Prospects.Department of Fisheries and Oceans,Bulletin 205,Ottawa. Beaver,D.1984.Memorandum to E.Gemperline,Harza-Ebasco Susitna Joint Ve"ntu re,dated October 12,1984. Beaver,D.1985.Memorandum to E.Gemperli ne,Harza-Ebasco Susitna Joint Venture,dated April 5,1985. Bray,D.I.1972.Generalized Regime-Type~Analysis of Alberta Rivers. Ph.D.Thesis,presented to the Un iversity of Alberta,Edmonton, Canada,232 p. .... Bredthauer,S.,1984. ments on the Memo to J.Bizer:in Alaska Power Authority Com- Federal Energy Regu latory Commission Draft 6-3 R24/3 68 En vi ronmental Impact Statement Slough Geohydrology Studies. Alaska. of May 1984,Vol.9,Appendix VII - Alas ka Power Authority,Anchorage, - Brune,G.M.1953.Trap Efficiency of Reservoirs.Trans.Am.Geophys. Union,June.U.S.Department Agr.Misc.Publ.970,p.884. Chow,V.T.1964.Runoff.Section 14,in V.T.Chow (editor),Handbook of Applied Hydrology,McGraw-Hili Book Company,New York. Dolan,R.,Howard,A.and Gallenson,A.1974.Man's Impact on the Colorado River in the Grand Canyon,American Scientist,62 (4),pp. 392-401. E.Woody Trihey and Associates (EWT&.A)and Woodward-Clyde Consultants (WCC).1985.Instream Flow Relationships Report,Volume No.1 (working draft).Alaska Power Authority,Susitna Hydroelectric Project.Prepared for Ha rza-Ebasco S·usitna Joi nt Ventu reo February. Gottschalk,L.C.1964.Reservoir Sedimentation,in Chow,V.T.(Ed) Handbook of Applied Hydrology.McGraw-HilI,New York. Harza-Ebasco Susitna Joint Ventu reo 1984a.I nstream Study,Susitna Hydroelectric Project.Doc.No.1986. Alaska Power Authority.October. Ice Simulation Prepared for .... Harza-Ebasco Susitna Joint Venture.1984b.Middle and Lower Susitna River,Water Surface Profiles and Discharge Rating Curves,Volumes I and II Draft Report.Susitna Hyd roelectric Project Document No. 481.Prepared for Alaska Power Authority.January . 6-4 R24/3 69 ..- Ha rza-Ebasco Susitna Joint Ventu reo 1984c.Reservoi rand River Sedimentation,Susitna Hydroelectric Project.Doc.No.475. Prepared for Alaska Power Authority.April. Harza-Ebasco Susitna Joint Venture.19184d.Lower Susitna River Sedimentation Study:Projec:t Effects on Suspended Sediment Concentration.Draft report.Prepa red for Alas ka Power Authority. November. ,~ Harza-Ebasco Susitna Joint Ventu reo 1985.Middle Susitna River Sedimentation Study:Stream Channel Stability Analysis of Selected Sloughs,Side Channels,and Main Channel Locations.Draft report. Prepa red for Alaska Power Authority.March. Hey,R.D.,J.C.Bathurst and C.R.Thorne (editors).1982.Gravel-Bed Rivers;Fluvial Processes,Engineering and Management,John Wiley and Sons,New York. Jokela,J.B.,S.R.Bredthauer,and J.H.Coffin.1983.Sedimentation in Glacial Lakes.Paper presented at Cold Regions Envi ronmental Engi- neeri ng Conference,May 18-20,1983,Fai rban ks,Alaska.Spon sored by University of Alaska,Fairbanks,and University of Alberta, Edmonton. Kellerhals,R.1982.Effect of River Regulation on Channel Stability. In:Gravel-Bed Rivers:Fluvial Processes,Engineering and Management (R.D.Hey,J.C.Bathurst,and C.R.Thorne,eds.). John Wiley and Sons,New York,New York. Kellerhals,R.,Church,M.,and Davies,L.B.1977.Morphological Effects of Interbasin River Diversions,in Third National Hydroelec- trical Conference,Quebec,30-31,May 1977,Canadian Society for Civil Engineering,pp.833-851. 6-5~~'_M_"""~""";;;''''::''·_--C-~---~_ - ,.... R24/3 70 Kel/erhals,R.and D.Gill.1973.Observed and Potential Downstream Effects of Large Storage Projects in Northern Canada.Proceedings, 11th International Congress on Large Dams,Madrid,pp.731-754. King,N.J.1961.An Example of Channel Aggradation Induced by Flood Control.U.S.Geological Survey Prof.Papers 4248,15,pp.29-32. Klinger,S.and W.Trihey.1984.Response of Aquatic Habitat Su rface Areas to Mainstem Discharge in the Talkeetna to Devil Canyon Reach of the Susitna River,Alaska.Prepared for Alas ka Power Authority, under contract to Harza-Ebasco Susitna Joint Venture.Doc.No. 1693.June. Knott,J.M.and S.W.Lipscomb.1983.Sediment Discharge Data for Selected Sites in the Susitna River Basin,Alaska,1981-82.U.S. Geological Survey Open-File Report 83--370.Prepared in cooperation with the Alaska Power Authority. Knott,J .M.and S.W.Lipscomb.1985.Sediment Discharge Data for Selected Sites in the Susitna River Basin,Alaska,October 1982 to February 1984.U.S.Geological Survey Open-File Report 85-157. Prepared in cooperation with Alaska Power Authority. Lane,E.W.1955.The Importance of Fluvial Morpholqgy in Hyd rau Iic Engineering:Proc.,ASCE,Vol.21,No.745,17 p. Leopold,L.B.,and T.Maddock.1953.The Hydraulic Geometry of Stream Chan nels and Some Physiograph ic Impl ications,USGS Prof. Paper 252,57 p. Leopold,L.B.,Wolman,M.G.and Miller,J.P.1964.Fluvial Processes in Geomorphology.W.H.Freeman and Company,San Francisco,522 pp. 6-6 R24/3 71 Mavis,F.T.,and L.M.Laushey.1948.A Reappraisal of the Beginning of Bed-Movement Competent Velocity,I nternational Association for Hydraulic Research,Second Meeting,Stockholm.June. Moore,C.M.1969.Effects of Small Structures on Peak Flow,In Moore, C.M.and Morgan,C.W.(Eds.),Effects of Watershed Changes on Streamflow,University Texas Press,Austin,pp.101-117. 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