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HomeMy WebLinkAboutAPA2855St>~dn,i Jt)JPt v~'nture Dt)cunwnt 1\Junl!~t~l Plt'<lse Retw n To DOCUMENT CONTROL •' . ·.:;}'~\:~ .. ··.: . Jtt. •' ~ 'j. , ... .:< ' , """ ..... []:{J&OO~&c §IM&@@@ SUSITNA JOINT VENTURE INTRA-OFFICE MEMORANDUM LOCATION Anchorage DATE December 7,1984 TO FROM L.Gilbertson J.Bizer NUMBER 4.3.16/4.3.1.1 Page 1 SUBJECT Interpretation of ADF&G SuHydro Mainstem and Local Flow Values for Successful Passage Conditions - Sautner et a1 (1984)presents results of a study to define mainstem and local slough discharge requirements to allow passage of adult chum and sockeye salmon to spawning areas in sloughs and side channels.Estimates of mainstem discharge were calculated assuming a negligible slough discharge andl,conversely,estimates of slough discharges were calculated assuming negligible influence of mainstem discharges.For passage reaches near the mouths of the sloughs and side channels,the estimated mainstem flow requirements are·extremely conservative since they neglect local flow contribution.In fact,both mainstem discharge and local slough discharge interact to provide water depth in those passage reaches.The analysis presented by Sautner et al (1984)makes no attempt- to integrate the two sources of water which present passage condi tions. The purpose of this memorandum is to present a first approximation of how • local slough discharge and mainstem discharge may interact to provide adequate passiage conditions at mainstem discharges considerably less than the independent estimates of mainstem discharge backwater effects. In the evaluation of the effects of the proposed Susitna Project on aquatic resources downstream of the dams,a principle question centers on the maintenance of salmon populations which utilize habitats which are directly affected by mainstem discharge.The maintenance of these populations depends upon the effects of mainstem discharge on the inmigration of adult salmon through the main channel of the Susitna River,the mlovement of adult salmon into spawning areas,and the use of various habitat types of salmon for spawning,incubation and rearing. The evaluation of conditions necessary for salmon to gain access to spawning areas is a key step in the overall evaluation of the effects of the proposed project on existing salmon populations and their habitats. Approximately 15-25 percent of the chum salmon (approximately 5000 fish), which enter the Devil Canyon to Talkeetna reach of the Susitna River to spawn,utilize side slough and side channel habitats (Barrett,et'a1. 1984).Nearly 100 percent of the sockeye salmon (approximately 1500 fish)which enter the Devil Canyon to Talkeetna reach to spawn utilize side slough llOd side channel for spawning. Side sloughs are overflow channels of the mainstem which convey turbid mainstem water when mainstem discharge is relatively high.This occurs during the summer open water months.When mainstem discharge is lower, th~upstream ends of the sloughs are not overtopped and are similar to small tributaries which convey clear,local surface runoff and ground- water upwelling.These sources of water together are termed local flow or local discharge.During low mainstem discharge conditions,side 420972/12 Q:D&OO~&c §OO&®©@ SUSITNA JOINT VENTURE INTRA-OFFICE MEMORANDUM LOCATION TO FROM Anchornge L.Gilbertson J.Bizer DATE December 7,1984 NUMBER 4.3.16/4.3.1.1 Page 2 SUBJECT Interpr.etation of ADF&G SuHydro Mainstem and Local Flow Values for Successful Passage Conditions slough discharges upon whether or upstream ends of upward of sE!veral range from about 1-2 cfs to more than 10 cfs depending not small tributaries enter the sloughs.When the the sloughs are overtopped,slough discharges range hundred cubic feet of water per second. Side channels are similar to side sloughs in structure and hydrologic relationships with the mainstem.The principle distinction between these two habitat~1 is that the proportion of time which a side channel conveys mainstem water is considerably greater than that for side sloughs. Klinger and Trihey (1984)distinguish between side sloughs and side channels based on whether the channel is conveying mainstem water. A given channel is considered a side channel when it is conveying m~linstem water and is considered a side slough when it is not.For· purposes of this discussion,channels will be referred to as sloughs in this sense. The ability of salmon to gain access to spawning areas within sloughs is dependent upon the depth of water within a given reach of the slough.In general,the shallower.the water,the more difficult the passage conditions are for movement of salmon through the reach.The degree of di.fficulty i.s dependent not only upon the absolute depth of the water but also upon the length of the reach which must be traversed.Thus,salmon are able to negotiate very shallow water if the reach is short.However, somewhat greater depths are required if the reaches are longer.Reaches of the slough channels in which the water depths are sufficiently shallow to restrict movement of fish are termed passage reaches.Generally, passage reaches are located in riffle areas within the sloughs.For most sloughs,th.~depth of water through most passage reaches is dependent upon the slough discharge.Slough discharge,in turn,is provided by local surfa,ce runoff and groundwater upwelling.(This disregards the influence of mainstem d"ischarge sufficiently great to overtop the upstream endl of the channel).. For passage rea~hes located near the downstream ends of the sloughs, water depth is influenced not only by discharge from the slough,but also by backwater effects of the mainstem.The backwater effect on the depth of water in a given passage reach is evident when the water surface elevation of the mainstem at that passage reach is greater than that which can be solely attributed to local slough discharge. Studies conducted by ADF&G SuHydro during 1982 (ADF&G 1983a,b)resulted in estimates of the access conditions corresponding to various mainstem discharges amd water surface elevations at a limited number of sloughs. 420972/12 Iifl&OO~&c §OO&@@@ SUSITNA JOINT VENTURE INTRA-OFFICE MEMORANDUM LOCATION Anchorage DATE December 7,1984 TO FROM L.Gilbertson J.Bizer NUMBER 4.3.16/4.3.1.1 Page 3 SUBJECT Interpretation of ADF&G SuHydro Mainstem and Local Flow Values for Successful Passage Conditions .-. Results presented for the 1983 studies (Sautner et ale 1984)expand the number of sloughs and side channels studied and provide ind~pendent estimates elf local flow and mainstem discharges corresponding to threshold ~alues for successful and unsuccessful passage conditions. These resullts have raised several questions regarding the local and mainstem di!lcharges necessary to provide successful passage conditions for chum and sockeye salmon. The results presented by ADF&G SuHydro (Sautner et ale 1984)are the first attempts to show the relationship between mainstem and local flows in providing adequate access conditions to the sloughs and side channel~ for chum and sockeye salmon.Previous reports (ADF&G 1983a,band Trihey 1982)evaluated passage conditions only on the basis of mainstem flow.• In some cases,this led to a relatively low mainstem discharge require- ment since it did not account for local flow contribution to passage depths for salmon access into the sloughs.In other cases,the analyses resulted in high estimates of mainstem discharges required to provide adequate passage conditions for adult salmon~The latest report presents results of independent calculations of flows,either mainstem or local, which provide successful or unsuccessful passage conditions. In understanding these values,it must be kept clearly in mind that mainstem "flows and local flows required to provide successful passage conditions were calculated independently of each other ~In the report (Sautner et ale 1984),the mainstem flow determined to provide successful passage conditions was calculated under the assumption of negligible local flow,likewise,the local flow required to provide the same passage conditions was calculated assuming no direct mainstem backwater infl uence.A similar ra,tionale was used to calculate mainstem and local flows to meet the unsuccessful/successful-with-difficulty threshold criterion.By integrating the mainstem and local flow calculations,a somewhat better appraisal of -passage conditions relative to mainstem -flow becomes apparent. To provide a basis for comparing conditions for a passage reach at various mahlstem discharges,ADFiiG (Sautner et ale 1984)established three passage conditions:unsuccessful,successful with difficulty,'and successful.These correspond to the terms acute,restricted and unre- stricted,respectively,as previously used by ADF&G 0983a,b).The three passage conditions are distinguished by threshold depths within the passage reac:hes.The specific threshold passage depths for the three passage conditions are also dependent upon the length of the passage reach;that is,the threshold depths are greater for long passage reaches 420972/12 OO&OO~&C1 §OOM@@ SUSITNA JOINT VENTURE INTRA-OFFICE MEMORANDUM LOCATION TO FROM Anchorage L.Gilbertson J.Bizer December 7,1984 DATE _ 4.3.16/4.3.1.1 NUMBER Page 4 SUBJECT Interpretation of ADF&G SuHydro Mainstem and Local Flow Values for Successful Passage Conditions than for short passage reaches.Two sets of criteria curves were developed by ADF&G and are presented in the latest report as Figures 6-4 and 6-5 (Saul:ner,et ale 1984).Two curves were developed to account for two differenlt types of passage reaches:uniform channel and non-uniform channel. An explanatil)n of the results obtained for Passage Reaches (PR)I and II at Slough 11 is provided below to demonstrate how these results can be integrated into an analysis of access conditions. In the 1983 ADF&G Reports (1983 a,b),it is estimated that a mainstem- discharge of 6,700 cfs is sufficient to provide successful (unrestricted) access conditions into Slough 11.Results of the 1984 analysis indicate • that mainstem discharges of 16,200 cfs and 33,200 cfs are required to provide suc~::essful passage conditions at Passage Reaches I and II respectively.These results were obtained by determining the streambed elevations lit the highest points of the thalweg profile JJ in the passage reaches,determining the water depths and water surface elevations required to meet the passage criteria,and then determining what mainstem discharge is necessary to provide those water surface ~evations (depths).This portion of the analysis was based upon the assumption of a negligible local flow from the slough itself. For PR I,the critical point in the passage reach (that is,the highest point along the thalweg)is at an elevation of 667.75 ft,mean sea level, (MSL).This is shown on Figure 6-E-7 of the ADF&G report (reprinted here as Figure 1)at approximately Station 3+50.By adding the passage depths which distinguish unsuccessful from successful-with-difficulty and successful-with-difficulty from successful,(0.32 and 0.41'ft,respect- ively)the water surface elevations for unsuccessful and successful conditions are less than El.668.09 and greater than El.668.16, respectively'.(The passage depth requirements are from Curve I,Figure 6-4 and assume a passage reach length of 250 ft).The water surface elevations ~lnd thalweg elevation are depicted in Figure 2 as constants over the range of mainstem discharges. ~I The thalweg elevation is defined as the lowest elevation or the deepest point of a cross-section through a water channel.A thalweg profile is constructed by connecting the deepest points of several cross- sections alemg the length of the channel. 420972/12 IJ:{J£OOl6£CI §OO£®©@ SUSITNA JOINT VENTURE INTRA-OFFICE MEMORANDUM LOCATION Anchorcllge TO 1..Gi Ibertson DATE December 7.1984 NUMBER 4.3.16/4.3.1.1 FROM Page 5 SUBJECT Tnterpretati on of ADF&G SIlHydro Ma jns tem and Local Flow Values for Successful Passage Conditions "...,, By superimposing the stage-discharge relationship from the data obtained from a staff gage located at the mouth of Slough II (ADF&G Gage 135.3W1) (Quane,.et.al 1984),it is possible to determine the mainstem discharges corresponding to unsuccessful and successful passage threshold conditions.The staff gage data are plotted on Figure 2.Based upon this curve along,and assuming no influence of local flow,mainstem discharges less than 15,200 cfs result in unsuccessful (acute)access conditions at PR I and mainstem discharges greater than 16,200 cfs result in.successful (unrestricted)passage conditions. A seco~d superimposition of local flow vs water surface elevation within- PR I onto Figure 2 requires the definition of the relationship between local flow and mainstem flow for values of mainstem discharge less than .. that which will overtop of the upstream berm.This relationship is highly vari.able since the local slough flow is a composite of local surface runoff and groundwater upwelling. A relationship between mainstem discharge and groundwater upwelling has ~ been defined for Slough 11 (Beaver 1984).The relationship is based on discharge data recorded at the R&M recording station in Slough 11 near PR III (Figure 1).Since there is little local runoff into Slough 11 (i,t has a small drainage basin),it was assumed that all local flow was due to groundwal:er upwelling.The relationship between slough groundwater flow (S)and mainstem discharge measured at Gold Creek (G)is: S =1.51+0.000102G (1) ~. For various mainstem dischrges,this equation defines the corresponc;ling groundwater discharge at "the recordig station in Slough 11.At p<?ints further downstream from the recording stat~on,e.g.within PR I,addi- tional loca,l flow is acquired from further groun-dwater upwelling. Woodward-Clyde (1984)estimated that the local flow at PR I is approx- imately 145 percent of the flow calculated at the Recording Stat i,1Q. (This assuml~S a linear increase in slough reach and also assumes the discharge at the'recording station is 100 percent).Therefore,local slo~gh flow at PR I can b~scaled to mainstem discharge by the following equation: 420972/12 S(PR I)=1.45 (1.51 +0.000102G)(2) .- IJ:{]&OO~&CI §[ID&@@@ SUSITNA JOINT VENTUR E INTRA-OFFICE MEMORANDUM LOCATION TO FROM Anchorage L.Gil bert son J.Bizer DATE NUMBER December 7.1984 4.3.16/4.3.1.1 Page 6 SUBJECT Interpretation of ADF&G SuHydro Mainstem and Local Flow values for Successful Passage Conditions Use of Equation 2 mainstem discharge. bottom x-axis scale allows scaling of slough The scaling for PR I in in Figure 2. flow to the corresponding Slough 11 is shown as the .... - J&!l\'!!i'l Based upon field observations and estimates (Sautner et al.1984).the local flows which present unsuccessful and successful passage conditions at PR I in Slough 11 (assuming no mainstem backwater effects)are less than 3 cfs and greater than 4 cfs.respectively.By converting these to mainstem discharges using equation 2.3 cfs corresponds to a mainstem discnarge of 5.480 cfs and 4 cfs corresponds to a mainstem discharge of 12.240 cfs. By plotting these values on Figure 2.where 3 cfs is the unsuccessful threshold criterion (at WSEL 668.07)and 4 cfs is the successful thres- hold criterion (at WSEL 668.16).a relationship between local £lows and mainstem discharges which provide various access conditions is described. Successful access conditions are provided through the groundwater mecnanism when mainstem discharge is greater than 12,200 cfs.In contrast mainstem discnarge provides successful passage conditions through backwater effects alone at PR I only wnen mainstem discharge exceeds 16,000 cfs. A similar analysis for PR II within Slough 11 is presented in Figure 3. In this case the thalweg reference elevation is at EI.670.0 ft MSL and the passage depths corresponding to the unsuccessful and successful threshold criteria are 0.32 and 0.41 from Figure 6-4 (ADF&G 1984)for a passage reach length of 745 ft.The .corresponding water surface eleva- tions are 670.32ft.MSL and 670.41 ft MSL.respectively.The mainstem stage discharge relationship used in Figure 3 is the same as for Figure 2.at Staff Gage 135.3wl.A staff gage is located within PR II. However.the:stage-discharge relationship at the gage is highly influ- enced by slough discnarge and does not define a representative relation- ship between mainstem discnarge and water surface elevation assuming negligible slough flow.For this reason.the stage discharge relation- ship for staff gage 135.3Wl is used.. As derived in the ADF&G Report (Sautner et al.1984)mainstem discharges of 31,900 and 33.200 cfs are required to meet the WSELs corresponding to the unsuccessful and successful passage criteria thresholds.assuming no influence of local flow. The mainstellll discharges required for the respective passage depths via the groundw~lter mechanism are less than those which are required to 420972/12 G{]&OO~&CI ~!ID&®@@ SUSITNA JOINT VENTURE I"'TR.A-OFFICE MEMORANDUM LOCATION Anchorage DATE _D_e_c_e_m_b_e_r_7--<,_1....;.9_8_4 _ TO FROM L.Gilbertson J.Bizel" NUMBER 4.3.16/4.3.1.1 Page 7 SUBJECT Interprl~tation of ADF&G SuHydro Mainstem and Local Flow Values for Successful Passage Conditions provide passage depth via the backwater mechanism.Scaling of slough discharge to mainstem discharge assumes that slough discharge at PR II is 127 percent of the discharge at the recording station (Woodward-Clyde 1984).Therefore,the following equation was used to scale slough discharge (S)to mainstem discharge (G): S (PR II)=1.27 (1.51 ~0.000102G)(3) poII!liIU, Local flows at the unsuccessful and successful passage condition thres-- holds are elitimated to be 3 and 4 cfs J respectively (Sautner et al. 1984).Thes:e local groundwater flows correspond to mainstem discharges • of 8,350 and 16,075 cfs,respectively. A somewhat different relationship between groundwater upwelling in slough discharge and mainstem discharge is presented by Woodward Clyde (1984). The equation presented by Woodward-Clyde for Slough 11 is more conser- vative and includes data collected during the summer of 1984.The equations us.~d by Woodward-Clyde forPR I and PR 11 in Slough II are: S =1.45 (1.43 +.000087G) S =1.27 (1.43 +.000087G) for PR I for PR II (4) (5 ) The corresponding mainstem flows for 3 and 4 cfs flows through PR I and PR II ar~: Passage Conditions Unsuccesful Successful PR I PR II LOI::al Discharge Mainstem Discharge LOI::al Discharge Mainstem Disc):large <3 cfs <7340 cfs <3 cfs <10715 cfs· >4 cfs >15270 cfs >4 cfs >19765 The above allalyses and comparisons for PRs I and II in Slough 11 are summarized in Table 1.It is evident that passage conditions are dependent on mainstem discharge in one of two ways:directly as a function of the backwater effect and indirectly as a function of mainstem discharge influence on the rate of groundwater upwelling.From the information presented in Table 1,it is concluded that successful passage conditions are present at PR I when mainstem discharge is 12,240 cfs or greater.Similarly,it is concl uded that successful passage conditions 420972/12 ""'", [}{]£OO~£C1~[ID£~©@ SUSITNA JOINT VENTURE INTRA-OFFIICE MEMORANDUM LOCATION TO FROM Anchorage L.Gilbertson Jo Bizer DATE _D_e_c_e_m_b_e_r_7---<...,_1_9_8_4-'--_ NUMBER _4_0_3~0_1_6,;.../4_._3_0_1_0_1 _ Page 8 SUBJECT Interpretation of ADF&G SuHydro Mainstem and Local Flow Values for Successful Passage Conditions ..... - are present at PR II when mainstem discharge is 16,075 cfs 0 In both cases presen,ted above,the influence of mainstem discharge in providing successful conditions is via the groundwater mechanism.In other passage reaches in other sloughs,the influence of the mainstem via the backwater mechanism may be predominant 0 This determination of mainstem discharges required for each passage reach would provide a more comprehensive evaluation of effects of the project on adult salmon passage'into spawning areas. hg cc:E.Marchegiani,APA J 0 Thrall,HE 420972/12 • ..... - -- References Cited Alaska Department of Fish and Game.1983a.Susitna Hydro Aquatic Studies Phase II Basic Data Report Volume 4:Aquatic habitat and instream flow studies,1982.Prepared for Alaska Power Authori ty,Anchorage I Alaska" Alaska Department of Fish and Game.1983b.Susitna Hydro Aquatic Studies Phase II Report:synopsis of the 1982 aquatic studies and analysis of fish and habitat relationships Appendix B:Timing and passage of adult sialmon in the mainstem Susitna River and access into selected sioughsi upstream of the Chulitna River confluence.Prepared for Alaska Power Authori ty,Anchorage,Alaska. Barrett,B.~l.,F.M.Thompson,and S.N.Wick.1984.Report No.1:Adult AnadrOOlous Fish Investigations (May-October 1983).Alaska Department of Fish and Game Susitna Hydroelectric Project Aquatic Studies Team. PreparE!d for Alaska Power Authority,Anchorage,Alaska. Beaver,D.1984.Slough discharge regression equations.Memorandum to E.J.GE~perline,Harza-Ebasco Susitna Joint Venture.Dated October 12,1984. Klinger,S.and E.W.Trihey.1984.Response to aquatic habitat surface areas 1:0 mainstem discharges in the Talkeetna to Devil Canyon reach of the Susitna River,Alaska.E.W.Trihey and Associates.Prepared under contract to Harza-Ebasco Susitna Joint Venture.Prepared for Alaska Power Authority,Anchorage,Alaska. Quane,T.,P.Morrow and T.Withrow.1984.Chapter 1:Stage and discharge investigations.In:Report No.3:Aquatic Habitat and Instream Flow Investigations (May-October 1983),C.C.Esten and D.S.Vincent-Lang, eds.Alaska Department of Fish and Game Susitna Hydroelectric Project Aquatic Studies Team.Prepared for Alaskas Power Authority, Anchorilge,Alaska. Sautner,J.8.,L.J.Vining and L.A.Rundquist.1984.Chapter 6:An evaluation of passage conditions for adult salmon in sloughs and side channelS of the middle Susitna River.In Report No.3:Aquatic Habitat and Instream Flow Investigations (May-October 1983),C.C. Esten lind D.S.Vincent-Larry,eds.Prepared by Alaska Department of Fish and Game Susitna Hydroelectric Project Aquatic Studies Team. Preparli!d for Alaska Power Authority,Anchorage,Alaska. Trihey,E.W.1982~Preliminary assessment of access by spawning salmon to side slough·habitat above Talkeetna.Prepared for Acres American, Inc.,Anchorage,Alaska. Woodward-Clyde Consultants.1984.Susitna Hydroelectric Project:Fish mitigaltion plan.Submitted to Harza-Ebasco Susitna Joint Venture. Preparli!d for Alaska Power Authority,Anchorage,Alaska. 420972/REF 1 ~.-j J 1 ~I 1 J ] Table 1 I i j ]I 1 J 11~ Susitna Hydroelectric Project Summary of Mainstem Discharge Relationships to Slough 11 Passage Conditions Threshold Threshold Threshold Threshold Passage Water Mainstem Discharge Local Flow Mainstem Discharge Passage Depth Thalweg Surface Corresponding to Corresponding Corresponding to Reach Threshold Criteria Elevation Elevation WSEL via Backwater to WSEL WSEL via Local flow (Equations 2 and 3) (ft )(ft MSL)(ft MSL)(cfs)(cfs)(cfs) I Unsuccessful 0.32 667.75 668.07 15,200 3 5,480 I Successful 0.41 667.75 668.16 16,200 4 12,240 II Unsuccessful 0.32 670.00 670.32 31,900 3 8,350 II Successful 0.41 670.00 670.41 33,200 4 16,075 • 420972/12 • --- l""'- I ~ I I,Q a.ls.. ~ C'l.... ~ -•=8 _..:z2 ~c ~8 .. i =: 2c 161 8 =..lit !! 8 Q... 8i III fl-----'n J:I•.. ~.... 0• 0 .. Ci .... ~§ fu ~ I ~"......2...- o~0 ..e'•'"e 0 .. 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