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Home My WebLink AboutSUS518SUSITNA HYDROELECTRIC PROJECT FEDERAL ENERGY REGULATORY COMMISSION PROJECT NUMBER 711" GLACIAL LAKE PHYSICAL LIMNOLOGY STUDIES: ' EKLUTNA LAKE, ALASKA VOLUME 1 MAIN REPORT PREPARED BY: ~~-------------- R&M CONSULTANTS, INC . •••••••• ••OLo•••~ MYO•CM.aateT• .u•v•vo•e ANCHORAGE, ALASKA UNDER CONTRACT TO : ')USITNA JOIN T VENT0RE ANCHORAGE, ALASKA DRAFT REPORT JUNE 1985 DOCUMENT NO • .____ALASKA POWER AUTHORITY_----J R~-l /5 1 Document No. ALASKA POWER AUTHORITY SUSITNA HYDROELECTRIC PROJECT Federal Energy Regulatory Commission Project Number 7114 GLACIAL LAKE PHYSICAL LIMNOLOGY STUDIES: EKLUTNA LAKE, ALASKA VOLUME 1 -MAIN REPORT J UN E 1935 DRAFT REPORT Prepared By : R&M Consultants , Inc . Anchor·a g e, Alaska Under Contr·act To : Harza-Ebasco Susitna Joint Venture An c horage , Alaska R~-1 /~ 2 GLACIAL LAKE PHYSICAL LIM NOLOGY STL.:DIES S US ITNA H YDR OELECTRIC PROJECT List of Ta b les List of Figures List of Ph o tos Acknowledgments TABLE OF CONTENTS VOLUME 1 1.0 EXECUTIVE SUMMARY 1 .1 Purpose and Scope 1 . 2 Equipment and Method s 1.3 Summary o f Re s ults 2. 0 SCOPE OF STUDY 2.1 Purpose Page Ill vi xi XII 1 -1 1 -2 1-4 2 -1 2 .~ Summary o f Pr ·ev i o u s Studies and Availab l e Data 2-2 2 .3 Report Format 2-3 3.0 METEOROLOGICAL STATION AND WEATHER MONITORING 3. 1 Meth o dology 3 .~ Results and Discussi o n 4.0 LAKE INFLOW -EKLUTNA RIVER 4. 1 Methodology 4 . ~ Results and Discussion ~.0 LIMNOLOGY OF EKLUTNA LAKE 5.1 Methodology 5 . 2 Results and Discussion 6.0 LAKE OUTFLOW 6 . 1 Methodology G. 2 Results and Discussion 7.0 RIVER-LAKE SYSTEM RELATIONSHIPS 8.0 REFERENCES 3-1 3-2 4 -1 4 -3 5-1 5-5 G-1 6-4 7-1 8-1 R24 /5 4 Table 7 . 1 B . 1 B .2 B .3 B .4 B .5 B .6 B. 7 B .8 B .9 B. 10 B . 11 B . 12 B . 13 B . 14 B . 15 B . 16 B. 17 B . 18 B . 19 B .20 B .21 B .22 B .23 B .24 B .25 GLACIAL LAKE PHYSICAL LIMNOLOGY STUDIES SUSITNA HYDROELECTRIC PROJECT LIST OF TABLES Description VOLUME 1 Compar·ison of Eklutna Lake Infl ow and Outflow, Water Year 1984 VOLUME 2 Eklutna Lake Weather· Summary -December, 1932 Eklutna Lake Weather Summary -January , 1983 Eklutna Lake Weather Summary -Febr·uar·y, 1983 Eklutna Lake Weather Summar·y -March, 1983 Eklutna Lake Weather Summar·y -Apr·il, 1983 Eklutna Lake Weather Surnmar·y -May, 1983 Eklutna Lake Weather Summary -June , 1983 Eklutna Lake Weather Summary -July , 1983 Eklutna Lake Weather Summary -August , 1983 Eklutna Lake Weather Summary -September, 1983 Eklutna Lake Weather Summary -Octo ber, 1983 Eklutna Lake We a ther Summary -November, 1983 Eklutna Lake Weather Summary -December, 1983 Eklutna Lake Weather Summar·y -January, 1984 ~ klutna Lake Weather Summary -February, i984 Eklutna Lake Weather Summary -March, 1984 Eklutna Lake Weather Summary -April, 1984 Eklutna Lake Weather Summary -Ma y, 1984 Eklutna Lake Weather Summary -June, 1984 Eklutna Lake Weather Summary -July, 1984 Eklutna Lake Weather Summar·y -August, 1984 Eklutna Lake Weather Summary -September, 1984 Eklutna Lake Weather Summar·y -October, 1984 Eklutna Lake Weather Summary -November, 1984 Eklutna Lake Weather Summary -December, 1984 iii Page 7 -4 R24 /S 3 Appendix A Appendix B Appendix C Appendix D Appendix E Appendix F Appendix G Appendix H Appendix Appendix J Appendix K Appendix L Appendix M Appendix N Appendix 0 TABLE OF CONTENTS (Continued) VOLUME 2 Summary of Data Collect e d 1n Eklutna Lake Weath e r Data Summaries Ice Obser·vations and Fi e ld Wea ther Obser·vations Inflow Water Quality Data -East For·k and Glacier Fork, July 1984 Inflow Quantity DaL: -East Fork and Glacier For·k Par·ticle-Size Distributions -East Fork, Glacier Fork , and Tailrace (1934) Lake Pr·ofiling Data (Januar·y 1983 - November· 1934) Lake Ternperatur·e ls o pleths Eklutna Lake Light Pe netration M ea su rernents Eklutna Lake Tur·bidity and Light Transmission (Au g ust 1 6-20' 1984) Monthly Sumrnar·i e s o f Field Ob se rv a tions Outflow Wat e r Quality D a ta -Powe rplant Tailr·ace, July 1934 Data fr·orn Eklutna Wat e r Pr·oject DYRESM Input Data N. 1 Eklutna Lake Physical Data N. 2 We ather Data N .3 Wind Speed Data N. 4 Inflow Data N. 5 Outflow Data N . 6 Inflow Sediment Data Sediment Analy~:es by Par·ticle Data Laboratories, Ltd. ii Page A-1 B-1 C-1 D-1 E -1 F -1 G-1 H-1 1-1 J -1 K-1 L -1 M-1 N-1 0-1 R2-l /5 4 Tab le 7. 1 GLACIAL LAKE PHY S ICAL LIMNOLOG Y S TUDIES SUSI T NA H Y DROELECTRIC PROJECT LIST OF TA BLES Descript ion VOLUME 1 Comparison of Ek l u t na Lake I nf low a n d Outflow, \Va t er Year· 1984 VOLU ME 2 B .1 Ek l utna Lake \\l e at h er Summa r·y -December, 1982 B. 2 Ek l utna Lake Weather Summar·y -January, 1983 B.3 B .4 B.5 B .6 B . 7 Ek lu tna Ek l utna Ek l utna Ek l utna Eklutna Lake \\feathe r· Summa r·y -Feb r·ua r y, 1983 Lake We at h er Summa r·y -Ma r ch, 1983 Lake \\lea th er Summa r·y -Apri l , 1983 Lake \Veather· Surnma r·y -May, 1983 Lake \veather Summary -June , 1983 B.8 Ek l utna Lake \Veather Summary -July, 1983 B . 9 Ek l utna Lake Weather Summary -Aug u s t , 1983 B.lO Ek l utna Lake Weat h er· Summa r·y -Sep t ember, 1983 B.11 Ek l utna Lake \veather Summary -October·, 1983 B .12 Eklutna Lake \\leather Summary -November, 1933 B. 13 Eklutna Lake We a th e r Summary -December·, 1933 B. 14 Eklutna Lake \\l e ather Sumrna t·y -January , 1984 B .15 Ek l utna Lake \\leather Summary -Febr·uar·y, 1984 B .1G Ek l utna Lake v.:e ather Summary -Marc h , 1984 B. 17 B . 18 B . 19 B . 20 B . 21 B.22 B.23 El :l utna E klutna Eklutna Eklutna Eklu t na Ek l utna Ek l utna Lake We ather Summary -April, 1984 Lake \\l e ather Summary -May, 1984 Lake We ather Summary -June , 1984 Lake Weather· Summary -July , 1984 Lake \\leather Summar·y -August , 1984 Lake Weather Summary -S e ptember , 1984 Lake Weather Summary - O c tober , 1984 a . 24 Ek l utna Lake \\leat h er Summa ry -No vember , 1984 8.25 Eklutna Lake Weather Summary -De cember, 1984 iii P a g e 7 -4 R2 ·1/5 5 LIST OF TABLES (cont.) Table Description C .1 Summary of 1983-1984 Ice Conditions C . 2 Summary of Field Weather· Observations D .1 Summary of East Fork Water Quality Data (1984) D.2 Summary of Glacier· Fork Water· Quality Data (1984) E.1 1983 East Fork Mean Daily Dischar·ge E. 2 1984 East Fork Mean Daily Discharge E.3 1983 Glacier· Fork Mean Daily Discharge E. 4 1984 Glacier Fork Mean Daily Dischar·ge E .5 Eklutna Lake Inflow Dischar·ge Measur·ements F. 1 Particle-Size Distr·ibutions -East For·k (July 20, 1984) F. 2 Particle-Size Distributions -East Fork (August 28, 1984) F .3 Particle-Size Distributions -East For·k (October 23, 1984) F .4 Particle-Size Distributions -Glacier Fork ( J u I y 20, 1984) F . 5 Particle-Size Distr·ibutions -Glacier For·k (August 28, 198 -1) F . 6 Particle-Size Distr·ibutions -Glacier· Fork (October 23, 1984) F. 7 Par·ticle-Size Distributions -Tailr·ace (July 20 , 1984) F .8 Particle-Size Distributions -Ta i lrace ( August 28, 1984) F. 9 Particle-Size Distributions -Tailrace (October· 23, 1984) I. 1 Eklutna Lake Light Penetration In -Situ Measurements ( 1983-84) 1.2 Eklutna Lake Secchi Disk Measurements (1983-84) iv Page R24 /~ 6 LIST OF TABLES (cont.) Table Description Page K. 1 Monthly Summar·y of Field Observations -March 1984 K . 2 Monthly Summar·y of Field Obser·vations -Apr·il 1934 K .3 Monthly Summary of Field Observations -May 1984 K .4 Monthly Summar·y of Field Obser·vations -June 1984 K. 5 Monthly Summary of Field Obser·vations -July 1984 K .6 Monthly Summar·y of Field Observations -August 1984 K. 7 Monthly Summar·y of Field Observations - September 1984 K.8 Mo nthly Summary of Field Obser·vations -October 1984 K.9 Monthly Summary of Field Observations - November 1984 L.1 Summary of Tailrace Water· Quality Data (1984) M .l Raw \Vater· Analyses (Eklutna Water Project) M.2 Total Suspended Solids Measurements ( Eklutn a Water Pr·oject) N . 1 N .2 N .3 N .4 N.5 N.6 DYRESM Input DYRESM I !lput DYRESM Input D Y RESM Input DYRESM Input DYRESM Input File -Ekl utna Lake Physical Data File -Weather Data File -Wind Speed Data File -Lake Inflow Data File -Lake Outflow Data File -Inflow Sediment Data 0.1 Particle Data Laborator·ies Analyses on Eklutn2 Lake Suspended -Sediment Samples (1983 -84) v R24 /5 7 Figure 2 . 1 3 .1 3.2 3 .3 3 .4 4.1 4 .2 4 .3 4 .4 4.5 4.G GLACIAL LAKE PHYSICAL LIMNOLOGY STUDIES SUSITNA HYDROELECTRIC PROJECT LIST OF FIGURES Description VOLUME 1 Eklutna Lake Location Map Eklutna Lake Station Locati ons Site Sketch -Eklutna Lake Climate Station Seq uential Plot of Climatic Data , Eklutna Lake Sta tion, December 198 2 -September 1983 Sequential Plot of Climatic Data, Eklutna Lake Station, October· 1983 -December· 1984 1983 Inflow Data (Flow, Total Suspended Soilds, Tur-bidity, Temper·atur·e) -Eas t Fork 1983 Inflow Data -(Flow , Total Suspended S oi lds , Tur-bidity, T empera tur·e ) Glacier For·k 1984 Inflow Data -(Flo w, T o tal Suspended S o ilds, Turbidity, Temper·atu re) East For·k 1984 Inflo w Data -(F low, Total Suspended Soilds, T ur·bidity, Temper·ature) Glacier· Fo r·k 1984 East Fork Data: T o t a l Suspe nded Solids vs . I n stantaneo u s Flow 1984 Glacier Fork Data: Total Suspended S o lids vs . Instantan eo us Flow Page 2 -4 3 -5 3-6 3-7 3-8 4-7 4-8 4-9 4 -10 4-11 4-12 4. 7 1984 East Fork Data : Tur·bidity vs . Total Suspended 4-13 4 .8 4 .9 4 .10 Solids 1984 G lacier For·k Data: Tur·bidity vs . Total Suspended Solids Suspended Sed im en t Pa r·ticle-Size Distributions -East Fork, 1984 Suspended Sedime nt Par·ti c le-Size Di stribu tions -G lac ier Fork, 1984 vi 4 -14 4-15 4 -16 R24 /5 8 Figure 4.11 4 .12 4.13 4. 14 5.1 5.2 5.3 5 .4 5.5 5 .6 5 .7 5.8 LIST OF FIGURES (Continued) Description Diurnal Var·iation of Dischar·ge, Total Suspended Solids, Turbidity, and \Vater Temper·atu r·e -East Fork Following Cloudy Per·iod Diurnal Variation of Disch ar·ge , Total Suspended Solids, Tur·bidity, and Water Temper - ature -East Fork Following Sunny Per·iod Diurnal Variation of Dischar·ge, Total Suspended Solids, Turbrdity, and Water Temper- ature-Glacier Fork Following Cloudy Period Diurnal Variation of Discharge , Total Suspended Solids, Tur·bidity , and \Vater Ternperatur·e- Glacier Fork Following Sunny Per·iod lsother·m Depth v s. Time-Eklutna Lake at Station 9 , 1982 lsother·m Depth vs. Time -Eklutna Lake at Station 9, 1983 Isoth erm Depth vs . Time -Eklutna Lake at Station 9, 1984 Comparison of Station 9 Lake Ternperatur·es with Page 4-17 4 -18 4-19 4-20 5-11 5-12 5-13 5 -14 Windspeed, Direction and Air· Temper·ature -September 11-18 , 1982 Comparison of Station 9 Lake T e mperatur·es with Windspeed, Dir·ection and Air· Temper·atur·e- August 2-9, 1983 Comparison of Station 9 Lake Temperatur·es with \Vindspeed, Direction and Air Temperature - August 16-23 , 1984 !so-T urbidity vs . Time -Eklutna Lake at Station 9, 1982 !so-Turbidity vs . Time -Eklutna Lake at Sta tion 9, 1983 vii 5-15 5-16 5-17 5-18 R2-V5 9 Figure 5.9 5. 10 5 .11 5 .12 5. 13 5.14 LIST OF FIGURES (Continued) Description I so-Turbidity vs. Time -Eklutna Lake at Station 9, 1984 1982 Ek lutna Lake Sur·face Data: Extinction Coefficient and Secchi Disk Depth at Station 9 1983 Eklutna Lake Sur·face Data: Extinction Coefficient and Secchi Disk Depth at Station 9 1984 Eklutna Lake Sur·face Oata : Extinction Coefficient and Secchi Di5.k Depth at Station 9 E klutna Lake Su r·face Data: Secchi Depth vs . Extinction Coefficient Eklutna Lake Sur·face Data: Turbidity vs . Extinction Coefficient Page 5-19 5-20 5-21 5-22 5-23 5-24 5.15 Eklutna Lake Sur·face Data: Light Tr·ansmission vs. 5 -25 Extinction Coeff ;cient 5 .16 Eklutna Lake Sur·face Data : Secchi Depth vs. 5-26 Turbidity 5 .17 6 .1 6.2 6 .3 6 .4 7.1 7.2 Eklutna Lake Data : Tur·bidity vs . Total Suspended Solids Schematic Plan and Pr·o file o f Eklutna Project Featur·es 1984 Tailr·ace Data (Total Suspended Solids , Tur·bidity, Secchi, Temper·atur·e) 1984 Tailr·ace Data : Tur·bidity vs . Total Suspended Solids Suspended Sediment Particle-Size Distributions -Tailrace 1984 Eklutna Stream -Lake System Data : Tur·bidity 1984 Eklutna Stream-Lake System Data : Total Suspended Solids viii 5-27 6 -8 6 -9 6 -10 6 -11 7- 7- R2-t /5 10 LIST OF FIGURES (Continued) Figure Description 7.3 1984 Eklutna Stream-Lake System Data: Water Temperature VOLUME 2 B. 1 Eklutna Lake Weather Plot -December, 1982 B. 2 Eklutna Lake Weather Plot -Januar·y, 1983 B .3 Eklutna Lake Weather Plot -Febr·uar·y, 1983 B. 4 Eklutna Lake Weather Plot -Mar·ch, 1933 B.5 Eklutna Lake Weather Plot -Apr·il, 1983 B.G Eklutna Lake Weather Plot-May. 1983 B. 7 Eklutna Lake Weather Plot -June, 1983 B . 8 Eklutna Lake Weather Plot -July, 1933 B. 9 Eklutna Lake Weather Plot -August, 1933 B . 10 Eklutna Lake Weather Plot -September, 1983 B . 11 Eklutna Lake Wea ther Plot -October , 19 83 B . 12 Eklutna Lake Weather· Plot -Nov e mber, 1983 B.13 Eklutna Lake Wea ther Plot -December·, 1983 B. 1-t Eklutna Lake Weather· Plot -Januar·y, 1934 B .15 Eklutna Lake Weather· Plot -Febr·uary, 1984 B.1G Eklutna Lake Weather Plot -Mar·ch, 1984 B.17 Eklutna Lake \'leather· P lot -April, 1984 B. 18 Eklutna Lake \'leather Plot -May, 1984 B .19 Eklutna Lake Weather· Plot-June, 1984 B . 20 Eklutna Lake Weather Plot -July, 1934 B . 21 Eklutna Lake Weather Plot -August, 1984 B.22 B .23 B .24 8.25 Eklutna Eklutna Eklutna Eklutna Lake Weather Lake Weather Lake Weather Lake Weather Plot -September, 1984 Plot -October, 1984 Plot -November, 1984 P lot -December, 1984 E.1 Stage -Dischar·ge Rating Cur·ve, East Fork ix Page 7-;·· R2 -l/:J 11 Figure E.2 H. 1 H. 2 H .3 H.4 H .5 H.6 H. 7 H .8 H .9 H . 10 H . 11 H. 12 H . 13 LIST OF FIGURES (Continued) Description Stage -Dischar·ge Rating Curve, Glacier Fork Eklutna L.:~ke Temperature Pr·ofile, June 2, 19 33 Eklutna Lake Temperature Pr·ofile , July, 6, 1983 Eklutna Lake Temperatu re Pr·o f ile, August, 3, 1933 Eklutna Lake T emperature Pr·ofile, September 7, 1983 Eklutna Lake Temp era ture Pr·ofile, October 5, 1983 Eklutna Lake Temp e rature Pr·ofile , November· 1, 1983 Eklutna Lake Temper·a ture Profile, t\larch 23, 198-l Eklutna Lake Ternper·atur·e Profile, June 6, 1984 Eklutna Lake Temper·a tur·e Profile, June 21, 1984 Eklutna Lake Tcrnperatur·e Pr·ofile, July 5 , 1984 Eklutna Lake T crnpe r·atur·e Profile, July 19, 1984 Eklutna La ke Temperature Pr·ofile, August 3 , 198-l Eklutna Lake Temper·ature Pr·of il e, August 16 -20, 19 8-l H .1-l Eklutna L ake T emper·a ture Pr·ofile , September 3 , 198-l H.15 Eklutna Lake Temper·ature Pr·ofile, Scpteml>er 17 , 1984 H.16 H . 17 H . 18 H . 19 H . 20 J . 1 J .2 M . 1 Eklutna Lake Ternpe r·ature Pr·o file , O c t obe r· 1 , 1984 Ek lutna Lake T e mper·a ture Profile , October 15, 1984 Eklutna Lake Tempe r·ature P r·ofile , October 29, 19 8 4 Eklutna L ake Temper·aturc Pr·ofile , November· 12 , 198-l Eklutna Lake Tem pe rature Pr·ofile, N ovember 26, 1984 Ek lutna Lake Turbidity Pr·of ile, August 16 -20, 1984 Eklutna Lak e Light Tran s mission Profile, August 16 -20' 1984 Raw \Vat er Tur·b idity a n d Ternperatur·e (Eklutna Wa t e r· Pr·o j ec t) Page R2-t /5 11 . 1 LIST OF FIGURES (Continued) Figure Description M.2 Raw \Vater Particle -Size Distr·ibutions (Eklutna \Vater Pr·oject, May and June, 1983) M .3 Raw Water· Pa rticle-Si ze Dist ributio ns (Eklutna Water· Pr·oject, S E-p tember and Octo ber, 1983) ~.4 Lo gar·i thmic Particle -Size Distr·ibutions (Eklutna Water Pr·oject) M .5 Probability Plots of Total Suspended Solids Data ( Eklutna \Va ter Project) M.G Raw Water· Tur·bidity vs. Total Suspended Solids ( Eklutna Water Pr ·oject) xi Page R2-t/~ 12 Photo 3 .1 3.2 3 .3 3 .4 6 .1 GLACIAL LAKE PHYSICAL LIMNOLOGY SUDIES SUSITNA HYDROELECTRIC PROJECT LIST OF PHOTOS Description VOLUME 1 Eklutna Lake Climate Station S ite , Looking NW toward Eklutna Lake Eklutna Lake Climate Station Site, Look i ng SE towar·d Upper· Basin Sensor Arr·ay and Solar· Panel, Eklutna Lake Climate Station Auxiliary Sensor· Platfor·m, Eklu tn a Lake Climate Station Eklutna Hydr·oelectric Pr·ojcct T a ilr·ac e, Lookin g Upstream at Concr·ete Outlet Port S t r·uctu r·e (\Vi n t e r·) VOLUME 2 M. 1 Tr·ansmission Electro n Micr·ograph Photos of Raw Water Particl es ( Ekl utn a Water Project) M. 2 Scanning Electr·on Micrograph Photos of Raw Water Particles (Eklutna \Vater Pr·oject) )( i i Page 3-9 3-9 3-10 3-10 G-12 R24 /5 13 ACKNOWLEDGMENTS Field instrumentation was installed and oper·ated at Eklutna Lake by per- mission of the State of Alaska, Division of Parks, Chugach Division. The cooperation and assistance of the Chugach State Park r·anger·s is gr·atefully acknowledged . Lake outflow data were provided by Stan Sieczkowski of the Eklutna Pr·oject, Alaska Power Administr·ation. Transmissivity data were obtained on two of the 1984 lake trips with a transmissorneter loaned fr·orn the Institute of Marine Science, Univer·sity of Alaska, Fairbanks, with special assistance fr·om Gil Mimkin. Suspe nded sediment analyses wer·e per·for·med by Chemical a :1d Geological Labor·atories of Alaska, Inc ., in Anchorage and Particle Data Labor·atories, Inc., of Elrnhu r·st, Illinois . Special technical assistance throughout the pr·oject was provided by Dr·s. Tom Stuart and C . Y . Wei of Har·za -Ebasco Susitna Joint Ventur·e. Field data collection since 1982 was per·forrned by the hydrology staff of R&M Consultants . Br·ett Jokela and Bill Ashton coor·dinated the field pr·ogram and data compilation. Jeff Coffin was responsible for overall coor·dination and is the principal author of this r·eport. xiii R24 /~ 14 1 .0 EXECUTIVE SUMMARY 1.1 Purpose and Scope Numerical modelling of the Watana and Devil Canyon Reservoir·s in the Susitna Hydr·oelectr·ic Pr·oject was under·taken to r·efine estimates of the water t e mper·atu re, tur·bidity, and suspended sediment levels to be expected within state-of-the-art , the reservoirs one-dimensio nal and in DYRESM the river downstream. The (Dynamic Re servoir Simulation Model) computer model was sel e cted to simulate the two reser·voirs in the glacier·-fed Susitna River . Successful application of the model required calibration on an existing glacial lake system . Eklutna Lake, near Anchor·age, was chosen as the calibr·ation lake because of its hydr·aulic and morphologic similar·ities to Watana Reservoir. Both lakes have similar percentages of their drainage areas c o ver·ed by glaciers (5 . 2 and 5 . 9°o ), both have similar average r·esidence times w ithin the lake (1 . 77 and 1 .65 years), both have similar climatological conditions, and both are r·eservoirs operated or to be o perated for hydr·oe le ctr·ic power pro duction. For temper·ature modelling of Eklutna Lake, continuous data were required on inflow volume and t e mper·ature , o utflow v o lume and temperature, and on measur·ements of e nergy tr·ansferr·ed to and fr·om the lake . Sediment modelling requir·ed the same ther·mal d a ta to account for the mixing a nd circulation pr·oces s es with i n the l a ke. Sediment inflow and outflow quantities were required as well . Per·iodic profiles and samples were taken at selected stations in the lake to be used in the model verification and to docume nt the la ke's mixing en vi r·onment and sediment dynamics . Supplementary data were collected at the same time to define light penetration rel a tionships in the inflow str·eams and in the lake. The collection of continuous data began in June 1982 and proc.eeded until December 1984 . The 1982 data wer·e summarized in an interim report ( R&M Consultants 1982a); the cunent repor·t presents the 1983 and 1984 Eklutna Lake data . 1 -1 R24/5 15 The data collection program was designed to provide inp ut data for the D Y RESM model, to provide lake data for verification of the model, and to pr·ovide infor·mation on the lake processes which affect the internal and outflow temper·atur·e and sediment characteristics . The methods summarized below were used to document the meteorologic inputs; the water· discharge, sediment discharge, and temperature of the lake inflow str·eam; the temper·at ure and suspended-sediment patterns in the lake; and the water discharge, sediment discharge, and temperat ure of the lake outflow . 1 .2 Equipment and Methods Meteor·ologic data were measur·ed by a Weather \Vizard (a digital recor·ding weather station) which was loc a ted on the brush -covered floodplain at the head of the lake. Instantaneo us values wer·e recorded every 15 or 30 minutes for air temper·atur·e , r·e lative humidit y, solar· r·adiation intensity, and longwave radiation intensity . Curnulntive precipitation was measured and r·ecorded at the same time inter·vals. Aver·age wind speed and wind direction and peak wind gust observed over the preceding 15 o r· 30 minutes were also r·epor·ted . Data wer·e r eco r·ded onto magnet ic cassette tapes , which were r·ep lac ed once per month dur·ing inspection /maintenance visits. The cassettes were computer -p r·ocessed and summarized on a monthly basis by a hydr·ologist . The Eklutna Lake inflow enter·s the lake at one poin t at its southeast e nd . However, two primary tributaries comb i ne to form the Eklutna River a short distance upstream . Each str·eam was gaged and sampled separately because of the lack of satisfactor·y access and gaging sites downstream of their confluence . One tributary dischar·ges from Eklutna Glacier and was designated Glacier Fork; the o ther was called East Fork. A stilling well , float, and str·ip -char·t water level r·ecor·der were installed on each cr·eek and operated thr·ough the o pen -water· seasons (May -October) of 1982 -84 . Ryan thermographs were a ls o operated in the streams conc urrently , so continuous records were obtained of the water le vels and water temperature. Per·iodic discharge meas ure me nts were made to d e ter·mine 1 -2 R2-t /5 1 G stage-discharge r e lationships . The di s charges and temperatures wer·e reporte d as mean daily values for DY RESM input. Occasionally in 1932 and frequently 1n 1984 , depth -integrated water s a mples were c olle cted at the East Fork and Glacier Fo rk gaging stations and analyzed for tu r·bidity and t o tal suspended solids ( TSS) conce ntration . Fi e ld measur·e me nts of conductivity and Secchi disk d e pth were a lso made on thes e trips . Sampling in 1984 was done twice per week at each site fr·om ear·ly June thr·ough f r·eeze-up (about mid -Nov e mber). Add;tional suspende d sed ime nt samples were taken in July, August, and October and analyz e d f o r pa r ticle -size d i str·ibution by Particle Data Laboratories in Chicago . The s a m p ling prog r·am in the lake consisted of monthly trips in 1983 and bi-weekly tr·ip s in 198 2 and 193 4 . Sediment and tu r·bidity measurements were also made in 193 2 and 1984 . Temper·ature-profiling was conducted with a Martek ~lark VIII Wa ter Quality Monitor by lowering a sensor to depth and r·eco r d ing fr ·om a digit a l r·ecorder. Conductivity was also r·ecorded using the same instrument on most occasions. Sampling for· turbid i ty and TSS w a s perfor·med by low e ring a brass Kemmer·er sampler to the desire d depth , c ap tur·ing the s a m p le , and r·eturn ing it to the surface. Determina tions w e re then made of tur·bidity by R&M in the office and of TSS conce ntr·ati o n by Ch e mical a nd G eo lo gical Labora tor·ies of Alaska, Inc . in Anch o r·age. In mid -1934 , a turbidimeter was u s ed which permitted flow -thr·ough operation . The sampling procedure was then amended by pumping samples fro m the desir·ed depth and either into the turbidimeter for· a nal y sis or into a sample b o ttle for subsequent TSS ..1 nalysis . Light penetr·ation me asur·e rn e nts wer·e a lso made using a quantum sensor and a Secchi disk . Lake sampling was done at up to 15 diffe rent stations on the lake . An infl a table boat was used during the open-wate r seasons, and winter sampling was done tlu·ough the ice. 1 -3 R2.t /5 17 Measuremtnts of lake outflow volume and temperatur·es on a daily basis wer·e pr·ovided by personnel of the Eklutna Hydroelectric Project, Aiaska Power Administration, from r·o utine recor·ds kept for the hydr·oelectric plant operation. Lake levels were surveyed weekly by Eklutna Pr·oject operators and then starting in 1983 were recorded continuously by the U.S. Geological Sur·vey . Sampling of the outflow in the tailrace was undertaken in 1984 to define the suspended sediment being dischar·ged fr·om Eklutna Lake . Samples were taken twice per week on the same dates the inflow streams were sampled . Determinations wer·e made of turbidity, TSS concentr·ation, conductivity, and Secchi disk depth. 1 .3 Summary of Results Observed lake temper·atures r·anged from a high of about 15°C at the sudace in mid-summer· to 0°C just below the ice layer dur·ing the winter . Outflow temperatures r·anged between 3 and 13°C, remaining very close to 4°C throughout the ice-cove r·ed season . The lake experienced overturn twice a year: in May after breakup and in September or October· prior to fr·eeze-up. Sever·al instances were noted where temper·ature fluctuations in the outflow or in the center of the lake (Station 9) could be linked to major· wind events experienced at the lake. The inflow str·eam 's presence as a colder, mor·e tur·bid plume in the lake was detected at varying depths on differ·ent dates , depending on its temper·ature compar·ed to the lake 's . It was occasionally seen as an under·flow (on the bottom of the lake) but gener·ally appeared as interflow (at mid-depth), and could apparently be detected as far down-lake as Station 9, a bout three miles . Measured suspended-sediment concentr·ations ranged from 0 .15 to 570 mg /1 in the inflow streams, from 0 .1 to 200 mg /1 in the lake, and from 0 . 56 to 36 mg/1 in the outflow. Peak values in the inflow occurred in late July or early August, in the lake tn about September (as a depth-averaged concentration at Station 9), and in the outflow tn late July to mid- August . During the winter, inflow , lake and outflow suspended sediment concentrations were on the order of 0.1 mg /1. During the summer, the 1-4 R24 /5 18 average suspended sediment concentration were substantially higher than winter values and were incresed further following large rainfall events or per·iods of significant glacial melt. Prominent diurnal variation was seen in discharge, water temperatur-e, and TSS concentr-ation on both inflow tributar·ies, especially dur·ing periods of clear weather with war·m days and cool nights. Turbidity values generally f o llowed the trends in the TSS c o ncentr·at ion, dropping o ff in the winter at i nflow, lake, and outflow sites and peaking in mid-to -late summer . Values observed ranged from 0 .5 to 580 NTU in the inflow streams, from 1 .8 to 220 NTU in the lake, and fr·om 3 .0 to 4 6 NTU in the outflow . 1-5 R24/5 19 2.0 SCOPE OF STUDY 2 . 1 Purpose The Alaska Power Authority pr·oposes to develop the Sus itna River "s power potential by constr·ucting and operating dams and reservoir-s at Watana and Devil Canyon damsites in the Susitna Hydroelectr·ic Pr·o ject. The r·eser- voirs effects on temper·atur·es and suspended sediment r·eg imes within the reser·voirs and in the r·eaches downstream are of concer·n for management of fish resources and other envir·onmental issues. The reser·voir·s are being mathematically modelled with the Dynamic Reser·voir Simulation Model ( DYRESM), a state-of-the-art, one-dimensional model developed at the Univer·sity of Weste rn Austr·alia tlmberger et al. 1981). The or·iginal ver·sion of the model has been expanded to account for ice formation thermo-dynamics, circulation, and settling properties of suspended sel~iment . Pr·ior to application of the model on the Susitna reservoirs, the model is being calibrated using data fr·om Eklutna Lake, a glacial lake 100 miles south of the \Vatana damsite and 30 miles northeast of Anchorage (Figure 2 . 1). This report documents the field data collected at Eklutna Lake from December 1982 to Decem ber 1984 in support of the modelling efforts. A summary table of all the lake data collected in this period is included in Appendix A as Table A .1 . As noted in the Glacial Lake Studies Interim Report ( R&M 1982a), the Eklutna data collection progr·am was designed to : ( 1) provide input data for the DYRESM model; (2) pr·ovide lake temper·ature and sediment data for verification of the DYRESM model ; and (3) pr·ovide documentation o f the lake"s mixing environment and sediment dynamics. Little analysis is contained in the r·eport as its function is to present the data collected for subsequent anslyses. 2-1 R2..J /5 20 2 . 2 Summary of Previous Studies and Available Data Data collected from April through November· 1982 at Eklutna Lake were r·eported in the Glacial Lake Studies Interim Report ( R&M 1982a). Pr·ofiles at two-to four -week intervals of lake temperatur·e , conductivity , and turbidity from up to 15 stations around the lake inter·vals were presented , as wer·c daily values of inflow discharge and temper·atu re, outflow discharge and temperature, and local weather par·ameters . Suspended sediment and light transmittance characteristics were me a sured at selected stations through the year . Backgr·ound data available on Eklutna Lake and the inflow and outflow streams include dischar·ge, lake level, and water quality data from the U .S. Geological Survey (U .S.G.S.); additional lake water quality data from the Municipality of Anchorage; lake outlet geometry and outflow discharge and temper·ature data from the Alaska Power Administration; and weather data at nearby locations fr ·om the National Oceanic and Atmospheric Administr·at ion (N.O .A .A .). The U .S. G . S. data consist of lake inflow discharges from 1960-1962 , miscellaneous discharge measur·ement~ fr·om 1952-1956, lake level data fr·or.1 1946-1962, lake outflow discharges below the dam (rather than thr·ough the powerplant) from 1946-1962 , and stream water quality d ata fr·om below the dam fi'Om 1949-1952. Lake water quality d a ta wer·e obtained for the Municipality of Ar.chorage for water supply studies and have been r·eported by CH2M Hill ( 1981) and Montgomery Engineers ( 1984). I nfor·mation on the Eklutna Project powerplant and intake characteristics and oper·ating data wer·e obtained from daily records kept by plant person- nel (Alaska Power Administration 1982-1985 ) and from powerplant con- struction documents made available to R&M . 2 -2 R24 /5 21 We ather data (p r ecipitation and temperature) are repo r ted by N . 0 . A .A . ( 1982-1985) for the Eklutna Pr·o ject powerplant 5 miles north of E k lutna Lake and for Paradise Haven Lodge in Eagle River 12 miles southwest of the lake, collected by Alaska Power Administration and Chugach State Park personnel , respectively. These background data are not summarized herein because the emphasis of the present r e port is the specific period of sampling rather than for historical conditions . 2 . 3 Report Format The report pr·ovides d e sc r ipti o ns of data collection methods, discussions of results, and discussion of the river and lake relationships . Sections are included in Volume 1 , the t\lain Report, for weather monitor·ing , lake inflow, limn o logy and la ke o utflow data , Sections 3 through 6 . Relation- ships of the river and lake s y stems are discussed in Section 7. Section 8 lists refer·ences cited. Data of a "summary " nature are presented within the main text. Th i s includes plots th a t show how r·i v er and lake parameters vary with time or vary with respect to each other·. The appendices, Volume 2, present the supporting data that wer·e used to pr·epa re these plots. Tables wh ich summarize the types of data av a il ab le are a lso included in the appendices . 2-3 I· ------------------------------------------~-------- EKLUTNA LAKE Cflf)Jel~ • SB~!t~® $USHNA .IOINT VENTURE R&M CONSULTANTS , INC . LOCATION MAP ~============~------~-~---FI G. 2 .1 R2-l /5 22 3.0 METEOROLOGICAL STATION AND WEATHER MONITORING 3. 1 Methodology By special per·mission of the Chugach State Park, a weather station was established on June 3, 1982, at the south end of Eklutna Lake near an exrsting gr·avel air·strip (Figure 3 .1) The station was r·emoved December 14, 1984, following completion of the 1984 open-water season . The weather station consisted of a "Weather \Vizard'" monitor·ing system manufactured by Meteor·ology Resear·ch, Inc. (now par·t of Bel fort Instrument Company) and an Eppley Laboratories Precision I nfr·ared Radiometer·. The system measur·ed air temper·atur·e, precipitation, wind speed and dir·ection, peak gust speed, relative humidity ( RH), solar radiation, and longwave r·adiation. Temperature, r·elative humidity and radiation levels wer·e recor·ded as instantaneous values ever·y 15 or 30 minutes on a magnetic tape cassette. Wind data wer·e processed fr·om 15-second interval readings by the data logger and recor·ded as average winds and peak gust for each 15 or 30 minute interval. Pr·ec ipitation was r·ecorded as a cumulative amount using a tipping -bucket gage. Raw data from the tapes were edited and summarized in tables and graphs on a monthly basis. The station layout and photos of tile site are shown in Figure 3 . 2 and Photos 3 .1 and 3 .2. The sensor configurations are shown in Photos 3.3 and 3 .4 . Some of the data used for DYRESM input were not available in the data record from the site. The near·est first -order N .O.A.A. station, Anchor·age, was used to estimate Eklutna Lake values for sky cover and vapor pressure. Vapor pr·essure was computed to fill in gaps in the RH record and was estimated from the Anchorage values of RH and temper·atu r·e with a regression equation. Sky cover values (in tenths) wer·e taken directly from the Anchor·age data . 3 -1 R24 /S 23 3 . 2 Results and Discussion Graphical summaries of the recorded weather· data arc presented 1n a sequential plot of eac h parameter for 10-month and 1 S -rn on th pe1·iods in Figures 3 .3 and 3 .4, respectively . Larger copies of each mo nth 's p!ot and a copy of each month 's summary data table ar·e c o ntained in Appe1:dix B . Complete r·eports of monthly data are presented in annual r·eports for the Eklutna Lake weather· station ( R&M 1932b , 1984, 198~). Items particulal'ly wor·thy of note ar·e the windspeeds and wind directions. Events ac.:ompanied by occurr·ences of high windspeeds during open-water per·iods, especially if they last for more than a day at a time , ar·e instru- mental in causing considerable mixing in the lake. The windspeed patterns can be seen in the bottom graph of each monthly plot in Ftgur·es 3 .3 and 3 .4, when the tr·ace d eviat es fr·om th e zer·o level and gives consistent values of 4-8 met ers pe r s e co nd or higher. Such events were a ppar·ent dur·ing ice-free conditions for· August 6 -8 , 198 3 ; September 29, 1983; October· 9-11, 1983; on thr·ee occasions in November· 1983; June 28-29, 1984 ; August 23 -24 , 1984 ; Oc t o ber· 21-22, 1984 ; November 19-21, 19 84; and December 1 -5, 193-t . The s trong winds were pr·edominantly fr ·o m the south-southeast, 1. e. blowing fr·om the glacie r·s and down the lake; they ca u sed the air t e mpe r a tur·e to r·i se an d remain fair·ly steady thr·ough the day ; and they were o ft e n accompanied by sig nificant r~infall . The winds in gen e ral showed a stro ng tendency f o r coming either froM the nol'th -n o rthwest or from th e south -southeast, due to the alignment of the l ake and valley b e twee n hi g h mountains a long that axis. Winds at Eklutna also freq uent ly showed a diur·nal cycle in the summer, when ea rly mo rning winds fl o w e d down th e val ley (fr·om th e south-southeast) and aftemoon and evening winds came up the valley (fro m the north -nor·thwes t), typical of mountain dr·ainage wind p a tter·n s (note July 1984, f o r example). 3-2 R2-1/!J 24 Air temper·ature at the lake nor·mally showed a marked diur·nal fluctuation, with cool nights and war·mer days due to solar heating . The suns warrnmg ts gover·ned less effective in the winter, so temperature variation then is mor·e by movement of regional air masses than by daily fluctuations. The solar· radiation intensity natur·ally displays a daily and also an annual cycle. The daily peaks in December and January ar·e bar·ely visible on the plots (top graphs), but the summer peaks in May, June, and July are often ver·y high. Daily cycles ar·e quite evident for r·elative humidity ( RH) except during the winter, although several problems in reporting of the RH data were exper·ienced . Mor·e discussion of the meteor·ologic data collection and detailed data re- ports are contained tn the annual reports ( R&M 1984, 198!:>). The recor·ded data ar·e felt to be good wher·e reported, with the following comments regar·ding interpr·etation : 0 0 0 0 0 precipitation data are not recor·ded during freezing temperatur·es so ar·e not reported for winter months ( November·-Mar·ch). recorded solar· radiation data may be lower than actual values at times dut·ing the winter· due to frost or· snow accumulation on the sensor·. numerous wind speed and wind direction data wer·e lost dur·ing winter· months when the anemometer and /or the wind vane froze until freed by a str·ong wind or· thawed by warm temper·atures or solar heating . several periods of intermittent or complete loss of data occurr·ed when electr·on ic or· mechanical malfunctions occurred. Intermittent gaps ar·e evident in June and July 1983 , and t o tal gaps occurred in January, Febr·uary , November , and December 1983. Approximately one day of data was lost each in September 1983 and September 1984 when several sensors were removed for annual maintenance. the RH plots in Figure 3.3 were not adjusted before plotting, so the daily ··peaks" which show up at the bottom of the graphs should actually be plotted at the top, and the traces should be shifted 3-3 R~-t /5 25 downwar·d a similar amount. For example, a plotted vaue of 10 percent really correspo nds to an RH of 110 percent, indicating the sensor calibr·ation was 10 p o ints too high and should have been adjusted down 10 points . Also, the RH data were all lost from mid -February to early September in 1984 due to a faulty s ensor osci llator. Documentation of the la ke conditions through the winter of 1983-84 and dur·ing freeze-up in late 1984 , as well as a tabulation of weather obser·vations at the lake , are included in Appendix C . The da ily weather and wind speed values used as input for the DYRESM model ar·e listed in Appendices N.:? and N.3. 3-4 -'., ,'(. ""-.. .... I _. ; ,.,,~I . -: -.-.. "'0-f I ( :'~-: ~ --: --· I • ', ·o ) . ·' -__./ i ·---'. :. --. ~ .' ' . \ ~ ·.I ' ·i \ ~. / ' l\ I' \. I '{;) '· I I ~-., \ ' i ~ -I ~~I 1 ~ t -...... ' -. ' I! , I .. '--"T"" .... I ) ( I ·:J .... -i . .' ·-) I I I : . --... _P "-·r .... · IG i . r J,. • ... : • , I -----{)---- R &M CON S U LT AN TS. INC . EKLUTNA LAKE STATION LDCATIDfJS -·· '/ PRE PARED FOR : SUSIFNA JOINT VEN TU"£ FIG 3 .1 v J I a-. lsASE OF STEEP MOUNTAINS (400o .. ±) ~'--~~~ I~ ~\_ ,.._.;-/ B R US H ,_;-·-' 35mcler TRIPOD TO LINE ,-· -'RADIATION AND RH SENSORS J ~ SH ELTER ArJD < DIG I TAL RECOR DER ) ' l ) SEN SOR ARRAY HO US ING w /ANEMOMET ER AND WIND VANE SUPP O RT SENSOR ARRAY RADIATIO N SENSOR ~ \ PRE VA ILING WIND LW RADIATION ~ "H>---SENSOR AND ~· '2 . CLEARirJG FILLED W ITH SCATTERED, EKL~NA LAKE ') I . PLATFORMS ARE 10m± APART . (40011"'±) } ' SMALL BRUSH (1 -2m high), SURROUNDED AMPLIFIER / BY LARGER TREES . '- 3 . CLEARING 20-30m WIDE BY 50-70m LONG . TIPPING BUCKET 7 Q RAIN GAGE t ~ ~~ ~--v-v-'v------y-----....v-(t ~ ~ ~~~ ~4 ~ (/) ~ 'y ~ l'ly ~ / /'~ NOT TO SCALE ~ "o .q~;s~~ ..._ ( AIRSTRIP (lOOm±) J) It';~ ~ I ~ ~ "~-~ ~, -} ( LOCATED ON USGS MAP ANCHORAGE (8 -6) P REPARED BY : FIGURE 3.2-SITE SKETCH PREPARED FOR : = .:-~~~··!L1 o~--~o ~= _ ==' -· - EKLUTNA LAKE CLIMATE STATION ESTABLISHED JUtJE 3, 1982-OWNER : ALASKA POWER AUTHORITY-OPERATOR : RSM CONSULTANTS, INC . UNDER CONTRACT TO HARZA -EBASCO SUSITNA JOINT VE NT URE UD&~~& a griD&§©@ R&M CONSULTANTS, INC. SUS IH JA JO INT VU JI U llt ..... a, .... e•n • ueo~o.oo ••"• ""'on o ~o.or.t ••'• •u nv•'t on e ---,,,,,-f#:r--~~--~~-.6...f ----. -.. r ~ ., .__ J,.-p•~::;aoo """-.Afo •eoo:..• wn ....._,~ 'root• oOo•oo .. \. -•o • ,, A....tr.'\ ~ '<lr ----·~ ..... "OOT"'I •r---------------~ I ... .m.A. ..A J\ll~.L.. :. I 11 4'1 u ,.. " ,. .P-'-"-"-'-"-. • ....... -· ~-:~,trMtatL~ l~L .. \ :f I IltHL~IU_lJ[ ~ '''.{t1JL :f; . . ~ Jt .............. 'lll~·~· ltlnflttltlt-Y .. II ~I.~ ~ t Hb\l/Ul H~~~U~~l · > FIGURE 3.3 SEQUENTIAl PLOT OF CLIMATIC DATA, EKLUTNA LAKE STATION DECEMBER 1$82- SEPTEMBER 1883 3-7 Oc.tobt', 1981 ... , ...... ,_,., .. "'" ~· ~o." ~· ..... '"•' ........ •'M • I h~~~tiN:=wwWh~~~~~~~~::;:::;:=:::::::;:=:;F:::::::::=;t--;;(1;1~----l:r ! ••:!: l------------------~--~=---~--~-------------------------------~------------------------------~~------------------------------~:·7 NOH : A LAIIIIO I.llll C O,V ' ,LOT II INCLUD ED IN "''I.NOUI: •• FIGURE 3 .4 SEQUENTIAL PLOT OF CLIMATIC 1!ATA EKLUTNA LAKE ~1~-.~,_1 ,n~-.-.-~~~--~~rrT~~77.~~,-~~~--~--~-------.l---~~~----~------r----------i~-r~~------------------------l ;::! STATION, l,.l-11-f.l..,ll.,..,.. :::! OCTOBER 11B3• ,_~~~~--~J__L~~~~~~~L_~~~L_ __ -L~--L-~L-----~i---~L_L_ __________ _L ________ -1-L-L-L~----------------------1 :'; DECEMBER 1184 ·-· Photo 3.1 Eklutna Lake Climate Station site, looking NW toward Ek lutna Lake. Photo 3 .2 f. .... lutna Lake Climate Station si t e, looking SE t o w ard upper basin. Ph.:.t.:> 3 .3 Sensor array and solar· panel, Eklutna Lake Climate Station. Sensor array contains anemometer, wind van e , and radiation shield with temperature an d RH s e n so rs . . ,~r---. ' {• " .~· Photo 3 .4 Auxiliar-y senso r· pl a tfor·m, Ek lutna Lak e Climate Stat io n . Sensors includ ed (left to right) are solar radiation sensor, longwave radiation s e nsor, and tipping bucket preci pitation gage. 3-10 R24 /~ 2G 4.0 LAKE INFLOW -EKLUTNA RIVER 4 . 1 Methodology Data collection sites were established on each of the two pr·imary infl o w str·ea ms: East Fvrk and Glacier Fork of Eklutna River . On each stream, a str·eam gauge was install e d, and water samples w e re c ol lected. Site locations are shown on Figure 3 .1. These two creeks provide the princ i pal inflow to Eklutn .1 Lake, t o gether dr·aining about S0°o of the lake's 111 -squ a r·e -mile watershed l R &M 1982a). The two creeks intertwine in braided channels on a br·oad floodplain befor·e e nter·i ng the lake . The streams wer·e gaged and sampled separately, sever·a l miles fr·om the lake inlet, as the fir·st suita ble s ec tions for str·eamgaging wer·e upstream of their confluence . Ver·y littl e g r-o undwa ter flow is expected to augment the st ream discharge d o wnstrea m of th e gag ing sites. 4 . 1 . 1 Streamflow Stage -discharge relationships were established fo r b o th s treams . Stevens Ty pe F wa t e r· leve l reco rders w ith 30-day charts were util i z ed to continuously mo nito r· strea m s tages . The wa ter level recor·de rs were h o us e d in plywood g age houses on 16" di a meter polyethylene pipe stil l ing w e lls . Th e stil lin g wells w e r·e insta ll ed with 2 ~" diame ter PVC inl e t pipe s which ex le nde d i n t o the channel . D ischar·ge values in cubic fee t per second (cfs ) were calculate d fro m mean daily s t age r·eadings a n d converted to cubic meters per day (m 3 /d) for DYRESM us e. 4 . 1 . 2 Water Temperature Inflow t e mp e ratures w ere monito red continuously with Ryan Model J Ther·mograp hs , r e corde d on pressure -sensitive paper char·ts . These instr·um en ts w e re anchored to r·ocks placed in th e streams such th a t the sensors remained submerged . Temperatures wer·e also measured 4-1 R2-l /5 27 every sampling tr·ip with a mercur·y ther·mometer. All water temperatures measur·ed with the Ryan thermogra ph ar·e accurate to the nea rest half -degree C e lsius . 4 . 1 . 3 Light Penetration Secchi disk depths, as d e fined by Wetzel ( 1975), wer·e measured in the inflow str·eams using a disk painted in alternate quadrants of white and bl ac k to facilitate definition when submer·ged . Secchi disk meas urements wer·e r·epor-ted t o the nearest 0 . 1 foot. 4 . 1 . 4 Conductivity Samples of inflow wate r wer·e measured for conductivity at the R&M office using a YSI model 33 S -C -T meter (sample collection is de - scr·ibed in Suspended Sediment). E>o.cep tio ns to this were 24 -hour sampling trips in July and August 1934 when analyses were performed in the field . In e ac h case , temperature was measur·ed at the same time. Using the temper·atur·e, the mea sured conductivity was correct- ed to conductivity at 25°C (APHA et al . 1981). 4 . 1 . 5 Suspended Sediment De pth integr·ate d water· sa mp le s w e re collected for co n ce ntr·ation of total susp e nd e d solids (TSS), turbidity and conductivity analys e s using a U .S. DH -48 suspended sediment sampler (U .S .G .S , 19 78). Du r ing per·iods of lo w flow, the samples wer·e c o llected at estimated e qual -dis c h a rge increments across the stream . Higher· fl o ws made this impossible without unacce ptable risk to the collector. At these times, a w e ll -mix ed location near· the edge of the str·eam was used . Samples were refrigerated immediately after· collection until the lab analyses were conducted. Analyses were conducted within th r·ee days of sampling and usually within one day . 4-2 R24 /5 28 Concentrations were deter·mined by Chemical and Geological Laboratories of Alaska using standard procedur·es for detection of total nonfilterable residue (APHA et al . 1981). Filters with a pore size of 0.45 microns (0.45 x 10-3 millimeters) were used for the deter·minations of TSS concentration. Particle-size distributions and mineralogic analyses wer·e perfor·med by Particle Data Laboratories, Ltd., of Elmhurst, I Illinois. The size distributions were deter·mined by the electrozone method ( Karuhn and Berg 1982). 4 .1.6 Turbidity Samples taken for suspended sediment anal y ses were also analyzed for turbidity . Determinations were r·outinely per·formed within one day of sampling. A Hach Model 16800 Portalab Tur·bidimeter was used for this pur·pose fr·om 1982 until August , 1984 , when a Monitek Model 31 Nephelometer was pu r·ch a sed and used ther·eafter . Both instruments measur·ed nephelometr·ic turbidity (i.e ., 90° scattering of light). Standar·d methods for the measure of nephel o metric tur·bidity wer·e followed (APHA et al . 1981). Calibr·ation standards were supplied by the instrument manufacturers. Some differences were noted rn measurements made with the two instr·uments , so pr·eliminary values were adjusted using an empirical c o rrection r elationship . 4. 2 Results and Discussion Plots of mea n daily stream discharge and water temperat ure for the 1983 open-water period ar·e shown for East Fork and G lacier· For·k in Figures 4 .1 and 4.2 . Data for 1984 are shown in Figures 4 .3 and 4 .4 , which plot instantaneous instead of mean daily temperatures, and also plot instantaneous values of turbidity and total suspended solids ( TSS). Both stream basins are heavily glaciated (54°o for Glacier Fork 's 27 square miles and 20°o for East Fork's 40 square miles). The Glacier Fork streamg a ge is within two miles of the Eklutna Glacier terminus. The 4-3 R2-l /5 29 glacial influen c e is quite evident fr·om the low summer water temperatures and from the shape of the annual hydr·ographs . On frequent occas ions while standing in the stream making dischar·ge measurements , the hydr·ologists · le!=':> were bumped by large (sev er·al inches across) ch u n k s of ice floating downstream. The streamflows are character·ized by very low magnitudes in the winter and high , var·ia ble flows thr·o ugh the summer . The summer r·ise b e gins 1n la te May or early June and c o ntinues to a peak in late July or August . Summer fluctuations are p r oduced by rainfall or glacial melt e v e nts , or a c om bi n at io n of b o th factor·s . The me lt i ng of the glacier is a ccel e r a ted b y war·m ai r temper·atures and solar radiation , especially when a c c o mp a ni e d by str·o ng winds . The peaks of the year in 1983 were particularly sharp and high . They occurred on August 8 at each site foll o wing several d a y s o f wann t e mperatures , str·ong winds, and inter·mitte nt rainfall . The suspended -s e diment a n d turbid ity d a ta collected in 1984 affor·d s o me interesting comparis ons with th e str·eamf low and temperatu r e plots , shown in F igures 4 .3 a nd 4 .4 . High-turb id ity and high -TSS events coincide well, with both g e ner·ally coinciding w ith rises in the discharge . Some of the sharp peaks on the dischar·ge pl o ts , however, do not appear on the TSS and tur·bidity plot s , an d vice ve rsa. There are two reasons fo r this . Fi rst, dis c harge data are p lo tte d for· e v ery day , while TSS and tu rbidi ty data are av ai la bl e o nly fro m th e t ime s s a mpled, i .e. twice per week . Thus , the streamf lo w (Q) c o uld r·i s e and fall shar·ply betwe en sampl i ng trip s . The TSS a nd tur·bi d ity lev e ls would a lso pr·esumably have risen a n d f a llen in the meantime , but this patte rn w a s not sampl e d . A second factor infl uencing the apparent Q -TSS -turb idi r y relat io nsh ips i n Figures 4 .3 and 4.4 is the fact that the Q pl o tted is the me an daily value , while the other p arame ters are instantaneo us values . Cont i nuous r ecor·ds of water level and tempe r·ature at both gaging sites have shown a p r onounced diurnal variatio n in b o th parameters , especially at Glacier Fork . Cool, clear nights reduce gl a c !al melting and runoff anJ lower the temperature of the water . \\'a rm , sunny days promote melting and increase 4-4 R24 /5 30 the runoff and generally incr·ease the water temperature. Thus, levels observed ar·e quite dependent on the time of day. Mean daily values of a par·ameter may be relatively unifor·m over a period, with instantaneous values fluctuating significantly about the mean on a particular day . Relationships were derived between par·ameters of interest to help inter·polate between the discr·ete sampling times. Figur·es 4.5 and 4 .6 show the plots of TSS as a function of discharge at each gaging station. Instantaneous values of each were pair·ed to develop the relationships. The regression equations and correlation coefficients ar·e shown on the figures , indicating that the function 1s good in each case. These equations permit estimation of stream TSS concentr·ations when the discharge 1s known; they were used to provide estimates of daily suspended sediment load for use in the DYRESM model. Computed values of TSS are given in Appendix N. G. A relationship between TSS and turbidity was determined. two gaging sites are shown in Figures 4 . 7 and 4 .8, Plots for the with the •r corresponding regression equations . A fair·ly good relationship is agarn apparent, indicating that turbidity values in the stream could be estimated from TSS measure ments . It should be noted that the relationships are somewhat differe nt fo r each str·eam , so a pplication of the equations :.hould be site-specific a nd are f o r flow i ng water only (i .e. not f o r a lake). [Jifferences between s t r e ams a r·ise from d iffer·ences in sed•rr.ent size , particle size distribution, shape, density, and color. Particle-size distribution plo ts are presented in Figure 4.9 and 4 .10 for East Fork and Glacier For·k , r·e spectively. Samples were collected on three dates in 1984 : July 20 , Au g ust 28 , a nd October 23. The median particle size ranges between 5 and 16 micr·ons (10-G meters) at East Fork and between 4 and 17 microns at Gl a cier Fork . No rationale is apparent to explain the relatio nship of the three curves at either of the sites. The Glacier· Fork samples fit the pattern of d e creasing median particle s ize with decreas i ng TSS concentration, but this does not apply to East Fork ( inste: ntanecus discharge values and corresponding water quality 4-5 R2-l /5 31 parameters are shown chr-onologically in Appendix D, Table D. 1 for East Fork and Table D . 2 for Glacier Fork). The particle-size distr·i bution data are tabulated in Appendix F, T ab les F.1-F.6 . The var·i ation in dischar·ge and sever·al of the water quality parameters over a da;ly cycle was br·iefly discussed above. The significance of this diurnal var·iation was inv e stigated by collecting samples fr·om earh stream thro ugh a continuous 24-hour· per·iod. Samples were taken ever·y two hours . The results ar·e plotted in Figures 4 .11 and 4 .12 for East Fork and Figur·es 4 .13 and 4.1-l for· Glacier· Fo rk . The first figure in each case (4.11 and 4 .13) was fr·o m sampling done after several days of overcast weather, while the second sampling trip followed sever·al days mar· ked by clear skies and sunshine. The effect is masked somewhat by a r·ise in each strea m's hydr·o gr·aph toward the end of the ''cloudy '' per·iod , caused by the emergence of the sun. However, inspection of the two "cloudy " hydr-ographs sh ow s a ver·y flat hydr·ogr·aph between late after·noon and early the next mo rning . By contr·ast, the two "sunny" plots have an obvious peak in the flow in the late after·noon or evening anc a significant drop overnight . Th e TSS , turbidity, and water temper·atur·e follow patterns similar· t o that of the str·eamfl o ws . Mean daily dischar·ge values for· ea ch stream for 1983 and for· 1984 are t ab ulated in Appendix E , Tables E .1 -E.4 . Table E.5 lists the disch a r·ge measur·e ments and corr·esponding gag e he ig hts for each site, and stag e-dischar·ge r a ting curves are presented rn Figures E.1 and E .2. Appendices N .4 and N.G list the daily data for discharge and water temperature (N .4) and suspended-sediment quantities (N.G) for input to the DYRESM model. 4-6 1000 800 -U) LL. 0 -w ~ 600 a: < l: 0 U) ""' - I c 400 -....1 > .... -< 0 z < 200 w ::E 0 MAY PREPARE D BY: =:~t~Mr~~=-=-===·===== R&M CONSULTANTS, INC. ~ ............ .. JUNE JULY AUGUST SEPTEMBER 1983 INFLOW DATA EAST FORK FIGURE 4 .1 PR E P/IRED FOR : ~ m > z c > ,... -< ~ > -t m :a -t m r ~ , . -0 4 .0 0 2 .0 -OCTOBER "'" I 00 1200 1000 -U) LL 800 0 -· w " 1: ~ 600 ~ 0 en c > 400 _, ~ c z 200 <4 w ~ 0 3: m l> z 0 l> r--c ~ l> ~ m 2J ~ m ~ ·~······························· ·····:.............. 0 1 .0 0 ] 3 .0 :u ..... "'--~ ~ ................................. ~ 2.0- ~----------~----------~·~----------~------------~' ------------~'------~ - MAY JUNE PREPARED BY : _;~~ - R&M CONSULTANTS, INC. eNCIIN •• A. o •DLDOI •Te MYOAOLOOI•T• •uAVe YOAe FIGURE 4.2 JULY AUGUST 1983 INFLOW DATA GLACIER FORK SEPTEMBER OCTOBER PREPARED FOR : SUS II W \ .J O lt J I V l t J I Ull~ ~ f/1 -100 0 -u ,..- 800 ..Jw =i" :::~~~~ W(l) 200 ~0 PREPA RE D B Y : 0 - ::::: 4 00 E 2oo (.) 8 CZ::o w-8 1-a. 4 <~ :=w 2 1-0 MAY __;~1~b~=-================= R&M CONSULTANTS, INC. JUN JUL AUG SEP 1984 EKLUTNA LAKE INFLOW DATA: EAST FORK OCT MOO TEMP FIGURE 4.3 P RE PAR~D FOR : SU S IHJA J O I N T Vf:NliHIE PREPARED B Y : -til 1000 -u :::-~~ t\. 400 z~ (\r v 200 i~ rr -0 ~ 0 > 1- 400 Ci-; -.. IDe 200 -a:- :::l 1-..... 0 -8 a:(.) 6 w~ 1-ll. 4 <::::E 2 :itw 1-0 1984 EKLUTNA LAKE INFLOW DATA: GLACIER FORK FIGURE 4.4 PR EP ARED F OR : [j:{]£~3~& CJ ~00&®©@ S IJS I I ~JAJO it d 'I I NT I f!( ;:.. I .... .... 1000 800 600 400 200 100 80 60 40 " 20 m E 1ft 6 (f) 4 (f) 1- 2 1 .8 .6 .4 .2 . 1 (S) (S) C\J PREPA RE D BY: ."\o.:31 ...... ,,. UIJO ~U t.•b1'. HV OilU~OOit& I. •unv • Vt.n • + + .... + + + + ,;; + + + + + + -4 2. 2 4 + + + TSS:1.23 X 10 0 + + ,; 2 + R = 0 .88 + + + ++ + + + + + + + + (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) (T) '<T If) U) " CD en (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) C\J (T) '<T If) lD " CD en (S) INSTANTANEOUS 0 (cfs) FIGURE 4.5 1984 EAST FORK DATA: PRE PARED FOR: TSS vs. INSTANTANEOUS FLOW 1000 800 600 + + + + 400 + + + 200 + + + '-· 100 + ,.... 80 + " 60 m 40 E + TSS:1.61 00 .84 R2 • 0.91 U1 20 ~ U1 I I-...... 10 + N 8 + 6 + 4 2 1 (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) IS) (S) (S) (S) (S) (S) (S) (S) (S) C\J (T) ..,. 111 tD 1'-CD 01 (S) (S) (S) (S) (S) (S) (S) (S) (S) (S) C\J (T) ..,. 111 (D 1'-CD 01 (S) INSTANTANEOUS 0 Ccfs) FIGURE 4.8 PREPARED B Y ; 1984 GLACIER FORK DATA: PREPARED FOR : TSS ve. INSTANTANEOUS FLOW GD&~~& c §riD &~©© SUS I r r1 .\ J u lr·J r Vl:tJTI il ll , 5)J ~·:rr'l1 =!='!..:·--~-·-- R&M CONSULTANTS, INC. ef'loQI,_,. •• n. UUOt.Dl.leTe HYDAULDG1tl1'e .UMV e V O ... 1000 800 _ 600 - 400 200 1gg =:J 60 I-40 z 20 >- I-10 H 8 Cl 6 H 4 en 0::: 2 =:J + ~ I-I 1 ~ .8 w .6 . . 4 .2 Cll 'II' . PREPAR E.c~O~B=Y=:================= _;~ R&M CONSULTANTS, INC. ++ + + + + + ++ + co co ... Cll 'II' co coo 0 0 .. ... Cll 'II' TSS ( mg/ 1 ) 1984 EAST FORK DATA: TURBIDITY vs. TURB . = I . 78 TSS 0 '"' R2 = 0 .8 7 I I I I I I Ill 0 00 0 0 0 oo co co 0 0 0 0 oo ... Cll 'II' co coo ... FIGURE 4. 7 PREPARED FOR : TOTAL SUSPENDED SOLIDS SU SI HJA JO I NT V ENT U JlE "'" I f-' "'" ~~~~ 800 700 600 500 400 300 ::J I-200 z + >- I-~~~ H Cl 80 70 H 60 m + a:::: 50 + ::J 40 I-+ 30 + + 20 C\J (T) <T If) tD "CDa1Sl TSS C mg / 1 ) PREPARED B Y; 1984 GLACIER FORK DATA: ~h::::::::::=============================== TURBIDITY vs. R&M CONSULTANTS, INC. •NOIIIIIII.e~~te o•Ot..O OI•?e HY DADLOQie ~e a UAVa V DIIIIe TOTAL SUSPENDED SOLIDS + ++ + '+ + + + + + + + * + + + + T URB = 6 .00 TSS o .•so R 2 = 0 .8 0 (SJ (SJ (SJ (SJ (SJ (SJ (S)(S]S) (SJ (SJ (SJ (SJ (SJ (SJ (S)(S]S) C\J (T) <T If) tD "CDa1Sl FIGURE 4.8 PR E PA RE D FOR : (}{]£(ru~£c §[ID&~©@ SUSIT N A JOI NT VENTUnE (t) z 0 « 0 ~ z w !::! ,-·r---r I I l --,~--~ , ~ -~--·-t ··-~-l --·I··: :·! -t ~ · r I ! ------------·---· ··---·-·-----·-· --,--1 -·-·--t ! i>-i '' ·-: I · i 100 ---' ·--··----i-1 -·-------. (t) ~ '!--H ~j -~-----! ! I ~ i :.: .: ... : I : ___ r__ « I . 1 -I ' . I l ' ' ' < I ---I -· -.. . -. \ 1\ \:-·--·-11. I . 0 ' ;__ ~ ==:f:l -· -I ' -:------ ~--,---;~-~~-~~ r i-.------'· ~:·-. ·----,--,--1 l----1 J -1 --:-!·T-L~--r~...,.: ~_____, · n+ q~-· ·• : : · 1t:~: +.,-f\: ..... · :--1 !--·-··· ----;-·: ... , • · · i I. '1 · ~-.: t '' i • j I ' ; , . I:· I I : : . : . . . • I I . ' ~-I I f=L.-. 0 .1--,-I I ' ~=:=---~--· _._._._ '-----~----·+ ~ -'--·--· ----! ·-·---- ' ;~ -~-:--:_= _:-~:-~.:. ~:_-... ~~~:----.-·4 -~-, : .! ....... . . . . --~-----~ ---... I' --........ I .. . .. . I 99.9 99 90 50 10 PERCENT ('!!.) FINER BY VOLUME THAN INDICATED SIZE -1 --; ·--! . ..... I 1.0 0 .1 EAST FORK EKLUTNA CREEK S AMPLE DATE 0 7/20/84 8 8/28/84 ~ 10/23/84 FIGURE 4.9 PK[P~IIEO i3 Y · .... -'['. i ·-·'-~-.-·===--- ~&M CONSULTANTS, INC. SUSPENDED SEDIMENT PARTICLE SIZE DISTRIBUTION 4-15 PREPARE D FOR: [;{]£~~& 0 ~riD&®©@ ~ ... ·~1 r ·.A J 0 11'll 'If Nl ll'lf en z 0 a: 0 10 ::1: z w ~ en w ...I 0 ~ a: < 4. 0 .1 r ---·----.- I. ·--·--·-· ----- ---· t ----, ~ -i-: ----,---1 ·---·-··---,---~ .. ~-· ·-·-·---- I I . I. -·-.. ---~-~--'- I • ' ' ' • ·-·----- .... Ul "'' I .. ___ , . ;·:~~~:.; .. ,-·-1 .. • ·::::_;___:~• ·~-I -\ --~: :. ··-· .. L I ----~ -~ ~:~~~ --=-~:~-~ ' __ _:_ ___ -·---- , : , I !._._·_· . ..:. . ..: ___.·..-+r---;- --------.---!:_ .. , __ ·_-!_-. ~-·'-1 ~-- .. -t-. -.. .f .. , -·--\ ... -___ _L_L__I· 99.9 99 90 50 PERCENT ('Ill) FINER BY VOLUME THAN INDICATED SIZE .. , 10 1.0 0 .1 GLACIER FORK EKLUTNA CREEK SAMPLE DATE 0 7/20/84 8 8/28/84 6 10/23/84 FIGURE 4 .10 Pi!EP~RE C tl Y - _J~···.-Ll - R&M CONSULTANTS, INC. SUSPENDED SEDIMENT PARTICLE SIZE DISTRIBUTION 4-16 PREPARED FOR : [j{]&ffil~& 0 §00&®©@ ~U S ! I':A J O t~H V UH U'l~ "'" I f-' --.1 ~ >-200 .... c;-_:I 100 m ... a:.: :;) .... 0 = 200 ' 01 E 100 t/) U) .... 0 I r 0 0 •••• I L!r l I I I ax- .. --I . --- / I A -10 a:O 8 w-1-Q. e c(~ .. ~w 2 .... . . . . ·-.... -. -· !. -.. . . . . l <;>-cv--{'-'l)·--<:O:·>--......,"'t!)--"-...J~=---. :±:rT 1800 1800 2000 2400 0200 0400 0800 0800 1000 1200 1400 1800 1800 JULY 20, 1984 I JULY 21, 1984 INC. .N OINe.'*le o•OLDOieTe MYDAOLOOI•T• e VAV.VO ... TIME (AST) DIURNAL VARIATION OF DISCHARGE, TSS, TURBIDITY, AND WATER TEMPERATURE. EAST FORK FOLLOWING A CLOUDY PERIOD FIGURE 4.11 PREPARED FOR : D=O&[ru~& o moo&®©© SUSITNA JOINT VENT U nE rn ::l o .... LLI en 500 z-c(~ 1-400 z:: <o ........ rnu. 300 z = 200 ' 01 E 100 rn rn 1-0 >-200 1-c-; --100 CDc a:- ::l 1-0 .... 10 a:~ LLI- 1-a, 15 <:::e :!:LLJ 0 . 1-0 1000 1200 1400 1800 1800 2000 2200 2400 0200 0400 0800 0800 1000 1200 1400 AUGUST 14, 1984 I AUGUST 15, 1984 TIME (AST) FIGURE 4.12 PREPARED B Y; PREPARED FOR: __;~k==================== DIURNAL VARIATION OF DISCHARGE, TSS, TURBIDITY, AND WATER TEMPERATURE. [X]£00~& c ~EID&~©@ R&M CONSULTANTS, INC. EAST FORK FOLLOWING A !~~!~:·; ;:~n.uu SUS ITNI\ JO INT V ENTUf1E ~ 1 1-' 1.0 Cl) ::I o_ eoo wen I I . z-<~ I ~~ 1100 <o t-_, 400 en,. ....... , I z ...... 400 01 E 3 00 Cl) Cl) t- >-'"L 1- Ci-; --2 5 0 me a:- ::I t-200 -2 .0 a:o w- t-G. 1.0 <:Iii ~w t- 0 .0 PREPARED B Y: ~==~~~=================== R&M CONSULTANTS, INC. eNOI Ne.Ra o•O\.DOte T e ... 'I'DROI.OOie'Y e •u•v•V o lll e 0800 0800 1000 1200 1400 1100 18 00 JULY 20, 1984 JULY 21, 1984 TIME (AST) DIURNAL VARIATION OF DISCHARGE, TSS, TURBIDITY, AND WATER TEMPERATURE. GLACIER FORK FOLLOWING A CLOUDY PERIOD FIGURE 4.13 PREPARED FOR : SUS I TN A JO I N r VEN TUnE ~ I N 0 (/) :::;) o--w~ Zu 800 <- ~;: zo 500 <..,~ ~I&. (/) ~ . I z 400 400 --..... -. ' 01 E 300 (/) (/) .... 200 > 300• ~ c-- -:II CD .. a:.: 200 :::;) ~ 100' a:~ w- 2.0 ~A. 1.0 <:::E 3:w ~ 0.0 1800 1800 2000 2200 2400 0200 0400 0800 0800 1000 120 0 1400 AUGUST 14, 1984 AUGUST 15, 1984 PREPARED B Y: __;~~~===================== R&M CONSULTANTS, INC. aNOINe.A e a•OL.0018Te MVDAOLOOiaTe eUAV . YORe TIME (AST) DIURNAL VARIATION OF DISCHARGE , TSS, TURBIDITY, AND WATER TEMPERATURE. GLACIER FORK FOLLOWING A SUNNY PERIOD FIGURE 4.14 PR EPARED FOR : SUSI Hu\ JO I N T VE N TUfl E R~..t /5 32 5 .0 LIMNOLOGY OF EKLUTNA LAKE 5 .1 Methodology Fifteen data-collection stations were selected for the profiling of Eklutna Lake . Station locations are sho wn in Figure 3 . 1 . Profiling on most dates was done at Stations 1 , 2, 5, 9, and 15, in order to sample the lake center and the outlet end and to emphasize the inlet end. The pr·ofiling and sampling of Eklutna Lake concentr·ated on thermal and suspended -sediment measurements for calibrating and v€rifying the DYRESM model. Data of each type are presented in the interim report ( R&M 1982a). Additional lake data collected since 1982 include suspended sediment and light-transmissivity data dur·ing 1984 and temperature data during 1983 and 1984. 5. 1.1 Temperature and Conductivity Temper·atur·e and conductivity wer·e measured with a Martek Mark VIII Water Quality Monitor. A probe was lowered to depth and readings were taken from the digital display . A mercury ther·mom e ter was used for water surface temperature measur·ements . A Yellow Spr i ngs lnstr·ument Company (YSI) Model 33 S-C -T Meter measured conductivity and temperature fr-om 0 to 2 m, and in some cases conductivity from 0-14 m to verify the Martek readings . Conductivity was also measured with the YSI Model 33 on samples taken for TSS and turbidity analyses. The calibration of the Martek Mark VIII was checked pr·ior to making measurements at each station. Temperatures were reported to the nearest 0 . l°C and conductivities in micromhos per centimeter at 25°C (APHA et al. 1981). 5. 1 . 2 Continuous Temperature Monitoring A string of Ryan Mo del J Thermographs fixed at different depths was suspended from a buoy at Station 9 (Figure 3 .1) and provided 5-1 R24 /5 33 c o ntinuous temperature monitoring. These thermographs were maintained during pro filing trips which were per·formed once every two weeks . Data were reduced to deter·mine mean daily or instantaneous three-hourly temperatures (as needed). Temperatures were adjusted when necessary by comparison with Station 9 temperature profiling measurements. 5 . 1.3 light Extinction Light extinction measurements were performed using a LI -COR Model Ll 1858 Underwater Photometer·, with a model LI-192SB quantum sensor . This instrument measured the number of photons incident per unit time on the surface of a sensor at wavelengths comparable to the visible spectrum (400-700 nanometers or 400-700 x 10-9 meters). Readings were taken in the air, just below the water surface (less than em), and at several depths until complete extinction was reached . The sensor was horizontal, facing vertically upward. Readout from the sensor was via an analog meter in units of micro-Einsteins per squar·e centimeter· per second (one Einstein equals 6.02 x 10 23 photons). The values obtained from point measurements at each station wer·e used to determine the curve: 1 = I e-nz z 0 where lz is light intensity or irradiance at depth Z, 1 0 is irradiance at the surface, and n is an extinction coefficient (Wetzel 1975). Secchi disk depths were measured to provide backup data with the light extinction measurements made with the photometer. The disk was painted with alternate glossy quadr·ants of black and white to facilitate definition of the reflective disk surface when submerged. The Secchi depth, as defined by Wetzel ( 1975), was recorded to the nearest 0.1 foot. 5-2 R24 /5 34 5. 1 . 4 Transmissivity Transmissivity was measured on two sampling trips using a Sea Tech, Inc ., 25-cm Transrnissorneter. The instrument measured light emitted by an LED (light-emitting diode) at a wave length of 660 nano meters and incident on a synchronous detector . The LED and the sen s or were separated by a 25 -cm water path. The output signal was read directly as volts, and percent transmittance was calculated from the corrected (calibr·ated) voltage. Voltages were corrected through use of a calibration procedure spec- ified by the manufacturer. The percent transmittance was calculated using the following equation : V = {A/B) * (X-Z) where : V = Corrected output voltage (5 VDC corresponds to 1000., Transmission in water) A = Air calibration value (-L 735 VDC) B =Air calibration (present value) X = Data value (output v o ltage measured in water) Z = Zero offset with the light path blocked (0 .000 VDC) 5.1. 5 Turbidity From 1982 until August 1984, turbidity was measured from samples obtained at various depths at selected stations each sampling trip using a brass Kemmerer water sampler (APHA et al, 1981). These samples were analyzed at the R&M office using a Hach Model 16800 Porta lab nephelometric turbidimeter, normally within one day of sampling . Samples were kept refrigerated from collection until analysis . From August 1984 to December 1984 turbidity was measured 5-3 R24 /5 35 using a Monitek l'v1odel 31 Nephelometer . On profiling trips on August 16-19, September 3, September· 17 , and October 1 in 1984, samples were collected by pumping from depth using a gasoline-powered centrifugal pump and 3 /4 " and 1" rubber garden hose . The intake was weighted and lowered to the desired depth for sampling. Turbidity was measured in the field with the Monitek Model 31 . A 3 /8 " hose was run from the pump outflow into the nephelometer intake. Most of the flow was directed away from the instrument, taking most air bubbles and gases coming out of the solution with it. The pump was per·mitted to r·un long enough at the sampling depth to ensure that the hose was emptied completely of water from the previous depth. Samples were isolated in the instrument by valves , and condensation was wiped off the sample vial when necessary before reading the value fr-om the meter . When operational, this system pr·ovided very reliable data. Its operation was suspended after the October 1 sampling trip because water tended to fr·eeze rn the pump at cold temperatures. The Kemmerer sampler was used for the remainder of 1984 . Analytical procedures for tur·bidity were those described in Standard Methods (APHA et al . 1981). Calibr·ation standards were supplied by the instrument manufacturers. Some differences were noted in measurements made with the two instruments, so preliminary values were adjusted using an empirical correction relationship. 5. 1 . 6 Suspended Sediment Samples analyzed for total suspended solids (TSS) concentration were obtained using the same procedures as those acquired for turbidity testing, described above. Sampling between August 16 and October 1, 1984, inclusive, was per·for·med by retaining one-liter samples from the outflow of the centrifugal pump, after measuring the turbidity . Samples before and after this period were collected by lowering the Kemmerer sampler to the desired depth. After collection, samples 5-4 R24 /5 36 were kept refrigerated until delivery to Chemical and Geological Labo1·ato•·ies of Alaska, n01·mally the same day as or the day after sampling. Concentrations were determined by the lab using standard p1·ocedures (APHA et al. 1981). Filters with a 0.45-micron pore size wer(· used for the TSS dete•·minations . Particle-size distributions and mineralogic analyses were pedormed by Particle Data Laboratories, Ltd., of Elmhurst, Illinois. The size distributions were dete1·mined by the electrozone method ( Karuhn and Berg 1982). 5. 2 Results and Discussion The annual variation of lake temperature at Station 9 is presented in Figures 5 .1-5.3 for 1982-1984, •·espectively . Data were obtained from the pe1·iodic lake-profiling trips and f1 ·om the string of th ermographs suspended from a buoy moored at Station 9 at the center of the lake . The position of the lake surface in each plot corresponds to the elevation axis on the right. The depth axis on the left gives the distance from the bottom of the lake to any given point in the lake or on the lake surface . A dashed line indicates the estimated location of an isotherm. Typical of a reservoir operated for hyd•·oelectric power in a northern region, the lake level is highest in September and October (after the summer period of high inflow and low power demand) and lowest in June (following the low-inflow, high-power-demand winter pe1·iod). The observed annual fluctuation was about 12 meters (40 feet), with the maximum depth at full pool about 62 meters (200 feet). The lake profile data are presented in Appendix G . Profiles of the lake temperature for sampling trips with four or more stations sampled are presented in Appendix H. Eklutna Lake exhibits two overturn periods annually, indicated by a transition through the 4°C isotherm twice each year -while cooling in the fall and while warming in the spring . The lake becomes isot hermal at 6-/°C around October, then cools to maximum density at 4°C until November or early December . Ice formation can begin as soon as a small layer of water at the surface then cools to 0°C, but this is usually delayed 5-5 R2-t/5 37 by winds which keep the lake mixed and require further cooling of the surface layer. Timing of the freeze-up is dependent on the sequence and magnitudes of winds and air temperatures throughout the period; freeze -up occurred between the first and second weeks of December in each of the past three years. Disappearance of ice on the lake occurred between the second and third weeks of May in 1983-85 . Obser·ved lake temperatures ranged from 0°C immediately below the ice surface during the winter to over l5°C at the lake surface around August 1, 1983 . Timing and magnitude of the annual peak temperature in the lake are both dependent on the weather conditions experienced that particular summer . The primary factor would be the amount of wind experienced, as little or no wind would pr·omote for·mation of a thermocline and allow significant warming of the sur-face water. The 15°C surface temperature in 1983 occurred dur·ing several weeks of little wind activity (see Figure 3.3). The presence of more frequent or stronger winds would tend to mix the warmer surface water with the underlying cooler water . Notice the plunging of the 7° isother·m in mid-September 1982 (Figure 5.1 L which followed several days of str·ong, southeast winds blowing down the lake . The effects of the weather, especially wind , on the lake thermodynamics are shown in greater detail in Figur·es 5.4-5 .6 . Here, a one-week period containing a significant wind event was selected fr-om each year and plotted at enlarged scale. Hourly water temperatures were taken from the thermograph string at Station 9 and shown with 30-minute or GO-minute weather data (air temperature, wind direction, and windspeed) for comparison . Occurrences of the major winds produced a noticeable response : considerable '"r·ippling" and steepening of the isotherms (especially in 1983), indicating mixing in the lake . Plots similar to the isother·m plots were also prepared for turbidity : '"iso-turbidity" lines as functions of time and depth are shown in Figures 5. 7-5 .9 for Station 9 in 1982-1984 . The same conventions apply with the elevation, depth, and lake surface on the plots as were explained above 5-6 R2-t /~ 38 for the isotherm plots. The number and frequency of tur·bidity samples each year are indicated to pr·ovide the reader an indication of the data used to develop these plots . One noteworthy feature of the iso-turbidity plots is the range of turbidity observed (low values of 10 NTU and less in the spring and early summer before the glacial inflow begins, and high values of GO NTU and above in August and late September-early October). Another is the time and depth where the high values occur. These data are for the center of the lake, so the effect of the heavy sediment inflow at the head of the lake is delayed several days befor·e it is noticed at Station 9 . It is interesting that similar patterns appear in the turbidity values in August and September of both 1982 and 1984 (the data collected in 1983 may have been too sparse to measure it then). The high values (of 60 -70 NTU) first occurred in mid-August , about 10-15 meters below the surface . The sediment plume fr·om the inflow stream had apparently reached station 9 at this time, travelling as an interflow. Then the lake experienced some mixing due to wind, and the high concentration dropped to the bottom of the lake by mid-September ( 1982) or early October (1984). The lake may have become better-mixed thermally by this time, allowing the water density to be governed more by the concentration of suspended sediment and to become initially stratified on that basis . Further cooling of the surface water evidently promoted mixing of the entire lake depth, which diluted the highly-turbid water at the bottom . Settling of the sediment particles undoubtedly occurred as well . Figures 5 .10-5 .12 show variation in light-penetration characteristics of the lake surface water thr·ough the summer season-one plot for each year . Measurements of quantum extinction coefficient (in m-1 ) and Secchi disk depth are each plotted versus time on their own axes . Data for 1982 and 1984 are for Station 9 only, while the 1983 data are from various lake stations because of insufficient data at Station 9. Notice that the Secchi disk depth axis increases downward. A direct relationship is quite apparent : as the extinction coefficient increases, the Secchi disk deFth 5-7 R24 /!> 39 decr·eases, as one would expect . An increas ing extinction coefficient means that light is unable to penetrate as far below the water surface . Secchi disk depths ranged from 1 .2-8.0 feet, lowest in July and August and greatest in June. Extinction coefficients varied between 0 .4 and 2 .3 m-1 low in May and high in August . Corresponding euphotic levels, the depths at which only 1°o of the incident solar energy is available. ranged from 1 .9 to over 9 meters, for the 2 .3 and 0.4 extinction coefficients, respectively . The complete set of light-penetration data is presented in Appendix I : Table I . 1 gives the lake measurements of quantum extinction, and Table 1.2 lists the lake Secchi disk measurements. Extinction coefficient was compared with Secchi disk depth, surface turbidity (i .e. the tur·bidity in the euphotic zone), and surface transmissivity (Figures 5. 13-5 .17). Figure 5 .16 compares Secchi disk depth with surface tur·bidity measurements, and Figure 5.17 relates TSS concentrations with turbidity for all lake values. Figure 5 .13 shows an exponential or hyperbolic relationship between extinction coefficient and Secchi disk depth, asymptotic to a Secchi d isk depth of zero for a large coefficient and to a coefficient of zero for a large Secchi disk depth . The plot indicates that a Secchi disk reading could be used reasonably well to pr·edict quantum extinction coefficient in Eklutna Lake, though the relationship was not determined. Figure 5. 14, lake surface tur·bidity as a function of extinction coefficient, again indicates a fairly good relationship. There is some scatter in the plot at the higher end, adding uncertainty to prediction of extinction coefficients for higher turbidity values in the lake. There is one point with an extremely high turbid ity and extinction coefficient. This point is for data obtained at Station 1, at the mouth of the inflow stream. Data from Station are generally very unreliable to use in relationships between parameters. The inflow plume was often extremely variable in its horizontal position at the junction with the lake, shifting rapidly from side to side . In addition, the stream water immediately begins to entrain lake 5-8 R24 /5 40 water in the plume and dilute the sediment concentr·ation . Thus, if one attempts to correlate measurements made on a sample taken from the plume with measurements made in situ, there is uncer·tainty whether the same water conditions ar·e being compar·ed; the plume may be there for the sampling but not for· the profiling, or vice versa. Station data were collected to examine the inflow dynamics and to observe the ranges of the parameter·s experienced there, but the data wer·e normally omitted from regression relationships . The plot of surface transmissivity as a function of extinction coefficient in Figure 5 .15 shows some scatter. There is a scarcity of data, but if the data point in the upper· r·ight cor·ner is omitted, a weak exponential relationship is ev ident . A large extinction coefficient relates to a small tram:mittance, and vice ver·sa. The plot of surface turbidity as a function of Secchi disk depth in Figure 5.16 represents another exponential relationship . Finally , the relationship in Figure 5 .17 shows all lake values of TSS plotted against corresponding turbidity values . There is quite a b it of scatter evident in the plot ( R 2 =0.33), due to consolidation of the data for the entire lake. Differences in the r·elationship come from differences in the time of settling, changes in the sediment char·acteristics with time, and other factors. Supporting lake pr·ofiling data ar·e included in several of the appendices. Appendix G contains the individual tables from sampling trips, a sheet for each station on each date . Plots of lake isopleths are presented i n Appendices Hand J . Figu res H .1-H.20 show the temperature condition of the lake for each sampling date when profiles were taken at four or more la ke stations. Figures J. 1 and J . 2 present turbidity and light-transmittance isopleths, respectively, for a sampling trip in August 1984 when all 15 lake stations were pr·ofi led during a five-day period. I~ Appendix K , Tables K.1-K .9 provide a summary for each month from 5-9 R24 /5 41 March thr·ough November 1984 of all the field data collected at Eklutna Lake . 5-10 VI I ..... ..... 80 LAKE SURFACE~ y 0 3.0 START , -;; O 850 MEASUREME ~·c:__-/ \\\' -~·~g 80 3 .0 60 ' \ ' -:;:__-_____y o 7.0 4.0 3 .5 \ .: J I 5 .0 I I " ., ' ---~ ., 40 a.o 6 .0 800 ..... \ \ ---I E ~' \ 70~--s.o I J: .- Q. \ \ ·~ . w r- Q 30 )> w ~ m lll: I < \ \ ..J I 750 I I I m ""' r- I m 20 < \ ' I I )> I I -4 \ \ I 0 I z \ I .... ... .. ..., 700 10 "- FIGURE 5.1 o~MI~Fe&~~~~~~~~~~~~~~~~)_~--~--~ JAN FEB MARCH APRIL MAY JUNE JULy AUG SEPT OCT NOV DEC PREPARED FOR ; PREPARED BY ; _J=~,.------------------ISOTHERM DEPTH vs. TIME EKLUTNA I..AKE at STATION 9 1982 [}{]£00~& c §00&®©@ R&M CONSULTANTS, INC. e"'DINe•Ae a•OLOCI •• T. HYOIIOLOOieTe .UAVeYOINe SUSITNA JOINT VEN Tu nr Ul I I-' N ... E -:z: ~ A. "' 40 ·------4 .0 5.0 I! ( I I I \ ' ' I ' I ' 8 ·Q ' ..... 7.0 •, '--------"' . I 6.0 I s.o Q 30 "' ~ c _, \ 20 \ 10 I I I I I FIGURE 5.2 o~W.~F!H~~~~~~~~~~~~~~~~~_L __ l_ __ ~~ JAN FEB MARCH APRIL MAY JUNE AUG SEPT OCT NOV DEC PREPARED BY : PREPARED FOR: a eo 800 750 m ,.. m < > ~ -0 z ... -.. - 700 ~,.-----------------ISOTHERM DEPTH va. TIME EKLUTNA LAKE at STATION 9 1983 (}{}£00?6£c~[ID£@@@ R&M CONSULTANTS, INC. 8NOINee•e Q·D~OOI•Te HVD .. D&..OIIteT• au•vevo•e SUSITNA JOINT VENTURE ..... E -X I- A. 1&1 ~ --2.0 50 \ 3-0 -...../ I 40 4.0 / ··-r-··· 4.5 1 .0 ---... -~-1 7.0 I I I I ! LAST LAKE SAMPLE TRIP ON NOV. 26 Q 30 1&1 5 .0 \ -~~· /J I 6 .Q ~ c ,.j 20 10 I ) . . / I I \ \ \ •.-' ' \ \ \ \ 6 .0 FIGURE 5.3 0 ~MI~te~~~~~~~~~~~~~~~~~~~j_l_~_j JAN FEB MARCH APRIL MAY JUNE JULy AUG SEPT OCT NOV DEC PREPARED BY : PREPARED FOR : 110 100 ,.. ~ " '" 750 '" ,.. '" < ~ .. 0 z -.. .. .... 700 ~~-------------ISOTHERM DEPTH va. TIME EKLUTNA LAKE at STATION 9 1984 (}{]£00~£ c ~[ID£®©@ R&M CONSULTANTS, INC • • NCJIN···· aeOLDCJi eT• M'f'D•DI..OOI•Te eu•v•'f'OIII. SUSITNA JOINT VfNTIJRE 20 0 ~ .. ~ 10 .., .. k .. 0 !. z 0 o-zo--<> .... "' 0 0 I -.:.2o .... ,, E E Q ..... ...... 10 A.:> "'" QQ zz ii e :z: .. ... Ill Q .., "' .. -' 0 60 !SO 1-----8 40 7 30 /\ i ,/ '~ ? 20 10 0 360 270 110 90 0 20 10 0 z 0 ... .. > Ill ...J Ill 800 Ill "' c ...J 20-f--6 -----, ~ NOTE :TEMPERATURES ARE IN DEGREES CELSIUS . ? 700 10 FIGURE 5.4 1200 2400 9/11 1 PR£PAR[O B Y · 1200 9/12 2400 I 1200 9/13 ~ ~~~ 1========~=-----=-=a R&M CONSULTANTS, INC. ?400 1200 2400 1200 240C• I 9/14 1 9/1!5 1 COMPARISON OF STATION 9 SEPTEMBER 11-16, 1982 1200 2400 9/16 1 1200 9/17 PR EPARED FOR . 2400 1200 1 9/18 LAKE TEMPERATURES WITH WINDSPEED, DIRECTION AND AIR TEMPERATURE S US II ''A JO I NT V f NT IJrtf 5-14 u 0 .: :a ... .... 310 0 -270 z 0 ~;: 110 _u -~ 90 0 0 .!.~20 -. .......... .!! 0 :::~10 ~~ "'" o..,. zz i• E % .... ~ Ill 0 "' " c .... 30 20 ---7----- 20 10 0 20 10 ... " c .... ·-----------------------· 10 NOTE: TEMPERATURES ARE IN DEGREES CELCIUS. FIGURE 5.5 AUGUST 2-9, 1983 1200 2400 112 I 1200 1/3 2400 1200 1/4 2400 1200 I" 2400 1200 2400 1200 2400 1200 1/1 2400 1200 I PREPARE D BY . ~ ; ~~-. J I ' .l -=-"""""'"==':":"'~=~:=:~ R&M CONSULTANTS, INC. I I 11• 1 COMPARISON OF STATION 9 LAKE TEMPERATURES WITH WINDSPEED, DIRECTION AND AIR TEMPERATURE 5-15 111 I I 119 PREPAREO FOR : SUS II ~l .\ J C)I tH Vl NT U'l l 20 u !.. ..: :1 10 ... J .. .. "' '!.. ~ c-z>-_u I:"' .. Q 0 20 ~~ .!! ~:;; 10 "':> ~-.. ... ., .... · .. .:·-.. :~ . ..- "'a cz i£- •• 0 E % .. ... "' Q "' " .. ...J 5o,_ ___ _ 40 30 20 10 1-----9 1-----8 6 NOTE: TEMPERATURES ARE IN DEGREES CELCIUS. ~------5 ----------------- FIGURE 5.6 I I 1200 2400 1200 2400 1200 2400 1200 2400 1200 2400 8/16 I 8/17 I 8/18 1 8/19 I 8/20 I P~£ PARED B > . COMPARISON OF STATION 9 20 -10 0 270 90 -o 20 10 ······ 0 850 800 - z ~ .. "' > ... ...J ... 750 ... " "' ...J 100 AUGUST 16-23, 1984 1200 2400 1200 2400 8/21 1 8/22 I PR E PARED FOR : 1200 8/23 ~..-.J '. a:; l__b. _.- R&M CONSULTANTS, INC. LAKE TEMPERATURES WITH WINOSPEED, 01 RECT ION AND AIR TEMPERATURE $U SII~.A J 0 1 Nl VI NI IJ l 5-16 V'l I ...... -...) 4 3 2 4 6 7 4 eo CSANPLE FREQUENCY, TJP .l.} 50 40 .... E -: ... A. 11.1 Q 30 11.1 ~ c _, 20 10 0 FIGURE 5.7 JAN FEB MARCH APRIL PREPARED BY: ~,.----------------- R&M CONSULTANTS1 INC. aNOIN···· OeDL.DOieT• HYID .. OL.DIIIe'fe eu•veva .. e ' I 30 ( i 20 \ I 10 J I I I I I I I I MAY JUNE JULY AUG ISO-TURBIDITY vs. TIME EKLUTNA LAKE at STATION 9 1982 9 _...1· SEPT 4 OCT ICE COVER NOV PREPARED FOR : / 30 / I 40 I DEC 8!50 800 r ,. ,.. "' 7!50 "' r "' < ,. -t 0 z 700 [}{)£[ffi~£c~(ID£®©@ SUSITNA JOINT VENTIJR E -E -::t .... IL. Ill Cl Ill :.c Ul ~ I _, ~ co 50 40 3u 20 10 I 10 \ ------"' 30 -"'"'\ 40 \ 4 4 4 2 2 \...(SAMPLE FREQUENCY, TJp .l 30 \ ) 10 -------.---·· 20 I I 10 I ', I I o-~~~~~~~~~~~~~~~~~~~~~~----__j JAN FEB MARCH APRIL MAY JUNE JULY AUG SEPT OCT NOV DEC PREPARED BY: PREPARED FOR : 850 800 r )I> ~ "' 750 "' r "' < J> ..... 0 z --- 700 ,.---------------ISO-TURBIDITY vs. TIME EKLUTNA LAKE at STATION 9 1983 [}{]£00!b& c ~liD£®©@ R&M CONSULTANTS, INC. aNOtN•••• oeo&.a•••T• Mvo"o'-o•••.,.• au"vaYo•• SUSIT N A JOI N T V EN TURE .... E -:1: ... a. w 50 40 Q 30 w ¥ U1 c ~ _, 1.0 20 10 I 5 \ \ \ 10 FIGURE 5.9 \ o-JM~~~~~~~~~~~~~~~~~~~~~~--~__j JAN FEB MARCH APRIL MAY JUNE JULY AUG SEPT OCT NOV DEC PREPARED FOR : 850 800 750 -700 IT! r IT! < J> -i 0 z PREPARED BY : ~~----------------ISO-TURBIDITY vs. TIME EKLUTNA LAKE at STATION 9 1984 [}{]£00~£ c ~[ID£®©© R &M CONSULTANTS, INC • • N OIN •• III. O.O .. OOiaTe MYOIIIO .. OQi eTe eUIIIV.YOIII" SUS I TNA JO I NT VE NTURE Ul I N 0 zt-oz -"' 2.0 1-u .... U-'i La z "-E 1.8 t="'- 1 .4 >C ~ 1.2 "'u 1.0 0 .... 1 .. .. -% 1-a. 11.1 Q 2 % u u 11.1 en JULY AUGUST PREPA RED B Y : _ :~::-:-!f '-/1 1982 EKLUTNA LAKE EXT. COEFF. SECCHI SEPTEMBER FIGURE 5.10 PREPARED FOR : G~&~~& o ~riD&®©@ -R-&ivt -c oru~s u L.iJiN Ts , ,-Nc. --SURFACE DATA: .,.auw••n• u &t o ~o.c ~••T• H vo n o~o.o a•~t T e •uRv •voAe STATION 9 .._ ______________ __J _______ _::_:....::::._:_:~~~-------_j_--~S~iJ ~S I~I~iJ~,\~.JO I ~J f V UJl l il~l zt-oz -&&.1 .... P..O ... -.. uU• 1.11 ziA: e 1 .11 -~ ..... ... "' 1.4 ><o 1,:! "'u 1.0 EXT . 0 1 .... .. -..... % l11 2 ... . ~ • • SECCHI ·~ "' ...... Q . -% 3 u . u "' (/) . 4 MAY I ________ _____!_ ____ ~:---.J_ ___ ----1 -_ __j JUNE JULY AUGUST SEPTEMBER FIGURE 5.11 PREPARED BY : PREPARED FOR : 1983 EKLUTNA LAKE SURFACE DATA f:D £ffi~~£a ~fiD&®©CQ) ~ 1 1 s 1 1 • , :, h W lf 1. c r 11 , li lt -: -~¥~)[\;1 -R&M · coNSULTA"-JTs~-i Nc._, .,.Qihe•••• uuo~u ~••T • H¥O n ".u .. o oua'• e uuv e vl.ln• U1 I N N .... :1!.15 ~ I E ..... :1!.0 Zt-oz -w ... _ 1 .15 uu z--~ ... ~ 1.0 )(W wo u 0 .15 0 0 .... .. .. ..... 2 :z: ... a. "' 4 a -:z: u u • .... fl) MAY P REPARED BY : -:~~It ~~ ~--=--==-=--= R &M CONSULTANTS, INC. JUNE 1884 EKLUTNA LAKE SURFACE DATA: STATION I FIGURE 5.12 PREPAR E D FOR: G1l&OO~& c ~riD&®©@ Sl S l rt JI\ .J O IN r V i:f ll li iH Vl I N w 0 .0 -2 .0 - .--, -rJ 4- '-' I -4 .0 - r- Q_ w D I -6.0 I u u w U1 -8.0 -10.0 (S) (S) PREPAR ED B Y: ,-,~r-:ij \~ =-J '~-·---:__---...:~~ ==-=.=...=::.-. -· _.:,._....,; R&M CONSULTANTS, INC. •"-O ih •• U . U~DL U ~I D'f e H VOnOL.OOI YT e .URV .V U A . + + + + + • + • + 4: ...... t + . + • .. • ..... + + + ... • t + . + + + + + + .,. + .t ... ...t: .. + + + + + + +. (S) (S) Q Q ~ C\J (YJ 'it EXT i t'!C TION COEFF . (nf 1 ) FIGURE 5.13 EKLUTNA LAKE SURFACE DATA: P REPARED FOR : SECCHI DEPTH lh1&rn~~& o ~riD&~©© va. EXTINCTION COEFFICIENT SIJS I I : ~ .\ JO It J r V i t 1 1 J II l 1000 800 600 400 200 '""" :J t-100 z 80 60 >-40 t- H a 20 H Ul Ul I N 0::: 10 ~ :J 8 t-6 4 2 1 PREPAR ED BY : =: ~~~ .. ~~·~/1 -=---=== R&M CONSULTANTS, INC. + + + 41- + + *++ 1.3 9 TURB = 8. 70 EXT + + R 2 :0.77 + + +. + + C\J (T') v lf') lD 1'-axJ)-o C\J (T') v lf') lD 1'-CXXJtSl [ X T I N C T I 0 f\J C 0 F ~ . ( m -1 ) EKLUTNA LAKE SURFACE DATA: TURBIDITY va. EXTINCTION COEFFICIENT FIGURE 5.14 PREPARED FOR : [h1&r~~& a ~riD&~©@ suS I!: ~t. J1J11·1 r v 1 til , I 'l l i.11 I N i.11 11 .0 -ll. ->-10 .0 I-- H > H [J) 9.0 Ul H :L Ul z 8.0 ([ ~ I-- 1-- z ?.0 w u ~ w a_ 6.0 5 .0 lSI - PREPARE D BY : =--:]t.?·JL-====~--=-=-= R &M CONS ULTANTS , IN C. •"-ou• .. e •u• u l.!a._u ..... a 'f e M Y Of10lOO••T • •vnve vgne . + + + * • + + + .. lSI Q (\J (T) EXTINCTION COEF F. (m_,) FIGUR E 5.15 EKLUTNA LAKE SURFACE DATA: PREPARE D FOR : LIGHT TRANSMISSION DD&~~& o ~riD&®©@ vs. S IJ S II ~J AJ O IIH V U .l l lll l EXTINCTION COEFFICIENT 0.0 -- • • t •• r • • • • . :· • :r- -2.0 + •• 1·r· . + ,.... :t• ..t • -+J ......... + 4-. .._, -4 .0 ... p I + + r-+ (L w + D H -6.0 + I + u + u f.+ w U1 .. -8.0 ~ •• ~ -10 .0 _1 (S) ~ (S) (S) (S) l/1 (S) l/1 (S) --C\J TURBID IT Y CNTU) FIGURE 5.18 P REPA R ED FOR : PREPAR ED B Y: EKLUTNA LAKE SURFACE DATA : fh~&~~& 0 ~riD &®©@ l -,v;-,~rr \11 -I '·'· •. -~---=-~=-=--=----=-.: -==--= TURBIDITY -R&M -CONSU LTAN TS, IN C. SECCHI DEPTH vs • ~~J~li "J ,'\ J0 11Jf 1.1 ! t :T t H I • ,.a,.,. •• ,.. ouoLUt.IOT • .,...,o n o L.OU•II 1'e •u.-v e v o n e 1000 800 600 400 200 ::::J f-100 z 80 60 >-40 f-+ + H + + 0 20 H m v, 0::: 10 I N ::::J 8 -.) f-6 + •• + + 4 2 + + "' .. ID a NQIN ee fl 8 a •OLOG I •Ye MVOAOL D Oie T e e UAV .YO._. + + + + + + •••• ... + + •• + + + + ..... + + +.... + + ~ + + * + f + ~ •••• + •• ••• + + + ••••••• + + + ~ ... ...... + ++ •• + + + + .. ······ r. •"' ... ..,.. .• + + + + + + ... fir; + + + + + t TURB : 7 .98 T SS 0 4 " + •• co.- + ++ ~ ++ + + + + * •• + + ++ ++ "' .. + + + ID coo 0 ... "' TSS C mg / 1 ) 0 .. EKLUTNA LAKE DATA: TURBIDITY vs. R1 = 0 33 I 0 00 ID COO ... TOTAL SUSPENDED SOLIDS I I I I I !I.J 0 0 0 00 0 0 0 00 "' .. ID coo ... FIGURE 5.17 PREPARE D FOR : [}{]£(ru~£o~(ID£®©@ SUS I fNA JO IN r VENTUflE R24 /5 42 6.0 LAKE OUTFLOW 6. 1 Methodology Data on the Eklutna Lake level and outflow quantity and quality were obtained from three sour·ces : 1) Alaska Power Administration surveys and observations, 2) U.S. Geological Survey lake level measurements, and 3) R£,M sampling at the tailrace . The Power· Administr·ation performed level surveys of the lake elevation once per week until June 1983, when the U.S. G. S installed a water-stage recorder· to continuously monitor the level . Outflow data were provided by the Alaska Power Administration, as de- scribed below . Sampling and analysis done by Rr.M at the power plant tailr·ace (see Figur·e 2.1 for location) are also described below for each parameter measured . A view of the tailrace is shown in Photo 6.1. 6.1 . 1 Powerplant Data Personnel at. the Eklutna Pr·oject Hydr·oelectric Plant operated by the U.S. Department of Energy, Alaska Power Administration provided outflow temperature and discharge data to R&M. Temperature was measur·ed r·outinely three times daily, at 0800, 1600, and 2400 hours with a gage that sensed water temper·ature in a penstock within the powerplant. The flow passing through each turbine was calculated daily from production perfor·mance curves. Total lake outflow was reported by the Alaska Power Administration in acre-feet per day and converted by R£,M to cubic feet per second and cubic meters per day for DYRESM model input. During May to December 1984, twice-weekly samples of tailrace outflow water were collected for analysis of turbidity , c onductivity , and suspended sediment concentration. Samples were collected in the tailrace pond as close as possible to the turbine outlet ports , using the DH-48 hand-held, depth-integrated sampler (U .S .G .S 1978). During freezing conditions, the normal site directly above the ports 6-1 R24 /5 44 Illinois. The size distr·ibutions were deter·mined by the electrozone method ( Karuhn and Berg 1982). 6.1 .5 Temperature A mercury thermometer was used for instantaneous temperature mea- surements . Temperatur·es were read to the nearest 0.1 degree Celsi- us. These measurements compared favor·ably to those reported by the Alaska Power Administr·ation . 6 . 1 . 6 Light Penetration Secchi disk depths, as defined by Wetzel ( 1975), were measured using a disk painted in alternate quadrants of black and white to facilitate definition when submerged. Secchi disk measur·ements were reported to the nearest 0.1 foot . 6. 1 . 7 Powerplant Intake The layout of the Eklutna Hydroelectric Pr·oject wor k s, including the powerplant intake in the lake and the tailrace adjacent to the Knik River are shown schematically in Figure 6 . 1 . The intake works are for withdrawal at a single level in the reservoir (elevation 794 feet) and are located on the north shore of Eklutna Lake near Station 15 (Figure 3.1). The or·iginal intake structure extended over 200 feet along the lake bottom and was surrounded by gently-sloping ( 10 :1 slope) sides, as shown in Figure 6 .1. However, CH2M Hill (1981) reported that the intake had to be rehab i litated after the 1964 earthquake . The intake structure as replaced cons ists of a rectangular, reinforced-concrete box , open and pr·otected by trashracks on its top, front , and two sides . The trash racked po r tion is about 23 feet wide, 2u feet high, and 22 feet long in the direction of conduit flow, 6-3 R24/5 43 was often too icy and treacherous, so sampling was done at the edge of the pond, within 5 meters of the outlet ports . Temperature and light penetration measurements were also made at sampling times . 6 .1.2 Turbidity The tailrace water samples wer'e refrigerated between time of collection and time of analysis, which was normally within one day of sampling. Turbidity analyses were per·for·med at the R&M office using a Hach Model 16800 Portalab nephelometric turbidimeter until August 1984, when a Moritek Model 31 nephelometer was purchased and used . Analytical procedures for· turbidity were those described in Standard Methods (APHA et al . 1981). Calibration standards were supplied by the instrument manufacturers. Some differ·ences were noted in measurements made with the two instruments , so preliminary values were adjusted using an empiri ca l corTection r-elationship. 6 . 1.3 Conductivity Samples wer·e analyzed at the R&M office for conductivity using a YSI Model 33 S -C -T meter and adjusted to conductivity at 25°C (APHA et al. 1981). 6. 1 . 4 Suspended Sediment Analyses of suspended sed iment concentration were performed by Chemical and Geological Labor·atories of Alaska, Inc. using standard methods for detect io n of total nonfilterable residue (APHA et al . 1981). The samples were refrigerated after collection until analysis , which was normally the same day as or the day after sampling . Filters with 0.4~-micron pore sizes were used for determining the TSS concentrations . Particle-size distributions and mineralogic analyses were performed by Par·ticle Data Laboratories, Ltd., of Elmhurst , 6 -2 R24 /5 44 Illinois . The size distributions were determi ned by the electrozone method ( Karuhn and Berg 1982). 6 . 1. 5 Temperature A mercury thermometer was used for instantaneous temperature mea- sur·ements. Temper·atur·es were read to the nearest 0.1 degree Celsi- us . These measurements c o mpared favorably to those reported by the Alaska Power Administration. 6 . 1 . 6 light Penetration Secchi disk depths, as defined by Wetzel (1975), were measured using a disk painted in alternate quadrants of black and white to facilitate definition when submerged. Secchi disk measur·ements were reported to the nearest 0 .1 foot. 6. 1. 7 Powerplant Intake The layout of the Eklutna Hydroelectric Project works, including the power·plant intake i n the lake and the tailrace adjacent to the Knik River a ;·e shown schematically i n F igure 6 . 1 . The intake works are for withdrawal at a single level in the reservoir (elevation 794 feet) and are lo cated on the north shore of Eklutna Lake near Station 15 (Figure 3.1 ). The or·iginal i ntake structure extended over 200 feet along the lake bottom and was surrounded by gently-sloping (10: 1 slope) sides, as shown in Figure 6 .1 . However , CH2M Hill ( 1981) reported that the intake had to be rehabilitated after the 1964 earthquake . The intake structure as replaced consists of a rectangular , reinforced-concrete box, open and protected by trashracks on its top, front, and two sides. The trashracked portion is about 23 feet wide, 20 feet high, and 22 feet long in the direction of conduit flow, 6-3 R24/5 45 and the inlet channel is 100 feet wide and about 720 feet long (CH2M Hill 1931). 6. 1 . 8 Powerplant and Outlet Characteristics The Eklutna Project was constructed as a single-purpose, 30,000-plus-kilowatt hydroelectric project by the U .S. Bureau of Reclamation in the early 1950"s. It is now owned and operated by the Alaska Power Administr·ation, U.S. Department of Energy. The pressure tunnel is a 9-foot diameter, circular, concrete-lined tunnel, 23,550 feet long with a design flow capacity of 640 cfs . The penstock is 1395 feet of steel pipe encased in concrete, and has diameters of 91 ", 83", and 75'" in differ·ent portions of its length . The current total installed capacity of the two Francis-type turbines in the powerplant is 33,334 kilowatts. with a maximum gross head of 865 feet. Average annual energy pr·oduction from the plant between 1955 and 1980 was 156,000 megawatt-hours, ranging from 97,000 to 204,000 megawatt-hour·s in any year . The tailrace consists of a reinfor·ced -cono:rete pr·essure conduit, 209 feet long and of varying width and depth, which discharges into an open channel. The open channel has a 25-foot bottom width, side slopes of 2 :1, a depth of 12 .5 feet, and a length of about 2000 feet before emptying into the Knik River (CH2M Hill 1931). 6.2 Results and Discussion The variation of TSS , turbidity , Secchi disk depth, and water temperature of the outflow are shown for 1984 in Figure 6 .2 . Each data point is an instantaneous value obtained during sampling, which was conducted twice per week during the open -water season . The full data set is summarized chronologically in Appendix L, Table L.1 . The outflow water is withdrawn from Eklutna Lake in the vicinity of Station 15, so lake data obtained at Station 15 should be similar to measurements made at the tailrace . Comparison with the isotherm plots in Appendix H shows good agreement 6-4 R24 /5 46 with the measured tailrace temperatures. The recorded temperatures appear to be close to or slightly higher (1 °C or so outflow ) than those obser·ved at the intake level at Station 15 . This is reasonable to expect, indicating that either the intake may be drawing warmer water from nearer the lake surface or the water may be warming as it flows thr·ough the tunnel and powerplant . The observed water temperatures of the outflow ranged from a low of 3.8°C in November to a high of 12 .8°C in late June. Turbidity and TSS levels measured in the outflow were fairly uniform thr·ough the year, with a few upward spikes, likely induced by wind events at the lake . The base level of turbidity also rose during the July-:;eptember summer season . Turbidity over the whole period r·anged from 3 .0 NTU in ear·ly June to a peak of 46 NTU in late August and then dropped back down to 6.6 NTU by November before the lake froze up . The TSS values varied fr ·om a spring low of 0 . 5 mg/1 in June to a high of 36 mg /1 in late July and then a low again of 2.2 mg /1 in November . Only minor fluctuations between 2 .2 and 7 .6 mg/1 and 6 .6 and 15 .5 NTU were observed for TSS and tur·bidity after mid-September . The sharp peak in both plots in late August was probably due to strong southeast winds that blew down the lake and persisted for several days. These winds wo uld tend to tr·ansport more surface water down the lake and would also tend to move more of the turbid inflow down the lake . The tailrace temper·ature also rose slightly at this time, probably due to the presence of additional warm surface water in the outflow. Another possible explanation for the increases in turbidity and TSS :s that the winds blowing down the lake develop sizeable waves (up to 2 feet) at the northwest end . These waves beat on the shor·eline near the intake works and may entrain sediment in the water fr·om the banks of the lake . A plot of the comparison between turbidity and total suspended solids for the tailrace data is shown in Figure 6 .3 . The relationship is weak, with a correlation coefficient of 0 . 25. 6-5 R24/5 47 Particle -size distribution plots are p resented in Figure 6.4 for three 1984 samples of suspended sediment from the tailrace. The samples were collected on July 20, August 28, and October 23, the same dates the inflow streams were sampled . The data used for plotting the graphs are tabulated in Appendix F, Tables F .7-F .9, which were obtained from Particle Data Laboratories . Outflow data for use in the DYRESM model are tabulated in Appendix N . 5 . The table gives daily values of outflow volume, water temperature, and the level of Eklutna Lake , all of which were obtained from the Eklutna Water Project (from the U .S .G .S . for the recent lake levels). The Eklutna Water Pr·oject ( E\'JP), a project to transport drinking water from Eklutna Lake to Anchor·age, is currently being developed by the Municipality of Anchor·age Water and Wastewater Utility. The engineering contractor for the Municipality prepared a report which presented some newly -acquired water quality and sediment data (Montgomery Engineers, Inc . 1984). These data and suppor·ting infor·mation are included in Appendix M in Tables M. 1 and M.2, Figures M.1-M .6, and Photo s M. 1 and M.2 . Samples were co llected at the powerplant during three six -week phases in 1983: Februar·y -March , May-June, and September-October . Table 4 . 1 gives r·anges of numerous water quality par·ameters that were analyzed during their studies . Pl o ts of turbidity and water temperature are shown in Figur·e M. 1 ; samples were obtained daily for the entire period of mid-February th r ough late Octo ber 1983 . The observed temperatures ranged from 39°F (4°C) to 5G°F ( 13°C), and the measured turbidity values var·ied between 7 . 5 and 68 NTU. Several particle-size distr·ibution plots are sho wn, in Figures M.2 -M.4 . It should be noted , however , that these plots are for counts of par·ti c les -not particle volume or particle weight - so they may not be directly compared with the distributions in Figure 6 .4 and Appendix F . For c o mp ariso n , the tables of particle-size distributions based on count obtained from Particle Data Laboratories for the 1984 tailrace samples are also shown in Appendix F (particle-size distributions by POL w e re d e termi ned by count and by volume). Several measurements 6-6 R24 /~ 48 wer·e made for the E\VP of TSS concentrations in various size r·ar.ges and on sever·al dates. These data ar·e tabulated in Table 1\1.2 and plotted in Figure M. 5 . Figure M. 6 compares tur·bidities with TSS concentr·ations obtained from var·ious filter sizes. Finally, Photos M.l and M.2 show TEM (transmission electron microscope) and SEM (scanning electron microscope) photogr·aphs of par·ticles observed in the water samples. 6-7 0'1 I 00 ~ ,_J I( ~--,)(·--~ --SUM fAIT El.53<10 GOAT MOUNTAIN PLAN SOURCE: ALASKA POWER ADMINISTRATION, 1185 FIGURE 8.1 &hematic plan nnd pro!lle or Eklutna project features. "" I 1.0 ...... 40 (/)' (/) 1;7) 2 0 t-E 60 > 1- 4 0 _ c-; -.. ale 20 m; .... 0-;: . ---- :r 1--4 \ Q. Lll o .... ... ? _..,. X: .... (.) (.) Lll 0 (/) 12 (.) ,.. m;o I w-' II t-a: ../ .. cr::E :1:w 0 1- MAY JUNE P RE PAR E D 8 =)~-~~~~~~~==== =:' __ I; ."·1['·1_ -----==~ R &M CONSULTAN T S, INC . ··~~· ... ••••• U I.!O t..UW•l>T . ~-,0 11 0 '-0 Q !M te e u ~\.1 · 'f l..n • TURBIDITY SEC CHI ~ ..... ....--.. ..... ... ~~ _. /........._.._ JULY AUGUST SEPT OCTOBER NO V FIGURE 6.2 PR EPA RE D FOR : 1984 TAILRACE DATA 100 80 ?0 60 50 40 30 ,..... ::J 1-20 z ........ >- 1-1 0 H 8 Cl ? H 6 Cil C\ (Y 5 I ::J 4 ~ 0 1- 3 2 + + T URB . = 7 .40 TSS 0 ·111 + C\J ("') o;r U1 lD 1'-CD TSS Cma/1 ) 1984 TAILRACE DATA: TURBIDITY vs. R1 = 0 .25 TOTAL SUSPENDED SOLIDS (S) (S) (S) (S) (S) (S) (S) (S) C\J ("') o;r U1 lD 1'-CD (S) FIGURE 8.3 P R E PARED FOR : [}{]£00!6& c §00£®©@ SUSIT NA JOIN f VENTUflE tl) z 0 a: 0 :::E z w ~ (/) w ...I 0 .... a: c A. I . . . . ~ -: ~i ~~~:--; --: 1 ·:::~ ::: ::: .. j ... ! 10 -:-r---- . '--~--: !--L __ ! i . : .. i - .. I ·----,··-• . . . . . .. ' I • ···-·---.-. . . . . I 0 .1 -T--:~_! _ __: __ :_·~-:__~_ = ... t' l -----------. -----· I --r-·· --i----· ·-,--- 99.9 99 so 50 L .L_L __ _ ! : : : : ;_I -.-.-'-: -1 : i "j ··:· ·-·t-·--: j . ! :-. , -. _,_--I : I :. : I : I -f-------1 • : ,. :. :_:_ !_ ____ • - . i . --------. ---r--: -! .. : l-·- ·· r·· ----·-r - 10 1.0 r 0 .1 PERCENT ('!It) FINER BY VOLUME THAN INDICATED SIZE EKLUTNA POWER PLANT TAILRACE SAMPLE DATE 0 7/21/84 8 8/28/84 A 10/23/84 F IGURE 6.4 PR[P~NEO BY - SUSPENDED SEDIMENT PARTICLE SIZE DISTRIBUTION 6-11 PRE PARED FOR . f'hoto 6 .1. Lklutna Hydroelectric Project Tailrace, looking upstream at concrete outlet port structure (winter). 1'op of c oncrete wall is approximately 6 feet above the water surface . 6-12 R24 /5 49 7.0 RIVER-LAKE SYSTEM RELATIONSHIPS Time plots for 1934 which demo nstrate the seasonal variation in the parameters and also compare the measured levels in the inflow, in the lake , and in the outflow are s hown in Figures 7 .1-7.3 for turb idity, TSS, and water temper·atu re, respectiv e ly. Inflow (both East Fork and Glacier Fvrk) and o utflo w (tailr·ace ) data are plotted from the samples obtained twice per week fr·om mid-May thr·ou g h mid -No vember . The lake data were measured at the ce nte r· of the lake (Station 9) dur·ing profiling tr ips per·for·med mo nthly fr·om mid-r--1a r c h t o mid-May and twice per month from early June through late November . Sta tion 9 values fr·om the same depths where sedimen t samples w e re ob tained f o r a date were averaged to provide a single value for th e plot . Several trends ar·e evide nt in F i ~u r·e s 7.1-7.3, indicating that ther·mal and sediment effects may work th ei r· w ay through the system and out the lake . The tur·bidity a nd TSS plots f o ll o w each othe r fairly well in gener·al , so they can be conside r·ed t ogether . The minimum tur·bidity levels in the inflow streams occu r-red in early June, r o se sharply a few weeks later, and r·eached the obser·ved peak of the y ea r around July 1 . Levels fluctuated quite a bit but stayed hi g h f o r· almost all of July. The low tur·bidity at Station 9 occurr·ed in ear·ly June r·ose gradually thr·ough June and July, and did not pt·ak u ntil mid-July, a week or two after the streams · peaks . A lag is exp e ct1~d, consid e ri ng tr·avel t ime d o wn the lake, but d iffer·ences in sampling frequ e ncy could also e ff e ct the apparent difference in timing of the events. A further lag was seen at the tailrace: the rise rn turbidity began in late June and continued until the peak in late July . Secondary rises i n tur·bidity o n b o th str·eams in late July show up as high t urbidity values at Station 9 about 2 weeks la ter and then in the o utflow a week or so after that (late Au g ust ). Ther" we re also some winds in the third week of August which may h a ve affe cte d the turbidity of the outflow . 7 -1 R2-l /~ :,tl The peaks in late September· initially appear to be out of phase in the wrong direction, i .e. the high tur·bidity occurs fir·st at Station 9 i n the lake, then in the streams, then at the tailrace. However, the high lake and tailrace values were pr·eceded by str·ong southeast winds which had lasted almost two days and pr·obably produced mixing in the lake . The high str·eam tur·bitities and TSS concentrations followed a day where nearly an inch o f r·ain fell in 24 hours, causing a r·apid r·ise in b ot h creeks . The progress of the tempe r·ature changes thr·ough the r·iver-lake system is more subtle than the sedirnent/tur·bidity changes , likely due to the importance of factors exter·na l to the stream in influencing the lake·s ther·mal condition. The suspended sediment in the lake originates almost entir·ely in the East For·k and Glacier For·k tributaries , but summer war·ming of the lake come s pr·imar·ily fr·om atmospheric influences (solar r·adiation, thermal convection , and ther·mal conduction). The gener·al shape of the temperatur·e plots through the year is with a br·oad peak for the average Station 9 temperatur·es, a similar broad peak in the outflow but with fluctuations up or down a couple of degr·ees at a time , and generally unifor·m base str·eam temper·atures but with frequent variations . The Station 9 temperatures pl o tted w?re averages of measurements made at the same depths where TSS /tur·bidity samples wer·e taken; this gener·ally gave a slight b ias towar·d conditions at the lake surface , rather than for the full depth, as can be seen by compa ring to Figure 5 .3 . Station 9 war·med up fair·ly quickly 1n May and June , reaching the observed high for the year in mid-June. The outflow temperatures followed a similar pattern but occurr·ing slightly later , rising in June to peak late in the month . The temperatures in the streams fluctuated considerably early in the summer (May). This was before the glaciers had begun melting significantly, so streamflow was der·ived chiefly from snowmelt and groundwater inflow. On sunny days, the solar radiation would warm the stream water· directly, especially at Glacier· For·k where the discharge was still very low. Temperature fluctuations later· in the year were due to other environmental factors -air temperature, wind, solar 7-2 R24 /!> !>1 radiation, precipitation, and d egree of influence fr·om the glaciers. The pr·ox imity of the Glacier Fork gage to the Eklutna Gla c ier· ter·minus made it par·ticular·ly sensitive to activities of the glacier . The stream and outflow temper·atures plotted were instantaneous measur·eme nts made at the time of suspende d-sediment sampling . Some fluctuation is due to differences in samplin g time, as was discuss e d in Section 4 . Inspe ctio n of the monthly inflow to and outflow fr·om the la ke for a one-year per·iod (Table 7 .1) sho ws the total a nnual contr ibutions for East Fork and Glacier Fo rk to be near·ly iden tical tho ugh Gl a cial Fork had a higher· summer flow and lower winte t· base flow . Also , the sum of the East Fork and Glacier For k disch a r g es for the year, 188,000 acre -feet, was 91 °o of the lake outfl o w for the same p e r·iod . Thus, all but a very small shar·e of the lake inflow c o me s fr ·om the East Fork and Glacier Fork drainage areas . 7-3 TABLE 7. 1 C0~1PARI S ON OF EKLU'l'NA LAKE INFLOw AND OUTFLO\-J, WATER YEAR 1984 Eklutna Lake Monthly Inflows and Outflows (acre-feet) Month East Fo.rk Glacier Fork Sum Powerplant (EF) (GF) (EF&GF) Outflow ----- October 1983 5,5C.•O 4,.400 9,900 7,300 November 3,000 1,.800 4,800 8,500 Deccrr.ber 2,700 300 3 ,000 13,100 January 1984 2,000 0 2,000 2 3 ,700 February 1,800 0 1,800 24,9CO March 1,300 0 1,300 28,400 April 1,500 0 1,500 27,300 May 3,900 700 4,fiCO 20,500 June 13,400 10,000 23,400 21,300 July 23,500 30,900 54,400 12,500 August 27,100 38,600 6 5 ,700 9,100 Septembe r 7,400 8,100 15,500 9,000 TOTAL 93,100 94,800 187,900 206,200 Notes : 1. Inflow data were measured by R&M Consultants (June-September). Value<; for Noverr.ber-April were estimated, and Octcber and May values "ere partially estimated. 2. Outflow data were prcvided by Alaska Power Administration. 7-4 -..j I lJ1 -:::t .. c > 1- Q -ID a: ;::) 1- 600 ~ a: 500 0 ~00 u. 300 a: w 200 -u 100 < ..J 0 CJ 3 00 ~ a: 0 200 u. 1-IOU If) < w 0 61) 01 ~0 z 0 3() 1- 20 < 10 I-I/) .. ____ ~·· STATION 9 0 ----------------·---- PREPARED B Y: ~t " a: 20 ..J ;;( 0 I- MAR APR ~~ R & M co=N'::S=:=U::L.:=::T:=A:===N=T=S=, =I=N=C=. etw:CIIN •• A. UeO .. CO I •Te HVOnD ... DCII·1'· euAV.YOAe MAY JUN JUL AUG SEP OCT NOV 1984 EKLUTNA STREAM-LAKE SYSTEM DATA: TURBIDITY FIGURE 7.1 PREPARED FOR : [M)£00~& c ~[ID&®©@ SU SI TNA JO I N T VEN l unE ~ 600 a: 0 ~ •oo a: w 200 0 < ...J 0 (!) ~ 300 a: 0 ~ 200 .... ' t-100 01 1/) E < w 0 EAST FORK 1/) 1/) -....1 t-01 I z 0'1 12 0 8 t- < STATION 9 4 t- 1/) 0 w 0 40 < 30 a: 20 ...J 10 < 0 t- ---'---'-------'-- MAR APR MAY JUN JUL AUG SEP OCT NOV FIGURE 7.2 PREPARED FOR : [XJ£lru~& 0 ~00&®©@ 1984 EKLUTNA STREAM-LAKE SYSTEM DATA: . 8 ""'CI1..,.8 A e o •Ot..OQI·T· H'WOnOL OUie T • • ..,AV .VOA e TOTAL SUSPENDED SOLIDS SUS I HJA JO I N r VlNl UHE -..J I -..J .... 0 w a: :::;) ~ < a: w a. ::E w ~ a: w ~ < 3: PREPARED BY: 10 ~ 10 a: e 0 u. e ~ 4 1/) < 2 w 0 01 e z 0 ~ 4 < ~ 1/) 0 w 0 12 < a: e _, < 4 ~ 0 ~~ MAR APR ~~~-~~=================== R&M CONSULTANTS, INC. --' _L__ ____ L_ ___ _J.__ __ MA V JUN JUL AUG SEP NOTE: STATION II VALUES ARE AV E RAOES OF DEPTiiS WHERE TSS/TURBIDITY SAMPLES WERE TAKEN THE SAME DATE. TEMPERATURES FOR THE OTHER SITES ARE IN ST ANTANEOL•S VALUES . GLACIER FORK ,..... .. '\....,. A-_..._. STATION 9 TAILRACE -...._____. j __ - OCT NOV FIGURE 7.3 1984 EKLUTNA STREAM-LAKE SYSTEM DATA: PREPARED FOR : WATER TEMPERATURE SUS I H JAJ O INT V c NT U f1E R24 /5 52 8.0 REFERENCES Alaska Power Administr·ation. 1982-1985. Oper·ating records of outflow dischar·ge, outflow temperature, and lake level for Eklutna Hydroelectric Project and made available by Eklutna Project per·sonnel (unpublished). U .S . Department of Energy . American Public Health Association (APHA), American \Vater Works Asso- ciation, and Water Pollution Control Federation. 1981 . Standard methods for the examination of water and wastewater . edition, 1980 . APHA , Washington, D .C. 1134 pp. Fifteenth CH2M Hill, Inc. 1981 . Task 5, Eklutna Lake alternative water source evaluation . Eagle River Water Resource Study, Appendix V. Prepared for Municipality of Anchorage Water and Sewer Utilities. December. lmberger, J. and J . C . Patter·son . 1981 . A dynamic reservoir simulation model -DYRESM:5. In : Transport models for inland and coastal waters, H.B . Fischer (ed .). Proceedings of a symposium on Predic- tive Ability . Academic Press, Inc. Karuhn, R .F. and R .H. Berg. 1982 . Practical aspects of electrozone size analysis . Particle Data Laboratories, Ltd . Elmhurst , Illinois. Montgomery Engineers, Inc. 1984 . Task 7, Eklutna Lake water treatment pilot plant study . Prepared for Municipality of Anchorage Water and Wastewater Utility . March . National Oceanic and Atmospheric Administration (N . 0. A .A .). 1982-1985. Climatological data, Alaska. Monthly reports and annual summaries . National Environmental Satellite, Data and Information Service, Nation- al Climatic Data Center, Asheville , North Carolina. 8-1 R24/5 53 R&M Consultants, Inc. ( R&M). 1982a . Glacial lake studies, interim report. Susitna h .1·oelectric Project . Prepared for Acres American, Inc . for Alaska Power Authority. December . R&M Consultants, Inc . 1982b. P•·ocessed climatic data , June -September, 1982, Eklutna Lake Station (No . 0700). Volume 8 . Susitna Hyd•·oelectric Project. Prepared for Acres American, Inc. for Alaska Power Author ity. December. R&M Consultants, Inc . 1984. September 1983, Eklutna Susitna Hydroelectl·ic P•·ocessed climatic data, October 1982 - Lake Station (No . 0686 .5). Volume VII. P1·oject . Prepared under contract to Harza-Ebasco Susitna June. Joint Venture for Alaska Power Authority. R&M Consultants, Inc. 1985. December 1984, Eklutna Susitna Hydroelectric Processed climatic data , October 1983 - Lake Station (No . 0686.5). Volume 7. Project. Prepared under contract to Harza-Ebasco Susitna June. Joint Venture for Alaska Power Authority . U.S. Geological Su•·vey. 1978 . National handbook of recommended methods for water data acquisition. Chapter 3 -Sediment. Office of Water Data Coordination, Reston, Virginia . June. Wetzel , R . G. 1975 . Limnology . Saunders College Publishing/Holt. Rinehart and Wi n stn n. Philadelphia, Pennsylvania. 743 pp. 8-2