REC-ERC-81-10 LIMNOLOGY OF THE UPPER NORTH PLATTE RESERVOIR SYSTEM, WYOMING July 1981 Engineering and Research Center U. S. Department of the Interior Bureau of Reclamation 7-2090 (4-81) Water and Power TECHNICAL REPORT STANDARD TITLE PAGE I. REPORT NO. 3. RECIPIENT'S CATALOG NO. REC-ERC-81-10 ° ,. 4. TITLE AND SUBTITLE 5. REPORT DATE Limnology of the Upper North Platte Reservoir System, July 1981 Wyoming 6. PERFORMING ORGANIZATION CODE 7. AUTHOR(S) 8 PERFORMING ORGANIZATION J. J. Sartoris, J. F. LaBounty, S. G. Campbell, and REPORT NO. J. R. Boehmke REC-ERC-81-10 9. PERFORMING ORGANIZATION N■jME AND ADDRESS 1 0. WORK UNIT NO. Bureau of Reclamation Engineering and Research Center 11. CONTRACT OR GRANT NO. Denver, Colorado 1 3. TYPE OF REPDRT AND PERIOD COVERED 12. SPONSORING AGENCY NAME AND ADDRESS Same 1976-79 1 4. SPONSORING AGENCY CODE I S. SUPPLEMENTARY NOTES Microfiche and/or hard copy available at the Engineering and Research Center, Denver, Colorado. Editors: JMT EJH 1 6. ABSTRACT The baseline limnology of Seminoe, Kortes, Pathfinder, and Alcova Reservoirs, on the North Platte River in Wyoming, was studied by Bureau limnologists during 1976-79. The study period included 2 years of severe drought followed by two of higher than average runoff in the North Platte basin. The reservoirs differ greatly in volume and operating patterns: Seminoe (1.25 x 10° m3) is mainly for 6 8 power production; Kortes (5.88 X 10 m3) and Alcova (2.27 x 1 0 m3), flow regulation; and Pathfinder (1.25 x 10° m3), for storage. The three major system tributaries, - the North Platte, Medicine Bow, and Sweetwater Rivers, differ significantly in chemical composition and annual flow volume. Limnology of the Upper North Platte reservoir system is typical in many ways of the High Plains Region of the Western U.S.; i.e., the reservoir waters are dimictic and alkaline, with salinity averaging 369 mg/L and calcium carbonate hardness averaging 184 mg/L. Also, the bluegreen alga, Aphanizomenon flos-aquae, blooms in late summer. Study results showed that this annual bloom depends on a shift from phosphorus-limiting conditions in early summer to more nitrogen- limiting conditions by late summer. The study also indicated that nutrient dynamics, and hence primary production in the system, is heavily influenced by the interaction of three main factors: sys- tem operating criteria, annual runoff variations in the three major tributaries, and the presence of deep outlets in all four dams. 1 7. KEY WORDS AND DOCUMENT ANALYSIS a. DESCRIPTORS-- I *Iimnology/ *reservoirs/ environments/ ecology/ chemical properties/ *aquatic environment/ *benthic fauna/ *zooplankton/ light penetration/ *heavy metals/ nutrients/ chlorophyll b. IDENTIFIERS--! *Seminoe, Kortes, Pathfinder, and Alcova Reservoirs, Wyo./ *Kendrick Project, Wyo./ *North Platte Project, Wyo./ LM Region c. cosari F ieic/Group 08H C°WR R: 0808 sR 1m7 48G 1 8. DISTRIBUTION STATEMENT 1 9. SECURITY CLASS 21. NO. OF PAGES THIS REPORT) Available from the National Technical Information Service, Operations UNCLASSIFIED 129 Division, 5285 Port Royal Road, Springfield, Virginia 22161. 20. SECURITY CLASS 22. PRICE (Microfiche and/or hard copy available from NTIS) (THis PAGE/ UNCLASSIFIED GPO 831-316 REC-ERC-81-10 LIMNOLOGY OF THE UPPER NORTH PLATTE RESERVOIR SYSTEM, WYOMING by J. J. Sartoris J. F. LaBounty S. G. Campbell J. R. Boehmke July 1981 Applied Sciences Branch Division of Research Engineering and Research Center Denver, Colorado SI METRIC UNITED STATES DEPARTMENT OF THE INTERIOR * BUREAU OF RECLAMATION ACKNOWLEDGMENTS Partial funding for this study was provided by the Lower Mis- souri Region of the Bureau of Reclamation. The remainder of the support for the study was provided through the Division of Research's ongoing project, "Limnology for the Ecological Management of Reclamation Projects" (DR-409). Chemical analyses were performed by the Chemistry, Petrography, and Chemical Engineering Section of the Applied Sciences Branch. Soil analyses were done by the Soil Testing Section of the Geo- technical Branch. Valuable field assistance was rendered by personnel of the Casper Office of the Wyoming Game and Fish Department and by personnel of the Seminoe-Kortes Unit of the Bureau. With- out the timely help of these people we would have literally been "up the creek" on several occasions. As the Nation's principal conservation agency, the Department of the Interior has responsibility for most of our nationally owned public lands and natural resources. This includes fostering the wisest use of our land and water resources, protecting our fish and wildlife, preserving the environmental and cultural values of our national parks and historical places, and providing for the enjoyment of life through outdoor recreation. The Department assesses our energy and mineral resources and works to assure that their development is in the best interests of all our people. The Department also has a major respon- sibility for American Indian reservation communities and for people who live in Island Territories under U.S. administration. The information contained in this report regarding commercial products may not be used for advertising or promotional pur- poses and is not to be construed as an endorsement of any product by the Bureau of Reclamation. CONTENTS Page Acknowledgments ..........ii Application ..........1 Summary of findings ..........1 Recommendations for future study ..........2 Introduction ..........3 Description of study ..........3 Description of reservoirs ..........3 Description of area ..........3 Previous studies ........1 0 Methods and materials ........11 General ........11 Physical/chemical ........1 5 Chlorophyll ........16 Plankton ........16 Benthos ........16 Results ........16 Hydrology ........16 Light ........19 Physical/chemical profiles ........20 Major ions ........26 Heavy metals ........32 Iron ........33 Manganese ........33 Zinc ........33 Copper ........34 Lead ........34 Nitrogen-phosphorus plant nutrients ........34 Primary production ........45 Zooplankton ........49 Benthos ........60 Sediments ........65 Discussion ........67 Study limitations ........67 Reservoir characterization ........67 System overview ........69 System operating criteria ........69 Annual runoff variations ........69 Deep reservoir outlets ........70 Bibliography ........73 Appendixes ........77 A. Temperature profiles ........77 B. Dissolved oxygen profiles ........89 C. pH profiles ......101 D. Conductivity profiles ......113 E. Chlorophyll a ......125 III CONTENTS — Continued TABLES Table Page 1 General description of Upper North Platte reservoirs, Wyoming ........... 1 0 2 Sampling dates .......................................................................... 1 3 3 Analytical detection limits ............................................................. 15 4 Reservoir system inflows and outflows, water years 1976-79 ........... 1 7 5 Reservoir system mean depths, water years 1976-79 ....................... 1 9 6 Observed summer ranges of light extinction coefficients at deep reservoir stations .................................................................... 20 7 Observed summer ranges of physical/chemical profile data at deep reservoir stations .................................................................... 22 8 Upper North Platte reservoir system water chemistry - May through October - Mean ion concentrations and TDS ................................ 27 9 Upper North Platte reservoir system water chemistry - May through October - Mean heavy metal concentrations ................................ 32 10 Mean 1978 nitrogen and phosphorus concentrations ......................... 35 11 Tributary annual inflows and estimated nutrient loadings ................... 46 12 Mean chlorophyll a ...................................................................... 46 1 3 Comparison of areal chlorophyll a and light extinction coefficient, June-August .......................................................................... 50 14 Reservoir inflows ........................................................................ 51 15 Mean annual chlorophyll a concentrations ........................................ 51 16 Zooplankton abundance ............................................................... 59 17 Chironomids and oligochaetes, 1976-79 ........................................ 64 1 8 Chironomids, 1976-79 ............................................................... 64 1 9 Oligochaetes, 1976-79 ............................................................... 64 20 Average benthos values ............................................................... 65 21 Sediment classification and organic content .................................... 66 22 Heavy metals content of bottom sediments .................................... 66 23 Comparison of sediment particle-size analyses - Pathfinder Reservoir ................................................................................ 67 24 Major outlet locations - Upper North Platte reservoirs ......................... 70 FIGURES Figure 1 Map of Wyoming and Colorado showing the location of the Upper North Platte reservoir system ..................................................... 4 2 Seminoe Reservoir ...................................................................... 5 3 Kortes Reservoir ........................................................................ 6 4 "Miracle Mile" .......................................................................... 7 5 Pathfinder Reservoir