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| Blue Mesa Thermal Water Modeling * November 2002 *
Blue Mesa Dam and Reservoir were constructed in 1966 to provide hydropower, flood control, irrigation, and recreational uses. They are located on the Gunnison River approximately 30 kilometers (20 miles) west of Gunnison, CO. The Reservoir has a maximum storage of approximately 1.16x109 m3 (940,700 acre-feet) with a maximum depth of 104 m (342 feet). The reservoir is considered mesotrophic, and has an average residence time of about 0.6 years. The Scope of the project was to use the calibrated and validated CE-THERM model of Blue Mesa reservoir to investigate the effects of surface withdrawals via the surface spillway in lieu of exclusive hypolimnetic withdrawals on the reservoir thermal patterns. The results of the simulations of releases over the spillway indicated that overall water temperatures in the reservoir will be cooler, especially in the metalimnion, if releases are not made solely through the hypolimnion. The effect tends to increase with duration of spillway releases. Summer meteorologic conditions appear to dominate the surface water temperatures until the late summer or early fall when surface water temperatures cool when spillway releases have been used. Maximum temperature differences appear to be about 2°C at 20-50 m below the water surface for runs with the maximum feasible amount discharged over the spillway. When only half of the feasible amount is discharged over the spillway, similar temperature effects are seen at values intermediate between results for the simulations with zero and maximum spillway discharges. These results indicated that the amount of release over the spillway has an effect on the magnitude of change in water temperature. Further simulations should be made to determine if the duration and timing of release over the spillway also has profound effects on the magnitude of water change. Publications: Saito L, Koski M. 2006. Simulated effects of altered spillway releases on thermal structure and kokanee growth in a Colorado reservoir. Journal of the American Water Resources Association 42(3):645-658. Johnson BM, Saito L, Anderson M, Weiss P, Andre M, Fontane DG. 2004. Effects of climate and dam operation on reservoir thermal structure. Journal of Water Resources Planning and Management 130(2):112-122.
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