Flaming Gorge Dam Release Temperatures Bureau of Reclamation Upper Colorado Regional Office Flaming Gorge Dam Selective Withdrawal System • Constructed in 1977-1978 to improve thermal conditions for trout and endangered fish below the dam • Funded by USBR using CRSP Section 8 Fish and Wildlife funds (cost $6.5M; no cost shares) • Maximum operating elevation 40’ below reservoir surface to prevent vortex formation Flaming Gorge Dam Selective Withdrawal System “With improved tailwater temperatures, we predict the following fishery benefits Rainbow trout harvest will increase markedly. Rainbow trout growth rates will increase due to increased metabolic rate resulting from higher tailwater temperatures during the spring, summer, and autumn months. Conditions for two endangered fishes, the Colorado squawfish and the humpback chub, are also expected to improve. These fishes will extend their range moving back into the Green River upstream of its confluence with the Yampa River as a result of higher tailwater temperatures. It is possible that successful reproduction may occur again in tailwater reach of the Green River.” J.C. Peters, 1978. Modification of intakes at Flaming Gorge Dam, Utah, to improve water temperature in the Green River. USBR Engineering and Research Center, Denver. Full Pool 6,045’ msl 40’ { 190’ Winter Elevation Ca. 100’ Discharge via Penstocks at 5,650’ msl Current Operations End-of-month selective withdrawal elevation indicated by red star Pre-ROD Operations End-of-month selective withdrawal elevation indicated by blue star Pre- and Post-ROD Temperatures at Greendale + 0.5 C + 0.8 C + 0.2 C Uncertainties • Early surface withdrawal (ca. 40’ below surface) could delay development of thermal stratification (T. Vermeyan, USBR Technical Services Center) • Surface withdrawal generally results in less dissolved oxygen transfer to deeper strata • Early surface withdrawal could facilitate escapement of non-native fish • Peak flow magnitude (April-June) will always affect release temperatures: higher releases = lower temperatures Temperatures 2017 An Unusual Year Pikeminnow emergence Jul 2 Questions.