9305 - Laserfiche WebLink

Home Browse Search

30 on hydrologic conditions and Reclamation's water`r~e`~ease needs, a target flow for Jensen will-be selected in the range of 1,100-1,800 cfs which will remain in effect through the summer period. Fluctuations will deviate no more than 25 percent around-.the ~ stablashg,Ii~,£.l~w, wh i 1 e ~,,fi remaining within the 1,100-1,800 cfs range.; For example,-if 1,600 cfs is selected as the target flow, then flows as measuredt at Jensen will remain ,,~ ~ between 1~ . 0-.1_ .8 _D _cfs; or i f a target of 1,~,QQ cfs i s selected, then flows will remain between 1,100-1,625 cfs. These ranges are not daily ,~ means but are hourly values as measured at the U.S. Geological Survey gauge at Jensen, Utah. A summer freshet originating from the Yampa River or any other tributary would not require a change in release from Flaming Gorge Dam to compensate for the additional flow. We assume that these were natural events historically and can probably be tolerated by the native species. Releases from Flaming Gorge beginning July 1 and continuing until November 1 should be of the warmest water available, approaching 15 °C (highest lake levels). By releasing the warmest water available during this period, water temperatures in the upper Green River should not differ more than 5 °C from the temperature in the Yampa River at Echo Park and should average near 22-25 °C in Gray Canyon from July 1 to August 15. Autumn Autumn flows are a continuation of the late summer flows described above. However, if the year was classified as wet during the April coordination meeting and a need to release excess water still exists, the target flow may be increased to within the range of 1,100-2,400 cfs. If water conditions dictate, the new target may be selected on or after September 15. The 25-percent fluctuation around the target flow remains in effect. Green River flows (measured at Jensen) at or below 2,400 cfs should be sustained until November 1 of each year. During average and dry years, the target flows selected for summer will remain in effect. Flows after November 1 are addressed in the- winter period. Winter The goal for winter releases is to provide low, stable flows near historic levels. Winter flows should be stabilized once ice cover forms and remain so through normal spring breakup. The exception to this is when it becomes evident that higher winter releases are necessary to ensure meeting spring through autumn flows. Under ice conditions, fluctuating flows that promote ice breakup, dams, and shoreline scoring in the mainstream Green River are undesirable for adult fish. Under conditions when ice does not form or when specific research flows are not requested, flows may be operated within constraints of Reclamation's agreement with the State of Utah and the need to release water during wet years. If possible, fluctuations during this period should be moderated. The winter period also should be used to manage Flaming Gorge storage to ensure that flows needed for the following spring peak and summer low, stable period will be provided.