YAKIMA, Wash. – The Bureau of Reclamation will begin its annual “flip-flop” operation, beginning in mid-August, to aid in successful spawning and incubation of chinook salmon eggs and to improve winter reservoir storage in the Yakima basin.
Reclamation will begin diverting water down the Kittitas Reclamation District’s Spillway 1146 into the Yakima River near Thorp, the week after Labor Day weekend. Buoys and warning signs will be in place in the Yakima River by September 4 and remain until mid-October, or after the flow from Spillway 1146 has ended.
Reclamation urges those recreating or working along Yakima basin rivers to exercise caution, especially in the Yakima River near Thorp. Please avoid areas where spillway water flows into the river, portage around buoys, and stay away from dangerously turbulent flows.
Flows out of Keechelus and Cle Elum reservoirs in the upper Yakima River basin will gradually decrease, while flows from Kachess and Rimrock reservoirs will increase. This operation will affect flows in the Tieton and Naches rivers as well as the upper Yakima, Cle Elum, and Kachess rivers in the upper Yakima basin. In other words, flows from these facilities will transition, or “flip-flop.”
Flows below Cle Elum Reservoir will continue to decrease gradually from now until about August 26 when flows will decrease by about 140 cubic feet per second per day to the target flow of 180 cfs by about September 3. This transition is earlier than normal due to drought conditions. Rimrock Reservoir outflows from now to August 25 will increase gradually to between 900 and 1,200 cfs, as needed, to offset Cle Elum outflow reductions. Flows will be increased to between 1,500 and 2,300 cfs between August 26 and mid-September, depending on irrigation demands and weather conditions. Tieton River flows could be between 1,200 and 2,200 cfs during the Labor Day weekend, depending on prevailing conditions. Rimrock outflows will begin decreasing in late September and will decline to 50 cfs after October 20, the end of the irrigation season, to maintain required downstream minimum flows and improve Rimrock reservoir refill.
This annual operation maintains relatively low, more natural flows, which are important for chinook salmon spawning in the upper Yakima, Cle Elum, and Bumping rivers. It also allows Reclamation to reduce impacts on irrigation water supplies by allowing lower reservoir releases throughout the winter to improve storage for the coming season.
Real-time streamflow information can be found on Reclamation’s website at https://www.usbr.gov/pn/hydromet/yakima/index.html.