Environmental

Reclamation to begin ‘flip-flop’ operations at Yakima project

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Reclamation to begin ‘flip-flop’ operations at Yakima project
(Yakima River in the fall with Mt. Adams in the background. Shot taken from Thorp Road in Wapato, WA at 46°31'07.6"N 120°27'24.8"W. 11/7/2018 BOR Photo by Kirsren Strough)

The U.S. Bureau of Reclamation is beginning its annual “flip-flop” operation to aid in successful spawning and incubation of chinook salmon eggs and to improve winter reservoir storage in the Yakima basin.

The Yakima Project provides irrigation water for a strip of fertile land that extends for 175 miles on both sides of the Yakima River in south-central Washington. The irrigable lands presently being served total about 464,000 acres. There are seven divisions in the project: Storage, Kittitas, Tieton, Sunnyside, Roza, Kennewick and Wapato. Storage dams and reservoirs on the project are Bumping Lake, Clear Creek, Tieton, Cle Elum, Kachess and Keechelus. Other project features are five diversion dams, canals, laterals, pumping plants, drains, two powerplants and transmission lines.

Reclamation will begin diverting water down the Kittitas Reclamation District’s Spillway 1146 into the Yakima River the week after Labor Day weekend and anticipates flows to last until the middle of October.

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 until about Aug. 26 when flows will decrease by about 140 cubic feet per second per day to the target flow of 180 cfs by about Sept. 3. This transition is earlier than normal due to drought conditions. Rimrock Reservoir outflows from now to Aug. 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 Aug. 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 Oct. 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.

Reclamation is a federal agency under Interior and is the largest wholesale water supplier and second largest producer of hydroelectric power in the U.S.