Autumn is upon us and the Washington Department of Ecology is drawing down water levels at Lake Osoyoos to winter operational levels. Releases from Zosel Dam to the Okanogan River will increase in volume to bring the lake down about two-and-a-half feet from now until December.
Extra water stored in the lake this summer, due to drought declared in the region, provides an opportunity to boost streamflows and protect fish species in the river going into the fall, said Al Josephy, a water resources specialist with Ecology. This means the river will be running high this week, and those living downstream are advised to take adequate precautions.
“The Okanogan River has a tendency to build up sediments on the riverbed, which, over time, clogs gravels on the bottom, making spawning access for fish problematic,” he said. “Following discussions with local fish biologists, we plan to use the extra available water in the lake to flush those gravels by allowing short intervals of high flows to be released over several days during the middle of September.”
The plan is to ramp up flows to about 1,200 cubic feet per second for one or two days, beginning later in the week of September 16. People living and working along the river below Zosel Dam may experience bursts of high flows and may see conditions like those seen during spring runoff.
Lakeside residents can expect to see the lake drop about six inches sometime between Sept. 17 and 25. Following the flush, the drawdown will proceed in its usual course, and the lake levels will continue to decline. Throughout the year, the Lake Osoyoos Board of Control mandates the cross Canada-United States-border lake levels to meet seasonal needs.