Fall water level drawdown at Lake Osoyoos begins

DOE/submitted photo Zosel Dam is used by the Washington State Department of Ecology to regulate the water level in Osoyoos Lake. When spring runoff swells the  Similkameen River it can back up the Okanogan River from the point where the two rivers join at the confluence just south of Oroville. This causes the Okanogan to rise to the point  the dam can not control the flow as it reverses northward.
DOE/submitted photo
The Department of Ecology has begun drawing down Lake Osoyoos water levels by releasing water held back by Zosel Dam in Oroville to the Okanogan river. The lake will be drawn down two and a half feet to winter operational levels.

Water levels may rise on Okanogan River as pulse flows released

OROVILLE – 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.