Ecology makes seasonal water level changes at Osoyoos Lake

YAKIMAWater levels in Osoyoos Lake in north central Washington are being lowered over the coming weeks in anticipation of the changing seasons.

The lake will be gradually lowered to winter operational levels at Zosel Dam and maintained at about 909.5 feet until spring. Lowering lake levels in the fall provides more storage area for winter rain and melting snow and prevents shoreline damage from winter freezing and flooding. In March, dam operators will raise the lake to the prescribed level of 911.5 feet for normal summer operations.

As recreational activity on the lake begins to slow down in the fall, the Washington Department of Ecology lowers the level of the lake from its summer (March 1-Oct. 31) levels to winter operational levels. These levels are mandated under orders put in place by the International Joint Commission, a board made up of representatives from the United States and Canada. Originally developed in the 1940s, the orders have been adjusted twice, most recently in January 2013. Adjustments have been small and will not materially change the way the dam and lake levels are operated throughout the year, especially in winter.

For more information on the operation of Zosel Dam or Lake Osoyoos, contact Al Josephy at Ecology, (360) 407-6456, or by email at To track the progress of lake levels in “real-time,” as well as find additional information, go to the U.S. Geological Survey web page for Osoyoos Lake.


About Sandra Partridge

Sandra Partridge works for the Washington State Department of Ecology.

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