Seasonal water level changes made to Osoyoos Lake

YAKIMA – Water levels in Osoyoos Lake in north central Washington will be raised over the coming weeks in anticipation of the changing seasons.

The Washington Department of Ecology (Ecology) operates Zosel Dam at Oroville, Wash. The dam regulates the lake levels at Osoyoos Lake, which straddles the border between British Columbia and Washington state. The lake serves as a source of water for irrigation and summer recreation in both the U.S. and Canada.

The lake will be gradually raised to summer operational levels and then maintained between 911.5 and 912 feet until the end of October. Raising lake levels in the spring provides for additional storage to support irrigation of summer crops, recreational opportunities on the lake, and improved stream flows throughout the season in the Okanogan River. In the fall, dam operators will lower the lake level to protect property along the lake from freezing water surfaces and wind erosion.

Lake levels are mandated under orders put in place by the International Joint Commission (IJC), a board made up of representatives from the United States and Canada. This past winter, the IJC, in negotiations with interested parties on both sides of the border, completed new orders to replace the 25 year-old Orders of Control, which expired in February of this year. These new orders make few changes to the old orders, except to provide for a longer period for filling the lake in the spring. The effect of this is to allow the operator to manage the uncertainty of spring weather and run off more effectively.

For more information on the operation of Zosel Dam or Lake Osoyoos, contact Al Josephy at Ecology, (360) 407-6456. Additional information on the International Osoyoos Lake Board of Control and the new Order of Approval can be found 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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