The Zosel Dam is a dam in Okanogan County , Washington state . It dams the Okanogan River and forms the Osoyoos Lake . The dam was built as part of the larger Osoyoos Lake International Water Control Structure , a joint venture between the Washington State Department of Ecology and the British Columbia Ministry of the Environment . The dam was designed by the Canadian company Acres International Limited and built by the US company Rognlins Inc.
