A photo of Deep Lake

Deep Lake is a canyon on the east side of Dry Falls State Park. It is a tributary of the Grand Coulee. The natural lake is at least 150 feet deep and springs feeding the lake help maintain its deep blue clarity. The lake and canyon formed by erosion during the great floods created by the collapse of ice dams associated with continental glaciers in the upper Columbia River Basin region during the Quaternary ice ages (Alt, 2001; Baker, 1987; Beeson, 1987).