USGS Washington Water Science Center
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WA159 - Flushing Of Reservoir Sediment Deposits Through The Similkameen-Okanogan River Systems - Completed FY1972
Problem - Enloe Dam (about 54 feet high) and hydroelectric plant on the Similkameen River, 8.8 miles upstream from the mouth, was built about 1908. Fluvial sediment has been depositing in the reservoir. The dam restricts the movement of salmonoid fish, and since it is no longer being used a proposal has been made to remove it. Should the dam be removed, a major concern is the effect of deposition of sediment in the stream channel of the Similkameen River below the dam and the Okanogan River below the confluence of the Similkameen River.
Objectives - Predict the probable movement and deposition of sediment from the reservoir if the dam is removed.
Approach - The volume and particle-size distribution of the sediment in the reservoir will be determined by fathometer surveys and core samples. Present sediment deposits in the channel from Enloe Dam to the mouth of the Okanogan River will be examined. Relationships between water discharge and sediment concentration in the Similkameen and Okanogan Rivers have been developed. The capacity of the system to transport sediment will be related to the sediment available in the reservoirs, and a prediction made as to the probable movement of sediment in the system.