Large-Scale Side Channel and Mainstem Restoration in the Chelan River

The Chelan PUD constructed 4 acres of steelhead spawning and rearing habitat for Chinook and steelhead as part of the settlement agreement for the relicensing agreement for the Lake Chelan Hydroelectric Project.  The restored habitat was constructed in the Chelan River and Powerhouse tailrace.  The river habitat is situated in an area where spawning flows are on the order of 320 cubic feet per second (cfs), while annual flows approach 4,000 cfs.  An innovative restoration design was developed and constructed to provide suitable spawning and rearing depths and velocities that are acceptably sustainable over a range of flow conditions.  To address the challenges of highly variable flows, a grouted rock hydraulic control structure was constructed at the upstream end of the restoration reach to direct spawning flows into the side channel and divert higher flows to the existing overflow channel.  The natural functioning side channel uses log jams and boulders to form a pool and riffle sequence that will provide suitable depths, velocities, and substrate sizes for salmon spawning.