Fish Bypass System Impact upon Turbine Runner Performance at Rocky Reach Dam

Public Utility District No. 1 of Chelan County, Washington State, USA (Chelan) owns and operates the Rocky Reach and Rock Island Hydroelectric Projects located on the Columbia River. Several species of salmon and steelhead trout migrate through these projects. Downstream migrating juvenile fish pass through either the turbines, where they experience some mortality, or through migration-augmenting spill flows, which are marginally effective and very expensive. Chelan has developed a “Surface Collection” fish bypass system and “Fish-Friendly” turbines at its Rocky Reach Project to mitigate harmful effects to the downstream migration of the juvenile fish. The surface collection system will be installed within the Rocky Reach forebay, supported by the upstream face of the dam, and will encroach upon the generating unit intakes. This paper describes the modeling investigation used to define the effects the surface collector structure will have upon turbine operating characteristics and how that information will be used to balance bypass effectiveness with turbine performance.