Development of surface bypass and collection at Rocky Reach Dam, Columbia River
bypass, surface bypass, fish passage, diversion, diversion screen, screens, intake, turbines, guidance, guidance efficiency, efficiency, spillway, baffles, Wells Dam, prototype, juvenile, upstream, entrance, steelhead, transponder, chinook, fish bypass
Innovations in Fish Passage Technology
American Fisheries Society
Between 1985 and 1994, Chelan County Public Utility District (Chelan) used floatingrotating and passive diversion screens in the turbine intakes of Rocky Reach Dam to guide fishaway from the turbines and around the dam. Guidance efficiency of the diversion screen systemwas insufficient, rarely exceeding 25% of the total fish entering the turbine intakes. As a result,Chelan pursued the concept of surface collection based primarily on the success of spillwaybaffles at Wells Dam. Chelan tested a prototype surface collector in 1995 to see if the conceptwas feasible at Rocky Reach. Approximately 900, 000 juvenile fish passed through theprototype. Chelan concluded the concept of surface collection at Rocky Reach was feasible. In1996, we extended the floor of the surface collector upstream and added a sloping wall.Hydraulic and mathematical modelling showed that the new sloping wall and floor extensionnegatively affected the direction of water flow into the entrance of the collector. We removed theextended floor and sloping wall before the 2997 field season. In 1996, we observedapproximately 30% of the radio-tagged steelhead that entered the entrance of the collectorproceeded all the way through. In 1997, the percentage increased to 73%. The passiveintegrated transponder tag study in 1996 showed that approximately 25% of the juvenile Chinookand steelhead were guided by the fish bypass system. In 1997, the percentage improved to 47%The hybrid fish passage system (surface collector and diversion screens) appears to be thepreferred method for juvenile salmonid bypass at Rocky Reach Dam in the future.