Evaluation of Extended-Length Submersible Bar Screens at Bonneville Dam First Powerhouse, 2000

摘要

Submersible traveling screens (STSs) are installed in all turbine units at Bonneville Dam First Powerhouse to guide juvenile salmonid migrants into a juvenile fish bypass system. In tests conducted from 1989 to 1992, fish guidance efficiency (FGE) of these screens ranged from approximately 40% for yearling chinook salmon to 60% for coho salmon and steelhead during the spring migrations. During the same testing period, FGE for sockeye salmon was approximately 25%. During the summer migrations, FGE for subyearling chinook salmon was approximately 40% in June, then decreased to less than 10% by the second week in July. To look at the potential for increasing FGE, extended-length bar screens (ESBSs) were installed in Unit 8 at Bonneville Dam First Powerhouse and first tested in 1998. These screens are 40 ft long compared to the 20-ft long STSs and have been successful at increasing FGE at other middle Columbia and Snake River dams. To further improve FGE by increasing flows into the gatewell, operating gates were also raised in the A and C slots and the gate was removed in the B slot to accommodate a fyke-net frame used for FGE testing.