Water Velocities in Relation to Fish Behavior in the Design of Screens for Diversion of Juvenile Salmonids from Turbines at Hydroelectric Dams on the Columbia River, U.S.A.
Proceedings of the International Symposium on Fishways '90
Field research was conducted over the past 20 years to develop successful screens to divert juvenile salmonid (Oncorhynchus spp.) migrants away from turbines at hydroelectric dams in the Columbia River Basin, U.S.A. During the spring outmigration, guidance screens angled approximately 50 degrees upward from vertical and with a porosity of approximately 33% in water velocities of approximately 1.5 to 2.0 m/second were the most effective in diverting yearling (105- to 180-mm fork-length) fish. Results, however, were specific to each dam. Not all guidance screen installations successfully diverted juvenile migrants. In cases where water velocities above the screened area were decreasing, fish apparently avoided the area above the screen and moved below it. Even at the best installations, however, guidance screens only diverted between 20 and 40% of the subyearling (60- to 90-mm fork-length) salmonids during the summer migration.