Use of Louvers for Guiding Fish

Late in 1951, the U. S. Bureau of Reclamation completed construction of the worldˈs second largest pumping plant at Tracy, California. In connection with this project, it was found that facilities would have to be installed to prevent fish of several species and as short as 10 millimeters from passing into the pump intakes. Because of the magnitude of the project and lack of knowledge as to the best protective facility, a test structure with several types of fish screens was installed. Fish stopped by the screens were collected by a port and riser system. Tests revealed that none of these facilities adequately met fish protection requirements at Tracy. It was therefore necessary to consider other methods. Research by members of a team from the U. S. Fish and Wildlife Service and the Bureau of Reclamation developed a louver system for guiding fish. The louver system consists of a fence-like series of vertical steel slats set with their broad faces at right-angles to the direction of flow and placed across the channel in a diagonal line terminating at a narrow by-pass. When fish approach the louver slats, particularly when water velocities are high, they tend to avoid them and swim away at an angle of about 90 degrees. In maintaining this position, they place themselves somewhat broadside to the approach flow and are carried downstream, through the by-pass and either into the main stream or a holding pond. Efficiency studies of louvers in a test flume and in the pilot structure indicated that striped bass, salmon, shad, catfish, and other species can be successfully diverted and collected by this system.