Open-File Report 2010–1042
Screens commonly are installed at water diversion sites to reduce entrainment of fish. Recently, the Farmers Irrigation District (Oregon) developed a flat-plate screen design (that is, the Farmers Screen) that operates passively and may offer reduced installation and operation costs to irrigators. To evaluate the performance of this type of screen (its biological effect on fish), we conducted two separate field experiments in consecutive years. First, in 2009, two size classes of juvenile coho salmon (Oncorhynchus kistuch) were released over a small working version of this screen at Herman Creek, Oregon. The screen was evaluated over a range of inflow [0.02–0.42 cubic meters per second (m3/s)] and diversion flows (0.02–0.34 m3/s) at different weir wall heights. The mean approach velocities ranged from 0 to 5 centimeters per second and mean sweeping velocities ranged from 36 to 178 centimeters per second. Water depths over the screen surface ranged from 1 to 25 centimeters and were directly related to weir wall height and inflow. Passage of juvenile coho salmon over the screen under various hydraulic conditions did not severely injure the fish or cause delayed mortality. Injury or mortality did not occur even though many fish contacted the screen surface during passage. No fish were observed becoming impinged on the screen surface. Second, in 2010, we constructed a modular screen apparatus that had 34 meters of wooden flume connected to a 3.5-meter long section of the Farmers Screen to determine whether fish would refuse to pass over the screen and swim back upstream after encountering the leading edge of the screen under various hydraulic conditions. For these tests, smolting coho salmon and steelhead trout (O. mykiss) were released at the upstream end of the flume and allowed to volitionally move downstream and pass over the screen. Overall, 81 and 91 percent of the fish moved downstream through the entire apparatus within 5 and 25 minutes from their release and only 1 of the 275 fish released swam back upstream after encountering the screen. Collectively, our results indicate that when operated within its design criteria, the Farmers Screen provided safe and efficient downstream passage of juvenile salmonids under various hydraulic conditions. However, we do not recommend operating the Herman Creek screen at inflows less than 0.14 m3/s because water depth can be quite shallow and the screen can completely dewater, particularly at low flows.
First posted February 24, 2010
Revised November 29, 2010
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Mesa, M.G., Rose, B.P., and Copeland, E.S., 2010, Biological evaluations of an off-stream channel, horizontal flatplate fish screen—The Farmers Screen: U.S. Geological Survey Open-File Report 2010–1042, 18 p.
Results of Field Experiments
Biological Evaluation of Experimental Results