Field-Based Evaluations of Horizontal Flat-Plate Fish Screens, II: Testing of a Unique Off-Stream Channel Device—the Farmers Screen

Abstract

Screens are installed at water diversion sites to reduce entrainment of fish. Recently, the Farmers Irrigation District (Oregon) developed a unique flat-plate screen (the “Farmers Screen”) that operates passively and may offer reduced installation and operating costs. To evaluate the effectiveness of this screen on fish, we conducted two separate field experiments. First, juvenile coho salmon Oncorhynchus kisutch were released over a working version of this screen under a range of inflows (0.02–0.42 m³/s) and diversion flows (0.02–0.34 m³/s) at different water depths. Mean approach velocities ranged from 0 to 5 cm/s and sweeping velocities ranged from 36 to 178 cm/s. Water depths over the screen surface ranged from 1 to 25 cm and were directly related to inflow. Passage of fish over the screen under these conditions did not severely injure them or cause delayed mortality, and no fish were observed becoming impinged on the screen surface. Second, juvenile coho salmon and steelhead O. mykiss were released at the upstream end of a 34-m flume and allowed to volitionally move downstream and pass over a 3.5-m section of the Farmers Screen to determine whether fish would refuse to pass over the screen after encountering its leading edge. For coho salmon, 75–95% of the fish passed over the screen within 5 min and 82–98% passed within 20 min, depending on hydraulic conditions. For steelhead, 47–90% of the fish passed over the screen within 5 min and 79–95% passed within 20 min. Our results indicate that when operated within its design criteria, the Farmers Screen provides safe and efficient downstream passage of juvenile salmonids under a variety of hydraulic conditions.

Received November 17, 2011; accepted March 15, 2012

ACKNOWLEDGMENTS

We thank Julie Davies O’Shea, Daniel Kleinsmith, Les Perkins, and Roy Slayton of The Farmers Conservation Alliance for financial and technical support; Jerry Bryan for his expertise and advice on the Farmers Screen; Duane Banks and his staff from the Oxbow Fish Hatchery for use of their facility and technical assistance; Bryan Nordlund, Michelle Day, and Larry Swenson of NMFS for early discussions and advice on our study; and staff from the Columbia River Research Laboratory for their assistance in the field. Mention of trade names does not imply endorsement by the U. S. Government.