Use of Mild Electric Gradients to Guide Downstream-Moving Fish Away from Water Intake Canals and Hydropower Projects

摘要

Safe, effective downstream fish passage has been a high priority for both hydropower and fisheries managers. Many guidance technologies have been evaluated over the past several decades. These include physical structures (such as inclined planes and screens), sound in various forms, lights, and techniques such as bubble barriers — in attempts to guide downstream-moving fish away from water intakes. This paper focuses on the use of mild, pulsed DC electric gradients to control fish behavior and guide downstream movements. While most applications of Graduated-Field Fish Barriers (GFFBs) address upstream deterrence, several evaluations have been conducted on deployments that successfully relocate or direct downstream-moving fish, where approach velocities have not exceeded about 0.5 m/s. A few studies are highlighted. The first involves a GFFB installation to reduce juvenile salmon entrainment into an irrigation canal in Reclamation District 108 on the Sacramento River, CA. Despite poor barrier siting and river flows directed toward the intake, entrainment of downstream-moving juvenile fall Chinook salmon was reduced by up to 79%. The second is a recently installed downstream barrier to keep adult salmonids from entering the Gunnison Tunnel, an irrigation diversion structure near Montrose, CO (where future use will include hydropower). Examples of other downstream deterrence barriers and results of guidance research trials are also reviewed. An innovative, hybrid-design concept is proposed for future downstream guidance of fish. The concept incorporates graduated, pulsed electric fields in concert with low-frequency acoustics using pulse-pressure, seismic water-gun technology. This combination of approaches may be key to achieving high levels of success in downstream fish guidance applications.