Graduated-Field, Electric Fish Guidance Technology to Deter Salmonids from Hydropower Tailraces and Intake Canals: Two Hydropower Case Studies

The global hydropower community faces constant challenges in protecting various fish species from entering hydropower tailraces and intakes.  Many different technologies have been attempted.  Of the over 50 Graduated-Field Fish Barriers (GFFBs) in operation around the world, we review two case studies from projects designed to prevent fish entry into hydropower facilities using electric gradients.  At Vessy Hydroelectrique Station near Geneva, Switzerland, a bottom-mounted GFFB was constructed in the tailrace just above its confluence with the River Arve.  Of 339 radio-tagged brown trout released below the electric barrier, none were found upstream.  In the case of an array deployed near a hydropower diversion tunnel in Colorado, a series of vertically suspended electrodes created the electric deterrence fields.  The goal was to prevent downstream-moving, adult rainbow trout from entering this intake canal.  Preliminary observations suggest deterrence success.  More robust results will follow from surveys by government agencies when the structure is de-watered to assess whether fish entered or became stranded in the canal.  GFFB technology provides innovative approaches for deterring or blocking fish migrations near or into hydropower facilities.  Other applications for fish deterrence (e.g. in hydropower draft tubes) will be mentioned.