Increasing native fish survival with a fish-friendly canal screen: an Upper Colorado River basin success story

Authors: Cat Adams, Kevin Bestgen, David Speas, Mark McKinstry

Year: 2024

Abstract

Water diversions entrain substantial numbers of fish globally and are especially concerning when the species involved are rare and endangered. In the Upper Colorado River Basin, the Green River Canal (GRC) near Green River, UT, diverts up to 80 cfs of water from the Green River in summer for irrigation, but is dried over winter so entrained fish perish. Salvage operations to remove entrained fish before drying and data from stationary Passive Integrated Transponder (PIT) tag antenna arrays between 2013–2018 confirmed entrainment of hundreds of native fish per year into the GRC, including endangered Colorado Pikeminnow Ptychocheilus lucius, Humpback Chub Gila cypha, Bonytail Gila elegans, and Razorback Sucker Xyrauchen texanus. In 2019, an innovative weir and screen structure was installed at the GRC entrance which shunts fish back to the river while also supplying required irrigation water to the canal. Based on canal PIT tag antenna detections, tagged-fish entrainment at GRC was reduced by >99% during 2019–2023 from previous levels. While entrainment concerns were largely alleviated, survival and condition of fish after passing through the return channel, bypass channel, and over the screen was unknown because swift, turbulent flows may cause mortality or physical damage. To test this, we released 867 hatchery-reared Razorback Sucker (194–450 mm TL) and Bonytail (245–336 mm TL) between 2022–2024 to assess their survival and condition before and after passage through the bypass channel and over the screen. Survival of fish recovered after passage was 100% and injuries were negligible. An added benefit of the weir and screen is reduced debris and sediment in the canal downstream of the facility. Based on low entrainment, mortality, injury rates, and the ability to provide needed irrigation water, the innovative fish-friendly weir and screen at GRC is a success story for water users, managers, and native fishes in the Upper Colorado River Basin. This process also highlights the continued need for rigorous evaluation of actions aimed at fish recovery so scarce resources are used to maximum effect.