An Air-Lift Pump for Sampling Juvenile Salmonids at John Day Dam

Abstract

An air-lift pump system was designed and constructed to sample juvenile salmonid accumulations in the turbine-intake gatewells of John Day Dam on the Columbia River. A funnel concentrated fish into a 30.5-cm-diameter thin-walled pipe into which compressed air was delivered. Fish were lifted from water depths of 14–25 m to heights of 1–7.3 m above the water surface. With a 14-m Submergence and 1-m head, the Sampling system operated continuously, dependably, and economically, providing hourly estimates of salmonid passage with little or no injury to fish.