Efficacy of increasing discharge to reduce tow-mediated fish passage across an electric dispersal barrier system in a confined channel

Abstract The Electric Dispersal Barrier System (EDBS) in the Chicago Sanitary and Ship Canal (CSSC) was built to limit the interbasin transfer of aquatic invasive species between the Mississippi River Basin and the Great Lakes Basin. Commercial barge traffic, or tows, moving downstream through the EDBS can facilitate the upstream passage of small fish through the barrier by reducing the voltage gradient of the barrier and causing localized upstream return currents. This study tested whether it is possible to prevent upstream passage of small fish across the barrier by preventing upstream return currents. Measurements of water velocity, voltage gradient, and tow speed, as well as sonar-based observations of resident fish, were made as a tow transited the EDBS moving downstream. The results indicate that upstream return currents can be prevented for typical flow conditions in the CSSC (ambient velocity = 0.15 to 0.23 m/s) when tow speeds are