Impacts of Recreational Flow Releases on Macroinvertebrate Drift at Different Distances Downstream from Abanakee Dam, New York

Abstract

We examined macroinvertebrate drift at 4 sites downstream of Abanakee Dam on the Indian River, NY, on separate days at base-flow conditions and following days during recreational releases (rapid releases supporting white-water rafting enterprises). Macroinvertebrate drift rates were highest near the dam due to high numbers of drifting Simuliidae at both base flow and during a release. At the other 3 sites, Simuliidae were less abundant in the drift, and Chironomidae and Sphaeriidae had especially high drift densities during a release, suggesting a greater vulnerability to catastrophic drift. Macroinvertebrate drift was not affected by differences in stream gradients or shear forces that did differ between sites. Our drift densities during the recreational releases were higher than observations from other studies during natural floods, suggesting greater drift vulnerability to rapid increases (∼15 min) in discharge when flood gates are opened.