DOCUMENTING THE EFFECTS OF A RECENTLY-LICENSED RUN-OF-RIVER HYDROELECTRIC PROJECT ON BENTHIC MACROINVERTEBRATES IN THE SALMON RIVER, NEW YORK.

J.L. Hallock Jr., N.H. Ringler, and C.A.S. Hall. Department of Environmental and Forest Biology, SUNY College of Environmental Science and Forestry, Syracuse, New York, USA

The conversion of hydroelectric operations from "peaking-flow" to "run-of-river" (ROV) typically results in higher minimum instream flows, but can still alter natural hydrographs substantially. This study compares the water chemistry and benthic macroinvertebrates (BMI) of main-river riffle sites upstream and downstream of the 1996-licensed Salmon River Project (38.5 MW, epilimnetic release). From October 1999-June 2000, benthic samples and physical data were collected every 6-12 weeks to document community composition, density, biomass, and instantaneous growth of BMI at the generic level. Water chemistry data were collected between benthic sampling dates. Maximum water temperature was five °C higher at downstream sites. Total alkalinity was greater, and total phosphorus and dissolved organic carbon were lower at upstream sites. BMI density and diversity in November 1999 samples were greater at upstream sites. Mean density and biomass of collector-filterers were greater downstream than upstream of the Project, and decreased with distance downstream (4,243 m^-2, 3.596 gdw m^-2 and 2,783 m^-2, 1.760 gdw m^-2, respectively). Mean density and biomass of other taxa showed the opposite trend (4,786 m^-2, 2.091 gdw m^-2 downstream; 14,921 m^-2, 3.08 gdw m^-2 upstream). Instantaneous growth rates will be calculated once processing of October 1999 samples is completed in January 2002.