RONALD C. AHLE, South Carolina Department of Natural Resources, Division of Wildlife and Freshwater Fisheries, Rembert C. Dennis Building, P.O. Box 167, Columbia, South Carolina 29202, USA

South Carolina has many miles of streams that traverse five major ecoregions (e.g., Blue Ridge Mountain, Piedmont, Sandhills, Upper Coastal Plain and Lower Coastal Plain). Many of these streams, particularly in the Piedmont and Sandhills regions, have been impounded during the last two centuries. As a result, changes have occurred in the resident fish communities. Stream surveys have shown that indigenous fish assemblages have been altered by dam placement. Index of biotic integrity (IBI) applications using fish communities have indicated negative effects on stream health below and between impoundment locations. Potential effects of impoundments include altered flow regimes, blockage of nutrient transfer and fish migration, changes in water quality, species introductions, and erosion due to substrate scouring. To reduce impacts from impoundments, in 1989 we developed an ecoregion specific instream flow policy and guidelines for siting new impoundments. We have used these documents for evaluating FERC relicensing projects and Corps 404 permit applications. Analysis of case histories found these policies to be somewhat effective in assuring usable flow releases from existing facilities and protecting free-flowing streams.