studies document the improvements in water-quality brought about by years of investment in point-source controls. However, the Tennessee studies also indicate that investment in such controls and the corresponding improvement in water-quality can reach a point of diminishing returns. Further improvements in water-quality, in these situations, can only be achieved when the remaining issues, such as nonpoint-source pollution, are understood and addressed.

Hilsenhoff, W. L. 1987. An improved biotic index of organic stream pollution. Great Lakes Entomology 20:31-39.

Intergovernmental Task Force on Monitoring Water Quality. 1992. Ambient Water Quality Monitoring in the United States: First Year Review, Evaluation and Recommendations. Report to the Office of Management and Budget. Washington, D.C.: U.S. Government Printing Office.

Schindler, D. W. 1987. Detecting ecosystem responses to anthropogenic stress. Canadian Journal of Fisheries and Aquatic Sciences 44 (Suppl. 1):6-25.

Tennessee Department of Public Health. 1977. Water Quality Management Plan for the Holston River Basin. Nashville, Tenn.: Division of Water Quality Control.

Thackston, E. L., W. R. Miller, D. Durham, and L. R. Richardson. 1990. Tennessee Environmental Quality Index 1970-1990. Nashville, Tenn.: Tennessee Conservation League Report.