Planning Level Evaluation of Densities and Sources of Indicator Bacteria in a Mixed Land Use Watershed

The lower Buffalo River, NY, is environmentally impaired and the 38 combined sewer outfalls within this reach historically were believed to be the primary source of bacterial contamination. A planning level evaluation of bacteria contamination was done through sample testing and compilation of existing source data, in part, with the aid of GIS technology. The intent of such evaluation is to provide an overview of the magnitude and sources of the water quality problem without extensive resource commitments, as a first step in developing remediation strategies. Testing for fecal coliform and fecal streptococci was done at 12 sites within the watershed for one year, 1992–93. Indicator bacteria densities at all sites generally were high and the state guideline for primary contact (200 fecal coliform 100 ml−1) was exceeded in 69% of 277 samples. Bacteria densities were greatest during storm events, suggesting runoff as an important source pathway. Mean fecal coliform densities significantly increased downstream, with higher levels of urbanization. Fecal coliform: fecal streptococci ratios, combined with the source inventory data, successfully were used to identify areas of human sewage inputs. Although combined sewer overflows in the lower Buffalo River have an impact on bacteria levels, upstream sources also degrade water quality. The costly elimination of combined sewer overflows in the lower river will not entirely alleviate problems with high bacteria levels. Water quality in the lower river will improve only through a basin-wide, co-ordinated reduction of bacteria inputs from multiple sources.