Occurrence and distribution of microbiological indicators in groundwater and stream water

A total of 136 stream water and 143 groundwater samples collected in five i mportant hydrologic systems of the United States were analyzed for microbio logical indicators to test monitoring concepts in a nationally consistent p rogram. Total coliforms were found in 99%. Escherichia coli in 97%. and Clo stridium perfringens in 73% of stream water samples analyzed for each bacte rium. Total coliforms were found in 20%. E. coli in less than 1%. and C. pe rfringens in none of the groundwater samples analyzed for each bacterium. A lthough coliphage analyses were performed on many of the samples, contamina tion in the laboratory and problems discerning discrete plaques precluded q uantification. Land use was found to have the most significant effect on co ncentrations of bacterial indicators in stream water. Presence of septic sy stems on the property near the sampling site and well depth were found to b e related to detection of coliforms in groundwater. although these relation ships were nor statistically significant. A greater diversity of sites, mor e detailed information about some factors, and a larger dataset may provide further insight to factors that affect microbiological indicators.