USGS

Occurrence and Distribution of Microbiological Indicators in Groundwater and Stream Water *

By Donna S. Francy, Dennis R. Helsel, Rebecca A. Nally

Abstract

A total of 136 streamwater and 143 groundwater samples collected in five major hydrologic systems of the United States were analyzed for microbiological indicators to test concepts for monitoring in a nationally consistent program. Total coliforms were found in 99 percent, Escherichia coli in 97 percent, and Clostridium perfringens in 73 percent of streamwater samples analyzed for each bacterium. Total coliforms were found in 20 percent, Escherichia coli in less than 1 percent, and Clostridium perfringens in none of the groundwater samples analyzed for each bacterium. Although coliphage analyses were done on many of the samples, contamination in the laboratory and problems discerning discrete plaques precluded quantification. Land use was found to have the most significant effect on concentrations of bacterial indicators in streamwater. Presence of septic systems on the property and well depth were found to be related to detections of total coliforms in groundwater, although these relations were not statistically significant. A greater diversity of sites, more detailed information about some factors, and a larger dataset may provide more insight into factors that affect microbiological indicators.

(* Published in Water Environment Research, March/April 2000, Volume 72, Number 2, pages 152-161)


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