USGS Studies Bacteria in Streams

Fecal bacteria were detected in streams and rivers of the Wind River, Big Horn River, and Goose Creek Basins in Wyoming, according to a recently released report by the U.S. Geological Survey.

“It is not unusual to find these types of bacteria in streams when humans, wildlife, and domestic animals are nearby. The study found bacteria concentrations in the streams were related to land use--concentrations generally were lower in streams adjacent to forested and rangeland areas compared to streams adjacent to agricultural and urban areas.” noted Melanie Clark, the USGS hydrologist conducting the study.

The study measured both Escherichia coli (E. coli) (a bacterium found in the intestines of warm-blooded animals) and fecal-coliform bacteria (a class of bacteria found in the intestines of warm-blooded animals and other sources). The presence of either in a stream provides an indication that the water may have been impacted by fecal material from warm-blooded animals.

Clark found concentrations of E. coli and fecal-coliform bacteria were closely related. “This is significant, because the State of Wyoming is switching from a fecal-coliform standard to an E. coli standard for determining whether water is safe for recreational use”, according to Clark. E. coli is better correlated with swimming-associated illness because it provides more direct evidence of fecal contamination in streams. Results from this study will help regulators interpret newly acquired E. coli data in light of historically collected fecal-coliform data, thus easing the transition from the old standard to the new one.

Other findings in the report indicate that bacteria concentrations were generally lower in the Wind River Basin compared to the Bighorn River and Goose Creek Basins. Results from samples that were analyzed using a  microbial source-tracking method indicate that human and non-human sources contributed to E. coli at a site on the Bighorn River at Basin, Wyo. and a site on Bitter Creek near Garland, Wyo.

The USGS, in cooperation with its partners, continues to monitor bacteria at 18 stations around the state as part of an ongoing long-term monitoring program.

Copies of the report "A Synoptic Study of Fecal-Indicator Bacteria in the Wind River, Bighorn River, and Goose Creek Basins, June-July 2000" is available by contacting the U.S. Geological Survey office in Cheyenne or is available on the web at http://pubs.water.usgs.gov/wri034055/.

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