Microbial Contamination of Water Resources in the
Chattahoochee National Recreation Area, Georgia

ABSTRACTS

Frick, E.A., and Gregory, M.B., 2000, Microbial indicators in streams in the Chattahoochee River National Recreation Area Watershed, Metropolitan Atlanta, Georgia [abs.]: in Building Capabilities for monitoring and assessment in public health microbiology, Columbus, Ohio, March 2000, unpaginated. In the 48-mile reach of the Chattahoochee River downstream from Lake Sidney Lanier (Buford Dam) and within the Chattahoochee River National Recreation Area (CRNRA), fecal-coliform concentrations exceeding the Georgia Environmental Protection Division (GaEPD) standards are the principal reason for the Chattahoochee River and its tributaries not supporting or partially supporting designated uses of drinking water, recreation, and fishing. The extent of microbial contamination in the Chattahoochee River and tributary streams within the CRNRA is presented based on fecal-indicator bacteria data collected from March 1999 through February 2000 as part of a two-year U.S. Geological Survey (USGS) and National Park Service (NPS) project. Lake Sidney Lanier and this 48-mile reach of the Chattahoochee River are the principal drinking-water sources for Metropolitan Atlanta. The study area includes the entire CRNRA (an area of intense recreational use), six municipal water-supply intakes, and eight municipal wastewater-treatment-plant outfalls. Fecal-coliform, enterococci, and Escherichia coli (E. coli), concentrations were measured at three Chattahoochee River monitoring sites every five days during the summer-recreation season (May through October) and every eight days during the winter season (November through April). Synoptic surveys were conducted during summer wet-weather, summer baseflow, and winter baseflow conditions at four Chattahoochee River and eight tributary monitoring sites. Median fecal-indicator bacteria concentrations in the Chattahoochee River increased by approximately an order of magnitude from 9.5-13 colonies per 100 milliliters (colonies/100 mL) at the upstream site to 73-130 colonies/100 mL during the summer and 28-64 colonies/100 mL during the winter at the downstream site. In this highly regulated reach of the river, fecal-indicator bacteria concentrations poorly correlate with discharge and turbidity. Summer-recreation season fecal-coliform concentrations measured at the middle and downstream Chattahoochee River sites were significantly lower during the 1999 drought than those measured by GaEPD during the relatively wet summers of 1994 and 1995. Results from the synoptic surveys indicate (1) much higher fecal-indicator bacteria concentrations during wet-weather conditions than during baseflow conditions, (2) generally higher concentrations during summer baseflow than during winter baseflow conditions, and (3) generally higher concentrations in tributary streams than in the Chattahoochee River. During the two baseflow synoptic surveys, fecal-indicator bacteria concentrations were lower in the Chattahoochee River downstream from the major wastewater outfalls than concentrations were 2 miles upstream, possibly the result of residual chlorine in the treated effluent. Concentrations of Clostridium perfringens, thought to be an indicator for microorganisms entering streams with chlorinated and untreated municipal wastewater, ranged from 32-350 colonies/100 mL during the wet-weather summer synoptic survey and, with one exception, were less than 42 colonies/100 mL during baseflow synoptic surveys. Major sources and transport pathways of microbial contamination vary among and within tributary watersheds. In an attempt to identify potential differences in microbial sources among tributary sampling sites, a relatively new USGS organic sewage tracer laboratory procedure was used to analyze 47 constituents that may be useful as sewage tracers for samples collected during the summer synoptic surveys. Cholesterol and 3B-coprostanol are indicators of human fecal contamination and were 2 of 26 sewage tracers detected during wet-weather and 2 of 19 sewage tracers detected during baseflow synoptic surveys. Emphasis on evaluating wet-weather water quality in tributary watersheds and the development of improved methods for identification of major sources and transport pathways of microbial contamination are needed to aid in design of abatement programs. Project information and data are available on the project website http://ga.water.usgs.gov/projects/chatm. Authors: 1 Physical Scientist, U.S. Geological Survey, Atlanta, Georgia (706-369-7739; alfunk@usgs.gov) ; 2 Ecologist, U.S. Geological Survey, Atlanta, Georgia (770-903-9163; bgregory@usgs.gov

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Last Modified: Monday, 15-May-2000 14:39:44 EDT