Introduction: The Chattahoochee River and its lakes and tributaries are essential resources for metro-Atlanta; however, urbanization and other human impacts near these resources affects the quality of water. The objectives of this study are to describe the spatial and temporal patterns of Escherichia coli (E. coli), and examine the relationship between rainfall and E. coli levels in metro-Atlanta surface waters, including the Chattahoochee River and its lakes and tributaries.

Methods: The water quality data used for the study was originally collected and analyzed by the Chattahoochee Riverkeeper (CRK) Neighborhood Water Watch (NWW) program. For this analysis, sites with a total of 50 samples or more were subjected to descriptive analysis.

Results: Twenty-seven of the 36 sites had a mean E. coli concentration exceeding the US EPA’s recreational water quality criteria of 2.37 log Most Probable Number per 100 milliliters. Sites with the highest and lowest mean E. coli levels were located, on average, 2.77 and 20.22 miles from downtown Atlanta, respectively. Spikes in E. coli levels occurred 99 counts of 699 sampling events in the winter, 168/827 spring, 141/877 summer, and 170/950 fall. Seven of the 36 sites were analyzed to examine the relationship between 48-hour rainfall and E. coli levels. Four sites indicated that there was a significant positive correlation between the two variables. (r=0.52, p<.0001; r=0.67, p<.0001; r=0.39, p<.0001; r=0.38, p<.0001)

Discussion: The water quality in waterways closer to downtown may be attributable to combined sewer overflows and the urbanization and land use associated with the city. Overall, there was temporal variation in E. coli concentrations, however there was no distinct seasonal pattern. The relationship between 48-hour rainfall and E. coli levels of four of the seven sites analyzed was consistent with other studies.