Hydrologic transport and fate of Escherichia coli through a southeastern Piedmont watershed
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Escherichia coli (E. coli) is now the preferred indicator of pathogen loading to public waters. Although Georgia ranks ninth in the nation for pathogen-impaired waters, no E. coli fate and transport models exist for the southeastern United States. I examined hydrologic E. coli transport and fate processes in a 12.9-ha watershed and downstream 1.7-ha impoundment. Escherichia coli (n=53) were enumerated using a commercially available defined substrate medium and by ribotyping. Base flow and storm flow samples were obtained from natural areas and from penned animals over a four-month period. Seventeen water quality parameters were also monitored. Results grouped within three distinct factors: Physical effects, primarily turbidity (r 2 = 0.66, p << .001); chemical effects, primarily dissolved oxygen (r 2 = 0.39, p << .001); and biologic effects, primarily nitrite (r 2 = 0.53, p << .001). A unified conceptual model is proposed which describes the spatial and temporal variability of E. coli observations.