Water samples collected from 46 stream sites in the Upper Wabash River Watershed from June through September 1998 were analyzed for concentrations of the bacteria Escherichia coli (E. coli). Each site was sampled five times in a 30-day period. Twenty-one sites were sampled during June and July, and 25 sites were sampled during August and September. The concentration of E. coli in 145 of the 230 samples collected exceeded the Indiana standard of 235 colonies per 100 milliliters for a single sample for waters used for recreation. A five-sample geometric mean also was computed for each site. Concentrations in samples from 43 of the 46 sites exceeded the Indiana bacteriological quality standard of 125 colonies per 100 milliliters for a five-sample geometric mean for waters used for recreation.
Discharge during sample collection generally was greater than the long-term median daily mean discharge. To determine if the greater discharge affected the concentrations of E. coli, additional samples were collected at two sites. Statistically significant positive correlations between concentrations of E. coli and discharge were determined for these sites, indicating increased concentrations with greater discharge.