Risk Assessment and Mapping of Fecal Contamination in the Ohio River Basin

The leading cause of surface-water impairment in the US is fecal microbial contamination, which can potentially trigger massive outbreaks of gastrointestinal disease. It is well known that the difficulty in prediction of water contamination is rooted in the stochastic variability of microbes in the environment, and in the complexity of environmental systems.

To address these issues, we employ a risk-based design format to compute the variability in microbial concentrations and the probability of exceeding the E. coli target in the Ohio River Basin (ORB). This probability is then mapped onto the basin’s stream network within the ArcGIS environment. We demonstrate how spatial risk maps can be used in support of watershed management decisions, in particular in the assessment of best management practices for reduction of E. coli load in surface water.