Evaluation of Indicator Bacteria Export from an Urban Watershed

Studies have shown stormwater runoff is a contributor to elevated indicator bacteria concentrations in surface waters. These elevated concentrations may indicate a heightened human health risk and lead to water quality violations as concentrations exceed regulatory standards. Total Maximum Daily Loads (TMDLs) are commonly established for indicator bacteria, requiring modeling and watershed planning to reduce loadings. However, factors correlated to indicator bacteria build-up and transport in urban watersheds have not been fully explored. Thus, efforts to manage indicator bacteria in urban watersheds are hampered. A watershed monitoring study in Raleigh, North Carolina, used flow weighted samples to provide detailed mass loadings of fecal coliform, E. coli, and enterococcus from a 5.1 ha (12.5-acre) residential watershed. Loads were compared to multiple antecedent and in-storm hydrologic and meteorological parameters. The objective of this study was to determine which, if any, parameters can be linked to changes in indicator bacteria export from urban watersheds and to identify patterns in intra-storm indicator bacteria transport. This study will lead to a further understanding of how indicator bacteria can be modeled and managed in urban watersheds.