Assessing the Impacts of <i><scp>E</scp>. coli</i> Laden Streambed Sediment on <i>E. coli</i> Loads over a Range of Flows and Sediment Characteristics

Abstract Understanding sediment E scherichia coli levels (i.e., pathogen indicators) and their contribution to the water column during resuspension is critical for predicting in‐stream E . coli levels and the potential risk to human health. The U.S. Environmental Protection Agency's current water quality testing strategies, however, rely on water borne E . coli concentrations to assess stream E . coli levels and identify impaired waters. In this work, we conducted a scenario analysis using a range of flows, sediment/water bacteria fractions, and particle sizes to which E . coli attach to assess the impact of E . coli in streambed sediments on water column E . coli levels. We used simple sediment transport theory to calculate the potential total E . coli concentrations in a stream with and without the resuspension process. Results clearly indicate that inclusion of resuspending sediment attached E . coli is necessary for watershed assessments and data on sediment attached E . coli concentrations is much needed. When neglecting the streambed sediment E . coli concentrations, the model predicted average E . coli loads of 10 7 Colony Forming Units (CFU)/s; however, when streambed sediment E . coli concentrations were included in the model, the predictions ranged from 10 10 to 10 14 CFU/s. To evaluate the predictions, E . coli data in the streambed sediment and the water column were monitored in Squaw Creek, Iowa. Comparisons between measured and predicted E . coli loads yielded an R 2 ‐value of 0.85.

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