A Tale of Two Cities: Fecal Coliform Bacteria Modeling in Omaha and Wichita

Abstract

The Papillion Creek Watershed in Nebraska and the Arkansas River system in Kansas share many similar qualities. Both systems include cities that are roughly equivalent in size-Omaha, Nebraska and Wichita, Kansas. Both have a similar mix of urban and agricultural land use, and both share a similar topography. Both fecal coliform bacteria (FCB) studies used statistical modeling, trend line analyses, mass loading analyses and fate-transport dynamic modeling. Specific examples and findings are compared and discussed.While both studies shared similarities, the Wichita water quality study is unique in that, in addition to water column grab sample data, it includes sediment sampling data, Antibiotic Resistance Analyses (ARA), and dry weather and wet weather hydrographic sampling at fourhour intervals; the latter of which provided actual fate-transport patterns.Technical findings from the Wichita data add valuable insights about the potential longevity of fecal coliform bacteria. It has been widely believed that outside of the host organism, FCB will typically survive for 24 to 48 hours. Testing results from the Wichita study showed that FCB persist for extended periods of time in sediment, including relatively cold-water conditions. Hydrographic sampling during dry weather, non-runoff conditions uncovered a distinct diurnal pattern that was highly suggestive of sediment as being a significant source of FCB.Technical findings to date from water quality modeling for FCB for both studies suggest:• FCB levels are highly dependent on runoff events and sediment transport mechanisms.• FCB levels are well above surface water quality standards for "summer season" primary contact recreation. • Urbanized areas contribute approximately another order of magnitude above already high non-urban contributions of FCB under median weather conditions. • It is possible that background FCB levels from wildlife alone may be higher than standards currently allow.• Comprehensive best management practices will be required to control sediment, bacteria, and nutrients. • Regulatory compliance for FCB will be difficult. KEYWORDSFecal coliform bacteria, water quality modeling, WASP, MIKE11, watershed impairment.