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Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Pp. 234-241 in Total Maximum Daily Load (TMDL) Environmental Regulations–II Proceedings of the 8-12 November 2003 Conference (Albuquerque, New Mexico USA), Publication Date 8 November 2003.  .(doi:10.13031/2013.15566)
Authors:   M.G. Lindburg, M.W. Powell, L.R. Christensen
Keywords:   Fecal coliform, bacteria contamination, water quality modeling, agriculture, WASP, watershed impairment

The Papillion Creek Watershed (Watershed) consists of 402 square miles of drainage area with urban and rural land uses that spans three counties in eastern Nebraska. Numerous stream and reservoir impairments exist within the Watershed that impact primary contact recreation, aesthetics, fisheries, and overall water quality. Water quality modeling of fecal coliform (FC) bacteria was conducted to determine the extent of FC pollution and to determine recommended Best Management Practices (BMPs) that would control concentrations of FC bacteria. Statistical and dynamic water quality modeling were used in this effort.

The City of Omaha maintains a large network of water quality sampling sites within the Watershed. For each site, a standard set of statistical correlations were made for FC dependencies on flow, precipitation, and turbidity, which provided clues as to the pollution sources. FC mass loading probability curves were also developed that compared the maximum permissible levels of FC to values actually measured.

Fate and transport modeling for FC bacteria concentrations within the mainstem stream segments was accomplished using non-proprietary WASP software. FC loadings were indexed to the various land uses within the Watershed. Basic hydraulic parameters for both 2002 baseline and future growth conditions were used to develop the bacterial fate and transport mechanisms.

Technical findings from water quality modeling for FC bacteria to date suggest: FC bacteria levels are highly dependent on runoff events and sediment transport mechanisms.

FC levels are well above surface water quality standards for summer season primary contact recreation.

Urbanized areas contribute another order of magnitude above non-urban contributions of FC bacteria under median conditions.

It is possible that background FC levels from wildlife alone may be higher than standards currently allow.

Comprehensive BMPs will be required to control sediment, bacteria, and nutrients.

Regulatory compliance for FC will be difficult.

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