Proceedings of the International Academy of Ecology and Environmental Sciences, 2018, 8(1): 28-46
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SWAT modeling of fecal indicator bacteria fate and transport in a suburban watershed with mixed land uses

Zeyuan Qiu1, Subhasis Giri2, Lizhong Wang3, Biliang Luo4
1Department of Chemistry and Environmental Science, New Jersey Institute of Technology, University Heights, Newark, New Jersey 07102, USA
2Department of Ecology and Evolution, Rutgers, the State University of New Jersey, New Brunswick, New Jersey 08901, USA
3Environmental Monitoring and Science Division, Alberta Environment and Parks, Deerfoot Square, 2938-11th Street NE, Calgary, AlbertaT2E 7L7, Canada
4National School of Agricultural Institution and Development, South China Agricultural University, Guangzhou, Guangdong 510640, P.R. China

Received 10 December 2017;Accepted 21 December 2017;Published 1 March 2018

This paper presents a case study of modeling the fate and transport of fecal indicator bacteria (FIB) in Neshanic River Watershed, a suburban watershed with mixed land uses in central New Jersey using the Soil and Water Assessment Tool (SWAT). FIB loadings from livestock grazing, manure application, and wildlife were modeled as nonpoint sources while FIB loadings from direct deposit of livestock manure to streams during grazing period and failing septic systems were modeled as point sources. The simulated FIB concentrations were compared to the observed concentrations at seven monitoring stations in the watershed. The model was calibrated from 1997 to 2002 and then validated from 2003 to 2008. The percent bias (PBIAS) value for simulating fecal coliform was 13.81 during calibration, and 24.11 during validation at a long-term monitoring station in the watershed, which was satisfactory. The range of the simulated FIB concentrations was comparable to the observed concentrations at all monitoring stations. Failing septic systems, manure application and livestock access to streams contributed 46, 31 and 19 percent, respectively, of the FIB concentration in streams at the watershed outlet. Seasonal pattern of the simulated FIB loadings at the watershed outlet revealed the highest FIB loadings occurred in April when manure was applied in agricultural lands compounded by spring storms. There were also elevated FIB loadings in October due to the wash-off effect of the accumulative FIB from livestock grazing during the grazing season. These results suggest that the SWAT model is capable of simulating FIB fate and transport in suburban watersheds despite the difficulties of representing the spatial and temporal distributions of FIB sources.

Keywords bacteria fate and transport;SWAT;fecal coliform;Escherichia coli (E. coli);Neshanic River Watershed;mixed land uses.

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