SWAT Literature Database for Peer-Reviewed Journal Articles

Title:Modeling the effects of onsite wastewater treatment systems on nitrate loads using SWAT in an urban watershed of Metropolitan Atlanta 
Authors:Hoghooghi, N., D.E. Radcliffe, M.Y. Habteselassie and J. Jeong 
Journal:Journal of Environmental Quality 
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URL (non-DOI journals): 
Broad Application Category:hydrologic & pollutant 
Primary Application Category:on-site wastewater systems 
Secondary Application Category:nitrogen cycling/loss and transport 
Watershed Description:44 km^2 Big Haynes Creek, located east of the city of Atlanta in Gwinnett County, north central Georgia, U.S. 
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Validation Summary: 
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Abstract:Onsite wastewater treatment systems (OWTSs) can be a source of nitrogen (N) pollution in both surface and ground waters. In metropolitan Atlanta, GA, >26% of homes are on OWTSs. In a previous article, we used the Soil Water Assessment Tool to model the effect of OWTSs on stream flow in the Big Haynes Creek Watershed in metropolitan Atlanta. The objective of this study was to estimate the effect of OWTSs, including failing systems, on nitrate as N (NO3–N) load in the same watershed. Big Haynes Creek has a drainage area of 44 km2 with mainly urban land use (67%), and most of the homes use OWTSs. A USGS gauge station where stream flow was measured daily and NO3–N concentrations were measured monthly was used as the outlet. The model was simulated for 12 yr. Overall, the model showed satisfactory daily stream flow and NO3–N loads with Nash– Sutcliffe coefficients of 0.62 and 0.58 for the calibration period and 0.67 and 0.33 for the validation period at the outlet of the Big Haynes Watershed. Onsite wastewater treatment systems caused an average increase in NO3–N load of 23% at the watershed scale and 29% at the outlet of a subbasin with the highest density of OWTSs. Failing OWTSs were estimated to be 1% of the total systems and did not have a large impact on stream flow or NO3–N load. The NO3–N load was 74% of the total N load in the watershed, indicating the important effect of OWTSs on stream loads in this urban watershed.