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Journal of Environmental Quality Abstract - Landscape and Watershed Processes

Quantifying the Contribution of On-Site Wastewater Treatment Systems to Stream Discharge Using the SWAT Model


This article in JEQ

  1. Vol. 43 No. 2, p. 539-548
    Received: May 20, 2013
    Published: June 23, 2014

    * Corresponding author(s): cwoliver7@gmail.com
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  1. C. W. Oliver *a,
  2. D. E. Radcliffeb,
  3. L. M. Risseb,
  4. M. Habteselassieb,
  5. R. Mukundanc,
  6. J. Jeongd and
  7. N. Hoghooghib
  1. a College of Engineering, Univ. of Georgia, 597 D.W. Brooks Dr. Athens, GA 30605
    b Crop and Soil Sciences Dep., Univ. of Georgia, 120 Carlton St. Athens, GA 30602
    c Institute for Sustainable Cities, City Univ. of New York, 695 Park Ave. New York, NY 10065
    d Biological and Agricultural Engineering Dep., Texas A&M Univ., 212 Scoates Hall College Station, TX 77843


In the southeastern United States, on-site wastewater treatment systems (OWTSs) are widely used for domestic wastewater treatment. The degree to which OWTSs represent consumptive water use has been questioned in Georgia. The goal of this study was to estimate the effect of OWTSs on streamflow in a gauged watershed in Gwinnett County, Georgia using the Soil and Water Assessment Tool (SWAT) watershed-scale model, which includes a new OWTS algorithm. Streamflow was modeled with and without the presence of OWTSs. The model was calibrated using data from 1 Jan. 2003 to 31 Dec. 2006 and validated from 1 Jan. 2007 to 31 Dec. 2010 using the auto-calibration tool SWAT-CUP 4. The daily and monthly streamflow Nash–Sutcliffe coefficients were 0.49 and 0.71, respectively, for the calibration period and 0.37 and 0.68, respectively, for the validation period, indicating a satisfactory fit. Analysis of water balance output variables between simulations showed a 3.1% increase in total water yield at the watershed scale and a 5.9% increase at the subbasin scale for a high-density OWTS area. The percent change in water yield between simulations was the greatest in dry years, implying that the influence of OWTSs on the water yield is greatest under drought conditions. Mean OWTS water use was approximately 5.7% consumptive, contrary to common assumptions by water planning agencies in Georgia. Results from this study may be used by OWTS users and by watershed planners to understand the influence of OWTSs on water quantity within watersheds in this region.

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