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Journal of Environmental Quality Abstract - Landscape and Water Process

Modeling Sediment and Nitrogen Export from a Rural Watershed in Eastern Canada Using the Soil and Water Assessment Tool


This article in JEQ

  1. Vol. 40 No. 4, p. 1182-1194
    Received: Dec 17, 2010

    * Corresponding author(s): jamiesrc@dal.ca
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  1. Hafiz M. Nafees Ahmada,
  2. Andrew Sinclaira,
  3. Rob Jamieson *a,
  4. Ali Madanib,
  5. Dale Hebbc,
  6. Peter Havardb and
  7. Emmanuel K. Yiridoed
  1. a Dep. of Process Engineering and Applied Science, Dalhousie Univ., 1360 Barrington St., Halifax, NS B3J 2X4
    b Dep. of Engineering, Nova Scotia Agricultural College, P.O Box 550, Truro, NS B2N 5E3
    c Agriculture Agri-Food Canada, 32 Main St., Kentville, NS B4N 1J5
    d Dep. of Business and Social Science, Nova Scotia Agricultural College, P.O Box 550, Truro, NS B2N 5E3. Assigned to Associate Editor Raghavan Srinivasan


Watershed simulation models can be used to assess agricultural nonpoint-source pollution and for environmental planning and improvement projects. However, before application of any process-based watershed model, the model performance and reliability must be tested with measured data. The Soil and Water Assessment Tool version 2005 (SWAT2005) was used to model sediment and nitrogen loads from the Thomas Brook Watershed, which drains a 7.84 km2 rural landscape in the Annapolis Valley of Nova Scotia, Canada. The Thomas Brook SWAT model was comprised of 28 subbasins and 265 hydrologic response units, most of them containing agricultural land use, which is the main nonpoint nitrogen source in the watershed. Crop rotation schedules were incorporated into the model using field data collected within Agriculture and Agri-Food Canada's Watershed Evaluation of Beneficial Management Practices program. Model calibration (2004–2006) and validation (2007–2008) were performed on a monthly basis using continuous stream flow, sediment, and nitrogen export measurements. Model performance was evaluated using the coefficient of determination, Nash-Sutcliff efficiency (NSE), and percent bias (PBIAS) statistics. Study results show that the model performance was satisfactory (NSE > 0.4; R2 > 0.5) for stream flow, sediment, nitrate-nitrogen, and total nitrogen simulations. Annual corn, barley, and wheat yields were also simulated well, with PBIAS values ranging from 0.3 to 7.2%. This evaluation of SWAT demonstrated that the model has the potential to be used as a decision support tool for agricultural watershed management in Nova Scotia.

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