SWAT Literature Database for Peer-Reviewed Journal Articles

Title:Land use change impacts on water quality in three Lake Winnipeg watersheds 
Authors:Yang, Q., L.F. Leon, W.G. Booty, I.W. Wong, C. McCrimmon, P. Fong, P. Michiels, J. Vanrobaeys and G. Benoy 
Journal:Journal of Environmental Quality 
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URL (non-DOI journals): 
Broad Application Category:hydrologic & pollutant 
Primary Application Category:land use change 
Secondary Application Category:pollutant cycling/loss and transport 
Watershed Description:2,400 km^2 La Salle River, 1,102 km^2 Boyne River, and 4,000 km^2 Little Saskatchewan River in central Canada 
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Abstract:Lake Winnipeg eutrophication results from excess nutrient loading due to agricultural activities across the watershed. Estimating non-point source pollution and the mitigation effects of beneficial management practices (BMP), is an important step in protecting the water quality of streams and receiving waters. Use of computer models to systematically compare different landscapes and agricultural systems across the Red-Assiniboine basin has not been attempted at watersheds of this size in Manitoba. In this study the Soil and Water Assessment Tool (SWAT) was applied and calibrated for three pilot watersheds of the Lake Winnipeg basin. Monthly flow calibration yielded overall satisfactory Nash-Sutcliffe coefficient of efficiency (NSE), with values above 0.7 for all simulations. Total phosphorus (TP) calibration NSE ranged from 0.64 to 0.76; total nitrogen (TN) from 0.22 to 0.75; and total suspended solids (TSS) from 0.29 to 0.68. Based on the assessment of the TP exceedance levels from 1993 to 2007, annual loads were above proposed objectives for the three watersheds more than half of the time. Four BMPs scenarios based on land-use changes were studied in the watersheds: (ACHL) annual cropland to hay land; (WR) wetland restoration; (MACHL) marginal annual cropland conversion to hay land; and (WRMAC) wetland restoration on marginal cropland. Of all four land use change scenarios, ACHL had the greatest impact: TSS loads were reduced by 33-65%, TN by 58-82% and TP by 38-72% over the simulation period. By analyzing unit area and percentage of load reduction, the results indicate that the WR and WRMAC scenarios had a significant impact on water quality in high loading zones in the three watersheds. Such reductions of sediment, nitrogen and phosphorus are possible through land use change scenarios, suggesting that land conservation should be a key component of any Lake Winnipeg restoration strategy.