SWAT Literature Database for Peer-Reviewed Journal Articles

Title:Modeling the applicability of edge-of-field treatment wetlands to reduce nitrate loads in the Elm Creek Watershed in southern Minnesota, United States 
Authors:Gordon, B.A., C. Lenhart and J. Nieber 
Journal:Journal of Soil and Water Conservation 
Volume (Issue):77(5) 
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URL (non-DOI journals): 
Broad Application Category:hydrologic and pollutant 
Primary Application Category:wetland effects and/or processes 
Secondary Application Category:tile drainage effects and/or processes 
Watershed Description:2,688 km^2 Dasha River, which drains parts of northern Henan Province and southern Shanxi Province in east central China. 
Calibration Summary: 
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Abstract:Constructed agricultural treatment wetlands are key tools for removing nitrate (NO3–) from surface waters. Due to limited funds for NO3– removal practices, investments need to be in the most cost-effective practices. Furthermore, NO3– removal practices that take less land out of production may be more appealing for farmers. Therefore, three types of wetlands were compared to determine NO3– removal effectiveness and cost effectiveness across a watershed. The three wetland types included large wetlands with drainage areas greater than 60 ha; small, edge-of-field wetlands with drainage areas covering fewer than 60 ha; and small, edge-of-field wetlands with a dual treatment system of surface treatment and subsurface treatment following infiltration. The Agricultural Conservation Planning Framework (ACPF) toolbox model was used to determine best placements for each wetland type in the Elm Creek watershed in southern Minnesota, United States. The Soil and Water Assessment Tool (SWAT) model was used to estimate the volume of tile discharge and nitrate-nitrogen (NO3-N) concentration into each wetland over a 10-year period. A spreadsheet model was used to estimate the reductions of NO3– in each wetland over the same 10-year period. Small, edge-of-field wetlands with a saturated hydraulic conductivity (Ksat) of 0.17 m d–1 were more effective at removing NO3– for the area removed from crop production in order to create the wetland (kg ha–1 y–1) and as cost effective (US$ kg–1 NO3–N removed) as the large wetlands. When the small wetlands had a low Ksat (8.64 × 10–5 m d–1), they were more effective for each area removed from crop production (p = 0.06) but not as cost effective (p = 0.003). This study suggests that constructing many small, edge-of-field treatment wetlands with high conductivity, dual-treatment systems to reach nutrient reduction goals would cost the same as constructing large wetlands but would remove fewer hectares of cropland from production. If landowners are interested in removing only a few hectares from crop production at a time, the wetland restoration would possibly still be beneficial. Minimum hectares should not be a limitation for restoration program enrollment as long as the wetland to watershed area ratio is still viable. 
Keywords:agricultural best management practices, Agricultural Conservation Planning Framework, nitrate-nitrogen, Soil and Water Assessment Tool, treatment wetlands, watershed modeling