Strategically Siting Constructed Wetlands to Target Nitrate Removal Ess

Strategically Siting Constructed Wetlands to Target Nitrate Removal: A GIS Method Applied to an Agricultural Watershed in West Central Indiana Intensification of agricultural practices in the Midwest has led to increased nutrient losses in surface runoff and subsurface drainage, impacting downstream water quality and the problem of hypoxia in the Gulf of Mexico. Nitrate losses are especially significant in heavily tile drained land, characteristic of west central Indiana. Constructed wetlands have been shown to be effective in reducing nitrate loads leaving Midwestern crop land. Strategically targeting sites that intercept high nitrate loads, and sizing the wetlands according to the characteristics of their watersheds, can maximize wetland efficiency while minimizing costs and maintaining productive agriculture. The goals of this work were to develop a methodology for targeted wetland placement to remove nitrate and to estimate the impact of these wetlands in the landscape. Within the study region, 19 locations were found to be suitable for wetland placement, requiring conversion of 0.1% of the watershed. These wetlan ds would intercept 3% of flow from tile-drained lands, removing approximately one percent of all nitrate exported from all tile-drained land in the watershed. Wetland selection was most sensitive to criteria relating to contributing area, exclusion of streams where wetlands could be potentially located, and topography. While this approach efficiently identifies optimal locations for siting wetlands, best management practices in addition to these wetlands are needed to meet water quality goals in the Midwest. Keywords: Constructed wetlands, Nitrate, Geographic Information System (GIS), Water Quality, Wate... ...ould also be minimized. The main goal of this work was to develop a methodology for targeted wetland placement to remove nitrate from tile-drained agricultural lands. The specific objectives were to: 1) Determine suitable wetland sites in an 8-digit HUC in Indiana using GIS methods and wetland siting criteria; 2) Create preliminary wetland designs at each site; and 3) Estimate the nitrate removal provided for each wetland design, using a simple regression-based model. A key aspect of this GIS analysis was calculating the tile-drained contributing area draining to each location, which ensured that these wetlands intercepted large flows and maximized nitrate reduction in the landscape. This watershed-scale approach is critical to efficiently implement best management practices, such as constructed wetlands to reduce nitrate losses from agricultural watersheds.