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Targeted Wetland Restoration for Water Quality Improvement: Potential Impact on Nitrate Loads to Mississippi River Subbasins

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  701P0904,  . (doi: 10.13031/2013.17400)
Authors:   William G. Crumpton

Non-point source nitrogen loads to surface waters in the Midwest Corn Belt are among the highest in the Mississippi River Basin, and are suspected as a primary source of nitrate contributing to hypoxia in the Gulf of Mexico. Nitrate is transported from crop land primarily in subsurface drainage, especially in extensively tile drained areas like the Corn Belt. As a result, grass buffer strips, woody riparian buffers, and many other practices suited to surface runoff have little opportunity to intercept nitrate loads in these areas. However, wetlands sited to intercept tile drainage have the potential to significantly reduce nitrate loads, and this approach is particularly promising for heavily tile drained areas like the Corn Belt. A performance forecast modeling approach is used to estimate the total nitrate reduction that could be achieved using wetlands as nitrogen sinks in tile-drained regions of the upper Midwest. Not only does the extent of tile drainage vary among the subbasins, but also the efficacy of wetlands intercepting tile drainage varies among the subbasins. This is because several primary determinants of wetland performance vary longitudinally across the upper Midwest, including volume and timing of runoff, nitrate concentration, and temperature. Our analyses suggest that these would result in a roughly five fold range in mass nitrate removal per acre of wetland restored for different areas of the upper Midwest.

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