Thursday, May 29, 2008 - 2:15 PM
559

Importance of size on the effectiveness of constructed wetlands for retaining tile-drain runoff and reducing nutrient inputs into agricultural watersheds

A. Maria Lemke1, Krista G. Kirkham1, Michael P. Wallace2, and David A. Kovacic2. (1) Illinois Chapter of The Nature Conservancy, 301 SW Adams St., Suite 1007, Peoria, IL 61602, (2) Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign, 328 Temple Hoyne Buell Hall, MC-620, 611 East Loredo Taft Drive, Champaign, IL 61820

The Mackinaw River in central Illinois contains some of the highest quality tributaries remaining in the state; however, stream biodiversity is threatened by agricultural practices that dominate landuse within the watershed.  Rapid transport of tile-drained waters from agricultural fields directly into adjacent streams contributes to streambank erosion, high nutrient loading, and loss of wetland habitat throughout the watershed.  We have estimated 36-257 Mg of NO3--N and 0.9-2.0 Mg TP yr-1 were transported annually into the Mackinaw River mainstem from just 2 of 32 subwatersheds in the basin during the past 6 years.  Our current research is designed to measure how much farmland could be converted to wetlands to effectively reduce agricultural nutrient inputs to the river.  We have worked with landowners to develop a 250-acre demonstration farm with 3 tile-drained wetland units, each consisting of a series of three wetland subunits that drain 3-9% of the surrounding farmland.  Control gates and monitoring equipment set at inlets and outlets of the 9 wetland subunits are used to quantify nutrient concentrations and loadings as water drains from the agricultural drainage area through the wetland units.  Preliminary results show 32-90% and 51-100% reduction in nitrate-nitrogen and dissolved phosphorus loadings, respectively, during 2007.  


Web Page: nutrients, agriculture, wetlands

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