Environmental Benefits of Constructed Wetlands Integrated Within Agricultural Water Recycling Systems.
Barbara Baker1, Barry Allred1, Norman Fausey1, Lee Luckeydoo1, W.B Clevenger2, Gary Prill3, Greg La Barge2, Larry C. Brown4, Dwight Moody5, and Gwynne Rife5. (1) USDA-ARS Soil Drainage Research Unit, 590 Woody Hayes Dr, RM 234, Columbus, OH 43210, (2) Ohio State Univ Extension, 06879 Evansport Road, Defiance, OH 43512, (3) Ohio State University Extension, 1055 S Washington St, Van Wert, OH 45891, (4) Overholt Drainage Education and Research Program, Ohio State Univ, Dept Food, Ag, & Biol. Eng., 590 Woody Hayes Drive, Columbus, OH 43210-1057, (5) Univ of Findlay, Biology Dept, 1000 N Main St, Findlay, OH 45840
A Wetland Reservoir Subirrigation System, or WRSIS for short, is an innovative agricultural water management system used to capture, treat, store, and reuse surface runoff and subsurface drainage. There are three WRSIS demonstration sites, in operation since 1996/1997, located in northwest Ohio (Defiance, Fulton, and Van Wert Counties). WRSIS has three main components that include a constructed wetland and a water storage reservoir linked to farmland containing a network of subsurface pipes used at different times to either drain or irrigate crops through the root zone. The wetland is expected to partially remove nutrients and sediment from agricultural waters while providing a vegetation and wildlife habitat where one previously did not exist. WRSIS, as a whole, is also expected to provide crop yield benefits. Field surveys carried out during 1998-2001 identified 77 species of vegetation at the three passively established WRSIS wetlands, of which 45% were wetland indicator species. Wetland wildlife inventories were conducted at two of the WRSIS sites. Wildlife species increased from 75 in 1999 to 85 in 2003 at the Fulton County wetland and from 80 in 1999 to 100 in 2003 at the Defiance County wetland. Preliminary results indicate that WRSIS wetlands are effective in the partial treatment of agricultural waters. From 2003 to 2005, at the Defiance County location, average concentrations for nutrients and sediment in waters discharged from the wetland were significantly less than for waters entering the wetland. In particular, the average nitrate-nitrogen concentration leaving the wetland was only 18% of that for the subsurface drainage routed into wetland. As of 2005,WRSIS crop yield increases for corn and soybeans, respectively, were 30.8 % and 26.0 % during dry growing seasons and 18.8 % and 13.3 % overall. Consequently, WRSIS provides a win-win scenario with both increased crop yields and substantial environmental benefits.