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Agricultural Drainage Wells and Groundwater QualityIn parts of Iowa surface runoff and tile-drainage water from agricultural lands are directed into agricultural drainage wells (ADWs). ADWs "inject" drainage water, via gravity, into carbonate bedrock aquifers that are used by rural residents and small communities as drinking-water sources. ADWs range in depth from 10 to over 300 feet, are typically cased to bedrock, and are "open holes" from the bedrock top to their total depth. There are about 292 ADWs in Iowa, with the majority located in three areas: (1) adjoining parts of Humboldt and Pocohontas counties; (2) Floyd County; and (3) Wright County. The drainage water delivered to groundwater by ADWs often contains relatively high concentrations of nitrate-nitrogen and herbicides. Concerns exist about the transport of bacterial and viral constituents, particularly in areas with large numbers of livestock. The Geological Survey Bureau has investigated the effects of ADWs on groundwater quality. For more information contact Bob Libra (Robert.Libra@dnr.iowa.gov) at (319)335-1585 or Lynette Seigley (Lynette.Seigley@dnr.iowa.gov) at (319)335-1598. Currently, the Geological Survey Bureau is monitoring the groundwater quality near an ADW closure site in Floyd County. For more information on this project, click here for a November 1997 summary and a March 1999 summary. Agricultural Drainage Wells and Groundwater Quality Publications:Agricultural Drainage Wells in Iowa: Hydrogeologic Settings and Water-Quality Implications: GSB Technical Information Series 24 (Abstract) Groundwater Quality, Hydrogeology, and Agricultural Drainage Wells: Floyd and Mitchell Counties, Iowa: GSB Technical Information Series 29 (Abstract) Groundwater Quality Response to Closure of Agricultural Drainage Wells in Floyd County: GSB Technical Information Series 40 (Abstract) Closure of Agricultural Drainage Wells (ADWs) Improves Water Quality: Iowa Geology, 1999 |