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Title: NITRATE IN GROUNDWATER OF THE MIDWESTERN UNITED STATES: A REGIONAL INVESTIGATION ON RELATIONS TO LAND USE AND SOIL PROPERTIES

Author
item KOLPIN, DANA - USGS
item Burkart, Michael
item GOOLSBY, DONALD - USGS

Submitted to: International Union of Geodesy and Geophysics Meeting
Publication Type: Proceedings
Publication Acceptance Date: 7/30/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Since 1991, a network of 303 wells has been used to investigate the regional distribution of nitrate in shallow aquifers of the Midwestern United States. This region is of particular interest because of frequent measurements of large concentrations of nitrate thought to be associated with intense application of nitrogen fertilizer to cropland. Detailed land-use and soil data were compiled in a geographic information system (GIS) for areas surrounding 100 wells selected to represent a sample of aquifers made of sand and gravel. The results of the analysis characterized relations between nitrate concentrations in groundwater and soil and land-use factors. For land use, the amount of irrigated land was directly related to nitrate concentrations in ground water. For soils, the general water table depth and soil factors associated with rates of water movement were directly related to nitrate concentrations in ground water. The results of this research may be used by policy makers and water users to estimate areas where nitrate concentrations in ground water may exceed drinking water standards by knowing the soils and land use.

Technical Abstract: The intense application of nitrogen fertilizer to cropland in the Midwestern United States has created concern about nitrate contamination of the region's aquifers. Since 1991, the U.S. Geological Survey has used a network of 303 wells to investigate the regional distribution of nitrate in near-surface aquifers of the Midwestern United States. Detailed land-use and soil data were compiled within a 2-km radius of 100 unconsolidated wells in the regional network to determine relations to nitrate concentrations in groundwater. For land use, the amount of irrigated land was directly related to nitrate concentrations in ground water. For soils, the general water table depth and soil factors associated with rates of water movement were directly related to nitrate concentrations in ground water.