Characterizing the sources of elevated groundwater nitrate in Dane County, Wisconsin

Private domestic wells are the source of drinking water for approximately 25% of Wisconsin residents, and statewide it is estimated that 12% of these exceed health standards for nitrate concentrations. In Dane County, the exceedance rate is higher, and has been estimated at 25%. Despite the severity of the problem, little is known about the geographic distribution of nitrate in the shallow aquifer and trends in concentrations over time. The objectives of this study were to 1) Develop a comprehensive, updatable database of nitrate concentration data from shallow wells; 2) Identify county-wide spatial patterns and changes in these patterns and concentrations over time using geospatial and statistical analysis; and 3) Utilize the recently completed WGNHS Dane County Groundwater Model to characterize the age and origin of well water, and combine this information with nitrate and land use/hydrogeologic data to explore sources and changes in nitrate loading to groundwater over time.