National Water-Quality Assessment (NAWQA) Project

   Home    Headlines    Featured Studies    Liaison Committee    Informing Decision Makers    Data    Modeling/Software    Publications    Maps

Featured Studies
Special studies on source-water and drinking-water quality
Surface-water intakes
General Information

Groundwater-Quality Trends

Home National Results and Maps Background Factors Affecting Trends Simulation and Forecasting Data Trends Publications

Transport and Fate of Nitrate in a Glacial Outwash Aquifer in Relation to Ground Water Age, Land Use Practices, and Redox Processes

A combination of groundwater modeling, chemical and dissolved gas analyses, and chlorofluorocarbon age dating of water was used to determine the relation between changes in agricultural practices and nitrate concentrations in ground water of a glacial outwash aquifer in west-central Minnesota (Puckett and Cowdery, 2002).

Map showing the location of the study area.

Groundwater ages showed that maximum residence times were on the order of 50-70 years. Reconstructed nitrate concentrations, estimated from measured nitrate and dissolved nitrogen gas, showed that nitrate concentrations have been increasing in the aquifer since the 1940s. Since the mid- to late-1960s, nitrate concentrations have been above the 10 milligrams per liter (mg/L) maximum contaminant level (MCL) at most sites. Puckett and others (1999) showed that most of the nitrogen reaching the water table in the study area originated as fertilizer, and this increase in nitrate concentrations over time corresponds to a similar increase in the use of fertilizer nitrogen in the study area, particularly after the late-1960s.

Return to Factors Affecting Groundwater-Quality Trends

Accessibility FOIA Privacy Policies and Notices

Take Pride in America home page. FirstGov button U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information:
Page Last Modified: