National Water-Quality Assessment (NAWQA) Program

U.S. Geological Survey
Fact Sheet 092-96

Nitrate in the Ground Waters of the United States--Assessing the Risk

By Bernard T. Nolan and Barbara C. Ruddy

Nitrate risk map


Using data compiled by the National Water Quality Assessment Program (NAWQA), the USGS has evaluated the potential for nitrate contamination of ground waters in the United States. Soil-drainage characteristics and the amount of nitrogen contributed by fertilizer, manure, and atmospheric sources were found to markedly influence the concentration of nitrate in ground water. These two characteristics were compiled in a national map that shows patterns of risk for nitrate contamination of ground water. Areas with well-drained soils and high nitrogen input have the highest risk. Ground-water nitrate data generally verified the risk patterns shown on the national map. The verification analysis is based on over 10,000 samples collected through 1992.

Table of Contents

The quality of water that people drink depends on where they live
Risk of ground-water contamination by nitrate varies across the United States
Nitrate in ground water generally follows the risk map
Who is most likely to drink high-nitrate ground water?
Additional reading
The National Water-Quality Assessment Program

This report has been superseded by the following:

1. A National look at nitrate contamination of ground water. (1998)

2. Probability of nitrate contamination of recently recharged groundwaters in the conterminous United States. (2002)

3. Vulnerability of shallow groundwater and drinking-water wells to nitrate in the United States . (2006)

This report is available online in Portable Document Format (PDF). If you do not have the Adobe Reader, it is available for free download from Adobe Systems Incorporated.

Download the report (PDF, 1.3 MB)

Document Accessibility: Adobe Systems Incorporated has information about PDFs and the visually impaired. This information provides tools to help make PDF files accessible. These tools convert Adobe PDF documents into HTML or ASCII text, which then can be read by a number of common screen-reading programs that synthesize text as audible speech. In addition, an accessible version of Adobe Reader 8.0 for Windows (English only), which contains support for screen readers, is available. These tools and the accessible reader may be obtained free from Adobe at Adobe Access.

For further information about this report, contact the National Water-Quality Assessment Program office.

U.S. Department of the Interior, U.S. Geological Survey
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Last modified: Tuesday, November 29 2016, 06:10:19 PM
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