For release: UPON RECEIPT (Mailed August 24, 1995) Rebecca Phipps
NUTRIENT LEVELS IN WATER LINKED TO LAND USE NATIONWIDE
The most extensive study of nutrients in the nation's water resources -- 12,000 ground-water and 22,000 surface-water samples--found that the drinking water standard for nitrate was exceeded in 21 percent of shallow wells in agricultural areas, according to the U.S. Geological Survey.
The drinking water standard was exceeded in only 1 percent of public supply wells and in very few streams.
The study, conducted by the USGS National Water Quality Assessment program, indicates that nitrate levels in ground and surface waters are higher in agricultural areas, indicating patterns of contamination that relate to land use (see attached maps).
The highest concentrations of nitrate, a nutrient commonly derived from fertilizer, were found in shallow ground water, less than 100 feet below the surface. Concentrations in ground water were higher in parts of the Northeast, Midwest and on the West Coast, with concentrations generally lower in the Southeastern states. The concentrations were highest in areas that are dominated by row crops with well drained soils; concentrations were lower in poorly drained soils.
Nitrate concentrations in surface waters were elevated downstream from agricultural areas, but at significantly lower levels than in ground water.
Concentrations in surface waters rarely exceeded the drinking water standard. Ammonia and phosphorus levels were also elevated downstream from urban areas.
Study results indicate that patterns of contamination based on land use (agriculture or urban) are key to determining where water-quality problems may occur. Understanding regional patterns of contamination will be critical to the design of appropriate watershed management strategies.
The USGS National Water Quality Assessment (NAWQA) program is the first ever nationwide evaluation of the quality of the nation's water resources. This nutrients study is the first in a series of national synthesis studies of the NAWQA program. The goals of NAWQA are to describe current water-quality conditions, describe how water quality is changing and to improve understanding of natural and human factors that affect water-quality conditions.
Through the NAWQA program, the USGS is also conducting national synthesis studies of pesticides, volatile organic compounds and aquatic biology.
The report, entitled "Nutrients in Ground Water and Surface Water of the United States--An Analysis of Data Through 1992," by David K. Mueller, Pixie A. Hamilton, Dennis R. Helsel, Kerie J. Hitt, and Barbara C. Ruddy, Water Resources Investigations Report 95-4031, is available for $12.25 (paper) or $4 (microfiche) from the USGS Branch of Distribution at (303) 202-4210.
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(Note to Editors: Review copies of the report are available to the news media from the USGS Public Affairs Office, telephone 703-648-4460. For technical information on nutrients in the nation's waters, reporters may call the senior author of the report, David Mueller, in Denver, Colo., at 303-236-2102, extension 235.)