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A scientifically based nationwide assessment of groundwater quality in the United States


Beginning in 1986, the U.S. Geological Survey began an effort to develop a National Water-Quality Assessment Program. The basic premise underlying this initiative is that a better understanding of the quality of water resources across the country, both surface- and groundwater, is needed to develop effective programs and policies to meet the nation's water-quality concerns. The program will focus on water-quality conditions that are prevalent or large in scale, such as occur from nonpoint sources of pollution or from a high density of point sources.

The design of the program is substantially different from the traditional approach of a diffuse national monitoring network.

The major activities of the assessment program will be clustered within a set of hydrologic systems (river basins and aquifer systems), referred to as study units. In aggregate, the study units will account for a large part of the nation's water use and represent a wide range of settings across the country.

Unique attributes of the program include: (1) the use of consistent study approaches, field and laboratory methods, water-quality measurements, and ancillary data measurements for all study units; (2) the development of a progressive understanding of water-quality conditions and trends in each study unit through long-term studies that rotate periods of intensive data collection and analysis with periods during which the assessment activities are less intensive; and (3) the focus of considerable effort on synthesizing results from among the study units to provide information on regional and national water-quality issues.

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References Cited

  1. Hirsch, R. M., W. M. Alley, and W. G. Wilber, 1988, Concepts for a national water-quality assessment program: U.S. Geological Survey Circular 1021, 42 p.

  2. Seaber, P. R., F. P. Kapinos, and G. L. Knapp, 1986, Hydrologic unit maps: U.S. Geological Survey Water-Supply Paper 2294, 63 p.

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Alley, W.M., Cohen, P. A scientifically based nationwide assessment of groundwater quality in the United States. Environ. Geol. Water Sci 17, 17–22 (1991).

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  • Groundwater Quality
  • Assessment Program
  • Study Unit
  • Ancillary Data
  • National Monitoring