USGS Water Resources Information

graphic Stream Water Quality in the Conterminous United States -- Status and Trends of Selected Indicators During the 1980's

By Richard A. Smith, Richard B. Alexander, and Kenneth J. Lanfear
National Water Summary 1990-91 -- Stream Water Quality, U.S. Geological Survey Water-Supply Paper 2400)

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In the years since enactment of the Clean Water Act, formally known as the Federal Water Pollution Control Act Amendments of 1972 (Public Law 92-500), and its subsequent amendments in 1977, 1979, 1980, 1981, 1983, and 1987, major changes have taken place in the sources of water contaminants and in the efforts to control them. Population distribution, land use, industrial activity, agricultural practices, and pollution-control strategies have all changed significantly. The effects of these changes on water quality and the consequences on human and ecological health and the use of water resources are of major economic and social importance. Thus, the early 1990's are an appropriate time to examine national water-quality conditions and trends.

In contrast to the State summaries in this volume that portray water-quality conditions and trends within State boundaries, this article presents a summary of national water quality in the conterminous United States, represented by the status and trends of selected indicators. This article is based on water-quality data from Federal and State monitoring programs, generally from 1980 to 1989, and is intended to provide decisionmakers and the public with information on the progress being made toward water-quality goals. By necessity, the analyses presented in this article were compiled from a variety of data sources that, collectively, only partially address the diverse water-quality issues currently of interest. The major component of this article is an analysis of U.S. Geological Survey (USGS) monitoring data on several indicators of chemical and sanitary conditions in streams; secondary components are analyses of U.S. Fish and Wildlife Service (FWS) finfish-tissue data and analyses of USGS herbicide data from streams that drain agricultural areas in the Midwest.

This article is organized into three major sections, and much of the water-quality summary information is presented graphically. Thus, the following descriptions of the sections emphasize those illustrations.

  1. The characteristics and limitations of existing national water-quality data.
  2. The water-quality data selected for analysis and the geographic characteristics of the data. Because interpretation of water quality in the subsequent section is, in part, made on the basis of land use, this section introduces a land-use classification that is used in this article and shown in figure 37.
  3. A national summary of conditions and trends in stream water quality as represented by:

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