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Fact Sheet 2013–3033

The Quality of Our Nation’s Waters

Ecological Health in the Nation’s Streams

By Daren M. Carlisle and Michael D. Woodside

Thumbnail of and link to report PDF (6.83 MB)Abstract

Aquatic biological communities, which are collections of organisms, are a direct measure of stream health because they indicate the ability of a stream to support life. This fact sheet highlights selected findings of a national assessment of stream health by the National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey (USGS). The assessment was unique in that it integrated the condition of three biological communities—algae, macroinvertebrates, and fish—as well as measures of streamflow modification, pesticides, nutrients, and other factors. At least one biological community was altered at 83 percent of assessed streams, and the occurrence of altered communities was highest in urban streams. Streamflows were modified at 86 percent of assessed streams, and increasing severity of streamflow modification was associated with increased occurrence of altered biological communities. Agricultural and urban land use in watersheds may contribute pesticides and nutrients to stream waters, and increasing concentrations of these chemicals were associated with increased occurrence of altered biological communities.

First posted July 10, 2013

For additional information contact:
National Water-Quality Assessment (NAWQA) Program
U.S. Geological Survey
413 National Center
Reston, VA 20192

Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.

Suggested citation:

Carlisle, D.M., and Woodside, M.D., 2013, Ecological health in the Nation’s streams: U.S. Geological Survey Fact Sheet 2013–3033, 6 p.,

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