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Fact Sheet 2011–3114

National Water-Quality Assessment (NAWQA) Program

Regional Assessments of the Nation's Water Quality—Improved Understanding of Stream Nutrient Sources through Enhanced Modeling Capabilities

By Stephen D. Preston, Richard B. Alexander, and Michael D. Woodside

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The U.S. Geological Survey (USGS) recently completed assessments of stream nutrients in six major regions extending over much of the conterminous United States. SPARROW (SPAtially Referenced Regressions On Watershed attributes) models were developed for each region to explain spatial patterns in monitored stream nutrient loads in relation to human activities and natural resources and processes. The model information, reported by stream reach and catchment, provides contrasting views of the spatial patterns of nutrient source contributions, including those from urban (wastewater effluent and diffuse runoff from developed land), agricultural (farm fertilizers and animal manure), and specific background sources (atmospheric nitrogen deposition, soil phosphorus, forest nitrogen fixation, and channel erosion).

Revised October 14, 2011

First posted October 7, 2011

For additional information contact:
Stephen D. Preston
U.S. Geological Survey
1289 McD Drive
Dover, DE 19901–4639

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:

Preston, S.D., Alexander, R.B., and Woodside, M.D., 2011, Regional assessments of the Nation's water quality—Improved understanding of stream nutrient sources through enhanced modeling capabilities, 6 p., available at

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