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National Water-Quality Assessment Program

Nutrient Trends in Streams and Rivers of the United States, 1993–2003

By Lori A. Sprague, David K. Mueller, Gregory E. Schwarz, and David L. Lorenz

Abstract Trends in streamflow and concentrations and loads of total phosphorus, total nitrogen, and nitrate were determined for the period from 1993 to 2003 in selected streams and rivers of the United States. Flow-adjusted trends in concentration (the trends that would have occurred in the absence of natural changes in streamflow), non-flow-adjusted trends in concentration (the trends resulting from both natural and human factors), and trends in load (trends in the nutrient mass transported downstream) were determined, and the results were examined spatially to determine whether a consistent pattern of trends occurred across groups of sites at multiple locations. Relations between the trends and changes in nutrient sources and streamflow are examined. See document for complete abstract.

First posted May 28, 2009 Report PDF (12.3 MB) For additional information contact: Director, Colorado Water Science Center U.S. Geological Survey Box 25046, Mail Stop 415 Denver, CO 80225 http://co.water.usgs.gov/ 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:

Sprague, L.A., Mueller, D.K., Schwarz, G.E., and Lorenz, D.L., 2009, Nutrient trends in streams and rivers of the United States, 1993–2003: U.S. Geological Survey Scientific Investigations Report 2008–5202, 196 p.

Contents

Foreword

Abstract

Introduction

Purpose and Scope

Acknowledgments

Approach

Nutrient Trends in Streams and Rivers of the United States, 1993–2003

Summary and Conclusions

References Cited

Appendix 1. Study-site characteristics

Appendix 2. Model output for trends in daily mean streamflow from 1993 to 2003

Appendix 3. Model output for flow-adjusted trends in concentration, non-flow-adjusted trends in concentration, and trends in load from 1993 to 2003