Water-quality trends in the nation’s rivers and streams, 1972–2012—Data preparation, statistical methods, and trend results
Since passage of the Clean Water Act in 1972, Federal, State, and local governments have invested billions of dollars to reduce pollution entering rivers and streams. To understand the return on these investments and to effectively manage and protect the Nation’s water resources in the future, we need to know how and why water quality has been changing over time. As part of the National Water-Quality Assessment Project, of the U.S. Geological Survey’s National Water-Quality Program, data from the U.S. Geological Survey, along with multiple other Federal, State, Tribal, regional, and local agencies, have been used to support the most comprehensive assessment conducted to date of surface-water-quality trends in the United States. This report documents the methods used to determine trends in water quality and ecology because these methods are vital to ensuring the quality of the results. Specific objectives are to document (1) the data compilation and processing steps used to identify river and stream sites throughout the Nation suitable for water-quality, pesticide, and ecology trend analysis, (2) the statistical methods used to determine trends in target parameters, (3) considerations for water-quality, pesticide, and ecology data and streamflow data when modeling trends, (4) sensitivity analyses for selecting data and interpreting trend results with the Weighted Regressions on Time, Discharge, and Season method, and (5) the final trend results at each site. The scope of this study includes trends in water-quality concentrations and loads (nutrient, sediment, major ion, salinity, and carbon), pesticide concentrations and loads, and metrics for aquatic ecology (fish, invertebrates, and algae) for four time periods: (1) 1972–2012, (2) 1982–2012, (3) 1992–2012, and (4) 2002–12. In total, nearly 12,000 trends in concentration, load, and ecology metrics were evaluated in this study; there were 11,893 combinations of sites, parameters, and trend periods. The final trend results are presented with examples of how to interpret the results from each trend model. Interpretation of the trend results, such as causal analysis, is not included.
Citation Information
| Publication Year | 2017 |
|---|---|
| Title | Water-quality trends in the nation’s rivers and streams, 1972–2012—Data preparation, statistical methods, and trend results |
| DOI | 10.3133/sir20175006 |
| Authors | Gretchen P. Oelsner, Lori A. Sprague, Jennifer C. Murphy, Robert E. Zuellig, Henry M. Johnson, Karen R. Ryberg, James A. Falcone, Edward G. Stets, Aldo V. Vecchia, Melissa L. Riskin, Laura A. De Cicco, Taylor J. Mills, William H. Farmer |
| Publication Type | Report |
| Publication Subtype | USGS Numbered Series |
| Series Title | Scientific Investigations Report |
| Series Number | 2017-5006 |
| Index ID | sir20175006 |
| Record Source | USGS Publications Warehouse |
| USGS Organization | New Mexico Water Science Center |
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Lori Sprague
Program Manager, Integrated Water Availability Assessments
Hank Johnson
Research Hydrologist
James A Falcone (Former Employee)
Physical Scientist
William H Farmer, Ph.D.
Acting Director, Northeast Climate Adaptation Science Center
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In 1991, the U.S. Geological Survey (USGS) began a study of more than 50 major river basins across the Nation as part of the National Water-Quality Assessment (NAWQA) project of the National Water-Quality Program. One of the major goals of the NAWQA project is to determine how water-quality conditions change over time. To support that goal, long-term consistent and comparable monitoring has been cEcological community datasets used to evaluate the presence of trends in ecological communities in selected rivers and streams across the United States, 1992-2012
In 1991, the U.S. Geological Survey (USGS) began a study of more than 50 major river basins across the Nation as part of the National Water-Quality Assessment (NAWQA) project of the National Water-Quality Program. One of the major goals of the NAWQA project is to determine how water-quality and ecological conditions change over time. To support that goal, long-term consistent and comparable ecologPesticide concentration and streamflow datasets used to evaluate pesticide trends in the Nations rivers and streams, 1992-2012
In 1991, the U.S. Geological Survey (USGS) began a study of more than 50 major river basins across the Nation as part of the National Water-Quality Assessment (NAWQA) project of the National Water-Quality Program. One of the major goals of the NAWQA project is to determine how water-quality conditions change over time. To support that goal, long-term consistent and comparable monitoring has been c - Connect
Lori Sprague
Program Manager, Integrated Water Availability AssessmentsEmailPhoneHank Johnson
Research HydrologistEmailJames A Falcone (Former Employee)
Physical ScientistWilliam H Farmer, Ph.D.
Acting Director, Northeast Climate Adaptation Science CenterResearch Physical ScientistEmailPhone