Water-quality trends in the nation’s rivers and streams, 1972–2012—Data preparation, statistical methods, and trend results
Links
- Document: Report (9.90 MB pdf)
- Appendixes:
- Appendix 1 - Table 1–1 to Table 1–7 (976 kB xlsx)
- Appendix 2 - Table 2–1 to Table 2–4 (36.9 kB xlsx)
- Appendix 3 - (246 kB pdf) Laboratory method and change timeline
- Appendix 4 - (5.84 MB pdf) Step-trend analysis of changes in laboratory analysis and sample collection methods
- Appendix 5 - (6.01 MB pdf) Laboratory performance bias evaluation using percent recovery in U.S. Geological Survey Branch of Quality Systems double-blind reference samples over time
- Appendix 6 - (398 kB pdf) Analysis of trends in annual streamflow
- Appendix 7 - Table 7–1 to Table 7–5 (599 kB xlsx)
- Appendix 8 - (183 kB pdf) Comparison of trends determined using the Seasonal Kendall test and the Weighted Regressions on Time, Discharge, and Season (WRTDS) model
- Data Releases:
- USGS Data Release - Water-quality and streamflow datasets used in the Weighted Regressions on Time, Discharge, and Season (WRTDS) models to determine trends in the Nation’s rivers and streams, 1972-2012
- USGS Data Release - Pesticide concentration and streamflow datasets used to evaluate pesticide trends in the Nation’s rivers and streams, 1992-2012
- USGS Data Release - Ecological community datasets used to evaluate the presence of trends in ecological communities in selected rivers and streams across the United States, 1992-2012
- USGS Data Release - Daily streamflow datasets used to analyze trends in streamflow at sites also analyzed for trends in water quality and ecological condition in the Nation's rivers and streams
- USGS Data Release - Water-quality and streamflow datasets used in Seasonal Kendall trend tests for the Nation’s rivers and streams, 1972-2012
- USGS data release - Water-quality trends and trend component estimates for the Nation's rivers and streams using Weighted Regressions on Time, Discharge, and Season (WRTDS) models and generalized flow normalization, 1972-2012
- USGS data release - Daily streamflow datasets used to analyze trends in streamflow at sites also analyzed for trends in water quality and ecological condition in the Nation's rivers and streams
- USGS data release - Pesticide concentration and streamflow datasets used to evaluate pesticide trends in the Nations rivers and streams, 1992-2012
- USGS data release - Water-quality and streamflow datasets used in the Weighted Regressions on Time, Discharge, and Season (WRTDS) models to determine trends in the Nations rivers and streams, 1972-2012
- USGS data release - Water-quality and streamflow datasets used in Seasonal Kendall trend tests for the Nations rivers and streams, 1972-2012
- USGS data release - Ecological community datasets used to evaluate the presence of trends in ecological communities in selected rivers and streams across the United States, 1992-2012
- Project Site: National Water-Quality Assessment (NAWQA) Project
- Version History: Version History (7 kB txt)
- Download citation as: RIS | Dublin Core
Abstract
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.
Suggested Citation
Oelsner, G.P., Sprague, L.A., Murphy, J.C., Zuellig, R.E., Johnson, H.M., Ryberg, K.R., Falcone, J.A., Stets, E.G., Vec-chia, A.V., Riskin, M.L., De Cicco, L.A., Mills, T.J., and Farmer, W.H., 2017, Water-quality trends in the Nation’s rivers and streams, 1972–2012—Data preparation, statistical methods, and trend results (ver. 2.0, October 2017): U.S. Geological Survey Scientific Investigations Report 2017–5006, 136 p., https://doi.org/10.3133/sir20175006.
ISSN: 2328-0328 (online)
Study Area
Table of Contents
- Foreword
- Abstract
- Introduction
- Objectives and Scope
- Methods
- Trend Results
- Summary
- Acknowledgements
- References
- Appendix 1. Streamflow, Water–Quality, and Ecology Sites Included in Trend Analysis
- Appendix 2. Variations in Parameter Reporting for Selected Parameters
- Appendix 3. Laboratory Method and Change Timeline
- Appendix 4. Step-Trend Analysis of Changes in Laboratory Analysis and Sample Collection Methods
- Appendix 5. Laboratory Performance Bias Evaluation Using Percent Recovery in U.S. Geological Survey Branch of Quality Systems Double-Blind Reference Samples over Time
- Appendix 6. Analysis of Trends in Annual Streamflow
- Appendix 7. Trend Results
- Appendix 8. Comparison of Trends Determined Using the Seasonal Kendall Test and the Weighted Regressions on Time, Discharge, and Season Model
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Water-quality trends in the nation’s rivers and streams, 1972–2012—Data preparation, statistical methods, and trend results |
| Series title | Scientific Investigations Report |
| Series number | 2017-5006 |
| DOI | 10.3133/sir20175006 |
| Edition | Version 1.0: Originally posted April 4, 2017; Version 2.0: November 1, 2017 |
| Year Published | 2017 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Publisher location | Reston, VA |
| Contributing office(s) | New Mexico Water Science Center |
| Description | Report: xv, 136 p.; 8 Appendixes; 5 Data Releases; Project Site; Version History |
| Country | United States |
| Online Only (Y/N) | Y |
| Additional Online Files (Y/N) | Y |
| Google Analytic Metrics | Metrics page |