Water-Quality Trends
Managing Phosphorus in Streams Still a Challenge
Despite decades of efforts to reduce phosphorus loads in streams, phosphorus continues to be a problem in many U.S. streams and rivers, causing explosive growth of aquatic plants and algae. A new USGS study investigates why.
Learn MoreNitrate Loads to Gulf of Mexico Not Decreasing
Nitrate loads entering the Gulf of Mexico have not changed despite reductions at local scales, reports a new USGS study.
Learn MoreScience Center Objects
Is water quality getting better or worse? Answering this deceptively simple question has been a fundamental objective of the USGS National Water-Quality Assessment Project’s research. Learn about trends in contaminants in the nation’s streams and rivers, trends in contaminants that collect in the bed sediment of streams and lakes, and changes in the quality of the nation’s groundwater.
In 1991, Congress established the National Water-Quality Assessment (NAWQA) Project to address where, when, why, and how the Nation's water quality has changed, or is likely to change in the future, in response to human activities and natural factors. In response, the NAWQA Project developed multi-pronged approaches to characterize trends in diverse contaminants in the Nation’s streams, rivers, bed sediment, and groundwater.
Trends in Contaminant Concentrations and Loads in the Nation’s Streams and Rivers
The NAWQA Project, other USGS programs, and other Federal, State, and local agencies have collected years of water-quality data to support their assessments of changing water-quality conditions. For the first time, all of these data have been combined to support the most comprehensive assessment conducted to date of water-quality trends in the United States. Collectively, these data provide insight into how natural features and human activities have contributed to water-quality changes over time in Nation's streams and rivers. Data are updated annually. The online Water-Quality Trends mapping tool allows users to visualize trends in water chemistry (nutrients, pesticides, sediment, carbon, and salinity) and aquatic ecology (fish, invertebrates, and algae)
Tributaries contribute to water quality in the Arkansas River, one of hundreds of U.S. streams and rivers where water-quality trends are being monitored. (Credit: Stan Paxton)
Trends in Sediment-Associated Contaminants
Many contaminants adhere, or sorb, to sediment, so that standard water-quality sampling and analysis is often unable to detect changes in their concentrations over time. Sediment-associated contaminants include legacy contaminants, such as DDT and PCBs, and contaminants currently released into the environment, such as the pesticide bifenthrin and polycyclic aromatic hydrocarbons (PAHs). An alternative approach to determine trends in concentrations of these contaminants is the use of sediment cores collected from lakes and reservoirs.
Changes in Groundwater Quality
Monitoring groundwater quality at a public-supply well.
USGS scientists are characterizing groundwater quality in principal aquifers, the primary source of the Nation's groundwater used for drinking. Users can access an online tool to see how concentrations of pesticides, nutrients, metals, and organic contaminants in groundwater are changing during decadal periods across the Nation, and see in real time how chemical properties of groundwater at some sites are fluctuating.
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Date published: March 4, 2019Status: ActiveNational Water-Quality Assessment (NAWQA)
Our surface water, groundwater, and aquatic ecosystems are priceless resources, used by people across the Nation for drinking, irrigation, industry, and recreation. The National Water-Quality Assessment (NAWQA) Project is a leading source of scientific data and knowledge for development of science-based policies and management strategies to improve and protect our water resources.
Contacts: Gary L Rowe, Jr., PhD, Patty Toccalino, Ph.D.Attribution: Water Resources, National Water Quality Program
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Date published: March 2, 2019Status: ActiveWater Quality in the Nation’s Streams and Rivers – Current Conditions and Long-Term Trends
The Nation's rivers and streams are a priceless resource, but pollution from urban and agricultural areas pose a threat to our water quality. To understand the value of water quality, and to more effectively manage and protect the Nation's water resources, it's critical that we know the current status of water-quality conditions, and how and why those conditions have been changing over time....
Contacts: Lori SpragueAttribution: Water Resources -
Date published: February 28, 2019Status: ActiveGroundwater Quality—Current Conditions and Changes Through Time
Is groundwater the source of your drinking water? The USGS is assessing the quality of groundwater used for public supply using newly collected data along with existing water-quality data. Learn more about this invisible, vital resource so many of us depend on.
Contacts: Bruce LindseyAttribution: Water Resources, National Water Quality Program -
Date published: February 27, 2019Status: ActiveWater-Quality Trends From Lake Cores
Sediment cores let us look back in time at the contaminant history of a watershed. Learn about what lake and reservoir sediment cores tell us about trends in metals, organochlorine pesticides, polycyclic aromatic hydrocarbons, and other sediment-related contaminants.
Contacts: Peter C Van MetreAttribution: Water Resources
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Year Published: 2019Water-quality trends in US rivers: Exploring effects from streamflow trends and changes in watershed management
We present a conceptual model that explores the relationship of streamflow trends to 15 water-quality parameters at 370 sites across the contiguous United States (US). Our analytical framework uses discrete water-quality data, daily streamflow records, and a statistical model to estimate water-quality trends between...
Murphy, Jennifer C.; Sprague, Lori A.Attribution: Lower Mississippi-Gulf Water Science Center
Network controls on mean and variance of nitrate loads from the Mississippi River to the Gulf of Mexico
Excessive nitrate loading to the Gulf of Mexico (GoM) has caused widespread hypoxia over many decades. Despite recent reductions in nitrate loads observed at local scales, decreases in nitrate loading from the MRB to the GoM have been small (1.58 % during 2002-2012) with a low level of analytical confidence in this trend. This work seeks to...
Crawford, John T.; Stets, Edward G.; Sprague, Lori A. Assessing water-quality changes in U.S. rivers at multiple geographic scales using results from probabilistic and targeted monitoring
Two commonly used approaches for water quality monitoring are probabilistic and targeted. In a probabilistic approach like the US Environmental Protection Agency’s National Rivers and Streams Assessment, monitoring sites are selected using a statistically representative approach. In a targeted approach like that used by many monitoring...
Sprague, Lori A.; Mitchell, Richard M; Pollard, Amina I.; Falcone, James A. Recent trends in nutrient and sediment loading to coastal areas of the conterminous U.S.: Insights and global context
Coastal areas in the U.S. and worldwide have experienced massive population and land use changes contributing to significant degradation of coastal ecosystems. Excess nutrient pollution causes coastal ecosystem degradation, and both regulatory and management efforts have targeted reducing nutrient and sediment loading to coastal rivers. Decadal...
Oelsner, Gretchen P.; Stets, Edward G. Effects of antecedent streamflow and sample timing on trend assessments of fish, invertebrate, and diatom communities
Detecting trends in biological attributes is central to many stream monitoring programs; however, understanding how natural variability in environmental factors affects trend results is not well understood. We evaluated the influence of antecedent streamflow and sample timing (covariates) on trend estimates for fish, invertebrate, and diatom taxa...
Zuellig, Robert E.; Carlisle, Daren M. Water-quality trends in US rivers: Exploring effects from streamflow trends and changes in watershed management
We present a conceptual model that explores the relationship of streamflow trends to 15 water-quality parameters at 370 sites across the contiguous United States (US). Our analytical framework uses discrete water-quality data, daily streamflow records, and a statistical model to estimate water-quality trends between...
Murphy, Jennifer C.; Sprague, Lori A. Water-quality trends in U.S. rivers, 2002 to 2012: Relations to levels of concern
Effective management and protection of water resources relies upon understanding how water-quality conditions are changing over time. Water-quality trends for ammonia, chloride, nitrate, sulfate, total dissolved solids (TDS), total nitrogen (TN) and total phosphorus (TP) were assessed at 762 sites located in the conterminous United...
Shoda, Megan E.; Sprague, Lori A.; Murphy, Jennifer C.; Riskin, Melissa L. Modeling drivers of phosphorus loads in Chesapeake Bay tributaries and inferences about long-term change
Causal attribution of changes in water quality often consists of correlation, qualitative reasoning, listing references to the work of others, or speculation. To better support statements of attribution for water-quality trends, structural equation modeling was used to model the causal factors of total phosphorus loads in the Chesapeake Bay...
Ryberg, Karen R.; Blomquist, Joel D.; Sprague, Lori A.; Sekellick, Andrew J.; Keisman, Jennifer L.D. Increasing chloride in rivers of the conterminous U.S. and linkages to potential corrosivity and lead action level exceedances in drinking water
Corrosion in water-distribution systems is a costly problem and controlling corrosion is a primary focus of efforts to reduce lead (Pb) and copper (Cu) in tap water. High chloride concentrations can increase the tendency of water to cause corrosion in distribution systems. The effects of chloride are also expressed in several...
Stets, Edward G.; Lee, Casey J.; Lytle, Darren A.; Schock, Michael R.
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...
Oelsner, Gretchen P.; Sprague, Lori A.; Murphy, Jennifer C.; Zuellig, Robert E.; Johnson, Henry M.; Ryberg, Karen R.; Falcone, James A.; Stets, Edward G.; Vecchia, Aldo V.; Riskin, Melissa L.; De Cicco, Laura A.; Mills, Taylor J.; Farmer, William H. Using groundwater age distributions to understand changes in methyl tert-butyl ether (MtBE) concentrations in ambient groundwater, northeastern United States
Temporal changes in methyl tert-butyl ether (MtBE) concentrations in groundwater were evaluated in the northeastern United States, an area of the nation with widespread low-level detections of MtBE based on a national survey of wells selected to represent ambient conditions. MtBE use in the U.S. peaked in 1999 and was largely discontinued by 2007...
Lindsey, Bruce D.; Ayotte, Joseph D.; Jurgens, Bryant C.; DeSimone, Leslie A. Large decadal-scale changes in uranium and bicarbonate in groundwater of the irrigated western U.S
Samples collected about one decade apart from 1105 wells from across the U.S. were compiled to assess whether uranium concentrations in the arid climate are linked to changing bicarbonate concentrations in the irrigated western U.S. Uranium concentrations in groundwater were high in the arid climate in the western U.S, where uranium sources are...
Burow, Karen R.; Belitz, Kenneth; Dubrovsky, Neil M.; Jurgens, Bryant C. Paleoreconstruction of organic carbon inputs to an oxbow lake in the Mississippi River watershed: Effects of dam construction and land use change on regional inputs
We use a dated sediment core from Lake Whittington (USA) in the lower Mississippi River to reconstruct linkages in the carbon cycling and fluvial sediment dynamics over the past 80 years. Organic carbon (OC) sources were characterized using bulk (δ13C, ramped pyrolysis-oxidation (PyrOx) 14C, δ15N, and TN:OC ratios) and...
Bianchi, Thomas S.; Galy, Valier; Rosenheim, Brad E.; Shields, Michael; Cui, Xingquan; Van Metre, Peter C.-
Date published: January 1, 2018Changes in anthropogenic influences on streams and rivers in the conterminous U.S. over the last 40 years, derived for 16 data themes
This product consists of time-series calculations of anthropogenic characteristics derived for 16 data themes for multiple scales covering the conterminous United States. The characteristics are those which (a) have consistent data sources, and (b) have the potential to affect the water quality of streams and rivers. All 16 data themes are provided for Hydrologic Unit Code level-10 (HUC-10...
Attribution: Water Resources, National Water Quality Program
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Date published: March 4, 2019Water-Quality Changes in the Nation's Streams and Rivers
This mapper provides results from the largest-ever assessment of water quality changes in the Nation's streams and rivers. More than 185 million water-quality records from over 600 Federal, State, Tribal, and local organizations were screened as part of this assessment.
Attribution: Water Resources, Upper Midwest Water Science Center -
Date published: March 3, 2019Changes in imperviousness for U.S. urban areas, 1974-2012
This product consists of two sets of imperviousness calculations for 3,535 urban areas and urban clusters in the conterminous United States. Imperviousness is given as the percent of the area covered by impervious surfaces, such as roads, buildings, or parking lots.
Attribution: Water Resources -
Date published: January 1, 2018
Data from Decadal Change in Groundwater Quality Web Site, 1988-2014, Version 2.0
Evaluating Decadal Changes in Groundwater Quality: Groundwater quality data were collected from 5,000 wells between 1988-2001 (first sampling event) by the U.S. Geological Survey’s National Water-Quality Assessment Project. Samples are collected in groups of 20-30 wells with similar characteristics called networks. About 1,500 of these wells in 67 networks were sampled about 10...
Attribution: Water Resources, National Water Quality Program -
Date published: January 1, 2018
Changes in anthropogenic influences on streams and rivers in the conterminous U.S. over the last 40 years, derived for 16 data themes
This product consists of time-series calculations of anthropogenic characteristics derived for 16 data themes for multiple scales covering the conterminous United States. The characteristics are those which (a) have consistent data sources, and (b) have the potential to affect the water quality of streams and rivers. All 16 data themes are provided for Hydrologic Unit Code level-10 (HUC-10...
Attribution: Water Resources, National Water Quality Program -
Date published: March 21, 2017Ecological 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 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.
Attribution: Water Resources -
Date published: March 21, 2017Water-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
In 1991, the 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.
Attribution: Water Resources -
Date published: April 6, 2016
Classification of Chloride-to-Sulfate Mass Ratio for U.S. Groundwater With Respect to the Potential to Promote Galvanic Corrosion of Lead, 1991-2015; Water Well Data and Characteristic Values for States
Galvanic corrosion of lead in water distribution systems can occur when lead pipe or lead solder is in contact with a dissimilar metal such as copper. If the source water entering those systems has a relatively elevated chloride-to-sulfate mass ratio (CSMR), the potential for galvanic corrosion to occur is elevated (Gregory 1985; Edwards and Triantafyllidou, 2007), especially in w
Attribution: California Water Science Center
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Date published: January 22, 2020Nitrate loads entering the Gulf of Mexico have not changed despite reductions at local scales
Reducing delivery of nitrate to the Gulf of Mexico is critical to decreasing the size of the “dead zone”—an area of hypoxia, or low dissolved oxygen—in Louisiana coastal waters. A new USGS study reports that larger, more widespread decreases in nitrate loading to the Gulf are needed to achieve the target levels of a 25% reduction by...
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Date published: May 6, 2019Sampling design brings insights to changing stream quality
How does the choice of sampling approach affect our perception of whether water quality in streams and rivers has changed over time? A new joint U.S....
Attribution: Water Resources, National Water Quality Program -
Date published: June 2, 2016USGS Online Mapper Provides a Decadal Look at Groundwater Quality
A first of its kind, national assessment of an unseen, valuable resource used by millions of people.
Attribution: Water Resources, National Water Quality Program -
Date published: October 28, 2015U.S. Rivers Show Few Signs of Improvement from Historic Nitrate Increases
During 1945 to 1980, nitrate levels in large U.S. rivers increased up to fivefold in intensively managed agricultural areas of the Midwest, according to a new U.S. Geological Survey study. In recent decades, nitrate changes have been smaller and levels have remained high in most of the rivers studied.
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Date published: August 26, 2015Trends in River Pesticide Levels Echo Pesticide Use
Trends in pesticide concentrations in 38 major rivers in the U.S. during 1992-2010 reflect large-scale trends in pesticide use and regulatory changes, according to a new study by the U.S. Geological Survey.
Attribution: National Water Quality Program -
Date published: July 8, 2014
USGS Release: Large Rivers in U.S. are Becoming Less Acidic
Several large rivers in the U.S. are less acidic now, due to decreasing acidic inputs, such as industrial waste, acid mine drainage, and atmospheric deposition.
Attribution: Water Resources, Toxic Substances Hydrology Program