We think of groundwater as moving slowly, and groundwater quality as changing slowly—over decades or even centuries. But in some parts of some aquifers, groundwater quality can fluctuate rapidly, sometimes over just a few hours. Are such changes part of a long-term trend, or just part of a short-term cycle? And what does that mean for suitability for drinking?
Featured Study: Drivers of changes in Edwards aquifer water quality
Water level and geochemistry of unconfined/updip and confined/downdip parts of the Edwards aquifer, Central Texas, respond differently to rainfall/recharge events and multiyear dry/wet cycles. Learn more about this key karst drinking-water resource.
Featured Study: Temporal Variability of Arsenic in Groundwater
A new USGS study investigates how concentrations of arsenic in three drinking-water supply wells change at daily, seasonal, and yearly time scales. Arsenic variability and related factors identified have potential implications for human health.
As part of the National Water Quality Program, USGS scientists are investigating why, in some areas and at some depths, groundwater quality changes at short timescales—years to months to days to even hours, rather than decades. These fluctuations often occur in areas where groundwater and surface water interact. The Enhanced Trends Network study is evaluating these short-term fluctuations, identifying what causes them, and determining whether the water-quality changes are just part of a seasonal trend or are part of an overall long-term trend. For those chemical constituents with human-health benchmarks (thresholds for drinking-water quality), changes in constituent concentrations are being evaluated in the context of those benchmarks—in other words, are there certain conditions under which the groundwater might require treatment before drinking?
VIEW GROUNDWATER-QUALITY CHANGES IN REAL TIME
A major feature of this research is the development of instrumentation that collects and transmits high-frequency (hourly to daily) groundwater-quality data at 24 sites. Follow the links below to view data for specific conductance, dissolved oxygen, pH, and nitrate in groundwater in real time.
California
Delaware
New Mexico
New Hampshire
Oregon
Tennessee
Texas
Wisconsin
Interested in long-term trends in groundwater quality? Try the groundwater change tool and see how concentrations of pesticides, nutrients, metals, and organic contaminants in groundwater are changing during decadal periods across the Nation.
For information and science on additional aspects of groundwater quality, click here.
Explore the web pages below to learn more about USGS research on groundwater quality.
National Water-Quality Assessment (NAWQA)
Groundwater/Surface-Water Interaction
Predicting Groundwater Quality in Unmonitored Areas
Water-Quality Trends
- Overview
We think of groundwater as moving slowly, and groundwater quality as changing slowly—over decades or even centuries. But in some parts of some aquifers, groundwater quality can fluctuate rapidly, sometimes over just a few hours. Are such changes part of a long-term trend, or just part of a short-term cycle? And what does that mean for suitability for drinking?
Featured Study: Drivers of changes in Edwards aquifer water quality
Water level and geochemistry of unconfined/updip and confined/downdip parts of the Edwards aquifer, Central Texas, respond differently to rainfall/recharge events and multiyear dry/wet cycles. Learn more about this key karst drinking-water resource.
Featured Study: Temporal Variability of Arsenic in Groundwater
A new USGS study investigates how concentrations of arsenic in three drinking-water supply wells change at daily, seasonal, and yearly time scales. Arsenic variability and related factors identified have potential implications for human health.
As part of the National Water Quality Program, USGS scientists are investigating why, in some areas and at some depths, groundwater quality changes at short timescales—years to months to days to even hours, rather than decades. These fluctuations often occur in areas where groundwater and surface water interact. The Enhanced Trends Network study is evaluating these short-term fluctuations, identifying what causes them, and determining whether the water-quality changes are just part of a seasonal trend or are part of an overall long-term trend. For those chemical constituents with human-health benchmarks (thresholds for drinking-water quality), changes in constituent concentrations are being evaluated in the context of those benchmarks—in other words, are there certain conditions under which the groundwater might require treatment before drinking?
Sources/Usage: Public Domain.A large-volume public supply well in San Antonio, Texas. This well is being sampled for water-quality constituents as part of the NAWQA Enhanced Trend Network study. (Credit: Jennifer Wilson, USGS) VIEW GROUNDWATER-QUALITY CHANGES IN REAL TIME
A major feature of this research is the development of instrumentation that collects and transmits high-frequency (hourly to daily) groundwater-quality data at 24 sites. Follow the links below to view data for specific conductance, dissolved oxygen, pH, and nitrate in groundwater in real time.
California
Delaware
New Mexico
New Hampshire
Oregon
Tennessee
Texas
Wisconsin
Interested in long-term trends in groundwater quality? Try the groundwater change tool and see how concentrations of pesticides, nutrients, metals, and organic contaminants in groundwater are changing during decadal periods across the Nation.
For information and science on additional aspects of groundwater quality, click here.
- Science
Explore the web pages below to learn more about USGS research on groundwater quality.
National 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.Groundwater/Surface-Water Interaction
Water and the chemicals it contains are constantly being exchanged between the land surface and the subsurface. Surface water seeps into the ground and recharges the underlying aquifer—groundwater discharges to the surface and supplies the stream with baseflow. USGS Integrated Watershed Studies assess these exchanges and their effect on surface-water and groundwater quality and quantity.Predicting Groundwater Quality in Unmonitored Areas
Groundwater provides nearly one-half of the Nation’s drinking water, and sustains the steady flow of streams and rivers and the ecological systems that depend on that flow. Unless we drill a well, how can we know the quality of the groundwater below? Learn about how the USGS is using sophisticated techniques to predict groundwater quality and view national maps of groundwater quality.Water-Quality Trends
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. - Publications