A regional assessment of untreated groundwater in the combined Valley and Ridge and Piedmont and Blue Ridge aquifers in the eastern United States is now available from the U.S. Geological Survey.
These combined carbonate-rock aquifers underlie an area with a population of more than 40 million people in ten states and are an important source of public supply, providing about 195 million gallons per day for this use.
Scientists tested for a broad range of water-quality characteristics of untreated groundwater in the Valley and Ridge and Piedmont and Blue Ridge aquifers. Results show inorganic constituents present at high concentrations, meaning at levels exceeding human-health benchmarks, in about 15 percent of the study area. Human-made organic constituents (both pesticides and volatile organic compounds) were not detected at high concentrations. The study area includes water at the depth used for public supply. The study evaluated untreated drinking water, but compared results to drinking-water quality standards. The full report is available online.
Many inorganic constituents occur naturally in groundwater. The inorganic constituents found at high levels in this study area include radioactive constituents (specifically gross alpha activity), nitrate, strontium, iron and manganese. Concentrations of inorganic constituents can be affected by natural processes as well as by human activities. Results show one or more inorganic constituents present at high concentrations in about 15 percent of the aquifers and at moderate concentrations (between half the human-health benchmark and the benchmark concentration) in about 17 percent.
The scientists evaluated groundwater quality in the Valley and Ridge and Piedmont and Blue Ridge aquifers by sampling 60 spatially distributed public-supply wells in these two aquifers. This study area includes parts of New Jersey, Pennsylvania, Maryland, Virginia, West Virginia, Tennessee, Georgia and Alabama. Land use overlying the aquifers is primarily agricultural (35 percent) and urban (17 percent). Water-supply wells in carbonate-rock aquifers such as the Valley and Ridge and Piedmont and Blue Ridge are generally more productive than wells in other rock types, and might be particularly vulnerable to contamination from the land surface.
Groundwater provides nearly 50 percent of the nation’s drinking water. To help protect this vital resource, the USGS National Water-Quality Assessment, or NAWQA, Project of the National Water Quality Program assesses groundwater quality in aquifers that are important sources of drinking water.
Over the last two decades, USGS scientists have assessed water quality in source (untreated) water from 6,600 wells in extensive regional aquifers that supply most of the groundwater pumped for the nation’s drinking water, irrigation and other uses. This comprehensive sampling, along with detailed information on geology, hydrology, geochemistry and chemical and water use, can be used to explain how and why aquifer vulnerability to contamination varies across the nation.
Between 2013 and 2022, NAWQA will continue to assess the quality of the nation’s groundwater by sampling about 2,300 shallow wells and 1,400 deep public-supply wells for a broad range of water-quality constituents. In the future, USGS-led national- and regional-scale modeling will provide a three-dimensional perspective of the quality of the nation’s groundwater that can be used to inform management decisions. More information on USGS regional aquifer assessments can be found in this recent USGS Top Story.
To learn more, visit these websites:
USGS National Summary Circular, Quality of the Nation's Groundwater Quality, 1991-2010
Regional reports on principal aquifers of the U.S.
National Water-Quality Assessment (NAWQA) Program
USGS Groundwater Information
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