National Water-Quality Assessment (NAWQA) Project

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Groundwater Quality in Two Principal Aquifers

Regional assessments of groundwater quality in two Principal Aquifers add to those published previously for nine Principal Aquifers sampled in 2012-16. Almost 150 deep public-supply wells were sampled within the two Principal Aquifers: the Floridan aquifer system (southeastern U.S.) and the Mississippi Embayment-Texas Coastal Uplands aquifer system (south-central U.S.) Groundwater samples were analyzed for hundreds of water-quality constituents.

At least one inorganic constituent exceeded a human-health benchmark in 7 percent (Mississippi Embayment-Texas Coastal Uplands aquifer system) to 14 percent (Floridan aquifer system) of samples collected. However, organic contaminants rarely occurred at concentrations that approached human- health benchmarks. Radioactive constituents, from geologic sources, most frequently exceeded human- health benchmarks in these two aquifer systems.

"Nuisance" constituents-those that can affect water's taste, color or odor-were present at high levels, meaning they exceeded the Environmental Protection Agency's non-mandatory benchmarks, in 25 percent (Floridan aquifer system) and 52 percent (Mississippi Embayment-Texas Coastal Uplands aquifer system) of the two study areas.

About 140 million people-almost one-half of the Nation's population-rely on groundwater for drinking water. Regional assessments of groundwater quality are one component of the NAWQA Project's ongoing efforts to assess, understand, and forecast the quality of the Nation's groundwater.

Access a fact sheet that describes results for a Principal Aquifer by clicking on that aquifer’s pie chart.

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