Regional Assessment of Groundwater Quality in the Mississippi Embayment-Texas Coastal Uplands Aquifer System, Coastal Lowlands Aquifer System, and the Edwards-Trinity Aquifer System
 The National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey is assessing water quality in the Mississippi embayment-Texas coastal upland aquifer system, coastal lowlands aquifer system, and Edwards-Trinity aquifer. The aquifers in this regional assessment represent a contrast in groundwater hydrology. The Mississippi embayment-Texas coastal uplands and the coastal lowlands aquifer systems consist largely of unconsolidated sand and are confined in many areas by clay confining units. The Edwards-Trinity aquifer is a karst aquifer in carbonate rock and as a result may be more vulnerable to contamination than the sand aquifers in the Mississippi embayment-Texas coastal uplands and Coastal lowlands aquifer systems. These aquifers are important sources of drinking water, both for public supply and private use. For example in 2000, about 724 million gallons per day were withdrawn from the Mississippi embayment-Texas coastal uplands aquifer system providing water to about 8.9 million people throughout Texas, Louisiana, Mississippi, Arkansas, Missouri, Tennessee, and Alabama. Both the coastal lowlands aquifer system and the Edwards-Trinity aquifer also are important sources of drinking water (Maupin and Barber, 2005).
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Topics selected for the assessment of water quality:
- What factors affect the occurrence of nutrients, pesticides, and VOCs in shallow groundwater in Mississippi embayment-Texas coastal uplands aquifer system? (SIR 2009-5091)
- How does hydrology affect nitrate and pesticide concentrations and trends in the San Antonio segment of the Edwards aquifer? (SIR 2010-5129)
- How has the quality of shallow water in the Memphis, Tennessee urban area changed over time and how might it affect the deeper source of drinking water?
- How is occurrence of contaminants related to groundwater residence time in the Memphis aquifer? Can we predict groundwater age, travel times, and concentrations of contaminants with a regional flow model?
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- Nutrient, pesticide, and VOC occurrence in shallow groundwater of the Mississippi embayment-Texas coastal uplands aquifer system and the Mississippi River Valley alluvial aquifer is affected by soil properties, redox conditions, and land use near wells. For example, nitrate is rarely detected in samples from the Mississippi River Valley alluvial aquifer because of reducing redox conditions in this aquifer; however, these conditions may be an important factor contributing to elevated concentrations of dissolved phosphorus. (Download report)
- Most of the samples from 12 carbonate aquifers across the country sampled by NAWQA met drinking-water standards. The occurrence of anthropogenic contaminants was related to contaminant sources but also was affected by degree of aquifer confinement, ground-water age, and redox status. (Download report)
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Additional information about the Edwards-Trinity aquifer is available at the Edwards aquifer website. (Leaving USGS web site).
For more information, contact: James Kingsbury, Hydrologist
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U.S. Department of the Interior | U.S. Geological Survey
