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Improving the Geohydrologic Framework of the Edwards and Trinity Aquifers, South-Central Texas


To understand geologic controls on ground-water availability in south-central Texas.


This project is constructing 3-D geologic models of the Dallas/Fort Worth to San Antonio region of Texas from geologic, geophysical, and isotopic studies. These models are then being used to develop ground-water vulnerability maps through cooperation with the Edwards Aquifer Authority, Texas Bureau of Economic Geology, University of Texas Austin, and the San Antonio Water System. The Edwards/Trinity aquifers in Texas are some of the most permeable and productive carbonate aquifers in the U.S. They provide water for 2 million people, including part of Dallas/Fort Worth and all of San Antonio. Because San Antonio uses neither water treatment facilities nor surface storage, its water is susceptible to major disruptions from contamination or reduced aquifer flow. In nearby counties, the aquifers flow to the surface along faults as major artesian springs that provide unique habitats for at least 8 endangered species. To maintain the necessary level of flow to support these federally protected life forms and provide for the future water needs of south-central Texas communities, it is essential to understand the linkages between ground-water availability and ground-water flow paths, aquifer geometry, recharge, karst and fault characteristics, and saltwater intrusion. Recently, the Water Resources Discipline of the USGS has incorporated preliminary 3-D data into their MODFLOW modeling efforts. The study has found that in karst regions, leaching has expanded the size of the aquifer, while regions with faulting cause the aquifer to be discontinuous. Using new aeromagnetic maps, this team also has discovered hundreds of shallow igneous intrusive bodies that undoubtedly have a major impact on ground-water flow.

Study Area:


Anticipated Uses:

Hazards (Karst), Resources (Water)


Edwards Aquifer Authority (TX), San Antonio Water System (TX), Southwest Research Institute (TX), Texas Bureau of Economic Geology, U.S.D.A./Natural Resources Conservation Service, U.S. Fish & Wildlife Service, University of Texas at Austin

Project Status:

Current NCGMP Funding

Project Duration:


Duration of NCGMP Funding:


Contact Information:

Project Chief: Charles D. Blome (Central Earth Surface Processes Team)
Phone: 303-236-1278

Related Links:

Project Website: