Edwards-Trinity Plateau Aquifer
The rocks that compose the Edwards-Trinity aquifer are relatively flat-lying and are generally exposed at the land surface in the Trans-Pecos and the Edwards Plateau areas. The geologic formations that compose the Trinity and the Edwards aquifers generally are exposed in updip areas, but they dip eastward and southward beneath younger units and lie deep in the subsurface. The downdip boundary of each aquifer approximately coincides with the farthest updip extent of water that contains 10,000 milligrams per liter dissolved solids. The base of the aquifer slopes generally to the south and southeast. Most of the rocks that underlie the Edwards-Trinity aquifer are much less permeable than those that compose the aquifer and, thus, serve as a barrier to groundwater flow. Locally, however, the underlying rocks are permeable and are hydraulically connected to the Edwards-Trinity aquifer, thus extending the thickness of the flow system. The aquifer is generally recharged by direct precipitation on the land surface. Water is mostly unconfined in the shallow parts of the aquifer and is confined in the deeper zones.
Photos of Karst Features
Karst produces distinctive topographic features that can be prominent and distinctive. There are photographs available of the following karst features in the Trinity aquifer of the Edwards plateau:
- Jones, S.W., Lee, R.W., and Busby, J.F. (1997) Chemical evolution and estimated flow velocity of water in the Trinity aquifer, south-central Texas: USGS Water-Resources Investigations Report 97-4078, 19 p.
- Mabe, J.A. (2007) Nutrient and biological conditions of selected small streams in the Edwards Plateau, Central Texas, 2005–06, and implications for development of nutrient criteria: USGS Scientific Investigations Report 2007-5195, 46 p.
- Stanton, G.P., Kress, W.H., Teeple, A.P., Greenslate, M.L., and Clark, A.K. (2007) Geophysical analysis of the Salmon Peak Formation near Amistad Reservoir dam, Val Verde County, Texas, and Coahuila, Mexico, March 2006, to aid in piezometer placement: USGS Scientific Investigations Report 2007-5143, 72 p.
Featured Studies and Datasets
Aquifer-scale studies and the datasets they produce are a key component to understanding how karst aquifers behave, and the quality of water within them.
- National Water-Quality Assessment, South-Central Texas — A program to describe the status and trends in water quality of a large, representative part of the Nation’s surface-water and groundwater resources.
There are 3 USGS scientists you can contact for more information about this aquifer.
Additional information can be found at Bibliography for USGS Regional Aquifer Study and Assessment.