Deep Glen Rose Formation in South Texas (the 'Maverick Basin' aquifer)

Map of the deep Glen Rose Formation mapped by the Railroad Commission of Texas. Image shows Maverick, Zavala, Kinney, Uvalde, and Dimmit counties overlain by a contour map of formation depth, ranging from about 1000 to 8000 feet below land surface. The formation deepens as you move northwest to southeast

Image source: Railroad Commission of Texas, Groundwater Advisory Unit


The Groundwater Advisory Unit of the Railroad Commission of Texas recently identified and partially mapped a deep portion of the Glen Rose Formation in Maverick, Zavala, Dimmit, Kinney, and Uvalde counties that could be a potential source of freshwater for local communities. The aquifer currently has a working name of the Maverick Basin aquifer. Fresh groundwater is reported at depths between 5,000 and 8,000 feet below land surface.

The TWDB is working with the Railroad Commission of Texas and other entities, like the UT Bureau of Economic Geology and the Texas Water Resources Institute, who have researched this aquifer to assemble and evaluate available data on the occurence and characteristics of this possible aquifer. Additional data and information will be posted on this webpage as it becomes available.

What we currently know

  • Aquifer type: confined transborder aquifer with artesian flow
  • Formation: Glen Rose Formation, Trinity Group
  • Depth: greater than 5,000 feet
  • Area of aquifer in Texas: at least 3,000 square miles
  • Recharge zone: believed to be 50 miles west of the Rio Grande in Mexico

Status update

  • March 2022: TWDB BRACS staff are incorporating the Maverick Basin aquifer in their study of brackish groundwater resources in the Edwards-Trinity (Plateau) area. Currently, BRACS staff are identifying geophysical logs in the Glen Rose Formation in Maverick and surrounding counties, depth-calibrating the logs to incorporate with geologic mapping software, and interpreting stratigraphic surfaces on these logs.


TWDB Reports

ID Date Type Description
GMR17-01 April 2017 Groundwater Management Report Transborder Aquifers: A Summary of Aquifer Properties, Policies, and Planning Approaches for Texas, Surrounding States, and Mexico
LP-214 February 1995 Limited publication Evaluation of Ground-Water Quality in Texas Counties Bordering the Rio Grande
5617 December 1956 Bulletin Records of Water-Level Measurements in Dimmit, Maverick, and Zavala Counties, Texas
5203 March 1952 Bulletin Winter Garden District Dimmit and Zavala Counties and Eastern Maverick County, Texas
M302 1940 Historical Groundwater Report Records of Wells, Winter Garden District, Dimmit and Zavala Counties and Eastern Maverick County, Texas