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

Summary

In 2021, the Geologic Advisory Unit of the Railroad Commission of Texas identified reports of fresh to slightly saline produced water in a deep portion of the Glen Rose Formation in Maverick, Zavala, and Dimmit counties that could be a potential source of water for local communities. The aquifer currently has a working name of the Maverick Basin aquifer. Fresh and slightly saline groundwater is reported at depths between 5,000 and 8,000 feet below land surface.

Three dimensional map of the top of the Glen Rose Formation in the Maverick Basin, mapped by the TWDB BRACS department. Image shows Maverick, Zavala, Kinney, Uvalde, and Dimmit counties overlain by a polygon representing an approximate extent of the slightly saline water in the Glen Rose Formation, projected into the subsurface to the top of Glen Rose Formation. The approximate boundary of Maverick Basin aquifer from Draper and others 2025. The figure includes Mexico showing the top of Glen Rose Formation elevated in the Serrania del Burro Mountains west of Maverick County.

What we currently know

  • Aquifer type: confined transborder aquifer with artesian flow
  • Formation: Upper Glen Rose Formation, Trinity Group
  • Depth: greater than 5,000 feet
  • Area of aquifer in Texas: at least 650 square miles
  • Recharge zone: believed to be 50 miles west of the Rio Grande in the Serrania del Burro Mountains in Mexico

Conceptual cross section of the Glen Rose Formation. The Glen Rose Formation is over six thousand feet deep in the Maverick Basin in Maverick County, and shallows to the west in Mexico, outcropping in the Serrania del Burro Mountains. The view is to the north with west to the left and east to the right. Above the outcrop in the mountains are illustrations of clouds with rain indicating meteoric recharge in this area. Arrows in the Glen Rose Formation point east indicating the direction of groundwater flow down into the basin. In the Glen Rose Formation in the Maverick Basin, ellipses are drawn in the upper portion of the formation indicating increased porosity in this zone. This high porosity zone is positioned above faults of a graben complex drawn below the Glen Rose Formation, suggesting the enhanced porosity was influenced by underlying structures. Vertical lines indicating petroleum wells extend from the surface down into the enhanced porosity zones in the Maverick Basin, indicating the only known points of discharge, which is through the wells. Next to the wells, a small graph indicates oil volume is high when wells first begin to produce, but then declines to be mostly water over time. This conceptual cross section is from Draper and others 2025.

Contracted report

*Draper and others (2025)

TWDB Contracted Report 2300012710-2 - Maverick Basin aquifer

Three page report summary

Status update

  • TWDB BRACS staff have entered well logs into the BRACS database in the Maverick Basin and have created elevation and depth surfaces for the top of the Glen Rose Formation (top of Trinity Group) that includes the Maverick Basin area and extends into Mexico. Currently working on water quality calculations and lithologic analysis. Working geologic formation elevation and depth raster files are available for download.
  • On May 8th, 2024, the TWDB hosted a webinar where INTERA presented their findings on the likely structural controls on the aquifer, and their recommendations for performing aquifer tests.

Additional resources

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