What's under Texas? A LOT of brackish groundwater! February 2016

Resting under Texas, there is more than 2.7 billion acre-feet of brackish groundwater in the state's minor and major aquifers. To put that into perspective, the total conservation capacity (water supply) for reservoirs monitored by the Texas Water Development Board (TWBD) is 31.3 million acre-feet. That means there is nearly 90 times as much brackish groundwater residing under the state than what would be currently available through our state's reservoirs if they were all full.

While we know there is an abundant supply of brackish groundwater under Texas, we also know that not all of it can be used for water supply. There remains a lot to learn about brackish groundwater, the aquifers in which it resides, and the scientific obstacles to turning that supply into a reliable water source.

In response to the need for more scientific knowledge on brackish aquifers, the 81st Texas Legislature approved funding that helped establish the Brackish Resources Aquifer Characterization System (BRACS) program in 2009. The goals of BRACS include:

  • Mapping and characterizing the brackish aquifers of Texas in greater detail using existing geophysical well logs and available aquifer data
  • Building replicable numerical groundwater flow models to estimate aquifer productivity
  • Developing parameter-screening tools to help communities assess the viability of their brackish groundwater supplies

A typical BRACS study includes evaluating water well data and geophysical well logs to map the geologic structure of an aquifer and to estimate the salinity of water in an aquifer. The project information is then entered and stored into the BRACS Database, where it is analyzed by TWDB staff. Each project is summarized into a written report and published on the TWDB's website.

As a result of that funding, the TWDB has completed four internal studies on the Pecos Valley Aquifer, the Gulf Coast Aquifer (Corpus Christi), Gulf Coast Aquifer (Lower Rio Grande Valley), and the Queen City-Sparta aquifers. TWDB staff is also in the process of studying the Lipan Aquifer.

In 2015, the 84th Texas Legislature passed House Bill 30, providing $2 million in funding and directing the TWDB to identify and designate brackish groundwater production zones in four aquifers: the Carrizo-Wilcox Aquifer located between the Colorado River and Rio Grande, the Gulf Coast Aquifer and sediments bordering that aquifer, the Blaine Aquifer, and the Rustler Aquifer. These designations are due to the legislature by December 1, 2016. House Bill 30 also directed the TWDB to study the remainder of the state's aquifers and report back to the legislature by December 1, 2022.

Since the passage of House Bill 30, the TWDB has been actively engaging in the necessary steps to study the aquifers and deliver the reports to the legislature by the mandated due dates. TWDB has entered into contracts for studies on all four aquifers due to the legislature by December 1, 2016, as well as three additional aquifers (the Trinity, the Blossom, and the Nacatoch).

With time, the TWDB will come to know the intricacies of all the aquifers and determine how this vast water resource can serve as a water supply for Texas. Through BRACS and the direction given by the legislature, the TWDB is one step closer to understanding the complexities associated with the state's brackish groundwater supply. That understanding is key to developing another sustainable and reliable water source for Texas.