Texas: advancing storage in aquifers for managing droughts and floods

Although it goes without saying, water is critical for the environmental and economic health of the state of Texas or any other state for that matter. Variable surface water supplies and generally depleting groundwater supplies in many regions are increasing challenges for water management both in the short- and long-term.

The large variability in available water resources—from the humid East Texas Piney Woods and Gulf Coast to the arid and semiarid plains, hills, and mountains of West Texas—results in additional stresses in water resource management. The projected 73 percent population growth (2020-2070) and recurring extreme droughts and floods will increasingly challenge the reliability of future water supplies in the State.

Ultimately water demand will exceed water supplies, resulting in water scarcity.

Approaches to managing water scarcity include, (1) reducing water demand, (2) increasing traditional water supplies, and (3) storing and transporting water.

Texas is aggressively advancing water conservation programs to reduce water demand, particularly during droughts. There is a limit to the ability to meet all current and future water demands through conservation, however, because of necessary water supplies to meet essential human health needs.

Additional water supplies are being considered, including brackish groundwater and seawater desalination. Although reconnaissance studies in the early 2000s suggest that 2.7 billion acre-feet of brackish groundwater are available in Texas (or approximately 146 times the projected demand for water in 2020), the economic recoverability of this water, particularly outside the Gulf Coast or Carrizo-Wilcox aquifer systems, is not understood and is currently being evaluated.

Transport and storage are often considered for resolving spatial and temporal disconnects between water demands and supplies. While development of a statewide or regional water grid has been considered (ranging from the 1968 Texas State Water Plan to the 84th Texas Legislature in 2015) to move water from east to west Texas, the reality is that water is heavy, and transporting water long distances is expensive in terms of energy, economics, and adverse effects on the environment.

Storing water from times of plenty for use during times of drought has been used for centuries. The typical approach to storage, however, has been to rely on the use of surface reservoirs.

Surface reservoir storage capacity in Texas increased markedly up to the mid-1970s because most of the suitable sites for reservoirs had been built and it is almost impossible to obtain the necessary environmental permits from the federal government under the Clean Water Act for the construction of new surface reservoirs.

In addition, especially in the more arid areas of Texas, it’s now recognized that surface reservoirs are subject to large-scale evaporation, especially during drought conditions when water is most needed. However, there is a light at the end of the tunnel, namely the development of Aquifer Storage and Recovery (ASR) projects.

Conceptually, ASR is storing excess water in aquifers for later withdrawal and use to meet water supply needs during droughts, other emergencies, or interruptions in supplies, or during periods of peak demand. ASR provides many advantages relative to surface reservoir storage, including the elimination of evaporative losses, limited land surface impacts, and modular design that can be expanded as needed over time.

Nationally, Texas has significantly advanced in this area within the past few years with the passage of House Bill 655 by the Texas Legislature in 2015. This new law (HB 655) and accompanying regulatory framework adopted by the Texas Commission on Environmental Quality (TCEQ) has overcome many of the policy hurdles that were a deterrent to ASR in the past, including allowing water rights to be transferred to ASR without requiring a new permit or permit amendment, and thus a loss of seniority. 

Texas water quality requirements for ASR have been relaxed to better account for advances in ASR technologies. Previously, there was a non-degradation clause requiring that ASR projects not degrade groundwater.  It’s now known, however, that even if injected water mobilizes metals (such as iron or manganese) or causes other water quality issues, as long as the injected water (the injection bubble) can be controlled and managed, and water once withdrawn can be treated after it is recovered, then the ASR project is safe and within the requirements of the Safe Drinking Water Act.

A variety of water sources can now be considered for use in ASR projects, including partially treated surface water, imported groundwater (either locally or regionally), and reclaimed water. Authorization from Groundwater Conservation Districts (GCDs) is no longer required, removing the potential for conflicting regulatory standards between the TCEQ and locally controlled GCDs.

An excellent potential site for ASR is the largely depleted Northern Trinity Aquifer with artesian groundwater levels depleted by ~ 1,000 feet and nearby surface reservoirs in the vicinity of the Dallas/Fort Worth area that is often at or near capacity, except during drought.

With all of these advances, ASR is projected to expand substantially in the state and there are some 12 projects currently being considered in a variety of hydrogeologic settings and utilizing a wide variety of water sources.

ASR projects can also help alleviate environmental flow problems. According to many experts, the new regulations in Texas represent the most advanced of those in any state and should allow Texas to move toward more sustainable water management through increased water storage during times of plenty for use during times of need.

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Dr. Bridget R. Scanlon is a senior research scientist at the Bureau of Economic Geology, Jackson School of Geosciences at The University of Texas at Austin. Dr. Scanlon received the National Ground Water Association’s 2016 M. King Hubbert Award for major science contributions to the knowledge of groundwater. She is a member of the National Academy of Engineering (NAE). For more information, contact Dr. Scanlon at bridget.scanlon@beg.utexas.edu. Follow the Jackson School of Geosciences on Twitter @txgeosciences

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Editor's note: The views expressed by contributors to the Cynthia and George Mitchell Foundation's blogging initiative, "Can Texas's approach to sustainability inform a path forward for the U.S.?," are those of the author and do not necessarily represent the views of the foundation. The foundation works as an engine of change in both policy and practice, supporting high-impact projects at the nexus of environmental protection, social equity, and economic vibrancy. Follow the foundation on Facebook and Twitter, and sign up for regular updates from the foundation.

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