As the Central Texas Hill Country and I-35 populations continue to grow, so do demands on water resources. To adequately plan for this, many water suppliers and utilities are exploring alternatives to diversify their supply sources and long-term water supply strategies such as brackish & desalination systems, water reuse, rainwater harvesting, and aquifer storage & recovery (ASR) systems.
ASR could be an increasingly important tool for meeting future water demand as it has become a well-established technology used to improve the management of water resources in the state.
What is Aquifer Storage and Recovery (ASR)?
ASR is the injection (through a well) and storage of water in a suitable aquifer formation during times when water is available, and the recovery of that stored water during times when it is needed. If properly engineered and operated, the water stored in an aquifer storage and recovery system is not subject to the evaporative losses encountered in surface storage reservoirs and remains available for future use. Furthermore, ASR systems have a small footprint relative to surface-water reservoirs.
ASR activities in Texas began in the 1940s in El Paso and Amarillo. There is currently over 130 aquifer recharging programs across the United States. In Texas, there are some utilities that have successfully used ASR systems for a number of years such as San Antonio, El Paso, and Kerrville.
There are two local water suppliers in Hays County who have taken steps to perform feasibility and pilot tests for ASR. District staff have worked closely with the ASR project teams at the Ruby Ranch Water Supply Corporation (RRWSC) and City of Buda to collect data and review project plans. The District has set aside 2 cfs (472 MG/yr) of freshwater Edwards for ASR projects to be used during non-drought conditions. The District hopes that such water strategies will reduce dependence on the Edwards during times of drought and during peak demand.
RRWSC completed a four-phase ASR pilot study in September 2019 in an effort to learn more about the feasibility of injection freshwater Edwards into the Middle Trinity Aquifer. RRWSC has an existing Edwards and Trinity well pair. The project reports describe the results of the testing. RRWSC has received an ASR permit approval from TCEQ and the application was later approved by the District’s Board.
City of Buda ASR Permit
In 2016, the City of Buda completed an ASR feasibility study looking at injecting freshwater Edwards Aquifer water into the Middle Trinity Aquifer. The study evaluated the geology, hydrogeology, and water quality data of the Trinity Aquifer to be used in model and evaluate ASR feasibility. They also reviewed the results of an ASR system implemented for the Ruby Ranch subdivision immediately to the west of Buda.
After the Buda study yielded promising results, the City moved forward with drilling a Middle Trinity well and planning an ASR pilot project. They identified the project site near the Garlic Creek Booster Station and developed construction plans for drilling a Trinity Aquifer well near their existing Edwards Aquifer well.
The City of Buda gets roughly 25 percent of its annual water supply from the Edwards Aquifer through permits from the District. During drought Buda is subject to District drought curtailments that starts to limit that supply by 20 percent and potentially up to 50 percent during a drought of record. Development of an ASR system would allow the City to replace these pumping curtailments by recovering previously stored Edwards Aquifer water from Trinity Aquifer formations.