Frequently Asked Questions

  1. What is aquifer storage and recovery (ASR)?
  2. Are there other methods to transfer water into an aquifer?
  3. How many ASR systems are there in Texas?
  4. How many ASR systems are there in United States?
  5. Can ASR or AR be used to store any type of water?
  6. How much of the stored water can be withdrawn from an ASR system?
  7. What is the quality of water recovered from an ASR system?
  8. What are the main concerns regarding ASR in Texas?
  9. Can the TWDB provide funds for the construction of an ASR system?
  10. What is the role of the TWDB in ASR?
  11. What are the benefits of ASR?
  12. What are the most important technical factors needed for ASR to be a potential water management tool?
  13. Is ASR considered in the 2022 State Water Plan?
  14. How are surface water rights related to ASR and AR?
  15. How can I get more information about ASR?

Answers to Frequently Asked Questions

1. What is aquifer storage and recovery (ASR)?

Aquifer storage and recovery (commonly referred to as ASR) is the practice of storing water in a suitable aquifer through a well when water is available and recovering the water from the same aquifer when it is needed. Typically, the same well is used for both injection and recovery. Some people refer to it as a “water savings account”.

2. Are there other methods to transfer water into an aquifer?

Yes, two other common methods are spreading basins and vadose zone wells (in Texas, these are referred to as aquifer recharge (AR) projects, which are defined in Texas Water Code §27.201). If the soil between the land surface and the aquifer can transmit water, spreading basins can be used. In spreading basins, water is retained by engineered structures and percolates through the soil to the aquifer. If the soil at the surface is impermeable and the aquifer is shallow, vadose zone wells might be considered. Vadose zone wells typically are large diameter wells that penetrate through an impermeable soil layer to layers where water can infiltrate the soil and drain into the aquifer.

3. How many ASR or AR systems are there in Texas?

As of 2024, there are eight authorized ASR or AR systems in Texas. The longest running system is El Paso Water Utilities' Fred Hervey Water Reclamation Plant. It is a hybrid facility, established in 1985, and has used or is using ASR, AR, and indirect reuse. The ASR system at the City of Kerrville began operating in 1998, the San Antonio Water System's ASR facility at the H2Oaks Center began operating in 2004, the Ruby Ranch Water Supply Corporation ASR well was authorized for operations in 2020, and the City of Buda ASR well was authorized in 2024.

AR systems include the Edwards Aquifer Authority recharge dams (built 1974-1982), the Dell City flood and recharge dams (built 1982-1987), and the Onion Creek recharge structures (built 1997-2009). Additional facilities are in various stages of planning and pilot testing or may be unknown to the TWDB ASR program.

4. How many ASR systems are there in the United States?

According to a survey conducted in 2013 for the American Water Works Association and presented by Dr. Chi Ho Sham at the 2020 Groundwater Protection Council Underground Protection Control Conference in San Antonio, there are over 200 ASR systems in the United States. The first ASR facility in the United States was built in 1969 in Wildwood, New Jersey, and has been operating since then. The implementation of ASR systems in the nation has accelerated in recent years.

5. Can ASR or AR be used to store any type of water?

Stored water may come from a variety of sources, including surface water, groundwater from other aquifers (or other areas of the same aquifer), reclaimed water, and harvested rainwater. In Texas, surface water, groundwater, and reclaimed water have all been used in ASR or AR projects. Regardless of the stored water source, in Texas, operation of an ASR or AR project cannot alter the quality of the native groundwater to a degree that would:

  • render the groundwater produced from the receiving formation harmful or detrimental to people, animals, vegetation, or property or
  • require an unreasonably higher level of treatment for the groundwater produced from the receiving formation than is necessary for the native groundwater to be suitable for beneficial use.

The Texas Commission on Environmental Quality (TCEQ) evaluates ASR and AR projects based on factors unique to each project rather than relying on any prescriptive standards of source water treatment. A range of source water pre-treatment may be required depending on the various potential combinations of source water, native groundwater, and host rock composition that could make up an ASR project in Texas. For example, projects with wells, trenches, enhanced sinkholes, or other infrastructure regulated by the Underground Injection Control (UIC) program will need a Class V well authorization. Projects that would be used for public water supply or would utilize reclaimed water will need to coordinate permits with the Office of Water’s Water Supply and Water Quality divisions. More information on UIC regulation and permitting of ASR projects is available from the Texas Commission on Environmental Quality Underground Injection Control Class V Permits website.

6. How much of the stored water can be withdrawn from an ASR system?

In Texas, recoverability, or the percent of injected water that can be withdrawn from an ASR system, is based on a value authorized by the Texas Commission on Environmental Quality (TCEQ) Underground Injection Control (UIC) program. This value is determined as part of the authorization process based on modeling and cycle test results. Technical considerations that affect recoverability include geochemical compatibility, hydraulic gradient, hydraulic conductivity, and well operations. Therefore, recoverability can have a wide range of values resulting from the innumerable combinations of these aquifer characteristics and operation choices.

7. What is the quality of water recovered from an ASR system?

The quality of the recovered water will be the result of well operations and the chemical interactions between the source water, native groundwater, and host rock. For example, the longer the storage time, the more chemical interactions may happen. In some cases, the recovered water is expected to be of drinking water quality, in others, additional treatment such as pH adjustment or disinfection may be required. Water quality and treatment requirements are site and project specific.

8. What are the main concerns regarding ASR in Texas?

A 2011 study conducted for the Texas Water Development Board (TWDB) found that water purveyors who had considered ASR had the following concerns:

  • Ability to recover the stored water
  • Quality of the recovered water
  • Cost effectiveness
  • Potential for others to recover the stored water

While these concerns need to be considered, they have been successfully addressed in the aquifer storage and recovery systems operating in Texas and across the nation.

9. Can the TWDB provide funds for the construction of an ASR system?

One of the main functions of the TWDB is to provide financial assistance to support the development of recommended water management strategies in the regional and state water plans, including ASR. More information about the TWDB's financial assistance programs is available.

10. What is the role of the TWDB in ASR?

ASR projects have been and continue to be supported by the TWDB planning and funding programs. The role of the TWDB science and conservation programs in ASR evolves following actions taken by the state legislature. See the ASR program goals on the ASR Program Home Page.

11. What are the benefits of ASR?

When comparing ASR systems to surface water reservoirs, there are two main benefits which include no water loss due to evaporation and no loss of storage capacity due to sedimentation. ASR can also defer the need for additional capital investment by increasing the use of existing treatment facilities since they can be used during non-peak hours to pretreat ASR source water for storage.

12. What are the most important technical factors needed for ASR to be a potential water management tool?

Five factors of highest importance are:

  • Access to a water source. ASR only stores water, it doesn't create it.
  • Access to an appropriate aquifer in which to store and transmit the stored water at a rate and volume sufficient to meet the need.
  • Design and operation of the ASR system to minimize or eliminate potential migration of the stored water away from the storage site.
  • Proper controls (institutional or technical) to ensure that the stored water remains under the control of the project operator of the ASR system.
  • Design and operations that ensure source water, native groundwater, and host rock geochemical compatibility to avoid degradation of water quality and water supply infrastructure.

13. Is ASR considered in the 2022 State Water Plan?

Ten regions recommended ASR strategies. Associated with these strategies are 27 recommended projects that would establish ASR systems or pilot projects. Regions not recommending ASR strategies (Regions B, D, F, I, M, and P) cited reasons such as the lack of suitable geology in proximity to needs, cost constraints, or a lack of interested project sponsors.

14. How are surface water rights related to ASR?
Allocation of surface water for ASR was authorized by the 74th Texas Legislature with House Bill 1989. In 2015, the 84th Texas Legislature passed House Bill 655 that amended the statute to make the permitting process more conducive to implementing ASR projects.

15. How can I get more information about ASR?

If you have any questions about or need information on the TWDB's ASR program, please contact Andrea Croskrey at 512-463-2865 or andrea.croskrey@twdb.texas.gov.