Frequently Asked Questions
- What is aquifer storage and recovery (ASR)?
- Are there other methods to transfer water into an aquifer?
- How many ASR systems are there in Texas?
- How many ASR systems are there in United States?
- Can ASR be used to store any type of water?
- How much of the stored water can be withdrawn from an ASR system?
- What is the quality of water recovered from an ASR system?
- What are the main concerns regarding ASR in Texas?
- Can the TWDB provide funds for the construction of an ASR system?
- What is the role of the TWDB in ASR?
- What are the benefits of ASR?
- What are the most important technical factors needed for ASR to be a potential water management tool?
- Is ASR considered in the 2017 State Water Plan?
- 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 wells (in Texas, these are referred to as aquifer recharge (AR) projects). 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 systems are there in Texas?
Currently, there are three in Texas. The ASR system at the City of Kerrville began operating in 1998, and the San Antonio Water System's ASR facility at the H2Oaks Center began operating in 2004. Both systems continue to perform successfully and are viewed by their operators as a beneficial component of their water management. El Paso Water Utilities' Fred Hervey Water Reclamation Plant has what is considered a hybrid facility, established in 1985,has used or is using ASR, AR, and indirect reuse. In this system, reclaimed water is added to the aquifer using wells and spreading basins. This water is recovered from wells other than the ones used for injection. This facility may also be classified as aquifer storage, transfer and recovery (ASTR) system.
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 be used to store any type of water?
Yes, 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 projects. Regardless of the stored water source, in Texas, operation of an ASR 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.
TCEQ’s ASR project evaluations are 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. More information on 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?
If water is stored in a freshwater aquifer, it is possible to recover 100 percent of that water. If water is stored in a brackish aquifer, some stored water is left in the aquifer to create a buffer zone, ensuring that brackish water is not present in the recovered water. This buffer zone only needs to be established once. After establishing a buffer zone, high recovery efficiencies are possible. If long storage times are expected, flow in the aquifer may pose a risk of the stored water migrating away from the storage site. The potential for migration of stored water should be considered during the planning of an ASR project.
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?
Goals of the TWDB ASR Program:
- Disseminate information through public education
- Consolidate and map all available study materials
- Facilitate the application of best practices among entities considering ASR
In 2015, the 84th Texas Legislature appropriated $1 million to the TWDB to fund grants for demonstration projects for alternative water supplies. We provided funding to the Victoria County Groundwater Conservation District, the Edwards Aquifer Authority, and the Corpus Christi Aquifer Storage and Recovery Conservation District to acquire information about local geological conditions, water quality, aquifer properties, system design, and system operation and maintenance for possible ASR projects.
In 2019, the 86th Texas Legislature passed House Bill 721 that directed the TWDB to conduct a statewide survey of various major and minor aquifers to identify their relative suitability for use in ASR projects and aquifer recharge (AR) projects and to submit a report that summarizes the statewide survey to the Governor, Lieutenant Governor, and Speaker of the House of Representatives. Additionally, this update to Texas Water Code §11.155 mandates that TWDB conduct studies of ASR and AR projects identified in the state water plan or by interested persons and report the results to regional water planning groups and interested persons.
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; they can be used in 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 2017 State Water Plan?
In the 2017 State Water Plan, 9 of the 16 regional water planning groups (regions A, E, F, G, J, K, L, O, and P) have included ASR and AR as a recommended water management strategy. Collectively, there are 43 recommended water management strategies and 20 ASR or AR associated projects in the plan. If these strategies are implemented, ASR and AR would yield an estimated 152,000 acre-feet of new water supply per year by decade 2070, constituting about 1.8 percent of all recommended water management strategies.
On December 7, 2017, Guadalupe-Blanco River Authority (GBRA) amended the state water plan and changed the Mid-Basin Water Supply Project-Surface Water and ASR Water Management Strategy and its one associated project from recommended to alternative. It also removed the Texas Water Alliance Regional Carrizo Aquifer Development Water Management Strategy and its one associated project sponsored by Texas Water Alliance and designated them as alternative. These water management strategies are replaced by the GBRA Mid-Basin Conjunctive Use Water Management Strategy with one associated project sponsored by the GBRA. Therefore, there is an ASR component in conjunctive use.
As a result, the volume of new ASR water supply per year by decade 2070 reduced from 152,000 to 123,000 acre-feet and the ASR percent of all recommended water strategies reduced from 1.8 to 1.5.