The method
What Is Aquifer Storage & Recovery?
Aquifer Storage and Recovery (ASR) injects appropriately treated water into a suitable aquifer for later recovery. It can shift wet-period water into dry periods, but it does not create water. Source-water availability, treatment, geology, rights, and measured recovery efficiency determine whether it is a practical, economical choice.
Compare conservation, reuse, recharge, desalination, and other options →How it works, in four steps
01
Capture the surplus
Identify legally available source water after protecting downstream rights, ecological flows, and flood safety. High flows are not automatically surplus; they can support habitats, sediment transport, and estuaries.
02
Treat for aquifer protection and intended use
Treat source water to the standard required by aquifer protection and intended use. Test compatibility with aquifer chemistry, and verify whether additional treatment is needed after recovery.
03
Inject into the aquifer
Inject treated water into a suitable formation. Underground storage limits direct surface evaporation, but wells, treatment, conveyance, energy, and land are still required.
04
Recover it in drought
Recover stored water through validated well infrastructure when needed. Mixing, migration, water quality, and recovery losses determine usable yield; storage can be exhausted during prolonged drought.
What does ASR cost per acre-foot?
Compare lifecycle cost per dependable acre-foot delivered at the required location, quality, and season. Include drought reliability, recovery losses, treatment, power, conveyance, and environmental constraints. The legacy scenario inputs below are illustrative assumptions, not a current national ranking or project quotations.
| Option | Cost per acre-foot | Note |
|---|---|---|
| Aquifer Storage & Recovery | $200-800 | Potentially limited evaporation; wells and recovery require validation |
| Seawater desalination | $1800-2500 | ~$100M capex per MGD; $4.00/1,000 gal |
| Long-distance water imports | $800/yr | $5M per mile; political feasibility low |
| Continued groundwater mining | $100 | Scenario pumping cost; 10× long-run multiplier as levels fall |
A low pumping cost can omit depletion, domestic-well impacts, lost streamflow, and subsidence. Sustainable pumping limits and long-term impacts belong in the comparison.
Does ASR actually work? Projects already operating
These examples come from the site’s existing project dataset. Capacities, costs, and operating dates are historical entries; reuse with recharge and well-based ASR are different configurations and should not be compared as identical projects.
Orange County GWRS
- Capacity
- 130 MGD
- Investment
- $900M
- People served
- 1.0M
- Demand met
- 39%
- Cost per AF
- $850-1100
- Operating since
- 2008
San Antonio SAWS ASR
- Storage
- 120000-140000 AF
- Investment
- $186M
- Operating since
- 2004
Tucson Water ASR
- Storage credits
- 100,000 AF
- Investment
- $100M
Where is there enough stormwater to make it work?
ASR requires available source water and recoverable storage. In the legacy scenario model below, 7 are labeled excellent under the model’s assumptions. This is not verified source-water availability, permitted diversion capacity, or dependable drought yield.
| Region | Stormwater available | ASR potential | Net deficit | Deficit offset |
|---|---|---|---|---|
| Ogallala | 8.91 MAF | 6.24 MAF | 1.65 MAF | 378% |
| Central Valley | 1.02 MAF | 0.72 MAF | 2.77 MAF | 26% |
| Basin & Range | 10.75 MAF | 7.53 MAF | -0.39 MAF | — |
| Edwards | 0.22 MAF | 0.16 MAF | 0.14 MAF | 109% |
| Mississippi Embayment | 3.94 MAF | 2.76 MAF | 0.51 MAF | 542% |
| Columbia Plateau | 2.97 MAF | 2.08 MAF | 0.35 MAF | 594% |
| Great Salt Lake | 1.79 MAF | 1.25 MAF | 0.13 MAF | 985% |
| Denver Basin | 0.36 MAF | 0.25 MAF | 0.05 MAF | 472% |
On the figures
This page retains legacy cost assumptions and historical project entries. Stormwater availability and deficit offsets are modeled; they have not been recalculated or validated as firm supply in the new options assessment. National programme totals are stated on the investment page and are under revision. Start with the water-security options assessment for the comparison framework. Legacy method on the science page.