Best Bets for Texas Water

Aquifer storage and recovery

Aquifer storage and recovery, or ASR, is the process of injecting or pumping treated water into an underground aquifer, where it is stored so that it can be used at a later time. In some locations, water can be directed to natural recharge zones instead of mechanically injected.

During times of plenty, extra water can be stored underground so that it can be used during drought or other similar circumstances.

The supply source for ASR can be surface water from rivers, treated wastewater, groundwater from other aquifers, or even captured stormwater runoff.

Where is ASR being done?
11 countries, with 95 facilities in the U.S.A. The largest ASR injection system in the world is in Las Vegas, Nevada (it can inject water at a rate of 160 cubic-feet-per-second).
Three major facilities in Texas: El Paso, Kerrville and San Antonio
ASR is likely to become more common in Texas. The most recent (2017) State Water Plan recommends ASR projects to provide 1.8 percent of Texas’ water supply in coming years – still a small percentage, but double what it was in the 2012 Water Plan.
Aquifer storage and recovery report card
Environment
Relative to other strategies, this is as good as it gets – however, even a good strategy can be done poorly if it is not carefully implemented.

When done carefully and coupled with water conservation, ASR can be one of the more environmentally-friendly forms of new water supply.

True costs
This strategy is promising on some fronts, but there are some real concerns.

ASR costs include large, ongoing energy expenses and significant infrastructure costs. However, ASR can help communities avoid many of the financial and ecological costs, including significant evaporative water losses, associated with new reservoirs.

Long-term viability
Relative to other strategies, this is as good as it gets – however, even a good strategy can be done poorly if it is not carefully implemented.

With reasonable restrictions on when water is allowed to be taken from its source and injected underground, ASR can be a reliable water supply strategy that minimizes evaporation for Texas’ hotter, drier future. It can also help communities prepare for drought by “banking” water for later use.

Aquifer storage and recovery grade breakdown
Environmental impacts
Positive
  • When a community invests in ASR, they can offset the need for more environmentally-destructive water supply projects like reservoirs.
  • ASR has better water retention than reservoirs, which lose an immense amount of water to evaporation. Water that evaporates is wasted, leaving less water for human use and less water in streams and rivers for wildlife.
  • Depending on the rate of withdrawal, injecting water into aquifers can help replenish groundwater levels, which can prevent – but not reverse – subsidence (sinking land, often caused by withdrawing too much groundwater) and help maintain springflows.
  • In theory, ASR could also be used to release water into rivers when their flows become too low to sustain healthy fish and wildlife. However, cost and energy requirements may limit its usefulness for this purpose.
Negative
  • Water stored through ASR still has to come from somewhere; if too much water is taken out of rivers or other sources for ASR, it can threaten fish and wildlife that need healthy amounts of fresh water to survive.
  • ASR is usually very energy-intensive; water must be pumped, as well as treated before injection and after withdrawal.
It's very valuable during times of drought. When the other water sources aren't available, we still have ASR water available to us.
True costs

1 Initial costs typically include constructing intake, transmission and treatment facilities, as well as acquiring the land above the aquifer or achieving some kind of enforceable legal protections to prevent other landowners from pulling the stored water from the aquifer.

  • For example: San Antonio Water System purchased agricultural land for their ASR facility, H2Oaks, and now leases the land back to its previous owners so that it can continue to be cultivated and grazed by cattle. This agreement gives the water provider the rights to the water they store underground, while allowing the previous owners to continue to benefit for the otherwise unused surface lands.

2 There are ongoing operations and maintenance costs over the project’s lifetime. Because of various treatment and pumping needs, ASR projects have substantial energy costs. Energy costs continue throughout the life of the project so that water can be pumped and treated.

3 Communities that invest in ASR instead of a reservoir, which is the other primary water storage option, save money by avoiding costs associated with significant water evaporation and with the more extensive land acquisition required for reservoirs.

Long-term viability

1 Unlike reservoirs, ASR doesn’t suffer from large amounts of evaporative water loss and typically does not involve large-scale habitat destruction. This means that in the long-term, there are fewer financial and environmental costs with ASR than there are with reservoirs.

2 As with any water supply or storage option, communities must take into account the health of their water sources. If communities withdraw too much water for ASR or do so during dry times, rivers and groundwater could be depleted.

3 Because groundwater is owned by whoever owns the land above it but can travel across property lines, careful long-term planning is important to avoid future legal issues. Neighboring wells could potentially draw water away from community water supply aquifers, and vice versa.

4 Inadequately treated water could also cause problems with this strategy’s effectiveness over the long-term. These issues are not well understood and will require continued study.

5 ASR allows communities to “bank” water for later use, which can help them become more resilient during drought. If managed carefully, ASR could be used to reduce demands on rivers during times of drought.

Next up: Water reuse Keep Reading
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