Aquifer Storage & Recovery (ASR) – a Bank of Water for Future Withdrawal

If someone was to ask you what is the most valuable natural resource, how would you answer? Some might say gold or copper, others may state air, and others may answer oil and gas. But if you think about it, water is one of the most valuable and essential natural resources we have. We cannot live without it. 

Each area of the country has different weather patterns, but in Texas, we experience periods of drought with inadequate amounts of rain to sustain our needs. That is why aquifers play such an important role in water storage. In fact, the sole source of drinking water for San Antonio is the Edwards Aquifer, a massive underground geologic system that fills with rainwater as it falls to the ground (recharge), but when it does not rain much, the water levels fall, and the aquifer becomes depleted. Aquifer depletion results in water restrictions and in severe cases, rationing. 

Aquifer Storage and Recovery (ASR) is a process where water is captured from wet seasons, or rain events, before it runs off, and is directed and drained into an aquifer for storage. When the water is needed, it is withdrawn or recovered from the aquifer. Imagine a very rainy spring season and capturing the extra rain to save for later use by storing it into an existing underground aquifer; that is the essence of ASR.

There are several complex geologic and engineering controls that must be in place to make ASR feasible such stratigraphy and porosity of the aquifer host rock. Water is either injected into the aquifer through a well or it is allowed to percolate down through the surface naturally (recharge) in basins designed to funnel the water underground. 

Treated or reuse water can also be used in ASR systems. Before the water can be injected or funneled into the ground reservoir, it must meet levels of the Federal Sate Drinking Water Act. In Texas, surface water, groundwater and reclaimed water are used in ASR.

According to the Texas Water Development Board (TWDB), ASR is an environmentally friendly method of storing Edwards Aquifer water with no loss due to evaporation or storage capacity due to sedimentation, and ASR allows deferment of additional capital investments to retain water.

Currently there are several ASR programs in Texas—in Kerrville, Corpus Christi, New Braunfels and San Antonio (SAWS) according to the TWDB, and approximately 175 ASR systems in place across the US. ASR provides municipalities and water providers another tool to securely store water for future use. Have a water project? Our geology and engineering teams are knowledgeable in surface and underground water infrastructure projects. Email Curt Campbell, P.E. at ccampbell@westwardenv.com to learn more.