WATER BANKING YIELDS HIGH INTEREST

As demand for fresh water in parts of the United States out paces supply, utilities are exploring creative solutions. During a recent visit to London, I was interested to read an article in the International Herald Tribune discussing "aquifer storage".

What is this? Aquifer storage is essentially the reverse of drilling a well to pump water from an aquifer. Generally, water from the surface in injected through wells into the aquifer for storage . Then, when demand calls for more water, the stored water is pumped back up, treated and distributed to users. The full name for this process is "aquifer storage and recovery" or "ASR". In addition to injection wells, surface spreading and infiltration pits and basins may be used to feed the aquifer. Injection wells are regulated by U.S.EPA under its Underground Injection Control program.

A primary advantage of ASR is water can be stored during wet weather or low demand periods and then recovered in dry or high demand periods. Other advantages include" the additional water in the aquifer can defend against salt water intrusion and land subsidence; there is no evaporation issue with underground storage; crop land is not flooded and taken out of service; and aquifers may have more available storage space than surface reservoirs.

On the other hand, there may be some potential negatives: ASR may result in the injection of pathogens, particularly if treated wastewater is injected; if water is disinfected prior to injection, disinfection by-products may be introduced into the aquifer; and chemical differences between aquifer water and injected water could result in leaching of arsenic, manganese, iron, radionuclides or carbonates from the aquifer geological formation.

There, of course, may be an overriding legal issue: whose water is it, anyway? In other words, who has a right to the water in an aquifer; is a utility legally entitled to recover the injected water? In some jurisdictions, a landowner has a right to recover water under the person's land, even if some had been injected by a utility.

Several countries are utilizing ASR, including Australia, Belgium and The Netherlands. Even Thames Water, the utility serving London, stores water in an aquifer under that city.

In the United States, utilities in several states have developed or are planning to develop ASR facilities. For example, the San Antonio Water System Twin Oaks Aquifer Storage and Recovery facility is said to be the third largest ASR facility in the country, with 29 wells and some 60 mgd well field capacity. The Washington state legislature has adopted rules for review and issuance of permits for ASR projects and several projects are underway.

With dry weather in portions of the United States, and growing water demand in agricultural and population areas, resulting in depleted surface waters and aquifers, prudence may encourage more utilities to consider ASR to take advantage of storm water and treated wastewater when available.