ST. PAUL — Several growing cities in Minnesota could meet increased demands for water by pumping treated H20 into underground aquifers for later use, according to a new study from the University of Minnesota.

The little-used method of water storage holds promise particularly for communities in the state where droughts and population increases could strain existing groundwater supplies. But researchers caution that it should only be considered as a last resort after others have been exhausted.

"There is also value in reserving groundwater for future generations especially in an uncertain water future. Even if groundwater is not scarce now, its quality and availability vary across Minnesota," according to an excerpt from the study.

The study, released last week, touches on the ubiquitous-yet-critically-important resource that groundwater is to Minnesota. Approximately 75% of its residents get their drinking water from underground wells, springs and aquifers.

Manufacturers in the state rely on groundwater to make, cool, wash and even transport products. Farmers use it to irrigate their crops.

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One way to make sure there's enough of it to go around in the future, according to the study, is through a process called aquifer storage and recovery, or ASR. At its heart, it involves taking water from one place — such as an underground source or surface stream — treating it and injecting it into another aquifer already in use.

Bolstered supplies of water can then be drawn on during periods of high demand. Researchers said that Moorhead, for example, could hypothetically store extra water in the Buffalo aquifer, which supplies about 20% of the city's drinking water, to offset the effect that a drought would have on the Red River, which supplies the other 80%.

The aquifer was one of several that researchers identified as having sufficient capacity for additional water and as likely to be strained by future population growth or changes in the environment.

The technique is not without risk. Done improperly, it can introduce foreign contaminants to a given groundwater source or clog wells. So far, the city of St. Michael is the only in Minnesota that has adopted it.

"At this point in time, I would probably say that ASR technology would be the last option that we would pursue," Marc Pritchard, water plant supervisor for Moorhead Public Service, the city's water utility, said. "There's a lot of study that would need to be conducted to make sure that any type of water introduced to the existing groundwater matrix wouldn't cause any type of potential contamination concerns."

The city would be more likely to drill new wells or tap other surface waters, according to Pritchard, though there are currently no firm plans to do so.

Other cities that could successfully deploy the technology include Park Rapids and Rochester, according to the study, the latter of which relies entirely on groundwater.

Another way that Minnesota could meet future demands for water, provided that they materialize, is by rethinking and expanding its approach to wastewater recycling, according to professor Carrie Jennings, one of the study's authors. But the state's "siloed" governance of water makes on-site recycling systems difficult to implement.

Asking residents to limit their water use is another option that cities could face, she said, "but that's a really tricky thing."

"It's a balance between providing a necessary thing...and overcharging," Jennings said. "How do your water rates encourage people to conserve without them being punishing for low income families?"