Data center leaders, ASU water expert say the facilities use less water than assumed

Members of Arizona’s data center industry are aware the public is concerned about their water use. At an event hosted by the Arizona Data Center Alliance on Thursday, companies touted progress they are making to reduce water use in data center cooling, while representatives from SRP and the Kyl Center for Water Policy helped put this in the context of Arizona’s water system.

Tom Sullivan, chief operating officer of Air2O, a local heavy industry HVAC manufacturer, says most Arizona data center developers have changed their ethos when choosing cooling systems to focus on saving as much water as possible, rather than trying to save on their energy bill.

He says switching from open-loop or evaporative cooling systems to closed-loop cooling, where a fresh water-glycol mixture is constantly recycled to filter out heat from computer processors, has dramatically cut data centers’ water use. But it's about 33% more energy-intensive.

A midsize data center on a closed-loop system can use around 120,000 gallons of water for cooling one time, Sullivan says. Whereas an open-loop system might use more than a million gallons of water per day.

“So the numbers that the media use are true, but they are a true number from the past, and it's unfair to use a legacy number today, because it's not the way the data is being used today, the cooling has changed. The water conversation changed,” Sullivan said.

He acknowledged the closed-loop system may occasionally need to be flushed and refilled due to contamination. Sullivan did not have an average for how frequently this could take place, because it varies from company to company.

A QTS official at the event said they anticipate only having to flush their systems roughly once every 40 years.

By comparison, Sullivan says, water use at a midsize data center may be around the same as the annual use as 18 homes. That does not include water used in generating the power for the data center.

Sarah Porter, director of ASU’s Kyl Center for Water Policy and a panelist at Thursday’s event, says her team began looking into data center water use about two years ago as the community began to push back against development. She believes residents were responding to cases of hyperscale data centers using large amounts of water elsewhere, and they were worried that could happen here.

In her team’s research, she says, they haven’t seen much hyperscale data center development in the state, and moreover, she says data center developers and major tech companies have been eager to talk to her team about their water use. She says they want to understand the community concerns.

While some states have run into issues of data centers outstripping their proposed water use, she says that hasn’t been an issue in Arizona, due to how water is regulated in the state’s active management areas, or AMAs – urban areas where most data centers are located.

The Arizona Department of Water Resources monitors and regulates these AMAs. There are eight of them in the state and they are relied upon by many industries and 85% of the state’s population. Approval from the state and water use reporting is required to tap the aquifers in the AMAs.

Porter says reporting is generally robust, but it doesn’t provide specific quantities for water use in industrial cooling. Next to energy generation, this is the largest use of water among data centers.

This isn’t cause for alarm, she says. Utilities still know the total amount of water use, “but we don’t know specifically how much of the water that’s being reported for certain types of uses is being used for cooling,” Porter said.

Having that awareness is important for communities to be able to weigh trade-offs in approving data centers against other uses, or to allow them to work with industries to make their cooling water use more efficient, she says.

She encourages Arizonans to let their water provider know that they would like to see industries report that information as required.

On the power generation side, where data centers drive much more water demand, Porter says water use for power generation is also required within AMAs. So, the state knows how much water that energy utilities are using to operate power plants that use sources like coal, natural gas and nuclear. Porter says the Palo Verde Nuclear Generating Station is the largest industrial water user in the state.

“The other thing is we see utilities like SRP, APS Tucson Electric Power publishing water sustainability goals of various types, and part of their being accountable to those goals is to provide progress reports on it,” Porter said.

Since she began this work on data centers two years ago, she’s noticed a renewed public interest in how we manage water across the state. However, she thinks it could be directed at more than just data centers.

“People have decided to focus on data centers, and they don’t worry about other high water use industries for the most part,” Porter said.

She can understand the interest and concern, because data centers are tied to newfangled technologies like AI, “but my hope would be that people would get the facts and consider data center proposals based on the actual facts and not on concerns,” said Porter.

Porter says it's also important to keep an eye on how large industrial development takes shape outside of AMAs, as these rural parts of the state have fewer requirements for groundwater pumping.