This story was originally published by CalMatters. Sign up for their newsletters.
Data center builders don’t tell the public how much water they use, according to a new report — and the industry is encroaching into water-stressed and vulnerable communities.
The report, by the think tank Next10 and researchers at Santa Clara University, finds that planned data centers — the ganglia of artificial intelligence — are spreading to regions reliant on overtapped groundwater and strained surface water, with potentially major effects in the Central and Imperial Valleys.
But, reinforcing previous studies, the researchers found that a patchwork of state, federal and local policies allow data center operators to avoid publicly disclosing their actual water use.
California lawmakers tried to address this last year, but California Gov. Gavin Newsom vetoed the measure. Now, the Legislature is trying again, with bills mandating disclosures about water use and planning.
“We have this huge build out, and we have very little data,” said Irina Raicu, who directs the Internet Ethics program at the Markkula Center for Applied Ethics at Santa Clara University.
Paired with California’s precarious water supplies, Raicu said, “it’s just not a good combination.”
Shaolei Ren, an expert on the environmental impacts of AI at UC Riverside who was not involved in the study, said the findings point to a much broader problem.
“Limited publicly available information about data center water use makes it difficult for communities, water providers, and researchers to have meaningful public discussions and responsibly assess power-water trade-offs,” Ren said in an email.
Murky water use
Few environmental impact reports for California’s data centers were publicly available online, the researchers found.
Raicu and co-author Iris Stewart-Frey, a professor of environmental science, went looking for the reports, meant to assess and disclose a project’s impacts for both nature and people under the landmark California Environmental Quality Act.
They found almost none. The ones they did find were largely for facilities in the city of Santa Clara.
Through interviews with planning officials, they discovered that projects can slip through with little environmental review if they fall under certain size or water use thresholds, or if they meet a city or county’s criteria for other approval pathways. These include something called ministerial approval, which requires planning agencies to approve a project that meets local zoning and other standards.
Even for data centers that undergo more stringent environmental scrutiny, the researchers found that documentation is rarely available to the public.
In the few cases the planning documents were posted publicly, the information — on the data center’s owner or operator, size, type of cooling system, the amount of water used, whether it’s recycled or potable — was often “missing, contradictory, or vague,” the report said.
The researchers said they contacted water providers in areas where data centers cluster, seeking usage data. None responded.
A shift to vulnerable regions
California’s data centers mostly cluster in the south San Francisco Bay Area and the city of Los Angeles, with smaller concentrations in Sacramento and San Diego.
But the report noted large, planned projects in rural and less affluent regions — like in Santa Clara County’s Gilroy, as well as in the heavily agricultural Imperial Valley.
“They need a bunch of cheap land,” Raicu. “If we’re not careful, they will end up being pitched, very convincingly, to communities that have real needs — without enough attention being paid to the water part.”
Khara Boender, director of state policy for the Data Center Coalition, which has opposed bills mandating more granular water use reporting, said in an email the industry is “committed to being a good neighbor.”
Boender argues that data centers collectively “used significantly less water than other essential industries in 2025, including the agriculture, power, food and beverage, and semiconductor sectors,” but the coalition offers no data to back that up.
Collective use matters less than local impacts in a state where each community has its own mix of water supplies and strains, according to a previous study published by a team at UC Berkeley.
Whether data centers use a lot or a little water relative to agriculture or other industries, “what matters most is the scale of new local use compared to available local supply,” the Berkeley team concluded earlier this year. “Unfortunately, this picture is clouded by data deficiencies.”
In this week’s report, the Santa Clara University team drilled into those local supplies and community vulnerabilities to anticipated expansion.
“We’re at the brink of this happening in California,” Stewart-Frey, the environmental scientist, said. Her report, she added, isn’t advocating against data centers. But “communities should know what they’re getting themselves into.”
Debates over proposed data centers are erupting in a Kern County desert community with dwindling groundwater and in the hot Imperial Valley drawing from the strained Colorado River.
Monterey Park residents in the San Gabriel Valley successfully opposed one data center project over environmental concerns and inadequate information and secured an upcoming vote on a citywide ban.
In a letter to city officials, a representative for the developer dismissed opponents as “rage-baiting an uninformed mob to pressure your decisionmaking.”
Raicu pushed back. “If those communities are uninformed about the issue — whose fault is that? Who should be informing the people so that you don’t have this kind of pushback, if there is no need for it?”
New laws v. Big Tech
Last year, Assemblymember Diane Papan, a Democrat from San Mateo, authored a bill requiring data center operators to report estimated or actual water use to their water supplier when seeking or renewing a business license or permit.
Gov. Gavin Newsom vetoed the measure amid industry pressure, saying he was “reluctant to impose rigid reporting requirements about operational details on this sector without understanding the full impact on businesses and the consumers of their technology.”
Now Papan is trying again with two bills. One largely reprises last year’s measure, with additional reporting required to the city and county. The other would bar local governments from approving new or expanded data centers unless the developer discloses information about their water use and plans.
It would also set other requirements — like prohibiting development in overdrafted groundwater basins, like in the San Joaquin Valley, unless state water managers okay it.
“You cannot manage what you have not and cannot measure,” Papan said. “The public likes transparency, and they should.”
Both bills cleared a key legislative chokepoint this week but face staunch opposition from the tech industry and business groups.
“If they run out of water, guess what happens? And they can’t cool their systems — are they going to succeed?” Papan said. “To which I say, help us help you.”
