"Water! Water!" the crowd shouted as it stormed a compound with data centres, armed with empty plastic bottles and jerry cans.

There were about 300 of them, all residents on the Indonesian island of Batam, and they were furious that the taps at home had run dry, while the data centres in the new Nongsa Digital Park seemed to have enough water to protect their machines from overheating.

"Not a single drop has come through our taps for the last three months... Our water supply had been reliable until the data centres came," Dewi Susanti, one of the protesters, told the BBC.

People in her village, Bakau Serip, were now depending on tanker trucks that dispensed "dirty, cloudy and smelly" water, she said.

Batam's water utility told the BBC it was working to improve supply, but did not comment on whether the disruption was linked to demand from the data centres.

But BP Batam, the agency overseeing trade and industry, blamed it on a prolonged dry spell and denied allegations from locals that water meant for homes was being channelled to data centres.

This is not the first such protest in Batam, whose shrinking reservoirs find themselves under more pressure as the island tries to transform itself into a digital hub.

Following protests in August and September, authorities told the firms opening data centres in Batam that they must build their own desalination plants instead of relying on reservoirs for freshwater.

But locals say they are increasingly concerned that they must now compete with servers for water.

"Reliable data on data centre water use in Indonesia remains scarce, partly because companies treat it as proprietary information," says Agus Hasan, a professor at the Norwegian University of Science and Technology.

"We should build [data centres] rationally, transparently, and responsibly, and insist on seeing the numbers... [Otherwise] those kept in the dark while their taps run dry will push back, and rightly so," he adds.

A backlash has been building against data centres across the world, from the US to the UK to parts of Asia, as tech companies pour billions into AI infrastructure.

People are worried about how the huge, windowless buildings might change their neighbourhoods, the constant hum of machines, the security lights that could stay on all night, and the pressure this puts on water and energy resources.

While electricity powers the centres, the water keeps the servers from frying - engineers deploy elaborate cooling systems, which consume a lot of water.

Research in the US suggests a typical data centre consumes around 300,000 gallons of water a day, or about as much as 1,000 US households. A larger, 50MW facility could take as much water as 2,200 households per day, and enough electricity to power 22,000 homes, according to Malaysia's central bank. It's unclear how much water or electricity the data centres in Batam are consuming.

But the island routinely faces water shortages, and the levels are worse this year, possibly because of a historic "super" El Niño.

Devoid of natural freshwater sources, Batam's 1.3 million people rely on rainwater collected in six artificial reservoirs.

Nongsa reservoir, which supplies water to Bakau Serip, where Dewi lives, would dry up over the next month with no rainfall, simulations by local environmental non-profit group Akar Bhumi Indonesia suggest.

"The water shortage is affecting our livelihoods... Money that should be used to buy rice is now spent on water drums," Dewi says. "My husband has to wait up overnight to get water, and then go straight to work the next morning." Batam's water utility had earlier said that it would consider measures like cloud seeding should the water shortage continue. When asked about the recent protests, they pointed us to earlier statements.

Authorities in Batam have approved 10 data centres, six of which will be located in Nongsa Digital Park. Two are up and running, while a third is under construction. At least six more are currently under review for approval, BP Batam told the BBC.

Official figures put investment in data centres on the island at more than $6.7bn (£5.1bn) as of mid-2026, spurred in part by demand from Singapore, which is just an hour away by ferry.

Singapore paused construction of data centres in 2019, citing land and energy constraints. It lifted the ban in 2022 after introducing new efficiency standards, which prompted investors to look elsewhere.

Singapore has long been promoting the Riau Islands, which includes Batam, and the Malaysian state of Johor as "complementary" regions.

Quick to absorb the spillover, Johor approved data centre projects worth tens of billions. But this soon drew the ire of residents frustrated with noise, dust and water shortages. The state has since tried to regulate how much water and electricity data centres consume.

Across the strait, Batam is just as attractive to investors - from the US, China, Australia, Singapore - because of relatively low operating costs, proximity to Singapore and connections to major subsea cable routes.

Nongsa is home to a 13,000-sq-m data centre by Hong Kong-based private equity firm Gaw Capital and Indonesian developer Sinar Primera. In April, Singapore's DayOne signed a deal with an Indonesian state utility to build one of the country's largest data centres - around 450MW capacity, enough to power 350,000 average households. In June, DayOne, chip maker Nvidia and Australian AI start-up Firmus Technologies announced a 360MW "AI factory".

By 2030, power demand from data centres in Batam is expected to cross 1,100MW, which is enough to power nearly a million homes, according to the official estimates.

The BBC has contacted DayOne, Sinar Primera and Gaw Capital for comment.

Meanwhile, the spate of construction is worrying locals in Batam who urged authorities to prioritise their needs.

"Don't just sit at the top and keep approving these projects. Come down here and see for yourselves what we are wrestling with," says Marlinda, who lives in the district of Sei Beduk, which is also facing water shortages.

"We want the government to pay attention to ordinary people," another resident told the BBC.

"Don't make billion-rupiah investments while ordinary people are made to suffer... We are not asking for anything extravagant. We just want our water supply restored."