Across the world, huge data centres are being built to power our online lives. They allow us to store and access information instantly, but each one uses as much water as a small town. In water-scarce regions like Querétaro, Mexico, this is already causing significant disruption to daily life. “Our children had to go a week without coming to school, because we didn’t have water,” says Juana Sanchez Martinez. The centres are tightly guarded and secretive, making it difficult to know just how much water they consume. “It was like crossing a border; my passport was taken together with my laptop and they put stickers on my camera” recalls Dr Ana Valdivia from the University of Oxford. Meanwhile, state officials defend the industry. “They require no more cooling than an office building or a 300-room hotel,” says Secretary for Sustainable Development Marco Del Prete. But as our digital dependence deepens, the question remains — how sustainable is our thirst for data?