India, Aug. 14 -- Should you ever delete a photo to save water? Sounds odd. Yet a real government advisory in the UK suggested exactly that during a dry summer. It sparked jokes online, but also a fair question for all of us who live in the cloud.

Most of our pictures and emails sit in data centres. These are giant buildings full of servers that run hot. Cooling them safely needs a lot of water in many sites. Independent studies have tried to quantify this. Research from Oxford-linked academics estimates that a modest 1 megawatt facility can use tens of millions of litres of water each year for cooling alone. Utilities figures and company disclosures show the picture varies by region. Some operators now use recycled or non potable water....