In recent years, Spain has become a leading destination for tech giants to set up their data centres in Europe. Madrid even aims to become a "digital hub" on the continent, like Germany and the UK. But at what cost to the environment? To cool down their servers, data centres consume billions of litres of drinking water: a huge worry in Spain, one of the countries worst affected by drought in Europe. Our correspondent Armelle Exposito investigates the environmental impact of these data centres.