Almost no mining is possible without significant use of water. Chile’s copper industry – which involves BHP Billiton and Xstrata – swallows more water than most others, from one of the driest places on earth. This year, Chilean copper is estimated to consume 9m3/s = 42.840.000 litres an hour; or 1.028.160.000 litres a day. And by 2020, these figures are expected to double.
See http://www.minesandcommunities.org/article.php?a=9654.