The first global database of urban water sources and stress finds that one in four major cities use more than 40 per cent of the water available to them.
This proportion is lower than previous estimates, in part because the new study accounts for the fact that many cities draw on distant watersheds, rather than just the one they are in.
Water-stressed cities include Tokyo, Los Angeles and Beijing, but not Toronto and Montréal, the two Canadian cities examined. The study also finds that richer cities can pipe clean water in from further afield, and that while large cities occupy only 1% of the Earth’s land surface, their source watersheds cover 41% of that area.
Original research paper published in the the journal Global Environmental Change on June 2, 2014.
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