Seven out of 10 people on earth can count on running water to be available in their homes. That means it’s always there when we need it, whatever we need it for.
Until it isn’t: Cape Town, London, Sao Paulo, Jakarta, Istanbul, Tokyo, and Mexico City could be facing “Day Zero” — meaning they will run out of water — in the next few decades unless their water use radically changes.
Less than 1 percent of the world’s water supply is readily available for human use (the rest is salty, frozen at the poles, or trapped underground). Yet we use it in wildly inefficient ways: We lose it to leaky pipes. We dump waste in it. We try to grow some of our most water-intensive crops in the desert. Really.