How much water do you use a day?

If you lived in Cape Town, South Africa, you'd have to get by on just 13 gallons of municipal water per day – a little less than the amount it takes to flush a toilet four times. Use more, and the city reduces your pressure to a trickle, and your water bill can turn into a mortgage payment. The city government has already raised the probability of a “Day Zero,” when taps across most of the city would be shut off indefinitely. So, most people work hard to keep within the 13 gallon limit.

Since 2016 the city has cut its water use by half. Its biggest customers now use 80 percent less. Other cities have not been as lucky. When Melbourne, Australia, was in a drought period from 1997 to 2009, it did cut its water consumption by half, but it took 12 years, and at the end of it, residents were still guzzling 17 gallons a day. California has had similar results; between 2012 and 2016 it brought its home water use down 25 percent, to about 100 gallons per person per day.

An example of the techniques Cape Town residents use: 90-second showers and then flushing their toilets with the water they collected while doing it. They discuss water-saving techniques on Facebook. They exchange the names of local companies that will sink a personal well in your backyard. They use recycled wastewater from local factories and vineyards. And the police also track down those who use water in such pursuits as watering their lawns.