The climate is changing, Earth’s population is growing and more people are living in cities. That means urban areas—particularly those in arid or semiarid regions—need to update their water supply systems. The world was reminded of this earlier in the year with the water crisis in Cape Town, South Africa, which has a climate almost identical to that of Los Angeles. At the peak of the crisis, residents were required to limit daily water consumption to 50 liters (about 13 gallons), taking two-minute showers and letting their lawns and gardens dry up.