Environmental think tanks and journalistic outlets have published lists of cities that look likely to run out of water in the near future: São Paulo, Brazil, which faced its own Day Zero situation just a few years ago; Bangalore, India; Beijing, China; Cairo, Egypt; Mexico City; and—surprisingly, given its climate—Moscow, Russia. While each city has a very different set of reasons for its water woes, ranging from pollution to poor infrastructure to poor planning to desertification and drought, they all share a common challenge: Climate change will likely make the task of providing water harder, the populations thirstier, and the people angrier, even as many of the cities grow.