The South African city of Cape Town is running out of water. The city government estimates that "Day Zero" — when reservoirs are too low to provide potable water — will occur April 12. This is the first time that a major city faces such circumstances and offers important — and alarming — insight into the future of a world marked by climate change.

The city's plight is the result of a confluence of factors. First, Cape Town is in its third year of a severe drought, the worst in over a century. In fact, climate scientists believe multiyear droughts occur in southern Africa only once every 1,000 years. Second, and related to the drought, is climate change, which has shifted weather patterns and triggered the dry spell. Finally, there is Cape Town's rapid population growth. It is South Africa's second-largest city with a population of a little over 4 million people and its expansion has strained facilities and resources. While experts have been warning of the possibility of water shortages for over a decade, the city has been slow to find other water sources for residents and visitors.

The water stored in the city's six dams has been rapidly decreasing. In September 2015, water levels were 77 percent of capacity; they have fallen to 15.2 percent, and the last 10 percent is difficult to use because of water pressure and cleanliness concerns.