In the throes of a devastating drought, a city the size of Los Angeles is in grave danger of running out of water.

Cape Town, South Africa, a city of over 4 million people, has been suffering from a drought since 2015, and residents could be completely cut off from running water as early as June 4. Residents will then have to survive on a meager 6.5 gallons a day, which must be collected from the approximate 200 rationing centers spanning the 154 square mile area. Fortunately, vital services such as hospitals would still have access to running water, but officials are expecting high levels of unrest within the city should push come to shove.

In 2011, Cape Town had a population of over 3 million. And due to the city’s rapid population growth, Cape Town’s ecosystem has also encountered a deep crisis. There are over 300 plant species native to the region that are currently endangered, and 13 that have already gone extinct.  The region also has the unfortunate reputation of having the highest concentration of threatened species in the world. With a damaged ecosystem, longstanding drought, and a growing population, Cape Town has become a disaster moving in slow-motion.

The South African city isn’t the only place that’s in danger of losing its water supply. A UN report identified several key cities across the world that could experience water shortages in the future. In Sao Paulo, Brazil, the city of 21 million people experienced a water crisis in 2015, which lead to unrest and looting. Bangalore, India has encountered issues with managing its sewage system: due to heavy pollution, reports found that only 15% of the water supply was safe to drink. Beijing, China, ranked third for most likely to see a water shortage. In 2015, officials found that over 40% of Beijing’s water was not only unsuitable to drink – but was too contaminated for even agricultural or industrial use. While this was a wake-up call for the Chinese government to reduce water pollution, the region could still hit a breaking point.

There are even more cities that may deal with water scarcity in the near future. Moscow, Istanbul, London, and Tokyo could all face shortages due to numerous problems that include lack of rainfall, reliance on a sole water source, and/or pollution. These major cities are hoping to face these issues before they become emergencies. These concerns have meant looking at alternative solutions to existing water supplies, such as investment in desalinization. But with UN estimates stating that water demand will exceed the Earth’s supply by over 40% in 2030, we may face a more dire situation than many of us realize.