Mexico City is in the midst of a water crisis. Some experts have predicted the metropolitan region, which boasts the highest population of any metro area in North America at nearly 22 million people, may start to run out of water as early as June

Mexico City is in the midst of a water crisis. Some experts have predicted the metropolitan region, which boasts the highest population of any metro area in North America at nearly 22 million people, may start to run out of water as early as June, a day described as “Day Zero.” And while there are options available to the city, larger issues with water infrastructure and management may be harder to remedy in the short term.

At issue are the aquifers beneath the city, where most of the city’s water comes from. “When the Spaniards arrived on the continent, they drained the lakes on which the city was was built,” said Caroline Houck, senior editor at Vox. “And so all of the impervious surfaces that have been built on top of those don’t really allow for the rainwater that does fall to replenish the aquifers.” That infrastructure, along with moderate-to-severe drought conditions exacerbated by climate change, has drained the aquifers.