If nature insists on flooding, we flush the water away. Then we get thirsty.

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Several hundred years of urban development and population growth messed up the equilibrium. The lakes were drained to recover land for urban use. Land was paved over, reducing the earth’s capacity to absorb water. Pre-Columbian canals and levees were dismantled on the grounds that they retained water within the city limits. The rivers had to go too — largely intubated in the 1940s under the argument that they carried human waste and disease, but probably also because city planners wanted the riverbeds to carry cars instead.

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The growing population of city-dwellers needed water, of course. Having engineered an array of defenses to keep water out of the city, city planners had to get it somewhere else. Largely, they sought it underground. But as more water was pumped out than could be replenished, the earth started to give. The city has been sinking at a rate that has reached some 20 inches per year.

Today, most of the rainwater that falls on Mexico City and its surroundings is expelled through the drainage system. The lake system that once covered almost 600 square miles now covers about six. The city draws over twice as much water from its aquifers as is replenished every year. And that’s not enough.

The immediate problem is the “Cutzamala” network of reservoirs, pipelines and water treatment plants that was built in the 1980s and provides about a quarter of the city’s water from dams as far as 100 miles away. Its dams are now at barely above 27 percent of capacity, stressed by a three-year drought.

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“Day Zero” is not likely to happen anytime soon since most of the water to the city still comes from underground sources. Still, as climate change brings about longer droughts, and the valley’s aquifers are gradually exhausted by over-exploitation, the city could get there in the not-distant future.

There are estimates that every additional hectare of new urbanization reduces the replenishment of underground aquifers by some 660,000 gallons per year. And the city footprint has been expanding at over 3 percent per year. Moreover,........

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