Today, the city is sucking up water from the natural aquifers at twice the rate they are being replenished. The result: Mexico City is sinking, in some areas up to 16 inches a year, threatening its entire infrastructure. This includes the city's deteriorating drainage system, whose capacity has diminished by 30 percent since 1975 while the area's population has doubled.
"It's an alarming situation," says Felipe Arreguin, the technical general subdirector at Mexico's National Water Commission (Conagua), which is building the drainage tunnel. "We are taking [out] so much water, the city is sinking. What if an entire block were to go under?"
It nearly has. In 2007, a giant sinkhole swallowed a large swath of a busy street. At Revolution Monument, a water pipe installed over 75 years ago now stands near nearly 30 feet above ground. Given Mexico City's history as a "floating city" in the middle of a lake, it's no surprise that water is what vexes most urban planners here. When the Spaniards arrived to conquer the great Aztec Empire, the mode of transportation was not horses but canoes. Today, the city sits essentially on a bowl of pudding. Jose Miguel Guevara, the general coordinator for water supply and drainage projects at Conagua, calls this basin a giant "saucepan," with no natural exit for the torrential rains that fall each year. But these drainage problems and the corresponding threats of catastrophic flooding belie one of the great ironies of its urban plumbing. When it comes to water, the city is also facing the kind of shortages that plague the rest of the globe. Mexico City, which sits at an altitude of over 7,300 feet, must pump water up 3,000 feet to reach residents. Last year it had to ration water after one of the worst droughts in six decades. The drainage program includes plans for treatment plants to turn runoff into clean water for use by farmers.