If you've ever had a desire to visit Mexico City, you might want to go sooner rather than later. The world's second most populous city is sinking at a rate of about three inches per year. As a matter of fact, during the last century, the city sank about 30 feet!



So why is Mexico City sinking? Well, it's because the ancient aquifers that supply 72 percent of the city's ground water are being emptied faster than they can be refilled, and that is causing the ground to sink. Part of the reason the water is disappearing so quickly is that every year, 350,000 new people move to Mexico City, which is already bursting at the seams with 24 million residents.



The loss of ground water is the biggest problem facing Mexico City's engineers. Many of Mexico's finest buildings, some of which date back to the 1550s, are collapsing along with the soil. And though the city has spent millions of dollars repairing and strengthening these buildings, they're still in danger.



But buildings aren't the only things that are being damaged. Line 2 of the city's railway, which runs above ground, has gone from being absolutely horizontal to looking like a roller coaster. Then there's the issue of flooding, which has become a major problem, since the city now lies six feet below nearby Lake Texcoco. But the most serious damage is taking place underground, where the collapsing soil is rupturing sewer lines, water pipes, and subway tunnels. As if these problems aren't enough, Mexico City sits on a major fault line, and the loss of ground water and collapsing soil have made the city more vulnerable to earthquake damage.



Can anything be done to solve Mexico City's water problem? The obvious solution is to stop pumping water from the aquifers. Unfortunately, there are too many people and not enough other water sources for the city to stop using the aquifers completely. To help solve the water problem, the government has asked citizens to conserve and re-use water. But since the people of Mexico City are used to getting all the water they need from the city's ancient supply, this has proved to be easier said then done. If you were a city official, what would you do to solve the crisis?