Photo: Satellite Image of Mexico City
Mexico City is sinking. While this fact has been known for some time, over the last century, the sinking has gotten far worse.
It is estimated that in the last one hundred years or so, areas of the world’s third largest metropolis have sunk up to 42 feet (13 meters). As parts of the city sink, fissures and cracks occur, and they have caused a number of accidents in residential areas and immense damage to buildings, highways, roads and public infrastructure, including sewer lines that are now so slanted that they actually run backwards. The damage can easily be been seen in buildings’ uneven foundations and lopsided balconies.
In the 1300s, the city was founded on an island in the middle of Lake Texcoco. As the city outgrew the small original island, more artificial islands were created, and a network of canals was built, with the main roads built on the causeways between the mainland and the islands. When Spain gained control of Mexico City in the 1500s, they drained most of the water from the lake due to flooding problems. Today, due to the draining, about 70 percent of the city’s supply now comes from water pumped from aquifers under the city, which are part of the original lake. However, the water is being siphoned faster than it can be replaced by natural resources (i.e. rainfall), and the city’s foundation, now just a mud-like lakebed, is not strong enough to hold it up.
Scholars from the National Autonomous University of Mexico (UNAM) say the city’s fissures “are generating alarm among the population and even cause significant damage to buildings and (affecting provision of) public services.
Due to the angled, sinking city most of its wastewater can no longer flow out of the city naturally. It has to be forced out by a number of pumps to get it over the rise known as Sierra de Guadalupe.
Landmarks all over the city that are fastened to the bedrock and are not sinking with the rest of the city have had to have steps added over the years so visitors can reach them. Built on underground pylons in 1970, the Insurgentes Traffic Circle is now 12 feet higher than the streets leading to it.
Engineers say the only way to stop the city from sinking any farther is to stop siphoning water from the aquifers or inject water back into the lakebed. However, it is unlikely that returning water from the lakebed will reinflate it.
“You can’t raise the city again,” said hydraulic engineer Ramón Domínguez. “The only hope is to stop it from sinking further.”