Mexico city sinking 50cm every year, what does future hold for this city

Mexico City, home to over 21 million people and the largest city in North America, is sinking at a rate of 50 centimeters per year. This issue, which has been ongoing for over a century, is now irreversible.

The city’s reliance on underground aquifers for more than 70% of its drinking water is the main cause of this sinking. Although this is not a new phenomenon, recent studies published in Advancing Earth and Space Science indicate that the rate of sinking has increased in recent years.

What is causing Mexico city to sink?

Mexico City is sinking because it’s using up groundwater from below the city. This process, called subsidence, causes the city to sink as the water is replaced by things like sand and stones. It’s sinking as fast as the water it’s using. This is different from subduction, which causes earthquakes.

This isn’t just happening in Mexico. Cities like Jakarta, Venice, Bangkok, and Houston are also sinking for the same reason. But Mexico City has an extra problem: it’s built on weak foundations and is sinking very fast.

The city was first built by the Aztecs in the middle of a lake system. They changed the environment by building artificial islands to live on. This is known as land reclamation.

"This is how, little by little, Mexico started to sink. Throughout the 20th century, it only sank at a pace of 9 centimeters a year, but in the late 1950s, this figure increased to 29 centimeters. That's when authorities decided to implement the first strict measures, including a ban on drilling into the ground in the area to extract water, trying to reverse the situation. The sinking rate dropped back to the previous 9 centimeters and Mexicans declared victory. However, they did so prematurely."

How far has Mexico city sunk?

Records show that Mexico City has been sinking since 1800, and maybe even longer. This has been happening for so long that some people might think it’s not a problem, but that’s not true. Since 1950, the city has been sinking at a steady rate of 50 cm per year. In the last 73 years, it has sunk more than 36 meters. It’s not clear how much it has sunk since it was first built, but it’s likely more than 100 meters.

Mexico City has been sinking faster in the last 20 years, going down 10 meters at a rate of 50 cm per year. Researchers used different types of data to show that this sinking is almost completely irreversible. The city’s weight and its shallow foundations are compacting the soil. The layers of sediment under the city have been compressed by 17% and this could reach 30% in 150 years.

This means the city will sink another 30 meters by the middle of the next century. This will continue unless water levels rise again. But even if they do, the city won’t return to its original position or regain the lost water storage.

Different parts of the city are sinking at different rates. The Historic Center is one of the most affected areas. Some buildings with historical value are already showing cracks and unevenness.

In the northwest area of the city, where there’s less urban development, the sinking is much less.

Getting water in Mexico City is not easy, which worries researchers. They suggest that the city should look for alternative ways to get water.

Mexico City is sinking due to climate change

Climate change is causing Mexico City to sink. The city’s people are dealing with less rain, a shrinking water source under the ground, and unfair access to water.

Mexico City, a big city built on three dry lakes, is defined by its water issues. It floods when it rains a lot and faces droughts regularly. The city, home to 21 million people, uses more water from its underground source than it puts back. This has caused the city to sink 12 meters in the last 100 years and it might sink another 30 meters.

Many people in Mexico City can’t get water from their taps. In 2020, the city spent over $4 million on water trucks, and people spent about $187 million on bottled water.

The indigenous Mexica people made farms on the lakes to feed their city. Now, a group of researchers, city planners, and farmers are using this method to filter water for farming and lessen the need for underground water.

The state of Mexico is planting more trees on the slopes above the city. This should help catch rainwater and stop landslides during the stronger storms caused by climate change.

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