Mexico City has the unfortunate distinction as the fastest-sinking city on Earth. The city is sinking because it was built on top of a reclaimed lake by the Aztecs which was never designed to hold the modern structures and volumes of people it does today. Researchers warn that areas of Mexico City could drop 65 feet in the next 150 years, with some outskirts sinking even further. The impact on real estate is obvious. Have you checked your insurance policy for sinking risk lately?
Mexico City faces a crisis unlike any before. Frustrated residents have taken to the streets, protesting weeks of water shortages fueled by a confluence of factors. Ever-expanding urban sprawl stretches the water resources thin, and leaky pipes and inefficient systems further exacerbate the problem.
Lower rainfall has been a factor and consistent dry spells have depleted many city reservoirs. As an example, the Cutzamala System reservoir supplies water to six million residents and stands at a mere 39.7% capacity. In recent years it stood at 54% (2023), 62% (2022), 70% (2021), and 75% (2020) capacity. It's not a new problem, but it has gotten so bad now that kicking the can down the road is no longer an option.
Mexico City holds the unfortunate distinction as the fastest-sinking city on Earth. But it's not just the title that's alarming, it's the sheer rate and implications of the descent. The Aztecs first created the problem by establishing their capital city, Tenochtitlan, where Mexico City now stands on a reclaimed lake. The large lake covering the are was named Lake Texcoco. The Aztecs filled it with volcanic rock and soil from the lake bed to build their capital city atop. The Spanish continued what the Aztecs started as they favored Tenochititlan's central location and the existing Aztec infrastructure integrated nicely into the city.
Fast forward to today and parts of the city are sinking at an astounding 20 inches per year. Researchers warn that areas of Mexico City could drop 65 feet in the next 150 years, with some outskirts sinking even further. The different areas of the city were reclaimed in different manners and are composed of varied materials which sink at different rates. The unevenness of it all confounds the problem.
According to Enrique Cabral-Cano, Mexican geophysicist and Research Director at Instituto de Geofísica at the Universidad Nacional Autónoma de México (UNAM), the problem must unfortunately get worse before city planners take action:
"It's the difference in this subsidence velocity that really puts all civil structures under different stresses... That means that our buildings and everything built on top of the surface loses elevation, and that's lost forever... The city goes down—relentlessly, it goes down... It's not until you have a solid number—and it becomes a very large number—[that] we think that city managers are going to be looking at this more carefully."
The water shortages are occurring because as the sinking intensifies, soil compacts and water is squeezed out. Previous pumping of the groundwater for human consumption has quickened the sinking and once compressed it's not possible to reintroduce water into the mixture. Geophysicists Estelle Chaussard and Manoochehr Shirzaei explain the impact of pumping groundwater on the sinking.
"The human thought was that this [water] is an unlimited supply… Wherever you want, you can poke a hole in the ground and suck it out... We would not be able to see the ground go back up… Almost the entirety of the subsidence that we're seeing is irreversible."
Real estate investors in Mexico City should review insurance contracts and make sure the sinking risk is addressed and with the appropriate party. Here's a brief video describing the sinking in a different manner with imagery:
