Mexico City is sinking at one of the fastest rates in the world, with some areas descending by more than 2cm a month, according to new observations from NASA’s NISAR satellite system.
The joint mission between NASA and the Indian Space Research Organisation is using advanced radar imaging to monitor subtle changes in Earth’s surface in real time.
Scientists say the technology is providing the clearest picture yet of the Mexican capital’s long-running subsidence crisis.
Historic structures across the city show visible signs of the problem. Buildings around the central Zócalo plaza, including the Metropolitan Cathedral and the National Palace, appear tilted due to decades of uneven sinking.
Scientists say Mexico City’s descent is caused mainly by excessive groundwater extraction. Built on an ancient lake bed, the city sits on soft, clay-like soil that compresses as water is pumped out from underground aquifers.
NASA scientist Marin Govorčin told The Guardian the aquifer is being depleted at a rate far greater than natural replenishment from rainfall, causing the ground beneath the city to compact under the weight of urban development.
The underground aquifer still supplies about half of the capital’s water needs. Experts say the falling water table, which is shrinking by around 40cm each year, is worsening the crisis.
The effects are visible across the metropolitan area of about 22 million people, including warped roads, cracked water pipelines, and damage to the metro system. Engineers say leaking infrastructure now causes the city to lose an estimated 40% of its water supply.
Among the most striking examples is the Angel of Independence monument on Paseo de la Reforma. Since its completion in 1910, 14 steps have been added to its base as the surrounding land gradually sank.
Researchers say the Nisar system could also help monitor earthquakes, volcanoes, landslides, and climate-related changes worldwide. However, experts warn that stopping Mexico City’s sinking would require reducing groundwater extraction, a difficult step for a city already struggling with water shortages.