How Mexico City is Going Downhill due to Sinking

For decades, the sprawling metropolis of Mexico City has been confronting a silent and insidious threat beneath its surface – subsidence, the gradual sinking of the Earth's crust due to the depletion of underground water resources. This unsettling phenomenon not only poses a risk to the city's infrastructure but also exacerbates its vulnerability to earthquakes, creating a complex and urgent problem that experts are increasingly concerned about.

Marisa Mazari Hiriart, a researcher at the National Laboratory of Sustainability Sciences at the Institute of Ecology of the National Autonomous University of Mexico (UNAM), emphasizes the profound impact of subsidence on Mexico City. She contends that the excessive extraction of groundwater from depths ranging from 100 to 300 meters has been a primary driver of this geological crisis. As more water is removed from the ground, the land above gradually loses volume, resulting in the sinking of the earth's surface. Moreover, this subsidence is not just an isolated geological issue; it is tightly entwined with the city's seismic activity, rendering it more susceptible to earthquakes.

Enrique Cabral Cano, a researcher at the Institute of Geophysics, points out that such subsidence-related processes have been documented in Mexico for over a century, dating back to the late 19th century when the extraction of subway water began. This historical context underscores the enduring nature of the problem.

According to Cabral Cano, an alarming 853 localities within Mexico City are experiencing subsidence at a rate greater than 2.8 centimeters per year. This accounts for a staggering 15 percent of the total urbanized areas in the city, affecting less than seven million vulnerable homes and over 21.4 million people. Among the most affected areas are Gustavo A. Madero, Iztapalapa, Iztacalco, Tláhuac, and Venustiano Carranza, which also face significant socioeconomic risks due to subsidence and associated faulting.

The situation took a turn for the worse following the devastating earthquake in 2017, which accelerated the rate of subsidence. Nevertheless, there remains a startling lack of comprehensive plans to mitigate this phenomenon in the sprawling Mexican metropolis. “We cannot continue throwing water!” Cabral Cano emphatically declared, highlighting the urgency of the matter.

Mazari Hiriart emphasizes that Mexico City's seismic zone, in the ancient lakebeds of the valley, is like a moldable clay, making it highly susceptible to geological shifts. The combination of clayey soil, geological faults, fractures, changes in land use, loss of biodiversity, high population density, productive activities, and climate change converges to create what can only be described as a “zone of imminent disaster.”

The underlying issue at play here is water resources, a shared common good. With a population density that far exceeds the national average, Mexico City's relentless urban expansion since 2000 has caused it to consume a staggering 60 cubic meters of water per second. This insatiable thirst for water has resulted in the city's current predicament, where the exploitation of groundwater threatens not only its future but also the lives of its residents.

Carmen Casas Ratia, director of the National School of Social Work, acknowledges the pressing need to recognize this urban vulnerability. She stresses that addressing this complex challenge requires a multidisciplinary approach that brings together experts from various fields to identify opportunities for action.

In conclusion, Mexico City's battle against subsidence is a matter of utmost importance, not just for its residents but also for the entire nation. As the ground beneath the city continues to sink, it is imperative that a collaborative effort is made to formulate and implement sustainable solutions. Only through a concerted approach can Mexico City hope to safeguard its future against the looming threat lurking beneath its streets and buildings. Credit: UNAM