Mexico City is sinking into the ground. In some areas, the ground is sinking by as much as 50 cm per year, and this has been happening for decades. This is a measurable and ongoing reality. To understand why, we need to go back in time, to the very foundation of the city.

Mexico City was built on the ruins of the Aztec capital, Tenochtitlan.

Tenochtitlan stood on an island in the middle of Lake Texcoco. Nearby was another island city-state, Tlatelolco. The Aztecs were expert water engineers — they constructed dams, canals, and water management systems to regulate the lake’s level and protect their city from flooding.

But everything changed after the Spanish conquest.

When the Spaniards captured the Aztec capital, they destroyed the canals and began building a new city — the capital of New Spain — directly on the ruins. To expand the city, they started draining the lake. But they did so chaotically, without understanding the region’s geology or hydrology.

At its peak, Tenochtitlan had around 200,000 inhabitants. The Aztecs had expanded the island using chinampas — floating gardens. But the Spaniards saw the island as too small for the new capital city and began draining the surrounding lake to create more land.

The Spaniards recklessly and without proper planning filled in the lake. Although there was ample land available in the surrounding area, they chose to build precisely on the ruins of the former city to assert dominance, symbolically replacing the Aztec capital with their own.

On the other hand, this also allowed them to reuse existing infrastructure and maintain control over a strategic location. As a result, they continually expanded the island and filled in the lake, setting the stage for the city’s long-term instability.

To prevent flooding during the rainy season, the Spanish built levees and embankments around the lake. They diverted water to other areas or out of the basin entirely. Over time, this dramatically shrank Lake Texcoco and protected the new capital, but at a high long-term cost.

Once the lake was gone, Mexico City was left sitting on soft clay and silt — water-saturated soils that compress under heavy loads of colonial-era buildings. These unstable sediments are especially vulnerable in areas that were once underwater.

This is why modern Mexico City is literally sinking. What began as an effort to erase and replace an ancient city has resulted in a modern metropolis built on geological fragility — a direct consequence of the Spaniards’ short-sighted transformation of the lake into land.

Making things worse, the city is pumping water from beneath itself. To supply drinking water to millions of residents, Mexico City extracts vast amounts of groundwater every day. As this water is removed, the clay layers compact, causing the city to sink.

The process is irreversible: once the soils are compressed, even returning water won’t restore their original volume.

The withdrawal of groundwater creates voids that can no longer support the city’s weight. The clay compresses unevenly, leading to cracks in massive colonial buildings, ruptured roads and pipelines, tilted structures, and even collapses.

As a result, the city is sinking unevenly. This causes serious infrastructure damage, especially to colonial-era buildings in the historic center. And because Mexico City lies in a seismically active zone, the effects of earthquakes can be catastrophic when combined with ongoing subsidence.

There are visible signs of this subsidence everywhere.

The Zócalo (Mexico City’s main square) is now situated below the level where Lake Texcoco’s surface once was. The Angel of Independence originally had 9 steps. Over time, due to the sinking ground, 14 more had to be added so it would remain above street level.

The worst-affected areas include the historic center, as well as the boroughs of Iztapalapa, Venustiano Carranza, and Gustavo A. Madero. There, old buildings crack, facades tilt, and water and sewage systems are increasingly deformed.

Mexico City is sinking because of water, yet it suffers from a chronic water shortage.

The irony is painful: the more groundwater Mexico City pumps, the faster it sinks. And the more it sinks, the harder it becomes to deliver water. It’s a vicious cycle that has been unfolding for more than a century — and has only accelerated in recent decades.

To make matters worse, the city sits in a high-altitude valley surrounded by volcanoes.

Importing water from outside is costly and difficult. So Mexico City continues to pump from its aquifers, undermining its foundation. And being in an earthquake-prone area, the consequences of this slow collapse could become disastrous at any moment.

Almost all of Mexico City was built on the site of the former Lake Texcoco. Many historic parts of Mexico City, especially the historic center, are founded on the capital of the Aztec Empire, the city of Tenochtitlan.

Lake Texcoco was a natural body of water, primarily replenished by rainfall and the rivers and streams flowing into the Valley of Mexico. The lake also had underground springs that contributed to its replenishment.

Evaporation and filtration through the soil played an important role in regulating the lake’s water level. Sunlight caused evaporation, and water also seeped into underground aquifers, replenishing groundwater supplies.

Lake Texcoco served as a source of fresh water for the inhabitants of the valley.

With the arrival of the Aztecs, water management systems were developed, including canals, dams, and artificial channels, to utilize water, control flooding, and sustain life in the cities on the lake’s islands.

During seasonal rains, Lake Texcoco would periodically flood the surrounding lands. This natural fluctuation in water level prompted the Aztecs to build dams and canals on the lake to prevent flooding and secure the survival of their settlements.

The construction of dams and dikes by the Aztecs was crucial.

These dams allowed the creation of artificial waterways that supported the viability of their settlements on the islands. These waterways became an integral part of their lifestyle and culture, enabling them to successfully adapt to their environment.

Today, Mexico City rests on an unstable clay layer and volcanic rock, further stressed by extensive paving. Excessive extraction of groundwater depletes the aquifers beneath the city, causing it to sink.

Except for a few swamps and canals in the south, Lake Texcoco and other lakes have vanished. Former lake basins, now deprived of natural water flow, and deforested lands that once acted as sponges for floodwaters no longer serve as buffers between water and people.

The consequences of draining the lakes have been severe: the area has become semi-arid and now experiences water shortages. The soft lake sediments make the city vulnerable to soil liquefaction during earthquakes.

Mexico City faces ongoing impacts from construction on the aquifer, a problem that has existed since the mid-19th century. Although the underground aquifers are replenished, their recharge rate is only about 50% of the rate of groundwater withdrawal.

Mexico City suffered severe floods in 1555, 1580, 1604, and 1607, which led to a proposal to move the capital in 1630. However, after some consideration, the authorities abandoned this idea, and the floods continued.

During the rainy season, Mexico City was overwhelmed with water. The city experienced serious floods in 1645, 1674, 1691, 1707, 1714, 1724, 1747, and 1763. One flood was so severe that the entire city remained underwater for five years.

By the 20th century, much of Lake Texcoco had been drained, and flooding was no longer a major concern. However, as the city expanded and migrants from other states flocked in, Mexico City’s demand for water surged.

As more water was extracted, subsidence began. The phenomenon was noticed in 1891 in the old part of the city but wasn’t studied until 1925. By 1948, it was proven that subsidence was a result of groundwater depletion.

In 1954, water pumping in the city center was prohibited, and wells were relocated to the north and south. While subsidence in the city center has since stabilized, it continues to pose a problem in most areas of Mexico City.

Mexico City is built on two distinct geological foundations, each with very different characteristics affecting how water interacts with the ground beneath the city. These contrasting ground types also affect the stability of the soil and the overall environmental conditions of the city.

A portion of the land rests on fertile volcanic soil, which naturally has excellent water absorption properties. This allowed moisture to flow smoothly into underground aquifers without disturbing the soil’s structural integrity.

However, when developers constructed buildings on this volcanic soil and covered the surface with concrete and asphalt, water infiltration was blocked. As a result, water could no longer penetrate the soil or replenish the aquifers vital for the city’s water supply.

Other parts of Mexico City are built on clay, a soil type that does not absorb water. Instead, clay forms layered structures that trap water between them. When this water is extracted, the clay layers crack, collapse, and overlap each other, causing ground instability.

The impact of development

Not all of Mexico City was built on the lakebed. Southwest of the city lies the Pedregal region, resting on hardened lava flows. Until the mid-1950s, this area was largely considered uninhabitable.

Between 1950 and 1975, Mexico City’s population tripled, and developers began to see potential in Pedregal despite its challenging terrain. The region was subdivided into luxury residential complexes, attracting hundreds of families who rapidly built homes and formed neighborhoods.

This swift expansion had unforeseen consequences. From the mid-1950s to mid-1980s, the once expansive volcanic rock area of about 8,000 hectares was overtaken by streets and buildings. This rapid urbanization destroyed the unique ecosystem, covering almost all permeable surfaces.

As a result, despite the regular months of flooding during the rainy season, very little water manages to seep underground. Urban sprawl has sealed off natural drainage paths with pavement, blocking the city’s natural water absorption and worsening flooding during the rainy season.

To address the complex challenges, engineers and scientists have developed a range of specialized solutions. One key approach is the maintenance and restoration of building foundations, which helps stabilize structures on shifting or sinking ground.

Engineering measures are also used to correct and compensate for uneven slopes, ensuring buildings remain structurally sound. Regular inspection, maintenance, and repair are essential to preserve the safety and integrity of both residential and public infrastructure.

Experts are actively exploring ways to improve land and resource management. Reducing the impact of subsidence on buildings and urban infrastructure requires not only engineering solutions but also strategic planning around how the city uses its natural resources, especially water.

Scientists are working to implement more efficient methods of water extraction and distribution. These include systems to better regulate flow, protect aquifers, and minimize the environmental footprint of the city’s growing demand for water.

Using water pipes to bring water from distant sources can help manage Mexico City’s water problems and reduce further silt buildup. Many cities use this method to secure their water supply.

Pipelines from regions with higher groundwater levels or stable terrain reduce reliance on local aquifers, which are depleted and linked to land subsidence. This strategy lowers pressure on local resources affected by lake drainage and urban development.

However, building and maintaining such infrastructure is expensive. Despite high costs, these water projects can stabilize the supply and reduce further ground sinking. But it’s crucial to weigh construction, maintenance, and environmental impacts.

Deeper underground, stronger and more stable layers are found. Subway tunnels are built at these depths—usually 20–30 m, and up to 40–50 m in some areas. This ensures that tunnels avoid unstable ground and former lakebeds.

Engineers carefully assess all geological risks to protect the infrastructure. They also use soil stabilization, drainage systems, and earthquake-resistant methods to safeguard the subway from flooding and deformation.