Lake Texcoco was a large, shallow, saline lake that once covered much of the Basin of Mexico, the high-altitude valley where Mexico City now sprawls. It served as the foundation for the Aztec capital of Tenochtitlan, supplied food and water to one of the world’s great pre-Columbian civilizations, and then spent centuries being systematically drained by Spanish colonial authorities and their successors. Today, the lake itself is gone, but its legacy shapes nearly every challenge Mexico City faces, from catastrophic land subsidence to dust storms, seismic vulnerability, and rising temperatures.
A Lake Shaped by Millennia
The Basin of Mexico is an endorheic basin, meaning it has no natural outlet to the sea. For tens of thousands of years, rain and snowmelt from the surrounding volcanic mountains collected at the basin’s lowest point, forming a system of interconnected lakes. Texcoco sat at the center and bottom, receiving overflow from the fresher lakes of Xochimilco, Chalco, Zumpango, and Xaltocan. Because it had no outflow, dissolved minerals concentrated over time, making Texcoco markedly salty and alkaline compared to its neighbors.
Sediment cores drilled from the former lakebed reveal a history stretching back more than 32,000 years. Tiny crustacean shells preserved in those sediments show that the lake alternated between wetter and drier phases, but saline and shallow conditions have generally prevailed for the past 7,000 years. The driest interval on record occurred between roughly 18,000 and 7,000 years ago, when the lake occasionally shrank to little more than mudflats.1Journal of Quaternary Science. Late Pleistocene and Holocene palaeoecological reconstruction of Lake Texcoco (Basin of Mexico) based on its ostracod record By the time humans built the first permanent settlements in the basin, Texcoco was a broad but shallow body of water, rarely more than a few meters deep and too salty for irrigation or drinking.
The Aztec Relationship With the Lake
When the Mexica (the people commonly called Aztecs) arrived in the basin in the fourteenth century, they settled on an island in the western part of Lake Texcoco and built Tenochtitlan, the city that would become the seat of a vast empire. Living on a salt lake forced creative solutions. The Mexica constructed causeways linking the island to the mainland and developed chinampas, the raised agricultural plots often described as “floating gardens,” primarily in the fresher southern lakes. But Texcoco itself was not wasted.
The lake supported a distinctive food web. A sixteenth-century Spanish account describes how the Aztecs harvested a fine green slime from the surface of the water, dried it into cakes roughly the thickness of a coin, and ate it in quantity. They called this substance tecuitlatl. Modern researchers have identified it as a form of Spirulina-type blue-green algae, a high-protein food source that thrived in the lake’s alkaline chemistry.2University of Michigan Library. The Aquatic Component of Aztec Subsistence: Hunters, Fishers, and Collectors in an Urbanized Society Beyond algae, the saline waters supported waterfowl, insects, small crustaceans, and brine flies whose eggs and larvae the basin’s residents also collected and consumed. The lake was not a hostile wasteland to pre-Columbian people but a productive ecosystem they knew how to use.
Engineering Against the Water
Tenochtitlan’s island location gave it natural defenses, but it also made the city vulnerable to flooding, especially when seasonal rains swelled the surrounding lakes and salty water from Texcoco inundated the city and contaminated the fresher lakes used for chinampas. The Aztec response was a massive piece of hydraulic engineering: the Nezahualcoyotl dike, built around 1445. This stone-and-earth barrier stretched roughly 16 kilometers across the lake, separating the salty eastern waters of Texcoco from the fresher western zone where Tenochtitlan sat.3Reliability Engineering & System Safety. Reliability analysis of flood defenses: The case of the Nezahualcoyotl dike in the aztec city of Tenochtitlan The dike also served as a causeway and included sluice gates that could be opened to regulate water levels. It was one of the largest infrastructure projects in the pre-Columbian Americas and remained functional until the Spanish conquest in 1521.
After the conquest, the Spanish dismantled much of the Aztec water-management system and rebuilt Mexico City directly on top of Tenochtitlan. Without the dike and the aqueducts that had supplied fresh water, the new colonial city was repeatedly flooded. The worst inundation, in 1629, left much of the capital under water for five years and killed thousands. Spanish authorities decided that the only permanent solution was to get rid of the lakes altogether.
Centuries of Drainage
The colonial drainage project, known as the Desagüe de Huehuetoca, began in 1607. Its goal was to punch an artificial outlet through the mountains at the basin’s northern rim, allowing floodwater to drain out toward the Gulf of Mexico. The project was enormous, relying heavily on forced Indigenous labor, and it dragged on for centuries in various forms.4Hispanic American Historical Review. The Desagüe Reconsidered: Environmental Dimensions of Class Conflict in Colonial Mexico The initial tunnel and open cut at Huehuetoca never fully worked as planned, and flooding continued to plague the city through the colonial period.
The real death blow to Lake Texcoco came in the late nineteenth and early twentieth centuries, when the completion of the Gran Canal de Desagüe and later the deep-drainage tunnel system finally succeeded in moving water out of the basin at scale. By the mid-twentieth century, Texcoco had been reduced to scattered shallow pools and vast stretches of dry, saline mud. The other basin lakes shrank drastically as well, though remnants of Xochimilco survive as the famous canal system in the south of the city.
Dust, Salt, and Tolvaneras
Draining a saline lake does not produce farmland. It produces an expanse of exposed sediment loaded with mineral salts. That is precisely what happened at Texcoco. The desiccated lakebed became roughly 10,000 hectares of extreme saline-sodic soil, practically useless for agriculture or grazing.5Geoderma. Remediation of saline soils by a two-step process: Washing and amendment with sludge During the dry season, when winds sweep across the barren flats, they lift enormous clouds of fine, salt-laden dust called tolvaneras. These dust storms blow directly into the eastern neighborhoods of Mexico City, reducing visibility and carrying particulates that cause respiratory problems and can transmit infectious agents.
Lake Texcoco is not the only drained lake to produce this kind of dust hazard. Researchers studying windblown sediment from disturbed lake systems worldwide have placed Texcoco alongside Owens Lake in California, the Aral Sea in Central Asia, and the Lop Nor basin in China as examples of the same phenomenon: when humans dry out a playa or lake, the exposed bed becomes a major dust source.6Geomorphology. Eolian sediments generated by anthropogenic disturbance of playas: human impacts on the geomorphic system and geomorphic impacts on the human system The difference with Texcoco is that the dust blows into a metropolitan area of more than 21 million people.
The City That Keeps Sinking
Perhaps the most dramatic consequence of draining Lake Texcoco is the subsidence of Mexico City itself. The old lakebed consists of thick layers of soft, water-saturated clay. When groundwater is pumped from the aquifer beneath those clays, the clay layers compact under their own weight, and the land surface drops. This process has been ongoing for more than a century, and the numbers are staggering.
The sinking is not uniform. Areas built on the old lakebed, particularly in the eastern and central parts of the city, subside much faster than areas built on firmer ground at the basin margins. The rate correlates strongly with the thickness of the underlying clay layer rather than directly with how much water is being pumped at any given location. Analysis of satellite and ground-based measurements has shown that the subsidence is almost entirely irreversible: the compacted clay does not spring back when water levels recover. Projections suggest it could take around 150 years for the clay to finish compacting, with up to an additional 30 meters of sinking still possible in the worst-affected zones.7Journal of Geophysical Research: Solid Earth. Over a Century of Sinking in Mexico City: No Hope for Significant Elevation and Storage Capacity Recovery
The subsidence has already forced restrictions on groundwater pumping in the city’s core, though outlying areas continue to extract heavily.8Water Resources Research. Analysis of long‐term land subsidence near Mexico City: Field investigations and predictive modeling Buildings tilt, water and sewer lines crack, and the deep drainage system that was supposed to carry floodwater out of the basin by gravity now runs uphill in some stretches because the land around it has dropped. The city has had to install massive pumping stations to keep the drainage functioning, an ironic reversal: the infrastructure built to remove the lake now struggles because the lake’s absence caused the ground to collapse.
Why Old Lakebed Makes Earthquakes Worse
The soft clay beneath the former lake also amplifies seismic waves. During the devastating 1985 earthquake and again during the 2017 Puebla-Mexico City earthquake, damage was heavily concentrated in neighborhoods built on the old Texcoco lakebed. The clay acts like a bowl of gelatin on a shaking table, magnifying the ground motion several times over compared to nearby areas built on rock. The former Texcoco lake clays are softer and weaker than the clays beneath the old Xochimilco-Chalco lake to the south, which means the seismic amplification effect is most extreme in the central and northeastern parts of the city.9Soil Dynamics and Earthquake Engineering. Observed building damage patterns and foundation performance in Mexico City following the 2017 M7.1 Puebla-Mexico City earthquake
This means that earthquake risk in Mexico City is not just about proximity to a fault line; it is fundamentally shaped by which part of the old lake system a building sits on. Seismic microzonation maps of the city are essentially maps of ancient lake geography. The zones labeled “Lake Zone” in engineering codes correspond almost exactly to the footprint of Texcoco, and they carry the strictest building requirements precisely because the vanished lake’s sediments still dictate how the ground moves.
A Hotter City Without Its Lake
Replacing a large body of water with urban sprawl and barren mud also changed the local climate. Water absorbs solar energy and releases it slowly through evaporation, which moderates temperatures. When the lakes disappeared and concrete, asphalt, and dry soil took their place, the region lost that cooling effect. Climate modeling comparing pre-urban and modern land cover in the Mexico City metropolitan area has found that the land-use change pushed average daytime temperatures up by more than 4°C.10Journal of Geophysical Research: Atmospheres. Loss of a lake system in a megacity: The impact of urban expansion on seasonal meteorology in Mexico City
That 4°C figure is an average across the metropolitan area, and the effect is not felt equally everywhere. The former lakebed areas in the east, where bare saline soil or sparse informal settlements replaced open water, tend to see even larger temperature swings than the older western neighborhoods that were never lake. The loss of the lake also altered local rainfall patterns and humidity, though the magnitude of those effects is harder to pin down because the city’s explosive growth changed so many variables at once.
What Still Lives on the Lakebed
Despite the degradation, remnants of the Texcoco ecosystem persist. A series of artificial and semi-natural water bodies maintained in the former lakebed area, originally created as part of a 1970s-era reclamation project, have become unexpectedly important for birds. The site is recognized as a Globally Important Bird Area, serving as critical habitat for both migratory and resident waterfowl in a region where natural wetlands have almost entirely vanished.11Academia.edu. Current Threats to the Lake Texcoco Globally Important Bird Area Tens of thousands of shorebirds, ducks, and pelicans pass through during migration, and the shallow saline pools support some of the same organisms, including brine shrimp and salt-tolerant algae, that once thrived in the full lake.
The broader saline lake ecosystems of central Mexico, of which Texcoco was the largest example, support a characteristic community of salt-adapted organisms. These include blue-green algae like Spirulina, brine shrimp, specialized copepods, water boatmen, brine flies, and in less saline conditions, small native fish and even the axolotl’s relatives among the neotenic salamanders. The productivity of these ecosystems, modest as they look compared to a freshwater lake, sustained human populations for millennia before the drainage campaigns stripped them away.
The Airport That Almost Was
The former lakebed’s emptiness made it an attractive target for large-scale development, and in 2014 the Mexican government announced plans to build the New International Airport of Mexico City (NAICM) on the eastern Texcoco flats. The project was enormous: a six-runway airport designed by Norman Foster that would have been one of the largest in the world. But it ran headlong into the same problems the lakebed has always posed.
The site sat on unstable, compacting clay in an area with no authorized change of land use from the local government, and it directly conflicted with the ecological mitigation zone that had been established to protect the remaining bird habitat and control dust storms.12Revista CS. El nuevo Aeropuerto Internacional de la Ciudad de México en el exlago de Texcoco, Estado de México: problemática socioterritorial y ambiental Critics argued that building on actively subsiding ground would require constant, expensive maintenance, that the loss of the ecological zone would worsen dust storms and destroy irreplaceable bird habitat, and that the project had been designed without coordination with existing urban plans at any level of government.
In 2018, following a public consultation, the incoming administration of President Andrés Manuel López Obrador cancelled the partially built airport. The decision was itself controversial, given that billions of dollars had already been spent on foundations and earthwork. An alternative airport was built instead at the Santa Lucía military air base to the north. The Texcoco site was subsequently designated for a large ecological park, Parque Ecológico Lago de Texcoco, intended to restore wetlands, control dust, and provide green space for the eastern metropolitan area. Whether the park can deliver on those goals in a landscape this degraded remains an open question.
Restoring a Lake That No Longer Exists
The idea of bringing water back to the Texcoco basin has circulated among engineers and urban planners for decades. The reasoning is straightforward: if the absence of the lake causes dust storms, subsidence, heat, and lost habitat, then partially refilling it should help reverse those problems. Several pilot projects have demonstrated that it is possible to establish shallow wetlands on portions of the old lakebed, using treated wastewater and controlled flooding. The 1970s reclamation project that created the bird habitat proved that even modest water coverage can suppress dust and support biodiversity.
But the obstacles are formidable. The basin’s hydrology has been fundamentally altered: the drainage tunnels that took centuries to build now carry water out of the valley, and Mexico City’s water supply depends heavily on the same aquifer whose depletion drives the subsidence. Refilling the lake surface would not recharge the aquifer or stop the sinking, because the clay compaction is irreversible. The restored wetlands would sit atop a landscape that continues to drop. And the eastern fringe of the metropolitan area has been heavily urbanized since the lakebed was exposed, with millions of people now living on former lake bottom. There is no politically or physically realistic scenario in which Texcoco returns to anything resembling its pre-colonial extent.
What is feasible, and what the ecological park project aims for, is a patchwork of managed wetlands, grasslands, and reforested areas across several thousand hectares. Even that more modest vision faces competition from land developers, infrastructure projects, and the sheer economic pressure of a growing metropolitan area. The history of Lake Texcoco is, in many ways, a cautionary tale about the long-term costs of eliminating a natural system that a civilization decided was in the way. The lake is gone, but the city has not stopped paying the price for its removal.