As Mexico City grows, a once-mighty lake shrinks

"The urban stain has been expanding on what was previously land dedicated exclusively to cultivation and livestock,” a 2022 report by the Planning Committee for the Development of the State of Mexico stated. “Unprecedented accelerated urbanization contributes to the contamination of bodies of water, specifically Lake Zumpango, which has caused the cessation of fishing in the municipality.”

‘Myopia of the present’

Before colonization and when it still had water, Lake Zumpango was the northernmost of five large lakes in the Valley of Mexico, a fertile highland region which today includes the majority of the federal district of Mexico City and most of the states of Hidalgo, Mexico, Tlaxcala and Puebla. 

Together with the other four — lakes Xaltocan, Texcoco, Xochimilco and Chalco — the bodies once spanned an area of approximately 580 square miles. Volcanoes and mountains surround this region on all sides.

The historic downtown of what is now Mexico City was founded by the Mexica people in 1325. According to legend, the Aztec sun and war god Huitzilopochtli sent them a divine omen (an eagle perched on a nopal cactus with a serpent in its talons) to indicate where to build a city. That spot was on an island in the middle of Lake Texcoco, where the Mexica built the grand city-state of Tenochtitlán.

After colonization, Tenochtitlán became Mexico City, now the most-populous city in North America. The city’s unusual geography, coupled with government decisions in the centuries since, have had a profound effect on who has access to water and who doesn't.

A research paper from Resilience Alliance, an ecological research group, analyzed historical water infrastructure in Mexico City to argue there have been eight "critical decision cycles for human settlement" in the Valley of Mexico. 

The first was settling a city inside a lake. To do so, the Mexica had to determine how to manage the constant flow and presence of water and the resulting challenges, including sanitation, infrastructure and disease.

The second decision cycle began when the Spanish built their new capital on top of the sacked Tenochtitlán pyramids, destroying most of the chinampas built by the Mexica. 

A Mesoamerican agricultural technique, chinampas are small parcels of arable land used to grow crops on top of shallow lakes. They also serve as a crucial drainage system. Though still in use, notably in the southern borough of Xochimilco, chinampas and their drainage benefits are today far less common.

Next, there were two floods: one in 1555 and another in 1556. The Spanish deforested the surrounding mountains, increasing erosion, runoff and flooding while also diminishing groundwater filtration.

Another flood in 1629 killed 30,000 people and resulted in frequent epidemics of typhus and smallpox — leading the Spanish to attempt to drain the lakes completely. The city began to sink into the hollow ground underneath it, a problem that continues today. By current estimates, Mexico City is sinking almost 20 inches per year.

The fate of Lake Zumpango is just the latest outcome of decades of decisions that together have had a profound effect on water access in the Mexico City area, Hallie Eakin, a sustainability professor and global futures scientist at Arizona State University, said in an interview.

Officials have responded to each new crisis without considering the long-term effects of their decisions, said Eakin, a co-author of the Resilience Alliance paper. "We tend to have a myopia of the present.”

After officials drained the lakes, Mexico City’s water woes continued, with each new half-baked solution leading to new problems. 

In preparation for Mexico's Bicentennial celebration in 1886, city officials combined the storm and sanitary drainage systems to rid human waste. That ruined the water quality underneath the city, helping make Mexico a major consumer of bottled water even today.

The Mexico City subway system was inaugurated in 1969, pushing the physical and structural limits of the city even further and ironically causing more traffic and even worse air quality. In 1992, the United Nations declared Mexico City the most polluted city in the world. Mexico City responded by creating a conservation zone to battle pollution. That caused land values within the zone to skyrocket, pushing the city's poor further out into the state of Mexico and wider urbanization into rural areas.

Throughout the centuries, water has always been Mexico City’s great hurdle. But as officials have worked to tame the region’s mighty hydrology, the purported benefits have created new problems for those with relatively less political and economic power. 

As a result, “this natural resource becomes a social and political construct,” said Jeffrey Banister, associate research professor in the School of Geography and Development at the University of Arizona. 

“What are the disparities in access? How has technology attempted to conquer water?” Bannister asked rhetorically. “This has been an ongoing problem for centuries.”

Eakin, the ASU professor, concurred. "These patterns are predictable," she said. Going forward, "do we break with existing patterns, or do we force them onto the population?” 

“There is always that struggle between short-term financial profit and long-term environmental loss,” she added. Until Mexico City fully grapples with its complex relationship with water, officials here will likely keep “pushing the buck down the line."

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