The search for Mexico City’s lost water

Amidst the inundating floods in its poorest neighbourhoods, Mexico City finds itself in the grip of a severe water scarcity. Claire Potter explores the challenges and extraordinary initiatives by urban planners and environmentalists, as they work tirelessly to rescue their once water-rich city from climate change and depleted aquifers.

Mexico City faces a paradoxical water crisis. It is running out of water even as floods plague its working-class neighbourhoods.

The water table falls each year, forcing wells to plunge ever deeper. The city is sinking into its aquifer as it drinks ancient reserves of groundwater. In the oldest neighbourhoods, which have fallen more than 30 feet, blocks of colonial buildings have bent into the waves of a surrealist painting as the ground shifts and sinks. At least 30 percent of the urban population do not have access to a daily supply of water in their homes. Meanwhile, rain with nowhere to go floods the streets during summer downpours. Climate change will hasten the crisis; models suggest increased temperatures and reduced precipitation will shorten the rainy season and increase the risk of a severe drought.

Mexico City fills a high-altitude valley in the middle of the country. The first settlers thousands of years ago had an abundance of water. Rivers rushed down the surrounding mountains and fed five shallow lakes. The Aztecs built their capital, Tenochtitlan, on an island in the largest lake, Texcoco. Floods threatened the city since its founding, and the Aztecs built a complicated system of dikes and aqueducts to control water. They learned how to use water to their advantage. With time, they understood how water moved through their enclosed, or ‘endorheic’ basin where no water flowed out, but instead constantly cycled. They grew corn, beans and squash in rectangular plots interlaced with canals. Boats threaded through the capital and the entire valley, connecting the growing Aztec empire.

The Spanish conquered the Aztecs in 1521 and built their capital over the ruins of Tenochtitlan. But they did not know how to manage a capital city so interwoven with water. Without Aztec engineering, floods and water-borne disease plagued the city at higher rates than before. In a drainage project that spanned centuries, the colonial and then independent Mexican governments broke through the surrounding mountains, opened the water basin, and drained the lakes. By 2023, the city metastasized into a metropolis of over 22 million people. Unregulated construction paved over the drained lakes. All but one of the city’s 48 rivers were enclosed in sewage pipes. Today, havens of preserved wetlands and reservoirs hemmed in by ever-encroaching city blocks hint at Mexico City’s water-rich past.

Massive infrastructure projects replaced the natural water cycle with a linear system that extracts water and then discards it outside the water basin. Wells pulling from aquifers below the city supply over two-thirds of Mexico City’s water. A massive system of pumps, canals and tunnels working against gravity delivers water from other water basins to supply the rest. Meanwhile, the sinking city crushes its own infrastructure and 40 percent of its water is lost to leaks. The city barrels towards ‘day zero’ when water stops flowing. Its exact date is unknown: A drought could trigger a crisis, or Mexico City could make do for years. All that is certain is that if Mexico City does not drastically change how it manages its water, the crisis will come.

Mexico City has at once too much and too little water. Mexico City has abundant rainfall in the wet season from May through October, but its drainage system mixes the rainfall with sewage and industrial waste so it is too polluted for domestic use. Despite the shortage of potable water, a vast drainage system pumps wastewater out of the valley. The system periodically fails during heavy summer storms, leaving low-lying neighbourhoods flooded with polluted water.

Over the last 400 years, the drainage system in Mexico City has emptied and created aquifers in a massive transfer of water. To the north of the city, Mexico City’s untreated wastewater irrigates Mezquital Valley, a former desert that now produces alfalfa, corn and wheat in abundance. The valley’s irrigation water is the untreated waste of the capital. Even though it is polluted with lead, arsenic, bacteria, parasites, grease and plastic debris, it is a valuable agricultural resource. In 1992, Mexico banned growing plants whose edible parts would be exposed to the polluted water and sold for human consumption, although enforcement remains imperfect. Government studies show that using the ‘black water’, as Mexicans call it, for animal feed does not harm human health. The transfer of water has been so vast and prolonged that a new aquifer is forming below the fields of Mezquital. The rocks and soil clean the water as it percolates down to the aquifer below, and some scholars say the Mezquital Valley may be the largest natural water filtration plant in the world.

A new generation of urban planners, academics and activists argue that Mexico City needs to rehabilitate its relationship with water to survive. They advocate that green and blue infrastructure – designs that mimic nature rather than fighting it – are the only way to save Mexico City. The city needs to build a circular system where the same water is used, cleaned and used again, and it needs nature to do that, they say. Green and blue infrastructure projects used to rarely ever receive funding, but a burst of projects in recent years use wetlands, trees and native plants to rebuild the natural water cycle.

“We have had a wrong-headed relationship with nature,” says Fabiola Sosa-Rodríguez, an environmental scientist at the Universidad Nacional Autónoma de México (National Autonomous University of Mexico or UNAM). For centuries, the city has fought against natural water. “When in reality, for water security, we need to nurture water, to retain it instead of casting it out.”

Bringing wetlands into the city

Six lanes of cars rush on either side of the Ecoducto Río de la Piedad. The highway traces where a river once flowed. The Piedad was the first river that Mexico City enclosed because wastewater pollution made it a hazard to public health.

The ecoduct is a raised linear park and an attempt to resurrect the river. Elias Cattan, an architect and environmental activist, launched a movement to recover the Piedad River nearly 10 years ago. He dreams of reintegrating buried rivers into the urban water cycle. Thousands joined ‘Picnics at the River’ to persuade the government to rescue the river of sewage flowing below them.

After intense public pressure – and a police reaction that brought international attention – the government agreed to build a park that resurfaced the water hidden below the highway.

Alejandro Alva-Martínez, a biologist, designed small wetlands to clean 30,000 litres of sewage redirected from the enclosed river. While that is merely a fraction of the river’s flow, Alva’s design displayed how a nature-based treatment system could clean black water over the course of 1.6 kilometres. Biodigesters perched over the highway host microorganisms that feast on organic contaminants. Then, the water flows into a bed of hyacinths that draw out the sweet-sick odour of sewage. Gravity pulls the water through a series of small wetlands that grow in rectangular beds on either side of a path. At the end of the park, the water is supposed to be clear, as it was when the park first opened in 2017.

Green infrastructure may be economical, but it does require maintenance. During the pandemic, Alva says, gardeners who tended the wetlands lost their jobs. The vegetation became overgrown, and the water can no longer flow through the ecoduct, he explains.

Although it is not what he envisioned, he is still proud of the ecoduct. He likes designing with nature because it has a serendipitous way of defying human expectations. Without maintenance, the park transformed into a rain garden that grows abundantly in the wet season. Bees flit among thick beds of lavender. The scent of the herbs overwhelms the exhaust rising from the highway below.

Alva is excited by the potential of wetlands taking over the city’s camellones, the banks of grass and vegetation that separate multi-lane highways across the city.

“With this wetland that we have here, if you duplicate it for every camellon, each block could have its own water treatment plant,” he says. “My rule is: If I have black water, I have a park. Give me black water and I give you this.”

No one was interested when Alva built his first wetlands in 1996. But since the ecoduct, he has had a rush of projects.

“Now that they see it works, everyone wants to do it,” he says.

Cattan launched the Picnic at the River movement nearly 10 years ago, and all that time he has kept trying to change how his city manages water. He totters between grand visions for Mexico City’s future and pessimism about its capacity to realise them.

To him, the ecoduct is an example of Mexico’s failure to maintain projects from one administration to the next. While he says it is indeed progress that Mexico City’s government now sees green infrastructure as legitimate enough to fund, he has seen no progress at the scale necessary to address the water crisis. The city needs to restore the whole water basin rather than focus on scattered projects, he argues. He insists that Mexico City needs to abandon cars and divert the millions it spends on highways to green, regenerative projects.

“The solutions are there, the prototypes are there, the case studies are there, the budgets are there, everything has been proven,” he says. Yet, he watches as the government adds lanes to highways and invests in car infrastructure even though the majority of the city uses public transportation.

An ecological park twice the size of Manhattan

Nature-based solutions to the water crisis are emerging throughout Mexico City. Artificial wetlands cover a former landfill in Cuitláhuac, a neighbourhood often desperate for water. In one of the largest installations yet, artificial wetlands clean water in the Aragón Forest in the west of the city. More ambitious projects are in their early stages. For example, officials announced in August that a long-awaited USD 200 million project at the 513-hectare Lake Tlahuac-Xico is moving forward. The lake, itself under threat by illegal settlements built on piles of construction waste dumped into the lake, would become a source of water. The project would shift the city’s thirsty, impoverished western neighbourhoods towards water reuse, but its construction remains years away.

The Texcoco Ecological Park is the most ambitious environmental project under construction in Mexico City. The park will combine environmental restoration with public recreation, featuring artificial wetlands, restored lakes, hiking trails and sports fields. At nearly twice the size of Manhattan, it will be one of the largest urban parks in the world.

During former president Felipe Calderón’s tenure, from 2006 to 2012, Echeverria developed plans to restore the 35,000-acre, seasonally dry lakebed of Lake Texcoco. He envisioned how artificial wetlands and restored, man-made lakes could turn back the clock and recover some of Mexico City’s lost water. The Texcoco Ecological Park would help alleviate flooding, capture water and moderate temperatures.

At first, Echeverria struggled to cross the Rubicon from idea to project. The land sits next to Mexico City’s international airport, and the next president, Enrique Peña Nieto, decided to use the open space to build a new and expanded airport. But building an airport on the wet unstable soil of seasonal wetlands proved both costly and difficult. The current president, Andrés Manuel López Obrador, nixed Nieto’s airport. When Obrador found an old copy of Echeverria’s plans for an ecological park, he called him in for a meeting. Nearly 20 years after his first plans for Texcoco, Echeverria found himself managing the most ambitious green infrastructure project in Mexico City’s history since the Spanish conquest.

The lakebed is one of the last expanses of undeveloped land in Mexico City. Most open land, even if it has legal protections, has been paved over in Mexico City largely because of a decades-long pattern of unplanned developments. The city’s population spiked from 3 million in 1950 to over 22 million today.

The lakebed remains open only because floods and unstable soil have made construction impossible. In the popular imagination, the remnant of Lake Texcoco is a saline wasteland where dust swarms swirl and only desert saltgrass and ever-hardy, gray-green Tamarix trees grow. Driving over the park’s dirt roads, you see a flat expanse of red, dusty soil speckled with low-lying green shrubs and trees.

A few miles inside the park’s gate, an unnaturally rectangular lake with a 12-kilometre perimeter interrupts the arid landscape. Constructed in the 1970s, Nabor Carillo was an early, and successful, attempt at ecological restoration. Enrique Peniche, an engineer who recently helped repair Nabor Carillo’s banks, relishes in explaining every detail of its engineering. Pipes flowing from a water treatment plant fill it with semi-treated wastewater which then seeps through the subsoil, which naturally cleans the remaining contaminants. Then, a series of pumps extract the water for reuse in a poor neighbourhood on a mountain overlooking the lake. Peniche’s only regret was that few cities have space for massive holding ponds that use soil to clean and reuse water.

For now, the Texcoco Ecological Park is closed off to the public. Armed guards stood at the gates when I visited in the summer of 2022. Misinformation about the project is widespread, and everyone from my Uber driver to an acquaintance from an art class speculated that the park was behind schedule and failing to live up to the government’s ambitious promises of environmental restoration. But Echeverria says that progress is well underway, and that contrary to popular belief, the lakebed of Texcoco is not a wasteland.

While the soil’s levels of soluble salts and sodium exclude many plants, his team has found about 200 individual plant species. They have built a greenhouse within the park to nurture and reproduce the native species. With restoration at a large scale, the remnants of Lake Texcoco could become an ecological haven providing recreation, habitat for a diverse range of animals and plants, and much-needed water storage and green infrastructure to the crowded city surrounding it on every side.

Echeverria and his team were approaching the end of the first stage of the project in January 2023. The borders of Nabor Carillo have been built up and secured so that it can hold more water. The greenhouse promises a future of more biodiversity. Researchers monitor the abundance of birds that take refuge in Texcoco. A sports complex nearly the size of Central Park, complete with facilities for everything from American football to the ancient Mesoamerican ballgame, is nearly done. So far, the Texcoco project has cost about 4.5 billion pesos, or USD 248 million.

Echeverria argues that the project is worth every penny. “The city and the Valley of Mexico that we can imagine in 30, 50 or 100 years are radically different and economically much more valuable and resilient if we recover our ecosystems and our relationship to water,” he says. The completed park will quell dust storms, lower urban temperatures, and offer more storage water during the rainy season.

Even a project as massive as the Texcoco Ecological Park cannot solve the city’s crisis; it can only help. But Echeverria hopes that it will spark a much broader commitment to restoring the land. Perhaps, he hopes, it will even help the city return to a culture of water that predates Mexico City’s war with its most important resource.

Looking for a solution as big as the problem

Building even smaller, localised projects in Mexico City can take years because of political setbacks. Often when administrations change, the new party in power stymies the last party’s projects to undermine their opponent’s legacy, explained a political scientist on background. Many times, though, there simply is not enough money to see projects through.

Loreta Castro Reguera, a landscape architect, and Manuel Perló Cohen, an economist with experience in urban planning, saw potential in a 10-acre garbage dump in the crime-ridden neighbourhood of Iztapalapa. Water naturally pooled in the land where cracks in the soil let it filter down into the starved aquifer below. Castro and her team wanted to enhance natural infiltration. They developed designs for a public park that doubled as infrastructure. It would have volcanic stone terraces, rainwater-serviced public toilets, artificial wetlands and a small sewage treatment plant. They first presented a proposal for the park, called Quebradora, to the municipal government in 2013. But they faced a constant battle as they tried to muster the political will to build it. One mayor finally picked up the project, only for construction to stall after the first phase.

“It's an endurance race. It happens with every project. We need to be there all the time,” says Castro.

Determined to galvanise support for Quebradora, Castro and Perló entered the project for the Holcim Awards, an international competition for sustainable architecture. To their shock and delight, it won twice: First the Latin American gold in 2017, and then the global gold in 2018. The publicity around the prize motivated the government to finish the project, says Castro. But after just a few months of work, a new mayor took office and stopped the project. After a lengthy review, construction resumed. Quebradora opened in 2021, nearly 10 years after it was first proposed. Yet, Castro and Perló lost control of the project during its construction. The government had to reduce the scope of the project as it exceeded the initial budget. The wetlands, the water treatment plant, and rainwater toilets were never built, but Perló and Castro are glad that the water filtration system works and that Quebradora is popular with people who live in the neighbourhood.

Despite the frustrations of Quebradora, Castro and Perló embarked on building another water park in Ecatepec, a water-starved neighbourhood perched on the mountainous periphery of Mexico City.

“Some people might think that we are very incrementalist and that we need a drastic change,” says Perló. But he believes in the potential of small projects tailored to particular neighbourhoods and environments, especially if they formed a network across the city. The alternative, he argues, would be to wait for a catastrophic flood or drought to force the city to act.

There are also signs of hope. When Perló and Castro first proposed Quebradora 10 years ago, nature-based infrastructure projects were seen as hippy pipedreams that could never deliver the results of traditional gray infrastructure projects. But today, the city government is developing a ‘green infrastructure’ plan and there are established mechanisms to fund nature-based solutions. And while many sustainable solutions meet setbacks, household rainwater harvesting systems have exploded in popularity.

Enrique Lomnitz saw an opportunity in the vast quantities of unused rain that falls on Mexico City each year during the wet season. In all, nearly twice as much rain falls in Mexico City as in London. The Rhode Island School of Design graduate worked with other students to develop a small, durable rainwater harvesting system that collects and cleans the water that pounds on Mexico City’s rooftops in the rainy season. They provide about six months of water for a family and reduce flooding. Lomnitz co-founded Isla Urbana, a non-profit organisation that installs the systems, in 2009. So far, it has installed over 30,000 in Mexico. Other organisations have mimicked the technology.

Lomnitz discovered that the government was eager to buy and subsidise the rainwater harvesting systems. In the impoverished urban sprawl of Mexico City, running water is especially rare in neighbourhoods that were built up informally without any central planning or regulation. Infrastructure has yet to catch up with development. Municipal governments spend thousands on pipas, or water trucks, that go into neighbourhoods without running water and face backlash from communities frustrated by inconsistent and insufficient deliveries, he explains. Rainwater harvesting systems give the government a way to address the problem even if it fails to deliver regular running water.

Over time, Lomnitz learned just how useful Isla Urbana’s product would be for politicians. Water is a stressed resource in much of Mexico. When a drought hits, severe water shortages are not far behind. In 2021, the northern industrial city of Monterrey ran out of water. And when crises hit, municipal governments call Isla Urbana with urgent orders, says Lomnitz.

“These crises are complex crises. They actually don't have quick fixes,” he says. “And so whatever they want to do, whatever they need to do to fix these things, they can't do that quickly. And implementing these rainwater harvesting programmes allows them to do something that shows that they're doing something. It works. It's very fast. It's visible. And so it buys them a little bit of time.”

Long-term solutions to the water crisis in Mexico City would cost millions and take years. Each artificial wetland, rain garden and aqua park is a step forward, but protecting the city against day zero would require projects large enough to shift the city away from a linear water system and towards a circular model of reuse. While Mexico City operates one of the most expensive water systems in the world, finding the money to transform it is a near-paralysing challenge.

For many, solutions feel out of reach so long as the city fails to see itself within the web of nature. Cattan insists on using the word cuenca, or water basin, to shape his listeners’ identities around the natural limits of their water supply. For some, that philosophy is beginning to take hold.

Valeria Hernández, an environmentalist and a mother, sees a growing environmental consciousness in her neighbourhood. She lived in Xochimilco, a neighbourhood that is home to both crowded urban blocks and the most important wetlands remaining in Mexico City. There, indigenous communities whose roots predate the Spanish conquest still nurture traditional attitudes towards water.

“We are part of nature, part of the same ecosystem. We have to work for nature because we are part of her. Without her we don’t live,” says Hernández. On a hot July day, she and five other volunteers planted native plants in a small park under threat of development. They want to save the land to be a seed bank and public space.

When Hernandez, now 32, was a child, she asked her grandmother to describe canals and wetlands lost to urban development. She ached for water she never knew. She asked why so much was lost, and her grandmother told her that she didn’t know. Her work left her no time to pay attention. Hernandez does not want to tell the same story to her daughter.

This story was originally supported and published by the Pulitzer Center. All quotes except those by Lomnitz, Perló, Castro and Cattan were translated from Spanish by the storyteller.