When Mexico City’s Grand Canal was completed, at the end of the 1800s, it promised to solve the flooding and sewage problems that had plagued the city for centuries. But it didn’t. The canal was based on gravity. And Mexico City was sinking, collapsing in on itself.

Share story

MEXICO CITY — On bad days, you can smell the stench from a mile away, drifting over a nowhere sprawl of highways and office parks.

When the Grand Canal was completed, at the end of the 1800s, it was Mexico City’s Brooklyn Bridge, a major feat of engineering and a symbol of civic pride: 29 miles long, with the ability to move tens of thousands of gallons of wastewater per second. It promised to solve the flooding and sewage problems that had plagued the city for centuries.

But it didn’t, pretty much from the start. The canal was based on gravity. And Mexico City, a mile and a half above sea level, was sinking, collapsing in on itself.

It still is, faster and faster, and the canal is just one victim of what has become a vicious cycle. Always short of water, Mexico City keeps drilling deeper for more, weakening the ancient clay lake beds on which the Aztecs first built much of the city, causing it to crumble even further.

It is a cycle made worse by climate change. More heat and drought mean more evaporation and more demand for water, adding pressure to tap distant reservoirs at staggering costs or further drain underground aquifers and hasten the city’s collapse.

Much is being written about climate change and the impact of rising seas on waterfront populations. But coasts are not the only places affected. Mexico City — high in the mountains, in the center of the country — is a glaring example. The world has a lot invested in crowded capitals like this one, with vast numbers of people, huge economies and the stability of a hemisphere at risk.

One study predicts that 10 percent of Mexicans ages 15 to 65 could eventually try to emigrate north as a result of rising temperatures, drought and floods, potentially scattering millions of people and heightening already extreme political tensions over immigration.

The effects of climate change are varied and opportunistic, but one thing is consistent: They are like sparks in the tinder. They expose cities’ biggest vulnerabilities, inflaming troubles that politicians and city planners often ignore or try to paper over. And they spread outward, defying borders.

Around the world, extreme weather and water scarcity are accelerating repression, regional conflicts and violence. A Columbia University report found that where rainfall declines, “The risk of a low-level conflict escalating to a full-scale civil war approximately doubles the following year.” The Pentagon’s term for climate change is “threat multiplier.”

Nowhere does this apply more obviously than in cities. This is the first urban century in human history, the first time more people live in cities than don’t, with predictions that three-quarters of the global population will be urban by 2050. By that time, according to another study, there may be more than 700 million climate refugees on the move.

There’s much more at stake than the city’s well-being. At the extreme, if climate change wreaks havoc on the social and economic fabric of global linchpins like Mexico City, warns the writer Christian Parenti, “No amount of walls, guns, barbed wire, armed aerial drones or permanently deployed mercenaries will be able to save one-half of the planet from the other.”

Network of lakes

Mexico City occupies what was once a network of lakes. In 1325, the Aztecs established their capital, Tenochtitlán, on an island. Over time, they expanded the city with landfill and planted crops on floating gardens called chinampas, plots of arable soil created from wattle and sediment. The lakes provided the Aztecs with a line of defense, the chinampas with sustenance. The idea: Live with nature.

Then the conquering Spaniards waged war against water, determined to subdue it. They replaced the dikes and canals with streets and squares.

They drained the lakes and cleared forestland, suffering flood after flood, including one that drowned the city for five straight years.

Mexico City today is an agglomeration of neighborhoods that are really many big cities cheek by jowl. During the past century, millions of migrants poured in from the countryside to find jobs. The city’s growth, from 30 square miles in 1950 to a metropolitan area of about 3,000 square miles 60 years later, has produced a vibrant but chaotic megalopolis of largely unplanned and sprawling development.

The system of getting the water from there to here is a miracle of modern hydroengineering. But it is also a crazy feat, in part a consequence of the fact the city has no large-scale operation for recycling wastewater or collecting rainwater, forcing it to expel a staggering 200 billion gallons of both via crippled sewers like the Grand Canal. Mexico City imports as much as 40 percent of its water from remote sources and then squanders more than 40 percent of what runs through its 8,000 miles of pipes because of leaks and pilfering.

This is not to mention that pumping all this water more than a mile up into the mountains consumes roughly as much energy as does the entire metropolis of Puebla, a Mexican state capital with a population akin to Philadelphia’s.

Even with this mind-boggling undertaking, the government acknowledges that nearly 20 percent of Mexico City residents — critics put the number higher — can’t count on getting water from their taps each day. For some residents, water comes only once a week, or once every several weeks, and that may mean just an hour of yellow muck dripping from the faucet. Those people have to hire trucks to deliver drinking water, at costs sometimes exponentially higher than wealthy residents pay in better-served neighborhoods.

Overseeing the city’s water supply is Ramón Aguirre Díaz, director of the Water System of Mexico City, who is frank about the perils ahead.

“Climate change is expected to have two effects,” he said. “We expect heavier, more intense rains, which means more floods, but also more and longer droughts.”

The problem is not simply that the aquifers are being depleted. Mexico City rests on a mix of clay lake beds and volcanic soil. Areas like downtown sit on clay. Other districts were built on volcanic fields.

Volcanic soil absorbs water and delivers it to the aquifers. It’s stable and porous. Picture a bucket filled with marbles. You can pour water into the bucket, and the marbles will hardly move. Stick a straw into the bucket to extract the water, and the marbles still won’t move. For centuries, before the population exploded, volcanic soil guaranteed that the city had water underground.

Mexico City’s water crisis today comes partly from the fact that so much of this porous land has been developed. So it is buried beneath concrete and asphalt, stopping rain from filtering down to the aquifers, causing floods and creating “heat islands” that raise temperatures further and only increase the demand for water. This is part of the sprawl problem.

Sisyphean struggle

Deep below the historic center, water extracted from aquifers now can end up just beyond the city limits, in Ecatepec, at one of the largest pumping stations along the Grand Canal. The pump, completed in 2007, was built to move 11,000 gallons per second, essentially water that now needs to be lifted up from where the canal has collapsed, just so that it can continue on its way.

The man in charge of this undertaking is Carlos Salgado Terán, chief of the department of drainage for Zone A in Mexico City. According to Salgado, the Grand Canal today is working at only 30 percent of capacity because of subsidence, the gradual caving in or sinking of an area of land. He admitted that it was a Sisyphean struggle to keep up with the city’s decline. Parts of the canal around Ecatepec have sunk an additional 6 feet since the plant was built, he said.

The canal is wide open, a stinking river of sewage belching methane and sulfuric acid. Apartment blocks, incongruously painted cheerful Crayola colors, hug the bank.

The district of Tlalpan is on the opposite side of Mexico City. There, Claudia Sheinbaum, a former environment minister who developed the city’s first climate-change program, is now a local district president. “With climate change, the situation will only get much worse,” she said. She seconded what Aguirre had said about the threat of drought. “Yes,” she said, “if there is drought we are not prepared.”

For the time being, Well 30 helps supply Tlalpan with drinking water. One recent morning, large trucks, called “pipas,” crowded a muddy turnoff beside the highway. From a low cinder-block building, painted red, scrawled with graffiti and crowned in barbed wire, sprouted two long, angled pipes connected to dangling hoses. These pipes plunge 1,000 feet down to reach an aquifer. Trucks wait their turn to fill up, positioning themselves beneath the hoses.

There are places in Mexico City that even pipas can’t reach, where the precariousness of the entire water system, and by extension the whole city, is epitomized in a few scruffy acres.

Diana Contreras Guzmán lives in the highlands of the district of Xochimilco, where the roads rise almost vertically and dirt byways lead to shanties made of corrugated tin, cinder block and cardboard. A young single mother, she lives with nine relatives in a one-room shack.

Guzmán’s family earns $600 a month. Family members ultimately have to spend more than 10 percent of that income on water, enough to yield about 10 gallons per person per day. The average resident in a wealthy Mexico City neighborhood to the west, nearer the reservoirs, consumes 100 gallons per day, experts note. The wealthy resident pays one-tenth what Guzmán does.

Meanwhile, the Mexican federal government envisions constructing a giant new airport on a dry lake bed, exactly the worst place to build. It recently cut to zero federal money budgeted for fixing the city’s pipes and other critical infrastructure. At the same time, the federal government has its own agenda, promoting highways, cars and sprawl.

That disconnect between local and federal officials is not unique to Mexico. Often big cities find themselves undermined by state and federal politicians catering to a different electorate, as if in the end the consequences won’t be ruinous for everyone.

“There has to be a consensus — of scientists, politicians, engineers and society — when it comes to pollution, water, climate,” Sheinbaum, the former environment minister, stressed. “We have the resources, but lack the political will.”

It turns out Sheinbaum herself lives in a house that can count on water from the tap only twice a month.

So she, too, orders pipas to come to fill her cistern.