Mexico City Has Long Thirsted for Water. The Crisis Is Worsening.

A collision of climate change, urban sprawl and poor infrastructure has pushed Mexico City to the brink of a profound water crisis.

The groundwater is quickly vanishing. A key reservoir got so low that it is no longer used to supply water. Last year was Mexico’s hottest and driest in at least 70 years. And one of the city’s main water systems faces a potential “Day Zero” this summer when levels dip so much that it, too, will no longer provide water.

“We’re suffering because the city is growing immeasurably and it cannot be stopped,” said Gabriel Martínez, 64, who lives in an apartment complex that struggles to get enough water for its roughly 600 residents. “There aren’t enough resources.”

Mexico City, once a water-rich valley that was drained to make way for a vast city, has a metropolitan population of 23 million, among the top 10 largest in the world and up from 15 million in 1990. It is one of several major cities facing severe water shortages, including Cape Town; São Paulo, Brazil; and Chennai, India. Many are the consequence of years of poor water management compounded by scarce rains.

And while Mexico City’s problems are worsening, they are not new. Some neighborhoods have lacked adequate piped water for years, but today, communities that have never had shortages are suddenly facing them.

Experts were warning about dwindling water supplies almost two decades ago to little avail. If the capital’s water network was already held together by a thread then, now “some parts of the system are falling apart,” said Manuel Perló Cohen, an urban planning researcher who studies Mexico City’s water system.

“Mexico is the biggest market in the world for bottled water,” said Roberto Constantino Toto, who heads the water research office at the Metropolitan Autonomous University in Mexico City. It is a reflection, he added, “of the failure of our water policy.”

Exceptionally dry conditions are the immediate source of the city’s water plight. Mexico has long been vulnerable to droughts, but nearly 68 percent of the country is in moderate or extreme drought, according to the National Water Commission.

The Cutzamala water system — one of the world’s largest networks of dams, canals and pipes that supplies 27 percent of the capital’s water — is at a historically low 30 percent of its normal capacity, official figures show. At the same point last year, it was at 38 percent, and in 2022, it stood at 45 percent.

Officials have projected June 26 as an estimated Day Zero, when the Cutzamala system could drop to the 20 percent base line where it would no longer be tapped to provide water to Mexico City.

The water level at one reservoir fell so low that officials halted its use in April.

“It’s sad,” Juan Carlos Morán Costilla, 52, a fisherman who lives along the reservoir, said as he stood on heat-cracked ground that was once underwater.

Groundwater, which supplies most of the city’s water, is pumped out twice as fast as it is replenished, experts said.

The city’s water supply, some of which is brought in from far away, flows through old pipes along an 8,000-mile-long grid vulnerable to earthquakes and sinking ground, and where leaks have caused an estimated 35 percent water loss — more than the Cutzamala system provides.

The city’s water challenge has become an issue in elections next month.

President Andrés Manuel López Obrador, whose aides have said that Day Zero will not happen, has insisted that his government is already addressing Mexico City’s water problems. New wells were being dug, he said, and officials are working to end corruption involving water consumed by big industries. He has also proposed bringing more water in from outside the city.

Claudia Sheinbaum, Mr. López Obrador’s protégée who resigned as Mexico City mayor last year to become the leading presidential candidate, has defended her administration’s handling of the water crisis.

Scientists, she said recently, could not have predicted the prolonged drought, and, if elected president, she would present an ambitious plan to fix the issues.

The National Water Commission did not respond to repeated requests for comment.

Some areas of Mexico City have long been without sufficient tap water, including Iztapalapa, a working-class community and the capital’s most populous borough with 1.8 million people. Residents rely on municipal water trucks to fill cisterns or water tanks in homes or buildings. If that is not enough, people pay for private trucks or, in extreme cases, illegally tap water lines.

But as water has become scarcer, other areas of the city are facing increased rationing, including reduced flow and getting water during only certain times of the day or on certain days of the week. Water has been rationed to 284 neighborhoods this year, even to more affluent ones, compared with 147 in 2007.

“Boroughs that have never suffered from water problems in their life are going to have to really learn how to take care of it,” said Adriana Gutiérrez, 50, who manages and lives in a 154-unit apartment complex in Iztapalapa that relies on water trucks. Residents treat every drop as precious, using water from showers to clean their homes.

For 20 years, Dan Ortega Hernández, 50, never had a problem with running water at his barbershop in Mexico City’s Tlalpan borough. But in November, he said he turned on the faucet and nothing came out. Now, when he does get running water under the rationing plan, he fills a 1,100-liter tank and hopes it lasts until the next scheduled day for running water.

That is a more regular supply than at his home elsewhere in Tlalpan. He said municipal water trucks used to come every four days or so but now take longer, sometimes up to a month. Rather than using water at home, he washes the family’s clothes at a laundromat near his shop.

“It’s scary that we’re running out of resources,” he said.

There is no evidence that Mexico’s drought is attributable to climate change. But the effects are made worse by rising temperatures.

Mexico City’s average temperature rose by around 3 degrees Celsius (4.5 degrees Fahrenheit) in the past century, more than double the global average. Exceptionally hot days (above 30 degrees Celsius, or 86 degrees Fahrenheit) have doubled in some parts of the city, according to a 2020 study. That could partly be because of climate change, and partly because of the city’s exponential growth, with concrete and asphalt replacing trees and wetlands.

Heat aggravates a water crisis: People need more water and more water evaporates.

The latest Water Risk Atlas, published by the World Resources Institute, describes Mexico City as facing “extremely high” water stress, its highest category.

As Mexico prepares to head to the polls to elect a new president, the water problems have been largely overshadowed by other topics, like crime and the economy. Water has, however, been a main focus of the mayoral race.

Water will reach the entire city, regardless of where people live, one candidate said. The leaks that the governing party failed to repair will be fixed, another proclaimed. A master plan will be put in place, a third added, to unearth buried rivers that run through the capital.

“Now everybody is like, ‘Yeah, I’m going to solve the water problem,’” Dr. Perló said. “But I’ve heard this story many times before.”

Some progress has been made. An enormous $2 billion tunnel opened in 2019 to take wastewater from Mexico City to a distant water treatment plant. A program to harvest unutilized rainwater was launched in some poorer neighborhoods. A small section of Lake Texcoco, largely drained to build the city, was restored. More wells and aquifers are being explored.

But several experts said the steps taken so far had not been aggressive enough and others ill directed.

Most of the focus by city and national governments has been on seeking faraway watersheds that supply other Mexican states to quench Mexico City’s thirst. But the majority of the city’s treatment plants do not operate at full capacity. Many let wastewater go untreated, which is then discharged into rivers or lakes, polluting what could be alternative sources of water.

The estimated price tag for addressing the water crisis reaches as high as $13.5 billion, according to the city’s water agency.

The rainy season, which typically runs from roughly June to November, would usually help replenish Mexico City’s water systems. But the capital saw historically low rainfalls during last year’s rainy season.

The Day Zero warning by some experts has been a flashpoint in Mexico City, used to bash the governing party, which includes Mr. López Obrador and Ms. Sheinbaum. But it has also helped train the public’s attention to the deepening problem.

“It creates a feeling of fear, anxiety, worry,” said Fabiola Sosa Rodríguez, a water management and climate policy researcher.

Lizbeth Martínez García, 26, who lives in a hillside community in Iztapalapa where a weekly municipal water truck fills the tanks that supply the four families in her building, said she asked the delivery man about the future.

He told her, she said, that the future meant even less water.

“We’re scared,” she said.