A Lost and Thirsty City: Mexico City’s Water Crisis

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The United Nations recognizes the right to safe drinking water and sanitation as a human right essential to the full exercise of life and of all human rights. However, weak infrastructure and climate change challenge Mexico City’s ability to provide clean and adequate water to residents. Mexico City’s water is literally disappearing. “I have no doubt that in 2022 there will be a crisis, the reservoirs are completely exhausted,” says water expert Rafael Sanchez Bravo.

What is happening?

The ancient Aztecs originally designed the origins of Mexico City atop Lake Texcoco and left the surrounding natural freshwater lakes untouched. However, as the city grew, the lakes were drained to make way for infrastructure, homes, and a growing population. With the expansion came an increasingly serious water security dilemma. Much of the city’s water supply comes from an underground aquifer which is being drained at an irreplaceable rate. As the aquifer is drained, Mexico City is rapidly sinking at twenty inches per year.

Despite heavy flooding and torrential rains, the city faces a water shortage. In fact, more than 20 million people do not have enough water to drink for nearly half the year. According to the BBC, one in five people only have access to a few hours of running water from their tap per week and 20% have running water for part of the day. Relying on clean water is unreliable for many.

Current projections estimate that global demand for fresh water will exceed supply by 40% in 2030. Mexico City, one of the largest cities in the world, has nearly 22 million inhabitants and is growing steadily, with population growth ahead of reach 30 million by 2030.

Mexico City is one of 11 cities set to reach what is known as day zero, or the day the water runs out. It is nothing less than a crisis. “Every drop of water that crosses the Mexican capital tells a heroic, tragic and unfinished story of urban growth and human development”, writes Jonathan Watts for The Guardian.

Where is the water?

There are several reasons why a city at the top of an aquifer and with a very heavy rainy season has difficulty providing drinking water to its inhabitants. Specifically, water security challenges are widespread and difficult for urban designers, environmentalists and politicians.

A lack of sanitary sewage treatment throughout the city hampers water collection and poses a huge challenge in keeping existing water clean for use. Also, the pipes in Mexico City are old and leaky. According to the University of Pittsburgh, Mexico City is losing 1,000 liters of water per second due to an outdated water system that was crushed by the fall of the city and punctuated by thousands of small leaks. Finally, rainwater harvesting exists, but no city-wide system is in place. When it rains, the water often mixes with sewage and cannot be used.

Why is the city sinking?

Mexico City ended all groundwater drilling in the city center in the 1950s, but water is being pumped from below into surrounding areas and GPS data has shown the city continues to sink. As water extraction has driven groundwater deeper and deeper underground, the clay lake bed is now completely dry and the compacted mineral soil is causing irreversible compaction. This phenomenon, called subsistence, has no miracle solution.

In addition, water from rainstorms cannot seep into the concrete-covered city and fill the aquifer. A 2021 study claimed there was no hope for significant recovery in elevation and storage capacity. Much of the water must be pumped to the city through hydroelectric engineering from reservoirs located thousands of miles away.

Image courtesy of Journal of Geophysical Research: Solid Earth

Climate change is a threat multiplier

Mexico continues to experience one of the most widespread droughts in decades. Unusually low rainfall has already reduced access to water in the capital. Cutzamala’s reservoirs outside the city supply a quarter of the city’s water, but in 2020 the reservoirs were almost 18 percentage points below normal levels. As the levels of precious reservoirs drop, city authorities have reduced the flow from the reservoirs, which has affected access to tap water. Some residents rely on water delivery trucks and even donkeys.

This event should repeat itself. “Climate change has definitely altered rainfall patterns,” Rafael Carmona Paredes, director of Mexico City’s water system (SACMEX), told the Thomson Reuters Foundation. “We have to prepare in many ways to be able to deal with these variations in weather conditions.” The researchers estimated that natural water availability for the city could decrease by up to 17% by 2050 as temperatures rise.

“More heat and drought means more evaporation and even more demand for water, adding pressure to tap distant reservoirs at exorbitant costs or further drain underground aquifers and hasten city collapse,” writes Michael Kimmelman for the New York Times.

The researchers highlighted potential future problems facing the water supply. Global warming could exacerbate Mexico City’s water crisis with less rainfall, algal blooms in hot reservoirs, and increased demand for water due to global warming.

What was done?

Mexico recognizes the urgent water problem facing its largest city. Mexico City has launched the Green Plan project, which will continue until 2022 with objectives such as reducing groundwater losses and repairing hydraulic infrastructure, among others.

Former President Enrique Peña Nieto signed a series of presidential decrees in 2018 to create water reserves in nearly 300 river basins across the country. And $7.4 billion was earmarked for water crisis mitigation by Mexico City Mayor Claudia Sheinbaum Pardo in 2019.

An expert offers a solution

While the current state and local executive orders are a big step toward a necessary goal, according to Loreta Castro Reguera, a Harvard-trained water-sensitive urban design (WSUD) expert and architect, the most effective approach is a decentralized one. and sustainable as well as accessible to communities across the city.

WSUD is an emerging approach to urban development aimed at minimizing the hydrological impacts of urban development on the environment. Latin America Reports spoke to Requera about his Mexico City-based team and their mission to design the city through infrastructural public spaces that promote access for affected communities and understand different water management strategies.

“It’s a paradox. It’s a disaster. Right now we have a sinking city and our infrastructure is literally breaking. And on the other hand we have no way for the water to filter [into the aquifer] naturally,” says Reguera. “And you can imagine how expensive it is to change the entire piping system.”

Loreta Castro Reguera. Image courtesy of the Holcim Foundation

His projects demonstrate that public spaces can simultaneously serve as parallel water management infrastructures. Reguera and his partner Jose coined the term “retroactive infrastructure”. It is non-traditional infrastructure that can solve rather than exacerbate water problems. Some projects include water filtration systems and the use of open spaces to collect and store rainwater in tanks larger than can fit in a building. “We want these spaces to become decentralized infrastructures,” she says.

“For example, we completely transformed the landscape of a park in a very poor community. It was on a hill and instead of just a slope, we terraced the slope and filled the terraces with local volcanic gravel, which is very permeable. We created filtration terraces and made them into a sponge to capture rainwater and filter it back into the aquifer. We removed the fences, opened the entrances and kept all the trees.

“It’s not like we’re solving the water crisis with rainwater harvesting, but it could help a lot if we start making reservoirs all over the city,” she says. “So the question is how do we start turning these reservoirs into open, public spaces. They can provide enough water for the whole city.

Reguera is hopeful. The city has been active in creating wetland systems to treat wastewater that will eventually become a source of water for surrounding areas. “It’s really great to see how the city is making an effort,” she said. “They are experimenting to see how well open spaces can work. It’s something that only started three or four years ago, so we won’t see a transformation immediately. But there is a lot of awareness right now.

Reguera describes parallel infrastructure work as “putting the city together with open spaces”. There’s no easy solution to Mexico City’s water crisis, but perhaps it lies in accessible common spaces above ground rather than below.

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