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Mexico City’s problems with running water are acute: in the city’s poorest neighbourhoods such as Iztapalapa and Xochimilco, brown, murky water flows from the faucets just once a week, if at all. 

The irony is that water in this region abounds. Located in a valley 2250 metres above sea level, the Aztec city of Tenochtitlán – the precursor to today’s Mexico City – was once connected by a system of lakes and rivers. The Spaniards drained the basin to make way for their colonial city, and four centuries later, modernist urban planners put enormous effort into stemming the flow of water, drilling deeper and deeper into the earth to extract the resource, throwing the entire ecosystem off- balance. The lakes and rivers may be gone, but the ‘Venice of the Americas’, as the Spaniards called Tenochtitlán, remains etched in the collective memory as a symbol of a bygone era. 

Yet the water takes its revenge on the city every summer, when torrential downpours cause a series of deluges, leading authorities to declare a state of emergency and bringing the 25 million-megalopolis to a halt. On such days, streets turn into rivers, where the rainwater swirls with street pollutants, runs down the drain, and mixes with sewage coming from businesses and households. 

Harvesting rainwater for household use
Water scarcity has become such a fact of life that it has shaped the structure of homes in Mexico City. Many units have water cellars (‘cisternas’) with a capacity of up to 3000 litres, as well as containers (‘tinacos’) on the rooftops. When the government shut down the Cutzamala system for four days during a maintenance drill on November 2018, thousands survived without drawing from the network. 

Another innovation might become ubiquitous soon. At least that’s the vision of Enrique Lomnitz, one of the founders of the NGO Isla Urbana (Urban Island), which aims to turn every rooftop in the city into a rainwater-harvesting system. 

For ten years, Isla Urbana has been installing rooftop systems to collect this resource, which would otherwise go to waste. The idea was originally conceived as part of Lomnitz’s senior project at the Rhode Island School of Design. He teamed up with Renata Fermont to conduct ethnographic interviews and research the needs of low-income communities in Mexico City’s periphery. This led the pair to identify the fundamental flaws in the city’s water management. 

“We realised that the current model was drawing 2 or 3 times more water than it was putting in,” he says “and that changing this outdated model through infrastructure investment would be too costly: so we turned our attention to granularity.” This meant installing inexpensive (around USD 700) systems in every household without having to drill underground to update the old and inefficient infrastructure. 

The first system used spare parts from discarded materials found in the home of local resident Clara Gaitan. “There was a 3000-litre cistern in the house,” Lomnitz says, “and it was really exciting to see it overflow during those first rains.” Thanks to the system, Gaitan was able to survive for seven months without having to rely on water from the city’s network. 

Working from the community up
The system worked, but it needed improvements. To gain a better sense of the area’s needs, Lomnitz moved into a house in the periphery, where he lived for four years.

Those first systems made from repurposed materials served as a proof of concept. And as more people got involved, they started to attract attention from the local authorities. In 2011, Claudia Sheinbaum, an environmental scientist who was then the head of the District of Tlalpán, took notice and asked them to install 500 systems. This was the first time Isla Urbana had to contend with more complex logistics and developed a method to install and train families on a much larger scale. 

Today the patented system is highly adaptable to the conditions of each house. In its most basic form, water runs along the roof and down special drains, then through a patented filter called Tlaloque 500, through a leaf-filter, and finally into the cisterna for storage. More sophisticated versions include a water purifier and a carbon filter, which improves taste.

The water collected by most of Isla Urbana’s systems isn’t potable, but it can be used for cleaning the house, doing laundry, filling the toilets and showering. Since its foundation, Isla Urbana has been able to provide over 50,000 people with clean water (in some cases, year-round). 

Getting entire neighbourhoods off the water network
But the biggest challenge is yet to come: Sheinbaum, now Mexico City’s mayor, hopes to install 100,000 water filters on the rooftops of houses in Iztapalapa and Xochimilco. If the initiative works, Lomnitz believes that it could set a new precedent for urban governance, with entire areas of the city no longer depending on the government for daily access to water. 

On a cloudy Wednesday morning, I visited the installation of the filters in Iztapalapa. I rode in a pick-up truck with Javier Hernandez who, along with his brothers Gabino and Alejandro, has been installing the filtration systems since 2011. Javier, who comes from a low-income family and has an Isla Urbana system in his house, has overseen the installation of 16,000 systems.

Today he leads a group of 15 three-person brigades installing 36 systems a day in Iztapalapa. Together with his brother, who works installing systems in Xochimilco, they have installed 10,000 systems since the program started in April 2019. 

At Maria Contrera’s house, one brigade was busy installing a new system. In the 30 years since she has lived in Iztapalapa, Contrera has witnessed water gradually dwindle from the pipes. To ensure her nine family members have enough water to go around, she reuses the water from the laundry and showers and has installed water-savers in the toilets. “This is fabulous, it is excellent,” her husband, Ismael Garcia, tells me, as he overlooks the operation, “imagine how many litres of rainwater were going down the drain before!”

I visited another house whose system was installed in April 2019: “It was overflowing, two days ago,” Eugenio Reyes Lopez, the head of the family, told me excitedly as he pointed to the water collected, “it rained hard, but look at the water: it’s clear!”

We hang around with the family, discussing how much more water could be collected if they were to install a second system on another rooftop. As we make our way back, traversing a seemingly endless expanse of concrete streets, Hernandez reflects on his work: “We have installed 1000 systems in this part of Iztapalapa,” he tells me, “but I always like to go see the impact the system has on an individual family. This is what feeds my soul.”


Lead image: Lucas Espinosa, warehouse manager of Isla Urbana in Iztapalapa stands in front of the 3,000 litre cisterns. 

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