Photo: Isla Urbana

New Rainwater Harvesting Seek to Ease Droughts in Mexico

Environmental groups are partnering with municipal and rural governments to install systems that store rain in homes and schools to quench some of the nation’s thirst. 

Verónica Barrios, 44, didn’t give it much thought when two men arrived at her Monterrey City, Mexico, home in July with an invitation for her to participate in a rainwater harvesting program. She had experience with empty promises from people, often from the government, offering her things but never coming back. So when Isla Urbana, a nonprofit, installed the city’s first rainwater system in her house less than a week later, she was incredulous.

“It’s the first time I’ve won something,” she said.

Isla Urbana installed the system as a part of a pilot program between the company and the city government to ease the drought plaguing Monterrey residents. A total of 100 houses and 15 schools are expected to have water storage systems installed by the end of the year. The plan is to “trigger a massive project of several thousand systems starting next year,” said Emilio Becerril, managing director of Isla Urbana. The systems installed in Monterrey are intended to help the people most in need of water. 

Photo: Isla Urbana

To the company and the parched population, it was about time. Although rainwater harvesting systems are not new to the country, governments haven’t taken them seriously enough to invest in. But the increasing water shortage across the country driven by the overexploitation of the resource, populations concentrated in water-stressed areas, obsolete and poorly-maintained water infrastructure and, finally, climate change, has led some government leaders to reconsider. 

In 2017, for example, the National Water Commission launched PROCAPTAR, a program that aimed to provide water to the rural population of Mexico experiencing technical and economic difficulties getting supplied through the pipeline system. The problem is that the program’s guidelines are very strict, and many communities have rainfall levels too high to qualify for it, said Gabriel García, an engineer working at the Mexican Institute of Water Technology (IMTA).  “Evaluations for this program are not open to the public,” he said, which makes it very difficult to assess the real success or failure of the program.

So in 2020, IMTA joined forces with the Center for Rural Development Studies, a community foundation, to bring these systems to rural populations. Their plan is to show that the technology can work outside the government’s rigid rain-flow parameters, and determine how well people will follow the instructions to use it. The organization’s plan is to use their findings to advise the federal government on how to improve their manuals and policies for rainwater harvesting systems. The project, which began last year, is funded by the National Council for Science and Technology. 

Pursuing a similar goal for urban populations, the Secretariat of the Environment of Mexico City in 2018 launched the Programa Cosecha de Lluvia (Rain Harvest Program), which promised to have 100,000 rain harvesting systems installed in Mexico City by 2024. This effort resulted from collaborative research between Isla Urbana and the University of Arizona to determine which people in Mexico City who don’t have access to water could benefit from the technology.

Since then, in addition to Monterrey, other cities like Guadalajara and, potentially, San Luis Potosí have been trying to implement that program in their municipalities. Local governments invite nonprofits like Isla Urbana as well as for-profit companies to propose a project, and then they choose one to implement the capturing, storing and filtering technology.

Photo: Isla Urbana

But regardless of which communities get the programs and which companies get the contracts, the weather has to cooperate for them to succeed.

A day after her system was installed, more unexpected guests arrived at Barrios’ house in Monterrey. This time it was a crowd that explained they were there to inaugurate the system. “They showed the project to the mayor, how it worked and everything,” she said. But the excitement waned when the rains were slow to come and fill the system.

“What’s the use of having a water tank if you don’t have water?” her neighbors would tease. But when it finally rained, “it overflowed,” said Barrios, who rushed to do laundry, clean the house and do other things to bring down the levels of the container so it could collect more water. 

Depending on how much rain falls, the storage capacity of the tanks and how people ration water, the stored precipitation can last from thirty days to five or even eight months in places with long rainy seasons. 

The standard system that Isla Urbana and other companies install, designed to fit in the small spaces available in city houses, is of 2,500 liters (550 gallons). In the countryside, some tanks can hold up to 200,000 liters (44,000 gallons) or more. But the higher prices for larger tanks are unaffordable to people on their own, so those programs rely on investments from governments or private companies. 

Still, it is much cheaper to invest in the installation of these tanks than in a mega infrastructure project that costs billions of pesos, said Becerril. 

“This is like a decentralized infrastructure that you can relatively easily take basically anywhere as long as it rains,” he said. “But when you are dealing with this type of crisis, it is very important to integrate several solutions at the same time.”

Critical to the success of the programs are studies completed prior to their implementation to assess how much the communities could benefit from the technology and how much and how heavily it rains on them. Unlike Mexico City, Monterrey receives rain in just a few months of the year, but in very concentrated amounts. That translates to approximately three months of water autonomy annually from every 550 gallon tank. 

Solution From the Sky Depends on Programs, Education and Fixtures on the Ground

The systems’ effectiveness also relies on its users changing their water use habits to best utilize the technology and often to maintain it. That’s why it’s important that the technology is accompanied by public policies and incentives. 

In a study in Queensland, Australia, Suzanne Dallman, former Professor of Geography at California State University, found that measures implemented by the government after the so-called “Millennium Drought” of 2012 were successful on the whole due largely to the wide range of additional programs that accompanied the installation of 257,000 residential rain tanks of at least 792 gallons. Some of the actions included changing codes to require new buildings to have a rainwater capture system, and telling people they couldn’t water outdoors unless it was with water harvested from rain. They also considered how people’s behavior could impact the program.

“You’re relying on the users, on the homeowners, to maintain systems,” Dallman said. ”Sometimes they do, and sometimes they don’t.”

To encourage conservation, the government distributed more than a million shower timers, invested in rebates and incentives for water-efficient appliances and fixtures, rain tanks and home plumbing inspections and created massive public education campaigns. 

Photo: Isla Urbana

Water contamination poses another challenge. Especially in big cities, pollution in the environment the rain travels through, such as the roofing materials that the raindrops fall on before being captured, can taint the water. Some critics of the systems warn that toxic PFAS chemicals can contaminate the rainwater, making it undrinkable.

Of the countries that harvest rainwater as a solution, like Brazil, France, Germany and Australia, Mexico is the only one that allows distributing the water for drinking. But, that’s not as dangerous as it sounds, said Ian Cousins, a professor in the Department of Environmental Science at Stockholm University. 

“We actually had higher exposure [to PFAS] 20 years ago than we do now,” he said. 

The concern over the PFAS in the world’s rainwater developed from modifications in the national and international guidelines overseeing the safety of drinking water, he said. As the understanding of the chemicals changed, regulators, like the United States Environmental Protection Agency or the European Chemicals Agency, reduced the advised concentration levels of those substances in potable water. 

“You’re going to get them if you drink treated water or rain water,” he said of PFAS. “It doesn’t make any difference where your water comes from.” Cousins advises sending water through an activated carbon filter before drinking it to remove PFAS. 

Photo: Isla Urbana

Becerril, in Monterrey, has a system called a tlaloque that discards the first water from a rainstorm, which is often dirty with contaminants and debris from the surface where the precipitation lands. The cleaner water that follows then passes through a filtering system to remove solid residues and is stored in a tank. That water will go through two more filters and into a cistern that feeds the house’s water pipes. The cistern contains colloidal silver spheres to eliminate the formation of microorganisms. This water is good for bathing, washing clothes and watering plants, among other things, but before drinking it, it should be disinfected with  a calcium hypochlorite dispenser and an activated carbon filter. 

Both García, at the Mexican Institute of Water Technology, and Becerril highlighted that more responsible use of water is key to solving the region’s water crisis, and that can only happen with education and ongoing support for the programs. Both Isla Urbana and the IMTA projects do follow up visits to see if the technology is working for people or not, and help them develop a different relationship with the resource to promote conservation. In schools, more extensive programs about the project include lessons about water culture for new generations of users.

“The goal is that, despite the fact that generations are changing and older students leave school, everyone takes ownership of the project and continues with it,” said Becerril.

Photo: Isla Urbana

How widely people in Mexico will adopt this technology to quench their thirst remains to be seen. García and Becerril worry that the lack of transparency in programs such as PROCAPTAR opens the door to corrupt practices, and they know that rainwater harvesting is just one of many steps they need to take. 

In the meantime, however, people are grateful for every extra drop of water they can get.

“I think that’s a magnificent help because purified water to drink is where we are spending the most,” said Becerril, “especially right now with the heat you consume more water all day.” 

Isla Urbana is shortlisted for the 2022 Transformative Cities People’s Choice Award. Transformative Cities, a global process to search and support transformative practices and responses that are tackling global crises at the local level, helped finance the reporting of this story. You can still vote for the initiative that you find deserves more attention and resources to scale up until the 6th of November at: