Lluvia para todos: How rainwater harvesting transforms communities in Mexico

Editorial Note:
The following is the first installment of a series of three articles completed by Sean Donnelly, in conjunction with Isla Urbana USA, a 501(c)(3) group focused on addressing water scarcity through rainwater harvesting. The original article can be found on the Isla Urbana Blog.

By Sean Donnelly

Lluvia Para Todos: How Rainwater Harvesting Transforms Communities in Mexico

In November of 2024, I had the opportunity to travel with a cohort of graduate students and faculty from Virginia Tech’s Executive Master of Natural Resources (XMNR) program to Paraje Quiltepec, an informal settlement on the outskirts of Mexico City. We were joined by Delfin Montañana, Director of Socio-Economic Education at Isla Urbana, who guided us through the community and shared how the organization is working directly with families to address water insecurity by harvesting rainwater.

Seeing Isla Urbana’s impact firsthand inspired me to maintain a relationship with the organization and to do what I can to help them in accomplishing their mission. As part of that relationship, I’ve begun an investigation into the transformational work Isla Urbana is doing on the ground in Mexico.

The following is the first of three investigative reports on Isla Urbana and the impact their work is making on real people throughout Mexico City and the 31 surrounding states that form the Republic of Mexico.

The Promise of Rainwater Harvesting

Rainwater harvesting is an increasingly popular water management strategy — a highly sustainable practice that involves collecting and storing rainwater, typically from rooftops, for later use. It helps conserve potable water by providing an alternative source for non-drinking needs such as irrigation, toilet flushing, and landscape maintenance. This reduces demand on municipal systems and groundwater supplies — especially important in areas facing water scarcity.

When additional filtration methods are installed, a rainwater harvesting system can provide water that is safe for all uses, including cooking and drinking.

Rainwater harvesting also helps mitigate stormwater runoff, which can carry pollutants into local waterways and contribute to erosion or flooding. By capturing rain where it falls, the system supports local water cycles, decreases infrastructure strain, and builds resilience against climate variability. Economically, it can lower utility costs and delay the need for costly infrastructure expansions.

Rainwater harvesting empowers communities to manage their own water resources more sustainably and equitably, making it a key tool in both urban sustainability and climate adaptation planning. While Isla Urbana’s work focuses on rainwater harvesting in Mexico, the practice is gaining traction globally — including in the United States, perhaps closer to home than many realize.

Rainwater Harvesting at Virginia Tech

Virginia Tech incorporates rainwater harvesting as a key part of its sustainable water management strategy on the Blacksburg campus and at satellite campuses across the state. On the main campus, captured rainwater is used primarily for irrigation, reducing the demand on potable water supplies and supporting eco-friendly landscaping.

This practice aligns with the university's commitment to environmental stewardship and is integrated into both existing infrastructure and new building projects. Academic Building One at Virginia Tech’s Innovation Campus in Alexandria, Virginia, boasts a 50,000-gallon rainwater harvesting system. Water harvested from the building’s rooftop replaces potable water that would otherwise be used for purposes like flushing toilets and cleaning, greatly reducing the building’s overall water needs.

In addition to harvesting rainwater, the university utilizes efficient irrigation systems and drought-tolerant plants to further conserve water. These initiatives form part of a broader sustainable water management system that includes monitoring stormwater runoff, maintaining refill stations, and managing a complex utility network — all aimed at minimizing environmental impact and promoting long-term water resilience.

These efforts support Virginia Tech’s larger sustainability goals, including reducing greenhouse gas emissions and promoting responsible resource management university-wide.

Virginia Tech’s Executive Master of Natural Resources program (XMNR) has been working with Isla Urbana since 2022. Each year, students have had the opportunity to work alongside the organization as part of their 10-day Global Study and capstone project. The XMNR program is planning to work with Isla Urbana once again this fall, and the partnership continues to strengthen.

“The students are a lot of help. There have been a lot of ideas that have actually worked. One of the student projects helped our communications team. One helped with outreach,” Montañana said.

“For the future, I would really like to continue the relationship and also move into research or more formal educational processes.”

The water issue in Mexico

In the heart of Mexico City — one of the largest and most densely populated urban areas in the world — millions wake each morning uncertain if water will flow from their taps. Despite seasonal deluges and torrential summer rains, the city and much of the country face ongoing water challenges.

Decades of heavy demand, aging infrastructure, and a changing climate have placed strain on reservoirs and aquifers. In some neighborhoods, particularly on the city’s outskirts, residents may go days or even weeks without running water, relying instead on costly and inconsistent truck deliveries.

Across Mexico, 12 million people lack access to potable water, and only 14 percent of households receive water 24 hours a day. In rural areas, 8 out of 10 people live without access to basic water services.

In many parts of the world, when water is scarce, it is women and young girls who carry the heaviest load — literally. In households lacking piped water, women and girls are responsible for collecting it in roughly 7 out of 10 cases, with girls almost twice as likely as boys to take on this role.

Per UNICEF, this daily task consumes up to 200 million hours collectively around the world — time that could otherwise be spent in school, earning income, or participating more fully in community life.

But amid the scarcity, a quiet revolution is taking shape — on rooftops, in schools, and across both rural and urban communities. Rainwater harvesting, a simple yet powerful solution, is transforming lives.

According to UNICEF, just 1 out of every 100 liters of rainwater is harvested globally — and according to Isla Urbana, therein lies the opportunity to address water challenges in Mexico.

The Mexico City–based nonprofit organization has spent more than a decade demonstrating how simple rainwater harvesting systems can make a big difference.

According to Montañana, the organization was born out of necessity.

Isla Urbana started as a group of visionary young people who wanted to “do something in order to transform the current situation” with respect to water access in Mexico.

Since 2009, the group has installed more than 40,000 systems across Mexico — mostly in areas where water service is unreliable or limited. These systems collect, filter, and store rainwater from rooftops, giving families a steady, local source of clean water.

A well-designed rainwater harvesting system can meet a household’s water needs, including drinking water, for anywhere from five to twelve months each year, depending on rainfall and system size. By capturing and storing rain during the wet season, these systems help reduce reliance on overused aquifers, allowing them time to naturally recharge.

In addition to easing environmental stress, rainwater harvesting also lowers the financial and ecological costs associated with water transportation, offering both economic and sustainability benefits to communities. Isla Urbana estimates that their rainwater harvesting systems collectively harvest 6.6 billion liters of rainwater annually.

A Community Approach

Isla Urbana’s approach is unique in its recognition of the human dimension of the water challenge. By providing families with direct access to water, these systems alleviate daily burdens and create new opportunities, particularly for women and children.

From families who now cook and bathe with confidence to schools where children no longer miss class due to water shortages, communities are reclaiming agency over a resource long taken for granted. What began as a grassroots partnership to complement existing government efforts has become a model of resilience and environmental justice.

It’s a simple idea with far-reaching impact — one that could work in other parts of the world, if given the right support.

Isla Urbana’s rainwater harvesting systems are designed to be both effective and easy to maintain. Rainwater is collected from a clean, well-maintained roof and funneled into a system of gutters. From there, it passes through a first-flush diverter — known as a Tlaloque — which discards the initial flow of rain, removing roughly 75 percent of surface contaminants.

Water then passes through a secondary filter, which captures larger debris such as leaves and branches. The filtered water enters a storage tank through a calmed inlet that slows the flow and allows additional sediment to settle at the bottom. A pump with a floating intake draws water from just below the surface, where it is cleanest.

Depending on the system’s configuration and the level of water quality required, additional filtration can be added to remove finer particles. With proper design and regular maintenance, these systems can provide high-quality water for nearly all household uses. When equipped with a final purification stage — such as a gravity-fed filter — the water becomes safe for drinking and cooking as well.

Isla Urbana prioritizes initiatives that promote social and environmental well-being. Their webpage outlines community-centered programs and highlights how their work positively impacts women, schools, and indigenous communities. In the following passages, I explore some of the real-world impacts this organization is having on those groups — and share a few of their stories.

According to the University of Pennsylvania, about 22 percent of Mexico City and between 60 and 70 percent of the Mexican countryside consist of informal settlements. These communities were often built without the zoning and building codes needed to ensure access to municipal water networks. Accordingly, families in these areas must often find their own ways to secure water — a responsibility that falls overwhelmingly on women and girls.

Prior to Isla Urbana’s involvement, Paraje Quiltepec was one such community.

“Before there were public roads, the water truck could not arrive,” explained Elena Cruz outside her home in Paraje Quiltepec.

Accessing water was a daily challenge for Elena long before Isla Urbana’s rainwater harvesting system was installed. For years, her only source came through a hose extended from the home of a generous neighbor, running through several adjoining properties.

“If the hose became blocked — by debris or a kink in the line — I had to trace it back on foot,” she said.

“When the obstruction was located on someone else’s property and they weren’t home, there was little I could do but wait. They would use hoses from the nearest road to deliver the water to us. If the neighbors were not home that day or the hose was obstructed for any reason, we would simply go without water.”

Elena explained that water trucks, which only became an option after the community came together to build its own roads, were an expensive and inconsistent solution that added complications of their own. Her family had to request water through municipal channels or private providers each time their storage tanks needed refilling.

Private deliveries by truck can be costly — an average of about $75 per household per month. In comparison, a rainwater harvesting system like hers costs roughly $3 per month to maintain.

Additionally, each truck delivery requires scheduling in advance. Residents are told their water will arrive sometime between one and fifteen days. This means someone must remain at home during that window or risk missing the opportunity to resupply. Women are frequently the ones who take on this responsibility.

In communities like Elena’s, Isla Urbana works alongside residents to install rooftop rainwater harvesting systems that expand access to clean water while easing financial burdens. With a reliable water source, families are able to reallocate time and resources toward critical needs such as education and healthcare.

Elena credits the stability provided by the system with helping her children pursue university degrees and build successful professional lives. Consistent water access also contributes to improved hygiene, reduces strain on local infrastructure, and lowers the risk of waterborne illnesses — strengthening both individual and public health outcomes.

Isla Urbana’s systems have, quite literally, changed Elena’s life. Water security has opened doors to new opportunities for herself and her children. Harvesting rainwater has allowed her to increase the yield of the fruit trees in her yard, providing food for her family and an additional stream of income.

Her children were able to stay in school and pursue rewarding careers. Improved water security has completely transformed what is possible for her family’s future.

“Not only do we have clean drinking water,” Elena said, “but I also use the grey water to grow fruit trees. The fruits we gather produce jams that we sell, among other produce, which has financed my children’s education. They studied computer engineering.”

The impact of Isla Urbana’s work extends beyond reducing the time women and girls spend collecting water. Many women in the community are trained as system installers and advocates, challenging traditional gender roles and becoming agents of change.

Elena Cruz is one such example. She was the first in her community to invest in a rainwater harvesting system. Her example encouraged neighbors to place trust in Isla Urbana’s work and to explore the benefits of sustainable, community-driven water management.

The story of Paraje Quiltepec and Isla Urbana highlights the powerful connection between water security and gender equity, reminding us that, in some cases, solutions really can fall from the sky.

The organization’s work demonstrates that meaningful community engagement is essential — when residents are directly involved in the design and implementation of solutions, those efforts are more effective, more sustainable, and more widely embraced.

By improving access to water, Isla Urbana is not only helping women and girls reclaim their time and pursue opportunities; they’re also fostering leadership. When women are empowered to lead on issues of water access, the benefits extend far beyond the individual, creating ripple effects that strengthen entire communities.

In Mexico City, water represents more than survival. For many women, it means freedom, opportunity, and agency. Isla Urbana’s work is a testament to what becomes possible when water is seen not just as a basic need, but as a pathway to empowerment.

Through innovation, collaboration, and a commitment to equity, the organization is setting an example with global relevance — one rooftop at a time.

For Elena Cruz and thousands like her, rainwater harvesting is more than a technical solution — it’s a symbol of dignity, resilience, and possibility. In a city where water too often equals struggle, Isla Urbana is showing that hope — and equity — can truly fall from the sky, if we are only willing to catch it.