Enrique Lomnitz
Director General
Isla Urbana
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Is Rain Water Harvesting the Key to Mexico City’s Water Woes?

By Cas Biekmann | Wed, 10/06/2021 - 11:52

Q: Why is water shortage such a prominent issue in Mexico?

A: Mexico is a particularly vulnerable country when it comes to water issues, a fact evidenced by the reality that over 10 million Mexicans still do not have access to even the most basic water services. This problem has to do with the uneven distribution of water geographically. It is further compounded by highly unsustainable management, particularly in areas like Mexico City. Seventy percent of the water used in that city comes from aquifers directly underneath it, with overextraction so extreme that the city is literally sinking as a result. It is amazing that a city originally built on a lake is now among those most likely to run out of water in the world. Decisions made in the past, such as draining the lakes of the Mexico City basin and using the rivers as the main arteries of the sewage system, may have seemed to make sense at the time they were made. Nevertheless, the result is now an extremely unsustainable situation that is very difficult to reverse.


Q: What is needed to stop the process of continuous decay?

A:  It is very difficult to fix the underlying causes of Mexico City’s water crisis. The infrastructure and management model that brought us into the crisis has four hundred years of inertia behind it.  Furthermore, the city was built in such a way that halting the practice of draining water out of the city would result in immediate catastrophic flooding. In the most general terms, the city needs to reach an equilibrium between extraction and replenishing its major water resources. This means both cutting back on the amount of water pumped out of the ground and increasing the amount of rainwater that makes its way back in. Simple though that logic may be, in practice it is anything but.

We focus on promoting rainwater harvesting at a household level because it helps improve water access and resilience in the places that suffer the most. It also introduces a new way of thinking about water infrastructure. Decentralizing water infrastructure, which bases it more directly on renewable sources, generating autonomy and local management, makes sense to us. Rainwater harvesting might not solve the city’s crisis by itself but it is an important part of the solution. What is more, it is technically, economically, and politically viable to do right now, which is not the case with many of the more structural changes that need to happen. The city must eventually begin to seriously reduce its water extraction and must increase infiltration.

This will involve recycling wastewater, restructuring water tariffs, stopping the urban sprawl into recharge areas, among a host of difficult actions. Rainwater Harvesting is a sort of low hanging fruit that can help demonstrate that different models of water management could be both viable and effective.


Q: How did Isla Urbana prove its concept to begin building an applied portfolio?

A: When we started Isla Urbana, we were convinced that rainwater harvesting could improve water access in marginalized areas. By doing so, it could help broaden the vision on what water infrastructure would look like in a mega city. However, it was not until we installed our first pilot system in 2009 that we could point to a case study and show that this hypothesis was true. Still, isolated rainwater harvesting systems have always existed. The actual challenge was in solving for how this ancient practice could be adapted to a polluted, modern mega-city, and how it could be replicated at a significant scale.

It was by gradually designing better and better technologies and learning how to work with communities and local governments to implement larger projects that these challenges started getting worked out. By demonstrating in practice how viable it was to implement large scale rainwater harvesting programs our proposal began building proofs of concept.

Today, Mexico City has a rainwater harvesting program that we helped design and structure. We have worked with local governments and participated in the creation of building codes that concern rainwater systems. We have found that rainwater harvesting provides a great deal of potential political capital because it allows you to quickly improve water conditions in places, especially that are difficult to supply by conventional means. We are now seeing much interest beyond Mexico City, in places like Guadalajara, where we have just completed a pilot project with the state government. Our goal is to expand to the rest of Latin America. In Mexico City many active rainwater harvesting companies are active. We see this as an important development in the fulfillment of our mission.


Q: How can harvesting technologies help address other issues outside of providing water?

A: Rainwater harvesting has multiple benefits beyond the immediate improvement in local water access. It provides a great deal of benefit to any individual family adopts the practice, but when implemented at a district or city-wide scale, the benefits are multiplied. Mass implementation of rainwater harvesting helps mitigate of flooding by keeping heavy rain events from saturating the sewers. When multiple homes start harvesting rainwater, the result is a reduction in demand on the grid. This means less extraction from the ground, and more water available for other families. There is also much to say about the value of teaching and equipping the population to participate directly in their local water management. It is these sorts of systemic impacts from mass rainwater harvesting implementation that interest us especially.


Q: How can Isla Urbana help address the financing of these systems?

A: Financing rainwater harvesting is a tricky problem. Water is highly subsidized and access is very uneven. It is generally the case that the places that suffer most water access problems tend to also be the most impoverished. This means that even though rainwater harvesting systems are not particularly expensive, they are often beyond reach for those who need them most. We have often gotten past this hurdle by working directly with local governments which have funding and are interested in improving their constituents water access. However, to reduce dependence of government funding, we are currently in the process of piloting credit models whereby people can pay as they go. Using this, we can make rainwater systems directly accessible to those who need them most.

Isla Urbana is a startup focused on technology to capture rain. It aims to create self-sufficient, sustainable and resilient access to crucial water supplies.

Cas Biekmann Cas Biekmann Journalist and Industry Analyst