Isla Urbana: Rainwater Harvesting Systems (RWHS) in Mexico

Since 2009, Isla Urbana's rainwater harvesting systems (RWHS) have evolved through engineering, industrial design, and community understanding based on empirical knowledge gathered over the years. There have been challenges, such as creating innovative and efficient systems (without initial investment) that ensure good water quality with low material costs, while adapting to limited resources. The diversity of housing types in Mexico has led us to develop modular, adaptable systems. It has been a challenge not only at a technical level but also socially, helping us understand needs so the systems can be adopted, maintained, and effectively capture and filter rainwater.

The Isla Urbana RWHS provides a decentralized, autonomous, high-quality water source for 5-8 months a year. Its adaptive and modular, passive design ensures water quality in urban, rural, and industrial areas. The collectors are easy to operate and low-cost. Implementation methods and financing programs promote adoption, especially for those in need. The project has evolved through key stages: the Tlaloque as a first-flush device and icon, a shift from rotomolded to blow-molded manufacturing, massification while maintaining social focus, and now professionalization through knowledge systematization and improved quality controls. Interaction with users, monitoring, and follow-up has allowed for adaptation and optimization.

Isla Urbana was the first organization to design and implement large-scale rainwater harvesting projects and programs, detonating a rainwater harvesting market in Mexico, creating hundreds of jobs since then, and demonstrating its viability as a public policy tool. Environmentally, Isla Urbana has made an impact with 46,000 systems installed that capture 6 billion liters of water and save 200,000 water trucks annually. Socially, more than 500,000 people have been directly benefited by providing them access to water, thereby improving their general quality of life.

Key features of Isla Urbana's RWHS design are the “Tlaloque” and the “Tlaloquito,” the first-flush devices. Their design allows them to adapt to local environmental conditions (urban, periurban, rural contexts) and capture the first volume of water (0.5 to 2 L/m2 depending on location and roof surface connected), increasing harvested water quality by up to 70%. Both are self-cleaning thanks to their conical shape at the bottom, through which the initial rains exit without sediments. Additionally, to optimize costs, space, and efficiency, sedimentation and decantation is done within storage, thanks to Isla Urbana’s Turbulence Reduction and Floating Suction devices. These components are simple, affordable, passive and help address roof dirtiness and improve water quality without significant costs or complex operation. The other, equally important and key feature to Isla Urbana, is the development and improvement of the social methodologies that ensure the adoption of the systems: skill transfer and capacity building without which success is rarely achieved. From language used to didactic material produced and data collected, and the information generated by the ongoing interaction with users to inform our design processes.