via Co.Exist:
 
Managing water resources in a rapidly-growing city can be problematic. Floods give much-needed water, but too much rain at one time can overwhelm a system. Meanwhile, droughts leave people with no water at all, and keeping water clean is always an issue. In Mexico City, poor management threatens to leave 22 million people without water in the near future. Leaky pipes alone account for a 40% loss of water that is pumped from nearby mountains. Already, more than a third of households lack adequate access to water.

 Isla Urbana is trying to change this with inexpensive, sustainable rainwater harvesting systems. The project was conceived while two Mexican-American students, Enrique Lomnitz and Renata Fenton, were studying industrial design at the Rhode Island School of Design. “We repeatedly encountered the subject of water scarcity and became inspired to design rainwater harvesting systems for these communities,” says Lomnitz.

 They began physically installing systems in 2009, in the Ajusco Medio region of Mexico City, “because we met people there who were very interested in the system, and because the region combines extraordinary rainfall with chronic and widespread water shortages, making it ideal for rainwater harvesting,” says Lomnitz. Rainwater harvesting is pretty simple: the system captures water off the roof of a building. Then the water passes through a bypass that diverts the first rains of the season through a large first flush that separates the first 100 to 200 liters of rain from each storm. Only the later, cleaner waters of a rain event go into the cistern, says Lomnitz. The water generally gets stored in the building’s existing cistern, though sometimes a plastic tank is installed when a cistern is not available. The water is chlorinated, and goes through a sediments filter and an active carbon filter.

 Isla Urbana uses materials from local stores and trains local personnel to construct and install the systems--giving work as well as a way to gather and store water. The cost for each system is only about $350. Isla Urbana is a joint project between an NGO, theInternational Renewable Resources Institute and a small business called Solución Pluvial. Development and sale of rainwater harvesting systems is done by the business, and education, training, and subsidy models are done by the NGO. Isla Urbana’s rainwater harvesting is meant to complement the conventional water supply, not replace it “The water is then clean enough for all domestic uses, though we generally do not recommend it for direct drinking, unless additional filters are installed,” says Lomnitz.

In a drought, families can rely more on the conventional system, while during a wet year, the rain will displace more conventional water, he says. If rainwater harvesting were properly implemented throughout the city, Isla Urbana says that it could provide 50% of the city’s water supply. So far, the organization has harvested 29,300,000 liters of rainwater and installed 725 systems. In the future it hopes to develop better and more accessible systems that provide increasingly high quality and low maintenance water, something that will help everyone have a better life.