Rain. Coming back from a summer in Mexico, everyone expects me to be tanner. Like other assumptions about a country as big and diverse as Mexico, not necessary so… San Cristobal de las Casas was gorgeous. San Cristobal was interesting. San Cristobal had great coffee, chocolate, people, languages, music and fun. San Cristobal was not that sunny… in fact, it rained about an inch per week during the five weeks of Appropriate Technology classes. There is a dry season, we just weren’t there for it. The rain is enjoyable, but the waterborne and foodborne illnesses that affect many (including me and the students) are not. It was in that context that we were so excited to have one of the five projects for the Humboldt State University – Chiapas 2010, full immersion in Spanish and Appropriate Technology, summer abroad program be rainwater catchment systems.
Rainwater Catchment At A Glance
Description: Catching rainwater (often before it hits the ground), filtering and storing it for future use.
Outputs: Usable, potable if filtered, water
Improvements: reduced run-off and erosion, increased access to clean water, reduced time spent collecting and transporting water, reduced mosquito breeding areas near home
A team of four students collaborated with local designers and community members to build three systems: one with the appropriate technology demonstration home of Juan Hidalgo in San Cristobal and two with a community near Acteal. The student designers went through a few iterations at the demo house, testing and finding leaks, until they got it right. They then used that information to design and build the systems with the more rural community. They also worked with Otros Mundos to start the construction of two 20,000 liter ferrocement tanks for storage. Here is their rainwater system documentation in English and Spanish. Here is some of the needed math for design.
- Using a first flush in Chiapas (I haven’t seen it other places here)
- Using a PVC cap with one hole drilled high (for drainage and a cord for removing it) as the drain of the first flush. Having this hole high on the end-cap of a 90 degree elbow will keep it from plugging soon and keep the spray away from the house and into a bucket for reuse.
- Using used vegetable oil to protect the wood supports.
- Using costales (earth bags) for the base of one system.
- Using tamped sand, instead of concrete, for the supports of one system.
- Using wire to keep bent roofing metal in a channel shape.
- Finish the ferrocement tanks in the community.
- Revisit the systems in one year to see what went wrong.
- Build a database of local rainwater systems (see image) and feedbacks.
- Workshops and community meetings on rainwater collection and water in general.
*This image is not our rainwater system, but it is the coolest way I have seen PVC used as a gutter (which is usually a big pain and doesn’t work all that well). We are going to try out this system at Otros Mundos. In this image, Tania and Claudia are assessing its construction. Now take that system and get a first flush on it and you’d probably have one great system!