air, water and Roman ingenuity

A friend of mine from Chile told me a year ago about the use of nets for harvesting fog, and underground clay pots for irrigation where water is a very scarce resource. But I wasn't able to find a detailed description of these technologies - until now. UNEP has produced a Source Book of Alternative Technologies for Freshwater Augmentation in Latin America and the Caribbean, providing detailed descriptions of these and other water conservation systems and technologies.

I have been interested in drip irrigation for its higher level of efficiency and reduced waste in comparison with most other types of irrigation, but clay pot irrigation is even better for reduced wastage. It's best for home gardens or rural plots of up to a hectare. Subsistence farmers in the tropical, semi-arid parts of Brazil have are using this system, contributing to steady or even higher agricultural output owing to the highly efficient and economical use of water. A system of this kind was used centuries ago by the Romans, and initial experience in Brazil suggests that different varieties of plants can thrive in a range of soil types on small amounts of water using the clay pot technology. Chapters 4.2 and 5.7 of the UNEP sourcebook describe this system in detail, with illustrations.

The small coastal town of Paposo, Chile has a declining population of 300 residents, and so little water that it is trucked in periodically. Work on fog harvesting and other water systems is underway to try to reduce the town's reliance on external water supplies. Nonprofit groups like Water Aid and Arup Cause [see also page 24 of 2.4MB PDF file] are involved in projects to improve the sustainability of Paposo. FogQuest is involved in various countries - have a look at their pictures of fog harvesting.