Fog collection refers to the collection of water from fog using large pieces of vertical canvas to make the fog-droplets flow down towards a trough below the canvas, known as a fog fence.
Through a process known as condensation, atmospheric water vapour from the air condenses on cold surfaces into droplets of liquid water known as dew. The phenomenon is most observable on thin, flat, exposed objects including plant leaves and blades of grass. As the exposed surface cools by radiating its heat to the sky, atmospheric moisture condenses at a rate greater than that of which it can evaporate, resulting in the formation of water droplets.
The organized collection of dew or condensation through natural or assisted processes is an ancient practice, from the small-scale drinking of pools of condensation collected in plant stems (still practised today by survivalists), to large-scale natural irrigation without rain falling, such as in the Atacama and Namib desert. Several man-made devices such as antique stone piles in Ukraine, medieval "dew ponds" in southern England or volcanic stone covers on the fields of Lanzarote have all been thought to be possible dew-catching devices.
In the mid-1980s, the Meteorological Service of Canada (MSC) began constructing and deploying large fog collecting devices on Mount Sutton in Quebec. These simple tools consisted of a large piece of canvas (generally 12 m long and 4 m high) stretched between two 6 m wooden poles held up by guy wires, with a long trough underneath. Water would condense out of the fog onto the canvas, coalesce into droplets, and then slide down to drip off of the bottom of the canvas and into the collecting trough below.
The intent of the Canadian project was simply to use fog collection devices to study the constituents of the fog that they collected. However, their success sparked the interest of scientists in Chile's National Forest Corporation (CONAF) and Catholic University of Chile to exploit the camchanca or garúa clouds which blanket the northern Chile coast in the southern hemisphere winter. With funding from the International Development Research Centre (IDRC), the MSC collaborated with the Chileans to begin testing different designs of collection facilities on El Tofo Mountain in northern Chile. Once perfected, approximately 50 of the systems were erected and used to irrigate seedlings on the hillside in an attempt at reforestation. Once vegetation became established, it should have begun collecting fog for itself, like the many cloud forests in South America, in order to flourish as a self-sustaining system.
The success of the reforestation project is unclear, but approximately five years after the beginning of the project, the nearby village of Chungungo began to push for a pipeline to be sent down the mountain into the town. Though this was not in the scope of CONAF, which pulled out at this point, it was agreed to expand the collection facility to 94 nylon mesh collectors with a reserve tank and piping in order to supply the 300 inhabitants of Chungungo with water.
The IDRC reports that ten years later in 2002, only nine of the devices remained and the system overall was in very poor shape. On the other hand, the MSC states in its article that the facility was still fully functional in 2003, but provides no details behind this statement. In June 2003 the IDRC reported that plans existed to revive the site on El Tofo.
Dar Si Hmad
In March 2015 Dar Si Hmad (DSH), a Moroccan NGO, built the world's largest fog-collection and distribution system in the Anti-Atlas Mountains. The region DSH worked in is water-poor, but abundant fog drapes the area 6 months out of the year. DSH's system also included technology that allowed reporting and monitoring of the water system via SMS message. These capabilities were crucial in dealing with the effects Fog Collection had on the social fabric of these rural areas. According to MIT researchers, the Fog Collection methods implemented by DSH have "improved the fog-collecting efficiency by about five hundred per cent."
Despite the apparent failure of the fog collection project in Chungungo, the method has already caught on in various localities around the world. Nowadays the International Organization for Dew Utilization organization is working on foil-based effective condensers for regions where rain or fog cannot cover water needs throughout the year. Shortly after the initial success of the project, researchers from the various participating organizations formed the nonprofit organization FogQuest, which has set up operational facilities in Yemen and central Chile, while still others are under evaluation in Guatemala, Haiti, and Nepal, this time with much more emphasis on the continuing involvement of the communities in the hopes that the projects will last well into the future. Villages in a total of 25 countries worldwide now operate fog collection facilities. There is also still potential for the systems to be used to establish dense vegetation on previously arid grounds. Overall, it appears that the inexpensive collectors will continue to flourish.
- "A Beacon Project: Harvesting Water from Fog". Dar Si Hmad.
- "Into Action - Fog nets". Munich Re Foundation.
- Farnum, Rebecca. L. "North Africa: small glimmers of light in bid to stop violence against women". The Conversation.
- Toutohghi, Could Harvesting Fog Help Solve the World's Water Crisis? New Yorker. March 25, 2015
- Rioba, Benson Fog collectors net scarce water in Kenya, but face a cloudy future Reuters. March 25, 2016
- Nield, David Yemen is fighting its severe water shortage by harvesting its fog Science Alert. March 25, 2016
- Fog Harvesting, chapter from Source Book of Alternative Technologies for Freshwater Augmentation in Latin America and the Caribbean, UNEP International Environmental Technology Centre
- Renee Cho (2011-03-07). "The Fog Collectors: Harvesting Water From Thin Air". Water Matters: News From the Columbia Water Center. The Earth Institute, Columbia University.
- FogQuest: Sustainable Water Solutions, Canadian organization, historical information on fog collection projects in developing countries
- Dan Collyns (20 October 2009). "How Peru is netting water supplies". BBC News. Lima.