Fog collectors net water for mountaintop villagers
In the small Sherpa community of Kalpokhari, in the foothills of Nepal’s Himalayas, residents collect fog. A 6-by-12-meter structure resembling a large volleyball net traps water from the thick mountain fog and channels it into storage tanks, which deliver water to residents through an outdoor tap.
The collector is part of a pilot project involving several Canadian organizations, including a four-member team from the Nepal Community Development Foundation. It has consistently produced an astonishing volume of water—more than 500 liters a day.
Throughout the developing world, contaminated water is a key contributor to generally poor health. Although Nepal is rich in natural freshwater resources, it is mountainous, with small communities nestled into ridges and crests far above streams, rivers, or wells, and often far from drivable roads. Because traditional water-collection methods involve hours of walking each day, securing access to clean, safe drinking water has always been a formidable challenge.
“The first collector will be the seed for new ventures in many other Asian countries,” says Rick Taylor, a member of the Toronto-based Nepal Water from Fog Committee. “It is a necessary and viable alternative water-harvesting method.”
First tested in Chile, fog collectors are now operating in Ecuador, Mexico, and Oman. In an arid part of Peru, 20 large fog collectors produce enough water to keep a 450,000-liter reservoir full, year-round.
Fog collectors, nets of polypropylene mesh suspended between two upright supports, employ simple technology. Fog droplets are similar to raindrops, but much smaller; it would take billions of droplets to form a drop of water the size of a match head. Collectors placed vertically, perpendicular to the path of prevailing winds, can collect about 60 percent of the droplets pushed through by the wind. Fog collects in large drops on the mesh and trickles down to a PVC pipe at the bottom of the net. The water is then directed into a hose and collects in tanks; a closed system ensures that no contaminants enter the water before it reaches community taps.
The dimensions and pattern of the mesh, a lightweight, inexpensive polypropylene fiber net with strands one millimeter in diameter, are critical. The strands, spaced one centimeter apart, are woven into a grid pattern. Too fine a pattern would trap the water and prevent it from flowing to the bottom of the net. If the pattern were too coarse, moist air would pass through without leaving a water residue.
Besides providing abundant clean drinking water, fog water can be used for irrigation to improve agricultural yields. In parched Peru, fog water irrigated tree and shrub seedlings. After the trees reached a certain height, they took root and collected enough fog water to be self-sustaining. The system is affordable—about $500 per collector—but not perfect. Severe weather can damage collectors, and subzero temperatures put the deep freeze on water production.
Tony Makepeace (www.tonymakepeace.net) is a Toronto-based photographer, teacher, and writer. From Outpost: The Traveller's Journal (March-April 2000). Subscriptions: $18/yr. (6 issues) from 559 College St., Suite 312, Toronto, ON M6G 1A9.