How to Harvest Fog in the Mountains

Fog collectors net water for mountaintop villagers

| July-August 2000

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.

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