Fog Collectors: How They're Helping People around the World

John Hopewell
Published: January 25,2017

Nomvalo school pupils, stand in front of two nets used to collect fog and produce water for their needs, in the village of Taleni. Some Eastern Cape rural communities utilize innovative fog collectors as well as effective rainfall collectors to make optimum use of natural atmospheric sources of water, using large nets to collect fog or low clouds draining them to produce water.
(GIANLUIGI GUERCIA/AFP/Getty Images)

To the average Joe fog is usually a phenomenon that’s viewed as a hazard because it reduces visibility and makes it less safe to travel. To someone living along the bone dry Pacific coast of Peru and Chili, fog can be seen as life providing.

One of the driest places on Earth is also often foggy, and imbedded are tiny water droplets just looking for a way to escape. By erecting large fine mesh netting known as “fog-collectors,” air that blows through on a light breeze condenses and drips into a catchment basin. It’s even clean enough to drink. In the largest fog-collector arrays, thousands of gallons can be siphoned out of the sky per day.

“Fog is water droplets suspended in the air at the Earth's surface”, according to the National Weather Service. The close proximity to the ground is what separates fog from clouds. Fog can begin to form when the difference between air temperature and dew point is less than 4°F but conditions are optimal when dew point and temperature are equal. The sources of fog are typically close by, and in the case of Peru and Chili it is cool air moving off the Pacific Ocean and rising up the slopes of the Andes Mountains that does it.

Fog collection uses large canvas to trap the condensation contained in the fog, formating water droplets which are collected after flowing down the net, like these fog collectors on the Spanish canary island of Tenerife.
(DESIREE MARTIN/AFP/Getty Images)

A fog-collector is pretty basic, does not require electricity or have any moving parts; perfect for impoverished rural areas in the developing world. According to FogQuest, a Canadian nonprofit that installs and helps maintain fog-collectors, “the meshes are made of polyethylene or polypropylene. They have been chosen to be very efficient at capturing wind-blown fog droplets…very cheap, durable, produced in large sizes (13-24 foot widths), produce clean water, and drain the collected water quickly.”

Because of increased surface area, larger fog-collectors will capture the most moisture. On a good day, a single large fog-collector with a surface area of 430 square feet can produce 264 gallons of water. And “variability depends on the site. Choosing an appropriate site is of utmost importance. There are both day to day variations in fog-water production as well as seasonal variations, as is the case with rainfall,” states FogQuest.

As an added bonus fog-collectors also capture scarce rain, even more of it than the ground does. “A fog collector is a very good rain and drizzle collector,” FogQuest says. “This is because wind-blown rain falls at an angle. A 430 square foot fog collector will collect much more rain or drizzle than falls on a 430 square feet area on the ground.”

For poor rural folks who lack the financial resources to dig deep wells or maintain pumps, including purchasing expensive fuel to operate, fog-catchers provide cheap abundant clean water for drinking, bathing and agriculture. The biggest challenge is keeping them maintained along steep mountainsides that experience much harsher weather than gently blowing fog.