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Science

Fog nets provide easy-to-collect drinking water, scientists say

Fog is not universally loved, but at a recent conference in Germany, scientists have shown that it is more than just a blanket of gray. They've proven how useful it can be in South America and East Africa.

Mountains shrouded in fog

Where there's fog, there's water.

Fog is a pesky thing. It tarnishes views, dampens moods and causes accidents.

But at the 5th annual International Conference on Fog, Fog Collection and Dew held recently in Muenster, Germany, researchers discussed how fog can also be used as a surprisingly valuable source of clean water, which with the use of special nets, is relatively easy to come by.

The densely meshed woven nets, which average some 40 square meters in size, are attached to frames and strategically positioned in places known to have high fog density. The wind blows the fog - actually just clouds that touch the ground - into the nets where it deposits droplets of water that run off into gutters and subsequently collect in a depository.

As Otto Klemm, the conference host and a professor of climatology at the University of Muenster, told Deutsche Welle, the technology is highly effective given the right conditions.

Fog collecting net in Chile with two people standing underneath it.

A 40 square meter net can collect up to 200 liters of water per day.

"It only makes sense where there is a shortage of water and where clouds pass through without raining," he said, citing the Pacific coast of northern Chile as one such location. "There is almost always a lot of fog there so you can hope to collect more than five liters per square meter per day."

That adds up to an average of 200 liters a day, which he says is plenty to cover the needs of an entire local family. Alternatively, nets can be used to provide water for agricultural purposes and schools which currently require pupils to bring their own daily drinking supply.

While various peoples have known about fog collection going back thousands of years, conservationists are now trying to use nets in areas around the world that have moisture in the air, but little rain.

Smoke billowing out of a double chimney stack

Air pollution doesn't make for clean drinking water.

Stretching the supply

The Water Foundation, a German charity, has also been involved in a number of fog collection projects in Eritrea, some specifically aimed at harnessing drinking water for children. One village put up of 20 fog nets which collected enough water during the eight months of rain and fog in the region to keep two schools and 120 families in constant supply.

As Ernst Frost of the foundation told Deutsche Welle, the method provides a fantastic alternative for communities which ordinarily have to dig wells, walk miles up and down mountains to collect valley water or have to pay significant amounts of money for water sold off the back of tankers.

But how clean is it? That is an issue which comes up over and over again in the context of fog collection and Klemm says quality varies from place to place.

"In some areas it is safe, in others like Chile, there are power plants and mining plants that emit lots of air pollution, so we need quality controls."

Although that requires some initial financial outlay, once the fog for a specific area has been given the all-clear, the costs involved in its capture are negligable.

According to the Canadian charity, Fog Quest, its 40 square-meter net costs between 775 euros ($1,000) and 1,100 euros, and can last for up to ten years.

The Eritrean capital, Asmara

The Eritrean capital of Asmara could benefit from fog capture in the future.

Maintaining the nets remains a constant battle

Despite all of this potential success, there's also a slight problem, according to Ernst Frost.

"If there are strong winds and the nets tear, they need to be stitched up," he said. "But people don't yet feel responsible enough for them to do that."

He noted in the case of Eritrea in particular, that lack of a sense of ownership is not a result of not caring, but simply of having other things to worry about.

"A lot of people, men and women, are away from the villages doing their military service, so the population of these places is largely comprised of young mothers, children and old people," he said, adding that they are too preoccupied with day-to-day survival to think about patching holes in nets.

Klemm agrees that getting local populations to understand the importance of fog capture is vital if the practise is to be expanded and have any long-term future.

"The biggest challenge is convincing people to do it, to make them understand that there is a fresh water source that has been here for 2,000 years without being used."

But through good communication and the support of local and national governments, he is hopeful that many more people without ready access to clean water will come to recognise that fog has a silver lining.

Reporter: Tamsin Walker
Editor: Cyrus Farivar

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