Latin America & Caribbean

Trapping humidity out of fog in Chile

View of the Atacama desert Image copyright Fellipe Abreu
Image caption The Atacama desert resembles a Martian landscape

The dry, red earth could almost be mistaken for a Martian landscape.

It is in fact the Atacama desert in Chile, one of the driest places on Earth.

Average rainfall here is les than 0.1mm (0.004 in) per year and there are many regions which have not seen any precipitation for decades.

But while there is little rain, the clouds here do carry humidity.

Coastal fog forms on Chile's shore and then moves inland in the form of cloud banks. The locals call it "camanchaca".

Image copyright Fellipe Abreu
Image copyright Fellipe Abreu

The fog is made up of minuscule drops of water which are so light they do not fall as rain.

During a particularly severe drought in 1956, scientist Carlos Espinosa Arancibia had an idea.

Image copyright Fellipe Abreu

The retired maths and physics professor from the University of Chile carried out a series of experiments in the highest hills near the city of Antofagasta.

There, he came up with the idea of the fog catcher: netting with tiny openings of approximately 1mm across to capture the tiny water droplets in the fog.

The droplets accumulate in the netting and form a bigger drop which eventually runs off the netting into a canal underneath.

From there, it is channelled through a pipe to containers at the base of the hills, ready for use.

And the research continues today.

The town of Pena Blanca boasts one of the biggest study centres for the fog catchers. There are six big nets in the hills overlooking the town.

Technical adviser Nicolas Schneider says that thanks to the fog catcher they have managed to combat the desertification of the region.

Image copyright Fellipe Abreu
Image caption Fog catchers are nets which can catch minuscule droplets of water
Image copyright Fellipe Abreu
Image caption In the hills above Pena Blanca, scientists have built a research station
Image copyright Fellipe Abreu
Image caption The nets have tiny holes measuring approximately 1mm across

He says that 100 hectares now are again covered in the flora once typical for the region.

"We're planning to provide local families with water from the fog catcher in the near future," Mr Schneider says.

At the heart of the community is a small building which also uses water from the fog catcher: the town's small artisanal brewery.

Image copyright Fellipe Abreu
Image caption The Fog Catcher Brewery is small but its owner is particularly proud of only using water from the fog catcher
Image copyright Fellipe Abreu
Image caption The brewery produces 24,000 litres a year

Fog Catcher Brewery is small. It has three vats and one cold store producing about 24,000 litres per year, but it is the pride and joy of its owner, Miguel Carcuro.

"The water from the camanchaca is of excellent quality and gives our beer a special quality," he says.

The project's backers say the fog catchers are cheap and sustainable.

Image copyright Fellipe Abreu
Image caption The nets are easily maintained and affordable, its backers say
Image copyright Fellipe Abreu

An average-sized fog catcher of 40sq m costs between $1,000 (£635) and $1,500 depending on the material used.

They say its impact on the environment is minimal as the metal posts can be discreetly hidden among vegetation.

As the water is transported down the hill by gravity, there is no extra cost involved for transport, they say.

It is an idea which has been exported to other arid regions in Peru and Mexico.

The largest expanse of fog catchers is located in Tojquia in Guatemala, where 60 fog catchers trap 4,000 litres of water a day.

Prof Pilar Cereceda of the University of Chile says she hopes that within a decade Chile will have enough fog catchers to supply the whole Atacama region.

"I dream of the day in which the fog catchers can compete with desalination plants, which is not environmentally friendly."

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