Fog harvesting could provide water for the driest cities

Victoria Gill

Scientific correspondent, BBC News

Aerial image of an Alto Hospicio camp, Chile

Getty Images An aerial image showing a dense collection of houses and a playground in dirt in the Flor's camp in Poblacion in Alto Hospicio, Chile. The soil looks dry and dusty and there are sterile mountains in the background — Aerial image of an Alto Hospicio camp, Chile

The capture of fog water – on a large scale – could provide some of the drier -dryer cities in the world with drinking water.

This is what researchers from Chile concluded after studying the potential of the fog harvest in the desert city of Alto Hospicio in the north of the country.

Average precipitation in the region is less than 0.19 inch (5 mm) per year.

“The city also has a lot of social problems,” said Dr. Virginia Carter Gamberini, from Universidad Mayor. “Poverty, drugs, many slums.”

Without access to water supply networks, people in the slums count on the drinking water which is delivered by truck.

However, clouds of fog that regularly gather on the mountainous city are an unexploited source, according to researchers.

Fog harrowing systems consist of a fine mesh, through which the clouds loaded with humidity pass

Maria Virginia Carter Gamberini An experimental fog collecting system - composed of two sheets of fine mesh nets, each suspended between two poles. The nets are seated on a sterile hill in the mist — Fog harrowing systems consist of a fine mesh, through which the clouds loaded with humidity pass

How do you harvest the fog?

The capture of the water from the fog is remarkably simple – a mesh is suspended between the posts, and when the clouds loaded with humidity cross this fine mesh, the droplets form. The water is then channeled in the pipes and storage tanks.

It has been used on a small scale for several decades, mainly in rural southern regions and Central America – in places in good misty conditions. One of the biggest water harvest systems fog is found in Morocco, on the edge of the Sahara desert.

However, Dr. Carter says that a “new era” of the much larger fog harvest could provide a safer and lasting water supply in urban environments where it is most necessary.

Alto Hospicio is in one of the driest regions in the world, and some of the poorest areas in the growing city have no secure water supply

Maria Virginia Carter Gamberini The image shows a slum, or an informal colony of huts, in the Chilean city of Alto Hospico. There is a dense collection of low-level buildings in an arid environment with desert mountains in the background — Alto Hospicio is in one of the driest regions in the world, and some of the poorest areas in the growing city have no secure water supply

She and her colleagues have carried out evaluations of the quantity of water produced by the fog harvest and combined this information with cloud training studies in satellite images and with weather forecasts.

From this, they have concluded that the clouds that are regularly formed on the Pacific – and are blown through the city of the city of the coast – could provide residents with a lasting source of drinking water . They published their results in An article in the journal Frontiers of Environmental Science.

The fog of Alto Hospicio is formed on the peaceful ocean – when the hot and humid air flows on the cold water – and is then blown on the mountains. Flush conditions reliably here have enabled Dr. Carter and his colleagues to locate areas where the largest volumes of water could be harvested regularly in the clouds.

Based on an annual rate of average water collection of 2.5 liters per square mesh meter per day, the researchers worked:

17,000 m² of mesh could produce enough water to meet the weekly demand of 300,000 liters which is currently delivered by truck to urban cans
110 m² could meet the annual demand for irrigation of the city’s green spaces
Fog water could be used for soil -free agriculture (hydroponics), with yields from 33 to 44 lb (15 to 20 kg) of green vegetables in a month

Scientists say that “cloud water” could improve the resistance of certain arid cities to climate change

The Getty Images image shows a pier disappearing in the fog of the sea — Scientists say that “cloud water” could improve the resistance of certain arid cities to climate change

Alto Hospicio is on the verge of the Atacama desert – one of the driest places on the earth. With little or no precipitation, the main source of water in the cities of the region is underground aquifers – the layers of rock which contain spaces filled with water – which were filled thousands of years ago.

With the growth of urban populations and the demand for these water and industry water supplies, scientists say that there is an urgent need for other sustainable sources of drinking water.

Dr. Gamberini explained that Chile is “very special” for its sea fog “because we have the ocean the whole country and we have the mountains”.

His team is currently working on a “fog collecting card” in the whole country.

“The water of the clouds”, as Dr. Carter describes, could, she said, “improve the resilience of our cities with climate change, while improving access to clean water”.