How the “fog harvest” can provide water to cities with water shortage in Chile (and the world)

This is what researchers from that country have concluded after analyzing the potential for the collection of fog in Alto Hospicio, a city located in northern Chile, in the arid region of the Atacama desert.

With little or no precipitation, the main source of water in the cities in the area are underground aquifers, which last recharged thousands of years ago. The average precipitation is less than 5 mm per year. And, in some areas, water scarcity forces the population to supply the population with aljibe trucks.

But the city of Alto Hospicio has a geographical peculiarity that favors the formation and capture of fog.

“It is located in one of the fog entrance runners to the continent,” researcher Virginia Carter Humberini, from the Universidad Mayor de Chile, explains to BBC Mundo.

Precisely those conditions are those that could allow the city to rely on the fog harvest as a viable and sustainable alternative to supply drinking water to its population.

The conclusions of the study, which was published in February in the magazine Frontiers of Environmental ScienceThey suggest that fog clouds that accumulate regularly on the mountainous city are a missed source of this valuable resource.

With the growth of the urban population and the growing demand for water by mining and industry, researchers warn that it is urgent to find other sustainable sources.

Above all, considering that in the particular case of Alto Hospicio, there are serious poverty problems and reduced access from population sectors to clean water supply networks.

A “new era” in the fog harvest

The idea of ​​capturing fog water is not new.

In fact, Carter says that she has participated in similar projects in other areas of Chile, Guatemala, Canada and Africa.

One of the largest fog collection systems is found in Morocco, on the edge of the Sahara desert, While emblematic experiences in Latin America are those of Chungungo, also in Chile, or the catch of the hills of southern Lima.

The novelty, says the researcher, is that so far the projects of this nature had been understood with the perspective of supplying rural communities and not to urban populations.

“This points to a change of perception. It was always thought of using fog water to supply small towns or rural settlements. In this case, we want to explore the possibility of supplying a city,” he says.

“Our findings show that fog can serve as a complementary urban supply in arid areas where climate change exacerbates water scarcity.”

Carter emphasizes that a “new era” fog collection on a much larger scale could provide a safer and sustainable water supply in urban environments where it is most needed, not only in Chile but also in other cities in the world.

How do you capture the fog?

Capture fog water is extraordinarily simple: a mesh between two posts is hanging and tense and the “catch” is formed. When the clouds loaded with moisture go through that fine mesh, small droplets are formed, which are channeled towards pipes and storage tanks.

The Fog of Alto Hospicio is formed on the Pacific Ocean when the warm and humid air flows on cold water and is then pushed into the mountains. The constant fog conditions in the area allowed researchers to identify the areas where the highest volume of water could be collected on a regular basis.

With a field work that was extended for one year, they carried out evaluations on-sitewhat they combined with data obtained through a predictive method (Amaru), which processes weather information and crosses it with data obtained by remote sensors.

During the high season of the study, Between August and September 2024, the collection potential reached up to 10 liters per square meter per day, according to researchers.

Based on an average annual rate of water collection of 2.5 liters per square meter of mesh per day, they calculated that:

• 17,000 m² of mesh could produce enough water to meet the weekly demand of 300,000 liters that currently surrendered to trucks to urban marginal neighborhoods.
• 110 m² would be enough to meet the annual demand for irrigation of the green spaces of the city.
• Fog water could be used in hydroponic agriculture (without soil), with yields of 15 to 20 kg of green vegetables per month.

Carter explains that Chile is “very special” in the marine fog, “because we have the ocean throughout the country and we also have the mountain range.”

His team is currently working on a “fog collection map” with the aim of identifying other places where this model can be implemented.

The “cloud water”, as Carter describes it, could, according to her, “Improve the resilience of our cities in the face of climate change and, at the same time, improve access to drinking water.”

The researcher emphasizes, however, that the possibility of reaching those volumes in other areas that face a serious water shortage will always depend on her potential for formation and collection of fog, which is given by various elements.

“The key factors that influence the efficiency of fog collection include wind direction and speed, as well as geographical characteristics, especially the presence of mountains,” he explains.

For example, Petorca, one of the areas most affected by water scarcity in Chile, would not have – at first view – the same possibilities of stocking in large volumes of water from the fog. But other coastal areas of the country.

Water quality

“I have always taken fog water,” says Carter, but points out that the study they did do not contemplate a chemical analysis regarding the quality of water resource.

In that sense, it emphasizes that “it will be important to do other investigations … we already know how much water and where to find it. Then we will have to deepen the quality of the water and the most appropriate methods to purify it.”

“It may be that now it is fine to take it, the point is that we do not know,” says another of the researchers, Nathalie Verbrugghe, from the Brussels Free University.

The researchers are cautious about the expectations that have been generated around the findings of this research:

“We are not going to solve the water crisis of Chile or the Atacama Desert” and “this technology is probably either, but we hope it is a complement.”