Fog, an unexpected ally against drought

BarcelonaCatalonia has already had a historic drought for more than three years and, with the climate crisis, these episodes will become longer and more extreme. All of this requires the promotion of new measures and solutions to guarantee drinking and irrigation water in the future and to avoid the disappearance of current vegetation. Although projects are already underway to further enhance desalination and water regeneration in the coming years, another element has recently been put on the table that could be a new ally against drought: fog.

In the past, arid regions used fog droplets to generate water. And now this ancient technique is being recovered again, improved with current tools and technology. This is what has been done in recent years with the European project Life Fogs, in which the Centre for Ecological Research and Forestry Applications (CREAF) has participated. Researchers have installed fog collectors to reforest three arid areas with difficult regeneration using the collected water: a forest on the island of Gran Canaria, a quarry in Garraf and a forest devastated by a fire in Portugal.

The final results are very promising, as around 87% of the tens of thousands of trees planted in these areas have survived thanks to this technique; that is, twice as many as in traditional reforestation processes. In fact, the new collectors used especially in Gran Canaria have shown that they can collect between 300 and 400 l/m² of water per year.

In the case of the Garraf quarry, not only has the water from the fog been used to regenerate land damaged by human exploitation, but above all, the water produced by the dew from the humidity has been used. "This first test has been a resounding success," Vicenç Carabassa, a CREAF researcher who has led the scientific part of the Life Nieblas project, told ARA.

The data obtained opens the door for some areas of the country and around the world to take advantage of fog to help deal with an increasingly severe water shortage. "This technique does not collect large quantities of water like a desalination plant and cannot supply large urban centres, but it can be of help for remote areas, small towns or not very extensive dryland plantations," adds the researcher.

Not all fog is usable

When we talk about fog in Catalonia, we think of the Lleida plan or the Vic plain, two areas where this phenomenon usually occurs. But curiously, this type of fog stagnating on plains and inland hollows is not suitable. "We need fog, but also wind to push it through the collectors to catch the microdroplets and generate water, and these conditions are not so common in our country," says Carabassa, who points out that some of the areas that meet these requirements are the Central Plateau or the Coastal mountain range. In addition, the humidity of the Mediterranean generates a lot of dew water that the devices can also collect.

The success obtained in the reforestation of the Garraf quarry has made the company Promsa itself, owner of the land, want to replicate the process in another quarry located in the Riera de Gaià, in Tarragonès. Carabassa explains that CREAF has already requested new European funds to finance more projects with fog collectors in Catalonia, such as the reforestation of a quarry in Bages or the guarantee of irrigation for olive plantations in the Àger valley.

"The collection of fog water is one more element that should allow us to face a future that looks dry with better guarantees," explains Carabassa. And he concludes: "Beyond finding new sources of water, as a society we must reduce and adapt our excessive consumption to the new climate reality."

Different types of collectors

Several arid areas of the world have recently begun to use this technique again, such as the Atacama Desert in Chile. There are different types of collectors that are used depending on the weather conditions in each area. The most common are vertical meshes that collect water from the fog that passes through them in a tank or irrigation system.

In Gran Canaria, some of the devices used are innovative, as they imitate the leaves of a tree called garoé that the ancestors of the area used to collect water. In contrast, in Garraf, a type of structure has been used that surrounds each individually planted tree and that above all captures ambient humidity. "It is a technique with very high energy efficiency, as it practically does not generate emissions and uses reusable and biodegradable materials," concludes Carabassa.