Harvest Mist and Fog for Drinking Water in Arid Areas
Fog and Mist Nets
When I first read about the concept of fog nets, I thought this must be a kind of magic. Poor communities can get drinking water by harvesting mist and fog. They place a fine net in the cloud layer that cloaks their mountain tops or they can put one in the mist that rolls onto arid coastal areas. Amazingly, the tiny droplets that are caught coalesce in their millions and trillions to become a vital source of water.
Ancient first nation and aboriginal civilizations have always known about this cloud harvest, but until recently, the technique has been forgotten by the developed world. Rapid population growth and commercialization of water supplies has made it difficult for some communities to get enough water. Researchers have been investigating ways to make their living conditions more sustainable. This new version of an old idea is already helping to improve the lives of many marginalized groups and will no doubt be adopted more widely in the future.
How Do Fog and Mist Nets Work?
Cold air holds less moisture than warmer air does. There is a natural fluctuation in air temperature which results in water condensing out of the air mass as dew. This variation in humidity may be caused by diurnal rhythm i.e. day changing to night. It can also occur due to changes in elevation. As warm air is lifted by thermal currents it cools and so releases its water load.
A fine-mesh piece of netting is strung between poles so that it hangs as a vertical sheet. The fog or mist net captures the dew drops as they are released from the cloud. The volume of drops collected means that the water forms rivulets and runs down into a gutter placed at the bottom of the nets. From here the water is channeled into storage containers where it can be accessed by the local community. The water collected in this way is used as drinking water as well as to irrigate crops and for washing and cooking.
Cloud Catchers of Peru
What do you think about the idea of fog nets?
Coastal Fog and Low Clouds in Chile
The Atacama Desert in Chile is one of the driest places in the world. In fact, some parts of it have never, ever, had any rainfall at all. However, the area does get a lot of coastal fog. In recent years, researchers from MIT University, USA and the Pontifical University of Chile in Santiago have developed the meshes used to collect water droplets from the fog.
The scientists looked to nature for inspiration. They noticed that plants with narrow leaves are more efficient at catching small drops of condensate and incorporated this into their fabric design. By changing the mesh size and the surface materials used they have improved the mesh screen’s fog collecting efficiency by 500%. The video below shows how a fog nets are being used to provide water in the Atacama Desert region of Chile.
Harvesting Fresh Water from Fog in the Atacama Desert
Simple Technology Provides Sustainable Fresh Water
A communal system of suspended mesh nets harvests enough water for local agricultural and domestic use. However, the fog collecting nets are still at the experimental stage. Their success will only be assured if the local population is convinced that the idea is sustainable.
There are about 10 billion cubic meters of water available annually in Chilean coastal fog clouds. If just 4% of this is harvested, it would provide enough drinking water for the local population. Harvesting fog water as a source of fresh water is a better option than sea water desalination. It is a low-tech option and is much cheaper than desalination methods. Fog nets are inexpensive to produce and they have almost zero maintenance costs. Once poor communities understand the benefits of this novel water collecting system then it has great potential to be adopted in many areas of the world.
Cloud Catchers in Lima, Peru
Lima, Peru is a thriving capital city that receives less than 1 centimeter of rainfall per year. Large sections of the city’s population don’t have access to clean drinking water. Harvesting water from the sky can literally make the difference between life and death. A cheap and regular water supply means that people can grow their own food and survive in this arid area.
In the video below a villager describes how before they had mist nets to collect water they had to rely on a tanker that came to the village three times a week. The water was expensive and all their crops had to be watered by hand. All this changed a year ago when the villagers installed 30 mist nets. These simple structures are collecting 200 to 400 liters of water per day every day for the community. They can now use hosepipes to irrigate their crops and they have potable water for cooking, drinking and washing available all week. Cheap, clean water has changed their lives for the better.
Harvesting Water From the Sky in Arid Areas of Peru
Drinking Water is Essential for Life
It may be a cliché, but it’s true. We really do need water to survive. Humans are adaptable creatures and very few climates are uninhabitable once man (and woman) gets his thinking-cap on. Communities can use resources in various ways. Early communities tended to share essential resources like water, as it was in their common interest for everyone to be able to survive. As societies grow richer, some people become more inward looking and materialistic. They are less concerned about the overall wellbeing of their community and care only for their immediate family members. That’s when vital goods like water become a private tradable commodity rather than a utility available for the public benefit.
In countries with regular rainfall, poor people can collect water as the rain falls, but in dry areas of the world they have no option but to pay. Fog and mist nets seem to offer a workable solution to the problem. However, the people who might benefit from this new method of water collection still need to be community minded enough to pool their resources to pay for the initial installation of the nets.
Fog Harvesting Cloud Catchers All Over The World
Are There Other Parts of the World That Catch Water From Fog?
Yes, many communities in dry areas of the world are discovering the benefit of using nets to catch water from fog. The technology is simple and cheap. This makes it a good option for remote or poor communities that do not have a regular potable water supply.
One of the latest projects was constructed in 2015 in South-West Morocco. it is on the edge of the Sahara Dessert and is claimed to be the world's largest such installation. The bank of fog-catchers serves 5 villages with a total of 500 people and their livestock.
These Moroccan villages are in the mountains and there is little rainfall. Mountain fogs coat the man-made nets with condensed water on approximately 140 days per year. When enough droplets have accumulated, the water is piped to fields and homes nearby. The water is clean enough to drink without further treatment. The fog-nets in this project harvest 6,000 liters of water per day.
There are currently active fog harvesting projects in Yemen, Morocco, Chile, Peru, Ghana, Eritrea, Ethiopia, South Africa and California. The effect of these projects is life-changing and may help reduce migration pressures.