Fog Harvesting – A Source of Water in Some Dryland Situations
Here is an introduction to fog harvesting and a selection of Youtubes about projects in Peru, Morocco, Eritrea and Nepal.
I first learned about fog harvesting from Bill Mollison in 1986 when I attended his first Drylands Permaculture Deign Course. In recent years it is getting more press. In fact, it is nothing new. Nature has developed many sophisticated fog harvesting systems over millions of years. Fog harvesting, as it is known today, is a form of bio-mimicry. It is a technology developed by observation of nature.
The redwood forests of California comb the fog to produce up to 50% of their water supply. They produce a fog drip. Many other forests do this also, though I haven’t seen any figures on what % of global precipitation is produced in this manner. There are forests of Tamarugo (Prosopis tamarugo) in the Atacama desert in Chile which grow in an area which receives no rain. They rely on fog combing and extremely deep roots which can tap into groundwater. Some species of Prosopois have been found with roots 150 feet deep. Tamarugo is one of the most drought tolerant and salt tolerant trees in the world.
Fog combing plants need fog to survive and not every dry area has fog. Fog deserts are most common where there are upwelling, oceanic, cold currents off dry coastlines. Places like the Atacama Desert, the Namib desert and others. One of the water strategies for the Weather Makers Sinai Desert project is to use fog nets on the Sinai mountains.
Cloud forests found in high mountain regions are another example of forests that rely strongly on fog.
Dew and hoarfrost are two other mechanisms of water supply that benefit dry ecosystems. This was brought home to me when traveling one winter morning through the semi-arid Columbia Basin in Eastern Washington. The night had seen a freezing fog and every blade of grass, every shrub and every tree was enveloped in a thick coating of hoarfrost overnight. The next day the skies cleared and the bright sun soon started melting the hoarfrost and a cascade of ice piled up under every tree, I estimated that it was the equivalent of ¼ inch of precipitation. Some of the hoarfrost sublimated directly back into the atmosphere but much of it melted on the soil surface and sunk into the ground. The fallow wheat fields of the area received none of this hoarfrost water because they had no vegetation for the hoarfrost to collect on.
Desert Fog Nets Catch 10,000 Liters Of Water Daily
3:16. 84,897 views. Feb 14, 2021.
These fog catchers in the Atacama Desert, Peru, also known as the driest place on earth, capture 10,000 liters of freshwater a day for drinking and growing sustainable food. Link to source: https://www.creatingwater.nl/
What they miss in this video, is that you can also use fog net water to establish certain types of trees and shrubs that act as fog condensers. Water the trees to get them going and then they can make it on their own. So the fog nets can be rotated around the landscape leaving a forest in their wake.
World’s largest Fog-collector CloudFisher in Morocco – Producing drinking water from fog
9:30. 269,727 views. Sep 25, 2014
10.000 liters of water a day from the fog in Lima, Peru
https://www.youtube.com/watch?v=h8rQ5aHAnuE
196,554 views. Sep 19, 2016
Fog Water project in Eritrea
https://www.youtube.com/watch?v=_Xn7YTzPydE
9:13. 58,108 views. Nov 4, 2008
Fog collection project in Prathivara temple
https://www.youtube.com/watch?v=6MqfdXzPJP4
13,904 views. Mar 26, 2011.
This new 2-panel LFC project was completed in December of 2009. It is situated at a temple in eastern Nepal. It is currently working very well and producing 500 liters per day on average.
Functional Surfaces A4 – Fog Harvesting
22,489 views, Aug 22, 2013
How This Beetle Could Help Solve Our Water Crisis
5:13. 227,657 views. Aug 16, 2020.
The art of catching fog
https://www.youtube.com/watch?v=GreePOBXdtg
11:14. 49,119 views. May 17, 2018
Can Namib Desert Beetles Help Us Solve Our Drought Problems?
https://www.youtube.com/watch?v=TmyfqjXOf7M
In the last part of this section we looked at the Namib Desert Beetle. In this video we go further and study the Cotula Fallax plant species which has a 3-dimensional water capture mechanism. We also look at the issues faced by current fog harvesting nets and the next generation of biomimetic
I listened to a recent online talk by Walter Jehne and he talked about the currents of moist air that are circulating around the Earth, even above deserts. Some of this air moisture results in precipitation as rain or snow. This is measurable, but there are other ways that plants can utilize this atmospheric moisture.
A few quotes from the internet:
The water absorbed by these plants from the air is called “occult precipitation”.
Hoar frost: solid equivalent of dew; formed by sublimation of water vapour onto cold surfaces as feature-like crystals.
Rime (occult precipitation): freezing of water droplets from fog onto cold surfaces; includes artificial snow; crystals tend to be larger than in snow.
According to Brechtel (1990), occult precipitation can be divided into deposited (dew, hoar frost) and collected (fog, cloud-water, rime) precipitation. Deposited occult precipitation condenses or sublimates directly onto plant surfaces and other objects.
Plant canopies may intercept some of this precipitation where it coalesces into droplets that fall to the ground as “fog drip” providing moisture and nutrients to the plants through the soil. Leaves may also directly absorb the moisture in occult deposition and take up the nutrients. The capacity of leaves to intercept occult deposition varies with leaf morphology, with small narrow leaves being more common in areas prone to frequent fog. Small leaves intercept more canopy fog than larger leaves, and it is possible that this interception contributes to ecosystem nutrients. These observations suggest that occult deposition may provide water and nutrient to some ecosystems, such as the coastal Strandveld.
Fog, dew and cloud water inputs, aptly termed, occult precipitation”, are not traditionally quantified yet more than two decades of research has revealed their importance to a wide range of vegetation types. Utilizing stable isotope methods, field and laboratory based physiological measurements, and a suite of occult precipitation collection approaches we now know that plants inhabiting a wide range of ecosystem types from the coastal California.