This covert water input, in the mountainous and coastal regions of our planet, was called occult precipitation in the last century and the terminology persists in some of the literature to this day. The ever-growing need for fresh water in both developing and developed countries is indisputable and both increasing populations and the contamination of existing supplies will lead to constantly escalating demands. We must, therefore, begin to consider the use of non-traditional water supplies such as the collection of fog. As clouds move over hills and mountains, the hilltops and ridgelines are enveloped in fogs. Just as the leaves and needles of trees can collect some of the water in these fogs, large artificial collectors can produce a flow of potable water.
Some authors think so.
Two thousand years ago Pliny the Elder wrote about the Fountain Tree, or Holy Tree, on the island of El Hierro in the Canary Islands. From that time to at least 1800, the inhabitants obtained much of their water from fog that dripped from the leaves of one or more trees. Because fog droplets are so small they have very low settling velocities and to a good approximation go wherever the wind blows them. This means that a fog collector should be a vertical surface. The wind simply blows the droplets against the surface.