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FACTS ABOUT FOG Fog is a hydrometeor consisting of a visible aggregate of minute water droplets (or ice crystals), suspended in the atmosphere near the Earth's surface, generally reducing the horizontal visibility at the Earth's surface level to less than 1 km. Water droplets are only about 0.01 millimetres in diameter. A dense fog contains about 1,200 visible drops per cubic centimetre of empty space — barely enough water to wet an object’s surface. Historically, in the Atacama Desert (Chile), both dew and fog were collected by means of a pile of stones, arranged so that the condensation would drip to the inside of the base of the pile, where it was shielded from the day's sunshine. The same technique was employed in Egypt, where the collected water was stored underground. During a stop on El Hierro Island (Canarias) on his way to the Americas, Bartolome de las Casas took interest in the aborigine Bimbachos’ culture, which was already disappearing in the XVI century. The Bimbachos devoted a cult to a tree, the Garoe (Ocotea foetens), which supplied them with abundant freshwater. This ‘holy tree’ was capable of capturing the water held in the mist and drizzle, which allowed for agriculture in an area with very low rainfall. The Garoe was uprooted by a hurricane in 1610. Curiously, its disappearance coincided with that of the Bimbachos culture on El Hierro Island. The water for the 350 residents of the coastal village of Chungungo (north of Chile) had to be trucked in once or twice a week from a town 40 km away. Along the coast of Chile, there is a persistent and extensive cloud deck (camanchaca) that rarely results in rain but creates fog in the slopes and peaks of the mountains that intercept it. A group of scientists have developed a method of harnessing the camanchacas as a source of water: the fog moisture is caught using collectors that resemble oversized volleyball nets. As fog passes through the nets, beads of water form on the mesh. The water runs down the nets into gutters that drain into a 100,000-litre reservoir. The fog-catchers supply the village with an average of 10,000 litres of water every day. Every morning the Namib fog beetle (Onymacris unguicularis) makes an arduous journey to the top of a sand dune, where he turns his body into the wind, straightens out his rear legs and lowers his head. The fog rolling in from the sea gradually collects on his back, forming droplets of water, which glide downwards and hang from the insect's mouthparts. In this way, this beetle is always assured of a healthy morning drink, despite being miles from the nearest freshwater. 25% to 40% of the water in coastal redwood forests comes from fog. The trees get some of that water through their roots, when fog-saturated leaves and branches drip water onto the ground. About half of the 90,000 known higher plant species in the Neotropics, the world’s richest flora, are found in the montane zone.
Information from: Source: UNESCO Water Portal, April 2005
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