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DEW PONDS. AR eS AND "There is [in England] at least one wandering gang of © by Robert A. Nelson, Rex Research — men...who will construct for the modern farmer a pond umans need to drink at least two _ which, in any suitable situa- f — He [just over two litres] of water tion in a sufficiently dry soil, aie CHALK daily to remain alive. If groundwa- will always contains water. me est ae ter is not available, the atmosphere humidi- The water is not derived — DRY STRAW ty can be condensed instead to provide our from springs or rainfall, and or REEDS minimum requirements. is speedily lost if even the Figure 1: Dew Pond In 1993, Reginald E. Newell (of MIT) — smallest rivulet is allowed to . found 10 huge "atmospheric rivers" (five flow into the pond. "The dew pond will cease to attract the each in the northern and southern hemi- "The gang of dew-pond makers com- dew if the layer of straw should get wet, as spheres) with typical flow rates of 165 mil- | mence operations by hollowing out the _ it then becomes of the same temperature as lion kilograms of water per second. These — earth for a space far in excess of the appar- the surrounding earth and ceases to be a rivers of vapour are bands up to 480 miles ent requirements of the proposed pond. _non-conductor of heat. This practically wide and 4,800 miles long, about 1.9 miles They then thickly cover the whole of the always occurs if a spring is allowed to flow above the Earth. They are the main means — hollow with a coating of dry straw. The into the pond, or if the layer of clay (tech- of transporting water from the equator. It straw in turn is covered by a layer of well- _ nically called the 'crust') is pierced." should be possible to draw water from chosen, finely puddled clay, and the upper Additional construction details were these rivers. The problem of accessing that surface of the clay is then closely strewn explained in Scientific American (May height is not insurmountable, especially if with stones. Care has to be taken that the 1934): the construction is done atop mountains." margin of the straw is effectively protected "An essential feature of the dew pond is The means of collecting atmospheric by clay. The pond will eventually become its impervious bottom, enabling it to retain humidity is an ancient technology that has filled with water, the more rapidly the larg- all the water it gathers, except what is lost been largely ignored in modern times. The er it is, even though no rain may fall. by evaporation, drunk by cattle or with- most impressive example of this science "If such a structure is situated on the drawn by man. The mode of construction was discovered in 1900-03 during the summit of a down, during the warmth of a__ varies in some details. The bottom com- excavation of Theodosia (a Byzantine city summer day the earth will have stored a monly consists of a layer of puddled chalk dating to about 500 BC). considerable amount of heat, while the — or clay, over which is strewn a layer of rub- Archaeologists found numerous pipes, pond, protected from this heat by the non- _ ble to prevent perforation by the hoofs of about three inches in diameter, leading to conductivity of the straw, is at the same animals. A layer of straw is often added, wells and fountains in the city. The pipes time chilled by the process of evaporation above or below the chalk or clay. The were traced to a nearby hill and were found from the puddled clay. ponds may measure from 30 to 70 feet to originate from 13 piles of limestone, "The consequence is that during the night —_ across, and the depth does not exceed three each about 40 feet tall and 100 feet square. the warm air is condensed on the surface of _ or four feet."* This system of "air wells" produced as__ the cold clay. As the con- = much as 14,000 gallons of water daily! densation during the night is in excess of the evaporation Dew Ponds during the day, the pond Dew ponds have existed since prehistoric becomes, night by night, times, but today the technology is nearly gradually filled. forgotten. A few unfailing dew ponds can Theoretically, we may still be found on the highest ridges of observe that during the day, England's bleak Sussex Downs and on the _ the air being comparatively Marlborough and Wiltshire Hills. Though charged with moisture, evap- far from any marshes, springs or streams, oration is necessarily less they always contain some water that con- _ than the precipitation during denses from the air during the night. the night. In practice, it is Arthur J. Hubbard described a dew pond found that the pond will con- in his book, Neolithic Dew-Ponds and _ stantly yield a supply of the Cattleways (1907): purest water. Spiral Dew Pond, Oxteddle Bottom, Sussex, 1997 (Photo: Chris Drury) DEW PONDS, AIR WELLS AND FOG TRAPS umans need to drink at least two He [just over two litres] of water daily to remain alive. If groundwa- ter is not available, the atmosphere humidi- ty can be condensed instead to provide our minimum requirements. In 1993, Reginald E. Newell (of MIT) found 10 huge "atmospheric rivers" (five each in the northern and southern hemi- spheres) with typical flow rates of 165 mil- lion kilograms of water per second. These rivers of vapour are bands up to 480 miles wide and 4,800 miles long, about 1.9 miles above the Earth. They are the main means of transporting water from the equator. It should be possible to draw water from these rivers. The problem of accessing that height is not insurmountable, especially if the construction is done atop mountains." The means of collecting atmospheric humidity is an ancient technology that has been largely ignored in modern times. The most impressive example of this science was discovered in 1900-03 during the excavation of Theodosia (a Byzantine city dating to about 500 BC). Archaeologists found numerous pipes, about three inches in diameter, leading to wells and fountains in the city. The pipes were traced to a nearby hill and were found to originate from 13 piles of limestone, each about 40 feet tall and 100 feet square. This system of "air wells" produced as much as 14,000 gallons of water daily! Dew Ponds Dew ponds have existed since prehistoric times, but today the technology is nearly forgotten. A few unfailing dew ponds can still be found on the highest ridges of England's bleak Sussex Downs and on the Marlborough and Wiltshire Hills. Though far from any marshes, springs or streams, they always contain some water that con- denses from the air during the night. Arthur J. Hubbard described a dew pond in his book, Neolithic Dew-Ponds and Cattleways (1907): NEXUS = 43 © by Robert A. Nelson, Rex Research Spiral Dew Pond, Oxteddle Bottom, Sussex, 1997 (Photo: Chris Drury) DECEMBER 2002 — JANUARY 2003 www.nexusmagazine.com