Serendipity and hydraulic engineering 
Crédit photo © voyage-chine.com La sérendipité est le fait de réaliser une découverte inattendue au cours d'une recherche dirigée initialement vers un objet différent de cette découverte.
En partant des bâdgirs de Yazd en Iran et autres windcatchers (tours à vent), j'arrive à Karez en passant par Foggaras, Khettaras, Qanats, presque un abécédaire.
Un
Qanat est un système d'irrigation souterrain qui permet de récolter les eaux d'infiltration, aussi appelé
Foggara dans les regions of Adrar and Gourara at Mzab, Algeria, and
Khettara Morocco. There are many
Qanats Iran subsurface including Yazd, the city of badgirs. The Karez
(or
Quarez ), meanwhile, is a very old form of horizontal construction for the collection of water.
Inspired by the Persian system of
qanats , it was developed 2000 years ago to tap water from aquifers at Turfan (or Turfan), oasis city located in the Xinjiang Uighur Autonomous Region, bordering the north Great Desert Taklamakan.
Credit © Rongpuk Gallery - Flickr The city is 80 m below sea level and receives only 16 mm of rain per year, is one of the points Hottest China.
The vast Xinjiang has however very deep aquifers, especially in the nearby mountains, the mountains Flamboyants, but whose access is limited not only by the depth, but also by the crudeness of drilling tools available . The idea of locating these layers and digging an underground tunnel that would bring water to irrigate lands below, rather that make up water to the surface, was at least bold.
In the late eighteenth century was born this system, complex and ingenious, unique.
Credit © archiv.heart-of-silkroad.de 
Credit © roughandreadytours.com The Karez is made up of vertical wells dug all the original the eighty yards, and connected by a tunnel horizontal rarely exceeding 1.50 in height 0.80 m wide, a distance of 5-20 km.
The galleries, which were dug by hand, are fed by seepage, mainly due to the snowmelt raises the water table. Their paths underground
have the double advantage of not requiring any pump system since the water drops below the effect of gravity, the channel is built-in slope, and greatly limit losses due to evaporation, advantage invaluable given the outside temperatures are very high.
Credit © chinalandscapes.com At the outset, the Karez wells were 172 000 for a total estimated more than 5272 km. Currently it remains approximately 600-they total more than 1600 km of tunnels at 70-m depth, but the system still works.
They were built by the Khan Karez, or well drillers. Their work was difficult and dangerous. They worked in a wet environment, small and narrow galleries were low and showed the danger of collapsing at any moment. The Karez-Kan and enjoyed great respect and high wages.
Credit © travel-chine.com Today, no additional Karez is built, but each requires meticulous maintenance. Its cost is traditionally allocated to each village resident who benefits under the surface of fields he owns.
To facilitate this discussion, the Uighurs have built wells placed every 20 meters. The Karez-Kan may well go down to possibly clear a blocked duct, or back the land it is necessary to evacuate during annual maintenance work.
Credit © turkbilimi.com The Karez still serve the local population, they provide drinking water of very good quality, people have running water and, surprisingly in the middle of a desert-region also, and they continue to irrigate, as in the past, Fruit installed along a green valley that extends to the east of the city, in the foothills of the Tian Shan, regardless of the temperatures are around 50 ° in summer (cons -15 ° in winter).
Growing grapes in Turpan is 2000 years old
The Uighurs are producing hundreds of varieties known throughout China, the most famous being a white seedless grape, elongated, called mare's udder
. As soon as August the harvest is dried in long houses built of earth on the heights. The hot, dry wind that enters through holes in the wall turns grapes into delicious dried fruit.
Credit © enroutepourlasie.com
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