Google Earth Community: Qanat, Farah, Afganistan.

Qanat, Farah, Afganistan.

Qanats are constructed as a series of well-like vertical shafts, connected by gently sloping tunnels. This technique:

Taps into subterranean water in a manner that efficiently delivers large quantities of water to the surface without need for pumping. The water drains relying on gravity, with the destination lower than the source, which is typically an upland aquifer.
Allows water to be transported long distances in hot dry climates without losing a large proportion of the source water to seepage and evaporation.
It is very common in the construction of a qanat for the water source to be found below ground at the foot of a range of foothills of mountains, where the water table is closest to the surface. From this point, the slope of the qanat is maintained closer to level than the surface above, until the water finally flows out of the qanat above ground. To reach an underground aquifer qanats must often be of extreme length.

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Edited by sasroodkapje (11/28/07 01:10 AM)

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