Qanat is an underground gallery that conveys water from an aquifer or a water source to less elevated fields. In practice, a Qanat consists of a series of vertical shafts in sloping ground, interconnected at the bottom by a tunnel with a gradient more gentle than that of the ground.
The first
Shaft (mother well) is sunk, usually into an alluvial fan, to a level below the groundwater table. Shafts are sunk at intervals of 20 to 200 meters in a line between the groundwater recharge zone and the irrigated land.
From the air, a Qanat system looks like a line of anthills leading from the foothills across the desert to the greenery of an irrigated settlement.
qanat was invented by Iranians and its creation dates back to thousands of years ago. In spite of the lapse of such a long time this method is still prevalent and common for irrigation in some Iranian villages, residential areas, and farms.
This irrigation method has found its way to other countries and become globally known. We also talked of the process through which qanats are constructed and said that after assessing and choosing a proper place for building qanat a mother well is dug deep
...see more down having a diameter of 1 or 2 meters.
Then a chain of wells are dug with equal distances from each other whose depths successively decrease with their distance from the mother well. This chain of wells is interconnected from underground and water flows in them.
In Ardestan, Iran, there is a Qanat with two levels of water lying over each other, called the Moon Qanat. The 1st level is 30 meters deep, and the 2nd level is 27 meters deep, so the high difference is 3 meters.
The soil formation of this Qanat is such that the water from 2nd level does not penetrate the lower level.
The strangest qanat in Iran is the two-storey qanat of Moon-e Ardestan that was built approximately 800 years ago; it has ordinary wells together with different mother wells and side wells.
Reference:
http://www.icqhs.org/english/subject.aspx?sbid=9a21f816-71ae-4220-8c53-4c4d32542d6a
http://english.irib.ir/programs/Iran/item/66079-irans-rural-tourist-attraction-sites-37
