Throughout the arid regions of Iran, agricultural and permanent settlements are supported by the ancient qanat system of tapping alluvial aquifers at the heads of valleys and conducting the water along underground tunnels by gravity, often over many kilometres.
Each qanat comprises an almost horizontal tunnel collecting water from an underground water source, usually an alluvial fan, into which a mother well is sunk to the appropriate level of the aquifer. Well shafts are sunk at regular intervals along the route of the tunnel to enable removal of spoil and allow ventilation. These appear as craters from above, following the line of the qanat from water source to agricultural settlement. The water is transported along underground tunnels, so-called koshkan, by means of gravity due to the gentle slope of the tunnel to the exit (mazhar), from where it is distributed by channels to the agricultural land of the shareholders.
The levels, gradient and length of the qanat are calculated by traditional methods requiring the skills of experienced qanat workers and have been handed down over centuries. Many qanats have sub branches and water access corridors for maintenance purposes, as well as dependant structures including rest areas for the qanat workers, public and private hamams, reservoirs and watermills. The traditional communal management system still in place allows equitable and sustainable water sharing and distribution.
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The photograph ((C) S.H. Rashedi) of the post shows an aerial view of the persian qanat, Jupar, Bagh-e Shahzadeh (Mahan).