Introduction of Qanat
In early part of the first millennium BC ,Persians(Iranian ) started constructing elaborate tunnel systems called Qanat for extracting ground water in the dry mountain basins of present-day Iran
Qanat tunnels were hand-dug ,just large enough to fit the person doing the digging .Along the Length of the Qanat ,which can be several Kilometers, Vertical shaft were sunk at intervals of 20 to 30 meters to remove excavated material and to provide ventilation & also access to maintaining .
The main Qanat tunnel sloped gently down from pre-mountainous alluvial fans to an outlet at a village or farming lands .From there, canals would distribute water to fields for irrigation .these amazing structures help Iranian farmers to achieve their aims despite long dry period when there was no surface water be available. you might ask what is the differences between Alluvial fans and Delta. we could say that The main difference between alluvial fan and delta is that alluvial fans form due to the deposition of water-transported materials whereas delta form due to the deposition of sediment carried by rivers at an estuary , both can have triangular shape whereas alluvial fans happen in higher elevation, always in mountains, can vary in size, always in triangular shape but delta happen near ocean & lower elevation ,their shape varies with nature of moving and non moving water ,not always triangular shape.
advantages of Qanat
There are significant advantages to a Qanat water delivery system including
1-due to this system, majority of channels are located underground so it reduces water loss from seepage & evaporation
2-The system is run absolutely by gravity force so there is no requirement for any kinds of water pumping
3- Water can be use as renewable source that would lead to additional further discussion &will be discussed in other posts…
Thanks to huge amount of water flow in Alamut Valley whether in summer or winter , it has been described some Qanat in this region in order to manage surface water flow but it used most widely in plain area rather than the mountain area .
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