Qanat

Qanats (or Foggara)

It east can be the most important technological advance of all the history of the irrigation in Iran. It would have appeared in the North-West of the Iranian plate towards the end of and was developed starting from the mining techniques . The qanat , which is comparable with an underground aqueduct, was then spread on the Iranian plate and even further at time of the Achéménides, making it possible to open new zones with the human settlement. Contrary to the stoppings Sassanides, requiring many workmen lasting of the short periods for construction and maintenance, the construction of the qanats called only upon little people (three: one which digs and supports the gallery, one which sends the ground excavated in a skin in top, and one in top which empties the skin) over a longer time (work increases only by a few meters per day).

In spite of the variations of characteristics (length, depth, type of ground dug…) that one can find between the qanats , they measure typically more than 500 m and the " well mère" where the channel starts is deep of more than 10m. Longest qanat known measures more than 50 km (with Kerman) and the deepest well mother measures more than 300 m (with Gonabad). Yazd, Kerman and Gonabad is the most known zones for their dependence with an extensive system of qanats .

The manner of building the qanats differs much from the method of construction of the stoppings and request an political organization and a planning much less large. The type of investment required by the construction and the maintenance of a qanat is adapted more to the environment of the high plateaus. The merchants or the landowners gathered in small groups in order to finance the construction of a qanat . The political unification was thus not facilitated by this process. When the shares of a qanat are disproportionate, of the problems exist as for the maintenance of the system, and these difficulties were quoted in the arguments against the land reform of the years 1960.

In the middle of the 20th century, it is estimated that approximately 50.000 qanats were in exploitation in Iran. The system with the advantage of remaining with the natural disasters (earthquakes, floods…) and human (destruction in time of war), and to be not very sensitive to the levels of precipitation. A qanat typically delivers a flow of 8000 m ³ per 24 hours period.

the collecting of water

There exist 3 possible sources for the water of irrigation:

the Ground water: the water which runs gently under the Erg, in the old courses of rivers comes from the Saharian Atlas. Water is then with a few meters only and one can dig wells. It is the case for the Oasis of Taghouzi.

the Nappe of will foggaras: deeper than the preceding one, it approaches surface in the Plateau of Tadmaït what makes it possible to join it by digging level galleries, will foggaras them .

the Tablecloth albienne: very deep (several hundred meters), immense (it recovers all central Sahara as far as Libya), it seems to be inexhaustible. It is thus used for impressive projects of irrigation (as close to Adrar).

Foggaras

This type of irrigation, deeply original, gives to the oases of Gourara their specificity: one nowhere does not find it elsewhere in the Sahara (except in Touat -- area of Adrar).

The tradition wants that this system of irrigation came from current Iran, perhaps about the 11th century.

It consists in creating artificial “sources” by digging very weak inclined galleries which will join the tablecloth. Water oozes along the walls and forms a permanent brook.

These galleries are marked on the surface by glances for maintenance and an overflight of the area shows the extent of the network thus created: one estimates at thousands of kilometers the whole of will foggaras of Gourara and Touat.

The work of digging obviously was colossal and could not have been done without the work of many slaves. Currently the problem is to maintain will foggaras them which can crumble or ensabler. It is the stake of the current period: will one be able to give again with the gardens the water which they need?

Distribution

To be distributed water resulting from will foggara, the oasiens of Gourara developed a system as effective as esthetic: the combs (kesria). A specialist, Kiel el my, measurement the flow which passes between each tooth and remakes the operation each time foggara it is hollowed out again or maintained or when a landowner buys the right to water of another.

Water circulates then in channels, the irrigation channel, which take it along to the basin, the majen, where it accumulates until the farmer irrigates his cultures.

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