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Water
is distributed to each owner by a series of channels on the surface
and is temporarily collected in small basins called majen. The
shade of the palm trees and the formation of algae on the water
surface obstruct evaporation.
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The
dam of Beni Isguen, one of the settlements of the pentapolis of
Ghardaia. The dam is not used to create a water basin but rather
it retains the flows in the subsoil and water is drawn up from
the wells like that above on the right.
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The
dam of Beni Isguen in one of its sporadic moments of flood that
even occur every ten years, when the water intakes channel the
flows towards the single parts of the palm-grove and replenish
the water table.
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The
Hadramaut valley and the ancient walled town of Shibam surrounded
by the embankments and the channels of the traditional system
of flood sharing and cultivation of the fields, most of which
are now abandoned.
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Shibam
(Yemen). The ancient dam was not used to create an open-air basin
but rather to direct the floods to the embankments, the channels
and the depressions in the gardens.
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Gabarband
of Pir Munaghara (Belucistan). Dating back to before the Harappa
civilization, the device consisted of a series of 60-120 cm-high
terraced platforms made out of pebbles which decreased in height
as they went upwards. This device was used to keep the floods
under control and stop the alluvial sediments coming down the
hill.
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Combined system of sand accumulation dams and underground dams. The first (b) are generally built by overlapping different levels. The underlying principle is to limit the height of each level so that lighter material is transported by water out of the basin, whereas heavier material accumulates.
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