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Humidity
water supply to the foggara. The air full of moisture of the palm
grove is sucked out by the foggara in the opposite direction to
the water run-off; it condenses in the tunnel and comes out of
the shafts as dry air. During the night the temperature decreases
and determines a further moisture condensation on the soil surface
that is absorbed by the shafts and the tunnel.
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Aerial
photograph of part of the foggara network supplying the oases
of the Sebkha of Timimoun (Algeria). The underground drainage
tunnels, that are evident on the surface from the layout of the
excavation shafts, come up from the oases (lower left) and run
towards the riverbed of the fossil hydrographical network (upper
right).
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Structure
of the oasis. Water produced in the underground tunnel of the
foggara (A), which is visible thanks to the excavation shafts
on the surface (B), runs beneath the adobe habitat (C) and gathers
further along in decantation tanks (D), useful for drinking water,
ablutions and for cooling the dwellings. Once conveyed in open-air
channels by means of the kesria (F), which serve to measure and
distribute the water flow, water irrigates the palm groove (E)
subdivided into tilled parcels by low mud walls (G).[
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| The foggara network of an Algerian Saharan oasis. |
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| Graphical representation
of the water distribution in the oasis. The three families (A, B,
C) in the village (1) shared the water supply of the foggara (2)
by means of the kesria (3). As time went by water was distributed
to the generations (I-VII) by creating an intricate layout of channels,
water sharing devices and tilled parcels. |
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| Gravina in
Puglia. The underground tunnel of the water system, very similar
to the Saharan drainage tunnels, supplies the fountains in the historical
centre of the town, situated on the opposite side of the canyon,
by means of an aqueduct-bridge which is, in its turn, supplied with
water tapped on the hill of Botromagno. |
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| Oasis of Timimoun
(Algerian Sahara), the interior of the drainage tunnel called foggara.
The tunnel is dug out of the limestone rock and thanks to its linear
development it is able to catch the quantity of water contained
in the porous ground. |
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| Oasis of Timimoun
(Algerian Sahara). The water sharing system at the surface outlet
of the foggara. |
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| Oasis of Timimoun
(Algerian Sahara), kesria, a water quota sharing system. |
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The
heaps of stone on the surface, resulting from the excavation wastes
of the vertical air shafts, show the underground layout of the
foggara. On right, air shaft of the drainage tunnel which opens
beneath the built-up area into large cavities for ablutions and
cooling.
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