John Tyman's Cultures in Context Series EGYPT and the SAHARA www.johntyman.com/sahara |
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5.2 Irrigation : 369-377 |
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John Tyman's Cultures in Context Series EGYPT and the SAHARA www.johntyman.com/sahara |
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5.2 Irrigation : 369-377 |
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| .369. Permanent settlements like this are only possible where there is water. And since reliable sources of water are few and far between in the Sahara, settlements are widely spaced. (Djanet) |
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| .370. With the obvious exception of the Nile there are no rivers flowing year-round across the desert, so water for irrigation must be obtained from underground. Some settlements are blessed with natural springs: Tozeur, in Tunisia, is blessed with 200 springs, and has prospered accordingly. In most cases, though, water must somehow be raised to the surface ... and there are many ways of doing this. (Tozeur) |
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| .371. The best known is the shaduf, where a bucket is suspended from a counter-weighted pole. To drop the bucket into the well you simply raise the weight: to get water you pull down on the pole. However, the shaduf is suitable only for shallow wells, to around 10 metres in depth. (Oasis south of El Oued) |
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| .372. When the well if deeper -- say 10 to 70 metres -- the bucket can be raised using a pulley and a rope. When the well is deep the rope will be attached to an animal that is made to walk up and down a ramp -- the length of which depends on the depth of the well. (North of Touggourt) |
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| .373. Water wheels (sakiehs or norias) are used also, powered by farm labourers or draft animals. In this case a series of interlocking cogs lifts a chain of buckets filled with water. (Kom Ombo) |
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| .374. Where the flow from natural springs is adequate, water may be channeled direct to palm groves. And where landforms permit, it may be conveyed by underground channels (known as foggaras or quanats), which tap into the water held in gravel fans [see frames 314 & 315]. (El Golea) |
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| .375. Unfortunately, because of the demands placed upon it, the water table is sinking in many parts of the Sahara, and wells must be deepened from time to time ... like this one at Arak. |
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| .376. Elsewhere, deep bores have been drilled (in modern times) to tap artesian waters far below. These sometimes provide enough to irrigate large areas ... in the Central Sahara at El Golea, Ouargla and near Ghardaia for example; but the water is hot when it reaches the surface and must be cooled before it can be used in irrigation. Also, with each new well the volume of fossil water available in these artesian basins is reduced. (Warm water bore north of El Oued) |
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| .377. In addition, of course, the application of mineral-rich waters to palm groves year after year has resulted in saline soils and the need for better drainage facilities, and (if possible) quantities of fresh water to flush out the salt. (Salt encrusted soils near Touggourt) |
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