Wednesday, June 11, 2008

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Ouargla Oasis

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Ouargla, located in the sands of the northern Sahara Desert, overlies the North-West Sahara Aquifer (NWSA) which extends underneath Algeria, Tunisia and Libyan Arab Jamahiriya. Use of the superficial water table of the NWSA extends back to ancient times. In the 19th century, bore holes were drilled to access deeper parts of the aquifer. By the1970s there were roughly 2 000 bore holes on the NWSA. These wells now provide water to irrigate approximately 500 000 date palms surrounding Ouargla.

The region's traditional irrigation methods used sustainable amounts of water. Modern, more intensive irrigation methods can lead to degraded water quality, decreased water levels, and loss of artesian pressure, as well as salinization of the superficial water table and the soil. Natural drainage conditions and insufficient engineered drainage have already led to accumulation of water near the surface and a concentration of minerals. This salinized water at a depth of 0.5 to 1.5 m below the soil surface is detrimental to palm trees.

The 1976 image shows date palms surrounding Ouargla and Chott Aïn El Beda, a saline depression that has collected irrigation runoff for generations. The 2006 image shows a proliferation of irrigated land, which, without proper management, will not be sustainable.
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