Oasis
Geography

Oases in the Middle East and North Africa cover about 1,000,000 hectares (10,000 km), however, they support the livelihood of about 10 million inhabitants. The stark ratio of oasis to desert land in the world means that the oasis ecosystem is "relatively minute, rare and precious."

There are 90 “major oases” within the Sahara Desert. Some of their fertility may derive from irrigation systems called foggaras, khettaras, lkhttarts, or a variety of other regional names.

In some oases systems, there is "a geometrical system of raised channels that release controlled amounts of the water into individual plots, soaking the soil."
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