Oases occur in the desert wherever there is a permanent supply of fresh water. They vary in size from a few acres round a stream to vast areas of naturally watered or irrigated land. The house in the oases are built of clay and look like white cubes among the date palms which are the most important plants of desert people, known as the Tuareg, believe that the date palm should have its head in fire and its feet in water. For this reason farmers have built a system of underground canals in oases to bring water to the tree’s roots.

Where there are no such irrigation canals date palms are cultivated together in the middle of a large circular ditch. This ditch can be up to 10 meters deep in order to reach the water underground. Sand keeps sliding down the sides of the ditch and this has to be removed all the time to prevent the trees from being suffocated. In the past all the hard work needed to cultivate the date palm was sometimes in vain because enemies might rain the oases steal all the fruit. To prevent this the farmers in the oases would strike up a rough bargain with the Tuareg tribesmen. Under this bargain the farmers supplied the fierce nomads with dates and grain in exchange for protection against raiders and thieves. This arrangement was known as debiha. One of the requirements was a curfew which meant that everybody in the oasis had to stay indoors after dark. Only the watchman appointed under the debiha was allowed to stay outside and patrol the neighborhood. The watchman was always a Tuareg.