The Sahara desert covers nearly 90% of Algerian territory, it is crossed by “ergs”: sand dunes, “regs”: stony terrain, as well as volcanic massifs in the far south2. In the north, the grass of the steppe slowly becomes scarce as the species change to make way for the reg. The erg, the sand desert covers only one fifth of the Sahara. The great eastern erg borders the Wadi Righ, a succession of oases, stretches along the underground wadi. The Saoura valley limits the great western erg to the west. Between these two great ergs, lies the M'Zab valley cut into a plateau3. This northern Sahara, still dotted with oases, is opposed to that of the South, dominated by the Hoggar massif at an altitude of more than three thousand meters. Vast monotonous hamadas such as the Tademaït plateau between El Goléa and In Salah link the large geographical areas of the Sahara3. The Sahara is characterized by low rainfall, recording less than 100 mm per year. It does happen, however, that it snows and floods sometimes come to revive the wadis that have dried up since prehistoric times. The subsoil is full of water in the Albian tablecloth which extends under a large part of the Algerian Sahara, a vestige of the steppe climate that the region experienced 10,000 years ago2.