Tarso Mohi. In the center is Tarso Ourari at about . To the west, in the vicinity of Tarso Toussidé, is the aforementioned Tarso Tôh, a small plateau at just , and the even smaller Tarso Tamertiou at . The plateaus are strewn with volcanic spires and are separated by canyons that have been formed by the irregular flow of wadis. After often-violent rains, they see the formation of ephemeral streams and flora. The southern, southwestern and eastern slopes of the mountain range have a gentle rise, while the northern slope of the range is a cliff overlooking the vast Libyan desert pavement known as the Serir Tibesti. Hydrology Five rivers in the northern half of the Tibesti Mountains flow to Libya, while the southern half belongs to the endorheic basin of Lake Chad. However, none of the rivers travel long distances, as the water evaporates in the desert heat or seeps into the ground, although the latter may flow great distances through subterranean aquifers. The wadis in the Tibesti are called enneris. The water mainly originates from the storms that periodically rage over the mountains. Their flow is highly variable. For example, the largest wadi, named Bardagué (or Enneri Zoumeri on its upstream portion) and located in the northern part of the range, recorded a flow of in 1954, yet over the next nine years it experienced four years of total drought, four years of flow less than and one year where three different flow rates were measured: . Other major rivers cut into the mountains: the Enneri Yebige flows northward until its riverbed disappears on the Serir Tibesti, while Enneri Touaoul joins the south-flowing Enneri Ke to form Enneri Miski, which then disappears in the plains of Borkou. Their basins are separated by an high watershed that runs from Tarso Tieroko in the west to Tarso Mohi in the east. The Enneri Tijitinga is the longest wadi in the range, flowing some southward. It forms in the west of the range and peters out in the Bodélé Depression, as does Enneri Miski a little further to the east, along with other wadis such as the Enneri Korom and Enneri Aouei. Several rivers flow radially on the southern slopes of the Emi Koussi before seeping into the sands of Borkou and then reemerging at escarpments up to south of the summit, near the Ennedi Plateau. At the bottom of