page_title: Tibesti Mountains
section_title: Hydrology
hierarchical_section_title: Tibesti Mountains / Geography / Hydrology
caption_attribution_description: Camels in Guelta d'Archei, Ennedi, north-east Chad
context_page_description: The Tibesti Mountains are a mountain range in the central Sahara, primarily located in the extreme north of Chad, with a small extension into southern Libya. The highest peak in the range, Emi Koussi, lies to the south at a height of 3,445 metres and is the highest point in both Chad and the Sahara. Bikku Bitti, the highest peak in Libya, is located in the north of the range. The central third of the Tibesti is of volcanic origin and consists of five volcanoes topped by large craters: Emi Koussi, Tarso Toon, Tarso Voon, Tarso Yega and Toussidé. Major lava flows have formed vast plateaus that overlie Paleozoic sandstone. The volcanic activity was the result of a continental hotspot that arose during the Oligocene and continued in some places until the Holocene, creating fumaroles, hot springs, mud pools and deposits of natron and sulfur. Erosion has shaped volcanic spires and carved an extensive network of canyons through which run rivers subject to highly irregular flows that are rapidly lost to the desert sands.
  Tibesti, which means "place where the mountain people live," is the domain of the Toubou people.
context_section_description: Five rivers in the northern half of the Tibesti Mountains flow to Libya and are part of the Mediterranean Basin, 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 be carried great distances by subterranean aquifers.
  The wadis in the Tibesti are called enneris. The water 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 425 m³/s (15,000 cu ft/s) in 1954, yet over the next nine years it experienced four years of total drought, four years of flow less than 5 m³/s (180 cu ft/s) and one year where three different flow rates were measured: 4, 9 and 32 m³/s (140, 320 and 1,130 cu ft/s). This variability is partly due to the irregularity of the monsoon that can bring rainfall from the southwest up to 20 degrees north latitude, but in some years may retreat before it reaches this latitude. Two other significant rivers cut into the mountains: the Enneri Yebige flows northward until its riverbed disappears on the Sarir Tibesti plateau, 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 1,800-metre (5,900 ft) 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 400 km (250 mi) 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. The Enneri Douanré also flows southward. The Enneri Torku and Enneri Ofoundoui lie to the north; the Enneri Uri, Enneri Binem and Enneri Modiounga are in the east; the Enneri Yeo, Enneri Mamar, Enneri Tao, Enneri Woudoui and Enneri Dooze are to the west. 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 400 km (250 mi) south of the summit, near the Ennedi Plateau.
  At the bottom of many canyons are gueltas, wetlands that accumulate water mainly during storms and which can last most of the year. Above 2,000 m (6,600 ft), enneri beds sometimes contain sequential pools of water that remain largely unexplored. The water is replenished several times a year during flooding, and salinity levels are low. The Mare de Zoui is a small permanent body of water 600 m (2,000 ft) above sea level, located in the northern part of the mountains in the wadi of the Enneri Bardagué, 10 km (6.2 mi) north of Bardaï. Supplied by sources upstream of the wadi, in heavy rains it overflows and spills into small wetlands.
  The Yi Yerra hot springs is located on the southern flank of Emi Koussi, at about 850 m (2,800 ft) elevation. Water emerges from the springs at 37 °C (99 °F). A dozen hot springs are also located at the Soborom geothermal field on the northwest side of Tarso Voon, where water emerges at temperatures ranging between 22 and 88 °C (72 and 190 °F).
caption: A view of the Guelta d'Archei in the Ennedi Plateau, which is similar to the gueltas of the Tibesti Mountains
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