Most of the Lake Chad basin is covered by Quaternary sands. Below the sands, at about 75 m depth, appear the clays of the Pliocene with a mean thickness of approximately 280 m. Further down, a layer of sand of about 30 m thickness is encountered that belong to the Lower Pliocene. These sands give place to the real Pliocene aquifer, as the clays are generally considered as impermeable. Further down appear the sandstones of the Continental Terminal (Tertiary) with a thickness of about 150 m. The deepest aquifer is the Continental Hamadien (Cretaceous), which also consists of sandstone. The granitic and gneiss rocks of the basement at the bottom are considered as the base of the system. Given its geological characteristics, the Lake Chad basin has considerable groundwater resources. Effective infiltration varies between 5 mm around the 15th parallel and 100 mm around the 10th parallel. Groundwater exploitation was estimated at 438 million m3 in the early 1990s in the Conventional Basin. This level of exploitation is insignificant in relation to available reserves.

Name
Geology
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Surface Basin (Conventional)
Entire Basin
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