Document Type

Article

Publication Date

10-1-2017

Abstract

Groundwater resources in arid lands are crucial for súpporting life. Thus, delineation of low land areas, where surface runoff accumulated during pluvial periods assists in groundwater explorations. Therefore, the drainage patterns in northeastern Niger'using various sources of DEMs of optical (ASTER) and radar (SRTM) satellite data were extracted, These data reveal three palaeolakes in the Ténéré Desert. In addition, the DEMs toget her with the optical and radar satellite data were used to define a major watershed measuring 634,000 km², This watershed may have led to the formation of one major palacolake as an ancestor of the three palacolakes, The latter cxtend to 11.514 km². 17.571 km² and 18,453 km² The optical and radar satellites images show that the boundaries of these three lakes have been modified by extensive longitudinal and transverse sand dunes of consiclerable thickness. These dunes accumulated during a much later arid episode in geologic time. probably during the late Quaternary. Prior to that, the former marshlands received water from the Tibesti Mountains of northern Chad, the Ahaggar Plateau of southeaster Algeria and the Air Mountain of northern Niger. The drainage patterns clearly show the pathway of water down to the ground level. The longest drainage line is ema- nating from the Ahaggar Plateau and extends south west for 837 km. The water overflow of the southern- most lake led to the formation of another dlistinct drainage line, leading to the southwestern edge of the ancestral Megalake Chad. This drainage line begins in the vicinity ofthe town of Chehi and south- ward through the town of Dillia as a single tributary, and is here named the Dillia Palaeoriver. These observations, ~hich are based on the study of satcllite data require geophysical fieldwork to ascertain the interpretations, and ev aluate the potential for groundwater accumulation in the region. e 2017 Production and hosting by Elsevicr B.¥. on behalf of National Research Institute of Astronomy and Geophysics. This is an open access article under the CC BY_NC-ND license.

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