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Rise and demise of the New Lakes of Sahara

¹ Department of Geological Sciences and Engineering, Missouri University of Science and Technology, 129 McNutt Hall, 1400 N. Bishop, Rolla, Missouri 65401, USA
² Department of Geology, Faculty of Science, Sohag University, Sohag, Egypt
³ National Authority for Remote Sensing and Space Sciences (NARSS), 23 Joseph Brows Tito Street, El-Nozha El-Gedida, P.O. Box 1564, Alf Maskan, Cairo, Egypt
⁴ Department of Geosciences, University of Texas at Dallas, 2601 North Floyd Road, Richardson, Texas 75083, USA

Multispectral remote sensing data and digital elevation models were used to examine the spatial and temporal evolution of the New Lakes of Sahara in southern Egypt. These lakes appeared in September 1998, when water spilled northwestward toward the Tushka depression due to an unusual water rise in Lake Nasser induced by high precipitation in the Ethiopian Highlands. Five lakes were formed in local depressions underlain by an impermeable Paleocene shale and chalk formation. The lakes developed through three stages. (1) A rise stage occurred from September 1998 to August 2001; the area covered by the lakes reached 1586 km². In this stage the rate of water supply far exceeded the rate of water loss through evaporation. This stage was characterized by an early phase (August 1998–August 1999) when the area covered by the lakes increased by 75 km²/month. This was followed by a late phase (August 1999–August 2001), in which area increase averaged 28 km²/month. (2) A steady-state stage occurred from August 2001 to August 2003, during which the area covered by the lakes remained relatively unchanged and water lost through evaporation was continuously replaced by water supply from Lake Nasser. (3) A demise stage occurred from August 2003 to April 2007, during which water supply from Lake Nasser stopped completely and water was continuously evaporating. The area covered by the lakes decreased to 800 km² with an average loss of 17 km²/month. If this trend continues, the New Lakes of Sahara will disappear completely by March 2011. The spatial distribution of the New Lakes of Sahara is strongly controlled by morphologically defined east-, north-, northeast-, and northwest-trending faults. The water recharge of the Nubian aquifer by the New Lakes of Sahara is insignificant; much of the lakes' area is above an impermeable formation.

Keywords: New Lakes of Sahara • Western Desert • Egypt • Nubian aquifer