Mapping paleochannels in the Libyan Sahara with ground penetrating radar

Abstract

It has been well documented that the Sahara Desert experienced a number of humid periods during the late Quaternary, which resulted in the development of substantial lakes and fluvial networks. Today, the region is known for its hyper-arid conditions, with few isolated oases and no sizable surface drainage system. The remnants of these palaeochannels are now buried beneath the dunefields of the contemporary desert. However, their presence as potential groundwater migration pathways are of importance in understanding the palaeohydrological history of the Sahara, as well potential sources to tap for desert irrigation projects. Conventional means of locating these buried channels have used accurate terrain models to map contemporary seasonal drainage networks (wadis), or satellite-borne radar to penetrate a few meters beneath the sand sheet. An alternative approach is through the use of ground-based geophysics employing a deep-profiling ground penetrating radar technology. A survey over a 15 km × 18 km gravel plain in the Wädi al-Hayät in the Libyan Sahara reveals that ground radar technology can map buried channels rapidly and cost-effectively, given suitable ground conditions.