干旱区生态环境知识资源中心

SIR-C and Radarsat radar data have been used to map structural and fluvial features in south-western Egypt in order to identify new ground-water resources in fracture rock aquifer settings. These radar data show broad areas of the desert are dissected by a dense fluvial network of palaeochannels. Radar data are ideal for mapping palaeochannels since some are sand covered ( L-band has the ability to penetrate to at least 2 m beneath the sand in arid areas) and many show pronounced structural control (radar clearly depicts the scarp faces of faults). Strong structural control of drainage is consistent with the development of fracture rock aquifers. Five types of channel morphologies have been identified. These are: channels with a stepwise pattern; braided channels; dendritic and trellis-like channels with pronounced structural control; and flood features that follow regionally extensive faults (up to 50 km length). The regionally extensive faults drain numerous wadis and extend for tens of kilometres in length, and likely reflect the existence of several connecting horizontal aquifers in the subsurface. These regional faults converge on the Kharga Depression, indicating a principal megawatershed in south-western Egypt leads to the subsurface here. The other fault types are more local in extent, thus reflect fracture rock aquifers of more limited areal extent.