US Egypt Cooperative Research: Assessing the potential of natural resources for land use planning and development west of Aswan, Egypt
Principal Investigator: Magaly Koch
Co-Principal Investigator: Helmi Geriesh
Co-Investigator: Ahmed Gaber
Sponsor: National Science Foundation and Egyptian Science and Technology Development Fund
Duration: 2010 – 2013
A desert plain area near Aswan in Egypt has been investigated by a US-Egyptian research team to develop new techniques of multisensor data integration (from optical, infrared, thermal and radar sensors) for groundwater exploration and land use planning. Such research efforts are aimed to reclaim desert land for agricultural use in order to cope with increasing food and water demands for a growing population. The implementation of large agricultural activities in desert environments requires detailed knowledge about the soil and water characteristics, quality and availability. A combination of multispectral, thermal and microwave data obtained from space (ASTER and PALSAR) and supported by ground measurements (ground penetrating radar, field spectrometry and magnetometry) was used to investigate surface sediment characteristics of El-Gallaba Plain in the Western Desert near Aswan. This desert plain once hosted an ancestral river system long before the Nile even existed. At present the fluvial deposits are largely covered by aeolian and gravelly sands and thus only detectible with radar and thermal images.
Thermal and radar satellite sensors rely on different operating principles and have the potential to provide a wealth of information regarding the surface and near-surface sediment conditions, especially in desert environments. The thermal bands of ASTER images were used to calculate the Land Surface Temperature (LST). Results showed several broad strips of cooler temperature arranged in a linear fashion and diagonally crossing the alluvial basin. The surface sediments within the detected low thermal anomalies show generally higher reflectance values (higher albedo), and are well-sorted and finer than the surrounding sediments. The linearity of the thermal anomalies suggests that they are largely controlled by faults. To further investigate this point, images from ALOS/PALSAR radar sensor were analyzed. Due to its low frequency PALSAR L-band can penetrate loose and dry sand up to several meters, and therefore, image subsurface conditions. The ALOS/PALSAR full polarimetric data clearly revealed the buried faults and confirmed that subsurface structures form the boundaries of the thermal cooling anomalies in the desert plain area. The existence of such structurally controlled and largely hidden subsurface channels and depositional environments was further confirmed in the field by Ground Penetrating Radar (GPR) and magnetic surveys. The GPR profiles revealed obvious offsets in the subsurface stratigraphy suggesting the presence of highly fractured zones flanking the thermal anomaly strips. The magnetic survey on the other hand, detected the relief of the basement bedrock across the anomalies showing greater depths in the center and shallower depths toward the edges. This strongly suggests the existence of graben-like structures. The detected buried channels/depositional environments and faults may well form good groundwater traps or recharge conduits. Consequently, the structurally controlled El-Gallaba Plain basin could be a promising area for groundwater accumulation and exploration in the Western Desert of Egypt.