Multisensor characterization of subsurface structures in a desert plain area in Egypt with implications for groundwater exploration Magaly Koch* a , Ahmed Gaber b , Mohamed H., Gereish c , El-Sayed Zaghloul d , Sayed M. Arafat d , and Mostafa AbuBakr a a Center for Remote Sensing, Boston University, Boston, MA USA; b Geology Department, Faculty of Science, Port-Said University, Port-Said, Egypt; c Geology Department, Faculty of Science, Suez Canal University, Ismailia, Egypt; d National Authority of Remote Sensing and Space Science (NARSS), Cairo, Egypt ABSTRACT A desert plain in Egypt is being investigated to develop new techniques of multisensor data integration for groundwater exploration. A combination of multispectral, thermal and microwave data (ASTER and PALSAR) and supported by ground measurements (GPR, field spectroradiometry and magnetometry) were used to investigate surface sediment characteristics of the El-Gallaba Plain area, NW of Aswan. This desert plain once hosted an ancestral river system long before the Nile even existed. Nowadays the fluvial deposits are largely covered by Aeolian and gravelly sands and thus only detectible with radar and thermal images. Results show two broad strips of thermal cooling anomalies arranged in a linear fashion and diagonally crossing the alluvial basin. Spectral signatures collected along the linear land surface temperature (LST) anomalies show generally higher reflectance values (higher albedo) than the surrounding sediments. Both, the cooler LST and higher albedo, suggest that the surface sediments within the anomaly strips have lower emissivity values (low heat storage capacity). Furthermore, the homogeneity of these sediments was measured with a ground penetrating radar (GPR) using 250 & 100 MHz shielded antenna. The 12 GPR profiles across the LST anomalies confirmed that the near-surface sediments (up to 10 m depth) consist of thin horizontal layers of sandstone with very low gravel content. They show very different textural and compositional characteristics with respect to the surrounding areas suggesting a different depositional environment. Thus 12 magnetic profiles with 1.5 km average length were acquired across the LST anomalies to investigate deep seated structures. The results confirmed the existence of graben-like structures with a maximum depth to the basement of 150 m and shallower depths toward the edges of the LST anomalies. Consequently, these structurally controlled basins could be promising areas for ground water accumulation and exploration in the El-Gallaba Plain of the Western Desert in Egypt. Keywords: Multisensor, thermal anomalies, radar polarization signature, field spectroradiometry, GPR, magnetic survey, groundwater exploration, Western Desert of Egypt 1. INTRODUCTION In arid lands, water resources are a crucial source of life and a necessity for supporting land development activities. Current climate models predict an increase in aridity in the coming decades for most of America as well as much of Africa, Southern Europe and the Middle East, Australia, and Southeast Asia [1]. Thus persistent droughts will likely cause water shortages worldwide. In Egypt, the conventional water resources are scarce and mostly related to the Nile River. Alternative water sources are available from occasional flash floods that can be harvested through retention dams, or from groundwater that is largely non-renewable. This is the case in the Western Desert where vast amounts of fossil groundwater are stored in the Nubian sandstone aquifer. Mining these fossil groundwater reserves is a difficult socio- political decision and should be considered in a planned manner, i.e. by providing decision makers with relevant scientific information. Most of the groundwater in Egypt stored in the Nubian sandstone derives from past pluvial times, however, some of it is leaking into Quaternary aquifers which are presently recharged by occasional flashfloods from nearby mountains or Remote Sensing for Agriculture, Ecosystems, and Hydrology XV, edited by Christopher M. U. Neale, Antonino Maltese, Proc. of SPIE Vol. 8887, 888712 · © 2013 SPIE · CCC code: 0277-786X/13/$18 · doi: 10.1117/12.2029086 Proc. of SPIE Vol. 8887 888712-1 Downloaded From: http://spiedigitallibrary.org/ on 10/24/2013 Terms of Use: http://spiedl.org/terms