STRUCTURAL CONTROL OF GROUNDWATER FLOW, SOUTHERN SINAI, EGYPT: REMOTE SENSING CONSTRAINTS

The distribution of dikes and shear zones, their orientation, thickness, and density together with the rate and persistency of rainfall, absorptive characteristics of the land surface, permeability of the reservoir rocks, and slope gradient of land surface are the main factors that control the groundwater distribution and groundwater flow in southern Sinai. Precipitation generally occurs over the highly elevated Proterozoic basement rocks, and is channeled down stream as surface runoff in the valleys (wadis) or as groundwater flow in the alluvium aquifers flooring the valleys. Fractured basement can act as conduits for groundwater flow as well. We examined the temporal variations in backscattering values extracted from radar imagery to identify the water-bearing shear zones, dyke swarms, and valleys in the study area (southern Sinai). The adopted procedures were as follows: (1) spatial and temporal precipitation events over the basement complex were identified from Tropical Rainfall Measuring Mission (TRMM) data; a major precipitation event (34 mm) that occurred on January, 17 2010 was identified and selected for this analysis, (2) the shear zones and dyke swarms within the study area were delineated using false color Landsat band and band ratio images, (3) four Envisat ASAR (Advanced Synthetic Aperture Radar radar) scenes were selected, one before (November, 11 2009 ) and three after (20January 2010, 5 February 2010 , and 12 March 2010) the identified precipitation event, (4) the four images were co-registered, orbital corrected, multilooked, filtered, radiometric calibrated and at last beta & sigma nought images were produced.

Examining the generated backscattering images revealed that following a rain event, the water bearing dikes, shear zones, and valleys show evidence of retaining more water (high backscattering) than their surroundings. Ongoing research will focus on applying these findings to map all such aquifers in southern Sinai and to further test our findings by conducting geophysical techniques.