Applications of Integrated Geophysical Surveys in Delineating Groundwater Occurrences at Cairo-Bilbeis Region, East Nile Delta, Egypt

Abstract

The study area is located at Cairo-Bilbeis Desert rood,north-eastern part of Greater Cairo, the eastern part of the Nile Delta,Egypt. It is located between X-coordinates350940 and 352171 meter easting and Y-coordinates 3349671 and 3350543 meter northing at Zone 36 UTM-coordinate system. The study area is mainly covered by Tertiary and Quaternary sediments. The exposed section varies in thickness which increases toward the Nile Delta recording more than 1000 m.

The main objective of this study is to delineate the groundwater occurrencesbased on the identification of the geological formations, geological structures and groundwater aquifers in the study area. The second objective is the use of modern geophysical method(seismoelectric method) which is sensitive to the presence of fluids. The third objective is the integration between the different geophysical methods which are the shallow seismic refraction tomography, geo-electric and seismoelectricfor identifying how successful is; to use seismoelectric method, where it has not been used before in Egypt, by comparing the results of these geophysical methods in the study area. Finally the calculation of the near surface soil geotechnical parameters and dynamic characteristics.

Sixteen seismic refraction tomography profiles with 24 geophone with seven shot per each profile, 10 seismoelectric profiles with 24 dipole and pre-amplifier with three shots per each profile and finally three vertical electrical sounding with AB/2 500, 500 and 600 meter are the data acquired for this study.

Analysis and interpretation of the geophysical data indicates that there are two groundwater aquifers in the study area. The first aquifer consists of the Miocene sands and sandstone which is located at a depth of about 75-80 meter from the ground surface with an average thickness of about 38.3 meter and contains fresh water with low salinity. The second aquifer consists of the Oligocene sands which is located at a depth of about 195-200 meter from the ground surface but our measurementsdid not reach to its bottom. Finally by comparing between the seismic refraction tomography and geo-electric results with the seismoelectric method we found good matching between the results. _____________________________________________________________ Keywords: groundwater aquifers, seismic refraction tomography, geo- electric, seismoelectric