Hydraulic and electric anisotropy of shallow fresh coastal aquifer in Nabq, Sinai, Egypt
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ORIGINAL PAPER
Hydraulic and electric anisotropy of shallow fresh coastal aquifer in Nabq, Sinai, Egypt Mohamed H. Khalil 1
Received: 2 October 2015 / Accepted: 4 January 2016 / Published online: 28 March 2016 # Saudi Society for Geosciences 2016
Abstract The prospective of this research is to investigate the hydraulic and electric anisotropy of the fresh coastal aquifer. In this context, 44 Schlumberger DC soundings associated with the available boreholes data and numbers of measured and/or calculated hydraulic and electric parameters were carried out in Nabq area, Sinai. The inverted DC soundings revealed high potentiality of the fresh coastal aquifer toward the western part of the Quaternary and Pre-Quaternary. An increased tortuosity (T) toward the west direction was associated with coarser grains size and increase in resistivity (ρ) hydraulic conductivity (K), transmissivity (T), and a decrease in porosity (ϕ). The longitudinal hydraulic conductivity (Kl) was found to be greater than the transverse hydraulic conductivity (Kt) which implied a lower tortuosity in the horizontal direction than in the vertical direction. The decrease in the hydraulic anisotropy (λH) was associated by an increase in transmissivity. Minor variation in electric anisotropy (λe) could be observed as a result of alternating layers and intercalation of different grain sizes. Resistivity of the fresh aquifer was recognized by a liner direct relation with λH, whereas, no clear relation could be observed with λE. A polynomial relation with poor correlation coefficient could be observed between λH and λE.
Keywords Hydraulic anisotropy . Electric anisotropy . Tortuosity . Resistivity . Hydraulic conductivity . Transmissivity . Porosity . Fresh coastal aquifer
* Mohamed H. Khalil [email protected]
1
Faculty of Science, Geophysics Department, Cairo University, Giza, Egypt
Introduction Nabq is one of Egypt’s strategic tourist sites located on the Gulf of Aqaba, Sinai, Egypt (Fig. 1). The site of the present investigation covers an area of about 36 km2, lying between longitudes 34° 34′ and 34° 46′ E and latitudes 28° 12′ and 28° 22′ N. The area is bounded to the west by Nabq Mountains and to the east by the Gulf of Aqaba (Figs. 1 and 2). The absence of the freshwater resources in Nabq necessitates investigations of the local groundwater aquifers. Currently, groundwater constitutes the main source of economic freshwater in Nabq area. The exploited groundwater of Nabq is slightly brackish (TDS ∼650 ppm), and is used after treatment for drinking both in Nabq and Sharm El-Sheikh (SEAM Programme 1999). Reliable modeling for the conditions of the shallow fresh coastal aquifer constitutes the cornerstone for optimizing groundwater exploitation over time. In the past, the application of hydrogeophysics was limited to define the geometry of the target aquifer. Lately, hydrogeophysical measurements are being used to define the geohydrological and rock formations hydro-physical properties of aquifer (Christensen 1998; Worthington 2001; Slat
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