Aquifer boundaries explored by geoelectrical measurements in the Red Sea coastal plain of Jazan area, Southwest Saudi Arabia (original) (raw)
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2011
Geoelectrical resistivity surveys were carried out in Al Quwy’yia area, located at the centeral part of Saudi Arabia, to map the acquifer and estimate the groundwater potentuality. The acquired vertical electrical sounding (VES) data sets have been collected along three longitudinal profiles trending East-West, perpendicular to the basment/sedimentary contact. The data sets have been analysed using 1D to obtain the initial figure out of the resistivity layers along the areas. Then, the data were inversion resistivity section using 2D inversion scheme. Information from two boreholes were incorporated during the processing to enhance the results and constrain the resistivity models with geological layers. The results revealed mainly two geoelectric layers represent mainly the basement and sedimentary rocks. The basement rocks dip generally east ward, where the sedimentary section increases in this direction. The depth to the basement is about 50 m in the western part of the area and c...
Arabian Journal of Geosciences, 2013
ABSTRACT ABSTRACT: Several problems related to groundwater, such as less potentiality and inadequate quality were encountered during the reclamation of the studied area. The present area of study is one of these areas. It lies close to Km. 35, north of the Cairo - Alexandria desert highway with an area of about 16 km2. The delineation of the subsurface setting helps much in such circumstances. For this purpose, 16 Vertical Electrical Soundings (VES) were carried out. In addition, available data of 20 wells drilled in the area were utilized. The interpretation of the VES curves illustrated that the rock succession under the area consists of six layers; a surface layer formed of alluvial deposits with a thickness of up to 12 m. and electrical resistivity of 18 - 366 Ohm.m., followed downward with a thick dry zone with a thickness of 113 - 154m. and resistivity of 28 - 91 Ohm.m. This second layer is formed of sand , clayey sand and sandy clay. The third layer downward is similar in composition to the second layer but is saturated with water of the Miocene aquifer. It varies in thickness from 25 to 133 m. and in resistivity from 24 to 50 Ohm.m. the calculated clay percentage in this area were found to vary from 5.1% to 71.6%, which partly explains the variation in water salinity of this layer from 326 to 1587 ppm. The third layer is underlain by a clayey layer ranging in thickness from 9 to 24 m. and in resistivity from 6 to 18 Ohm.m. The fifth member of the succession is formed of basalt with a thickness of 32 - 47 m. and resistivity range of 106 - 928 Ohm.m. The last layer downward is formed of sandy clay and clay belonging to the Oligocene aquifer with a resistivity range of 5 - 69 Ohm.m. The interpretation of the geoelectrical data together with the available well data indicted the presence of six normal faults forming a basin in the middle part of the study area. Based on the depth to water, thickness, clay percentage (water quality) of the shallower aquifer, a priority map was constructed. The map indicated clearly that the promising parts of the area, as to the drilling of water wells, are the eastern and northern parts. In the southern and western parts, the deeper aquifer (Oligocene) lying under the basalt sheet may be utilized for relatively better water quality. VES stations 26, 35 and 36 are considered to be the best sites for the drilling of water wells reaching to the Oligocene aquifer in these part of the area.
The Quaternary aquifer of Wadi Ham, UAE has been overexploited during the last two decades to meet the increasing water demands. As a result, the dynamic balance between freshwater and seawater has been disturbed and the quality of the groundwater has deteriorated. In this paper, a 2D earth resistivity survey was conducted in Wadi Ham in the area between Fujairah and Kalba to delineate the seawater intrusion. Existing monitoring wells were used to measure the horizontal and vertical variations in water salinity and thus to improve the interpretation of earth resistivity imaging data. Results of vertical electrical soundings and chemical analyses of collected water samples were used to obtain an empirical relationship between the inferred earth resistivity and the amount of total dissolved solids. This relationship was used along with the true resistivity sections resulting from the inversion of 2D resistivity data to identify three zones of water-bearing formation (fresh, brackish, and salt-water zones). Along the four 2D resistivity profiles, the depth to the freshbrackish interface exceeded 50 m at the western part of the area and was in the order of 10 m or less in the eastern side near the shoreline. Depth to the brackish-saline water interface reached about 70 m in the western side and was in the order of 20 m in the eastern side. The thickness of the fresh water zone decreases considerably in the farming areas toward Kalba and thus the degree of seawater intrusion increases.
2020
n integrated geophysical survey including Vertical Electrical Sounding (VES), Transient Electromagnetic (TEM), and Electrical Resistivity Tomography (ERT) was conducted in the area of Wadi Sakhr, Northwestern Coastal Zone of Egypt. The objective of this survey is to characterize the conditions under which the groundwater occurs in the Middle Miocene carbonate rocks, which dominate the study area. The inversion results of 9 VES and 17 TEM measured sounding data revealed that the subsurface geoelectrical succession in most of the study area consists of five layers in addition to a sixth geoelectrical layer capping the succession at the northern part of the study area. The water-bearing zones were detected within the lower part of the third layer in the northern part of the area and the lower part of the fifth layer in the southern part of the study area. The inversion results of 11 ERT profiles revealed the detailed resistivity distribution of the subsurface layers and confirmed the r...
2023
A geophysical study was conducted to explore the shallow groundwater aquifer and to identify the subsurface structure on the basis of resistivity and geomagnetic surveys. The study area is situated in the southwestern portion of Saudi Arabia, southwest of the Najran region. The total intensity magnetic map is reduced to the northern magnetic pole. The estimated mean depths of the regional and residual magnetic sources are 3 km and 1.4 km respectively. Eighty vertical electrical soundings were measured using the Schlumberger configuration with AB/2 spacing of up to 700 m. Four geoelectrical layers were identified, and could be described from ground surface to deeper layers as the following: The first layer encompasses wadi deposits with true resistivity values ranging from 452 Ω.m to 1353 Ω.m and thicknesses of 2-4 m. The second layer is comprised of dry fine to medium grain-sized deposits with true resistivity values ranging from 104 Ω.m to 451 Ω.m, and thickness varying between 2 and 16 m. The third layer consists of water-bearing friable deposits beside the topmost part of the underlying weathered (fractured) basement. The true resistivity of this layer ranges from 22 Ω.m to 188 Ω.m, whereas the thickness of this layer is highly variable and ranges from 5 to 35 m. Generally, the resistivity values and the thickness of these three layers exhibit an increasing trend toward the main wadi stream. A fourth layer was also detected and is represented by a thin clay layer directly overlying the hard rocks of the basement complex. The dominant tectonic trends controlling the shallower parts are N-S and NNW-SSE. Meanwhile, the structural trend controlling the deeper parts is NE-SW, E-W, and. NNE-SSW. The ideal areas for drilling wells, according to the interpreted crosssections, are along the main stream of Wadi hubuna and other small wadis, as well as the lower portions of the wadi in the extreme east direction.