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Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt
Egyptian Journal of Aquatic Research (2016) xxx, xxx–xxx
H O S T E D BY
National Institute of Oceanography and Fisheries
Egyptian Journal of Aquatic Research http://ees.elsevier.com/ejar www.sciencedirect.com
FULL LENGTH ARTICLE
Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt M.I.I. Mohamaden *, H.M. El-Sayed, A.Z. Hamouda National Institute of Oceanography and Fisheries, Alexandria, Egypt Received 24 August 2016; revised 12 October 2016; accepted 31 October 2016
KEYWORDS El-Themed; Sinai Peninsula; Malha Formation; VES
Abstract The study area is located at south central part of Sinai Peninsula at El-Thamed area. Geoelectrical resistivity method was used by measuring eighteen vertical electrical soundings using the Schlumberger configuration with total current electrode separation ranging between 3 m and 4000 m in order to investigate the deep groundwater aquifer and to delineate the subsurface structures of this area. The geoelectrical cross-sections show that the subsurface section consists of six geoelectrical units. The first unit is Quaternary deposits with thickness ranging from 0.6 m to 30.9 m and the resistivity values ranging from 177 Ohm.m. to 39680 Ohm.m. The second geoelectrical unit is composed of Egma Formation, with thickness ranging from 9.2 m to 12.8 m and the resistivity values ranging between 21 Ohm.m. and 82 Ohm.m. The third geo-electrical unit is composed of Paleocene Esna shale, also not detected at the study area with exception at profile 2, its thickness ranges from 15.6 m to 166.5 m and resistivity range from 8.9 Ohm.m. to 20 Ohm.m. This layer has not been detected at the extremely southern part of this profile, its depth ranges from 9.63 m to 15.5 m. The fourth geoelectrical unit is composed of Nubian Sandstone of Malha Formation (Lower Cretaceous) with depth ranging from 0.5 m to 8.9 m and its resistivity values ranging from 14 Ohm.m. to 133 Ohm.m. This layer represents the main aquifer in the study area with thickness ranging between 14.2 m and 283 m. The fifth geoelectrical unit is composed of claystone of Naqus Formation with depth ranging from 14.2 to 349 m and its resistivity values ranging from 2.7 Ohm.m. to 13 Ohm.m., sometimes, it is extends to the maximum depth of penetration. The sixth geoelectrical unit is composed of Basement rocks. It is characterized by resistivity ranging from 970 Ohm.m. to 25462 Ohm.m. and depth ranging from 60.1 m to 283 m. This unit is detected at the eastern part of the study area. Structurally, the study area is affected by sets of faults trending mainly NE-SW (Aqaba Trend). Ó 2016 National Institute of Oceanography and Fisheries. Hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
* Corresponding author. E-mail address: [email protected] (M.I.I. Mohamaden). Peer review under responsibility of National Institute of Oceanography and Fisheries. http://dx.doi.org/10.1016/j.ejar.2016.10.007 1687-4285 Ó 2016 National Institute of Oceanography and Fisheries. Hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
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Introduction The study area lies between latitudes 29.246607°N and 29.532753°N and longitudes 33.988647°E and 34.674099°E with an area of about 2111.8 km2 (Fig. 1a). It is suffering from water shortage which is essential for domestic use and agricultural activities. The vertical electrical sounding (VES) method is used to provide reliable information about the shallow subsurface layers. The electrical resistivity method is a favorable geophysical tool which is commonly used for groundwater exploration. It provides beneficial information about the subsurface lithology and structures (Jakosky, 1961; Keller, 1967). Many authors used the geoelectrical tool for investigation of groundwater or the structure affecting the groundwater flow such as Mohamaden (2005, 2008), Mohamaden and Abu Shagar (2008), Mohamaden et al. (2009), Santos et al. (2006) and Sultan et al. (2009a). Other geoelectrical studies have been performed around the study area such as Hossein (1980), Shaaban (1980), Massoud (2005) and Sultan et al. (2006, 2009b, 2015). It is concluded that the groundwater aquifer is affected by various geologic structures trending in the of NE–SW and NW–SE directions. The main aims of the present study are to explore the Nubian Sandstone aquifer, evaluating the affecting structures and controlling the geometry of the aquifers configuration. Hydrogeological setting The hydrogeological evaluation of the main aquifer in east Central Sinai is Malha sandstone aquifer (Lower Cretaceous)
Figure 1
with high hydraulic parameters and good water quality (Shalaby and Seiam, 2012) . The groundwater of Lower Cretaceous aquifer exists under confined conditions (Ghoubachi, 2013). The top surface of the Lower Cretaceous dips steeply toward the southwest direction. The average sand percent of the penetrated aquifer attains 54%. The groundwater flow direction of Lower Cretaceous aquifer is concentric to the center of study area related to the influence of the graben block which controlled by the fault-fold patterns. The general hydraulic gradient ranges from 0.0011 to 0.0028. The average effective porosity and transmissivity and hydraulic conductivity of the Lower Cretaceous aquifer are 17.3%, 416 m2/day and 1.4 m/day, respectively (Ghoubachi, 2013; Shalaby and Seiam, 2012). They increase toward the northeast direction with increasing of the sand percentage. The groundwater salinity increases coinciding with groundwater flow. The groundwater salinity of the Lower Cretaceous aquifer is brackish water and varies from 2510 to 5256 ppm (Ghoubachi, 2013). Geologic setting The central part of the study area is characterized by relatively low elevation with drainage system collecting the rain water from the surrounding parts of the study area (Hamouda, 2006). The study area is located nearly to the active tectonics region (Gulf of Aqaba) which is characterized by left lateral strike slip fault. The recent main major earthquake sequences for their foreshocks and aftershocks from the period from 1983 to 1996. The three characteristics of the main earthquake sequence have been discussed; i.e. epicenters and hypocenters
(a) Location map showing the study area; (b) Digital elevation model of Sinai.
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
Application of Electrical Resistivity and GIS for and Groundwater Exploration distribution of foreshocks and aftershocks, mechanisms of rupture process of movement, variation of stress drops in space and time domains, heterogeneous structures in the crust, and occurrence times of earthquakes (Hamouda, 2009a,b, 2011). The swarm seismicity along the central part of the Gulf of Aqaba, may be related to the effect of active tectonic process in this area that affect both the shallow and deep crusts. Also, it may be associated with the actual effect of mantle upwelling at the crustal thickness in this area (Hamouda, 2010). The main surface geology was described in the geological map of Sinai with scale 1:500,000 (Fig. 2). According to different studies on this area (Said, 1981; Bhattacharyya and Dunn, 1986; EGSMA, 1993; Kora and Genedi, 1995; Abdel-Gawad et al., 2006; Sultan, 2009b,c; Medhat, 2011), the subsurface stratigraphic units were described (Fig. 3)as follows: Quaternary Deposits; Most of the area is covered by Pleistocene alluvium deposits. Egma Formation; It is composed of chalky limestone of Lower Eocene. Esna Formation; It is composed of Paleocene marly shale. Suder Formation; It is composed of Upper Cretaceous chalky limestone intercalated with very thin bands chert with some marls and argillaceous limestone streaks of Maastrichtian age. Duwi Formation; It is composed of Campanian carbonate alternated with clastic. Matullah Formation; It represents the limestone of Coniacian–Santonian age. It is composed of basal shale followed by sandstone, marls, fossiliferous limestone and nonfossiliferous sandstone. Wata Formation; It is composed of Turonian-Coniacian dolomitic limestone with sandstone and shale intercalation. Galala Formation; It is composed of fossiliferous marl, dolomitic limestone, with a few shale siltstone interbeds.
Figure 2
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Malha Formation; It is formed from Lower Cretaceous nonfossiliferous sandstone intercalated with mudstone. Naqus Formation; It is formed from medium to coarse grained Sandstone. The basal units inter finger with Araba Formation. Araba Formation; It is composed of Cambrian sandstone and sandy claystone. Basement Rocks; It is Granitic Pre-Cambrian basement rocks. Materials and methods (i) Geoelectrical data In this study, eighteen VES’s (covering the study area) were performed in 2014 using Syscal-Pro instrument. Schlumberger configuration was used with total current electrode separation ranging between 3 m and 4000 m. The main aim is to detect the Nubian Sandstone aquifer in addition to the geologic structures in the study area (Fig.4). The geoelectrical parameters have been correlated by the geology obtained from previous work. (ii) Geographic information system Geographic information system (GIS) is a powerful tool that can help to overlay maps with different thematic data and facilitate map integration and analysis (Khalifa and AbdelHalim, 2013). It was used to build a geodatabase containing the study area and the field measurements in order to generate contour maps showing the spatial variation of the measured apparent resistivity values and the groundwater depth in the study area. The obtained data have been analyzed using the geostatistical analyst tools in ArcGIS software by examining the data
Geological Map of the study Area (modified after Conoco, 1987).
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
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M.I.I. Mohamaden et al. using the exploratory spatial data analysis (ESDA) which is a set of tools that allow graphically exploring the data distribution, looking for outliers, looking for global trends and examining the spatial autocorrelation (ESRI, 2003). Each parameter of the measured data was examined by ESDA tools such as histogram and QQPlot to determine whether it is normally distributed or not and to determine the suitable type of data transformation if needed. The presence of global trends was also checked in each parameter using trend analysis tool which provides a three dimensional perspective of the data. The semivariogram tool was used to explore the spatial autocorrelation of the measured data (ESRI, 2003). Based on the ESDA data examination, the suitable interpolation method has been chosen for each parameter. Kriging method is one of the most common geostatistical interpolation methods. It is a probabilistic predictor which uses the least square linear regression algorithms to estimate the value of a continuous attribute in any unmeasured location using the values of the surrounding measured points (ESRI, 2010; Krivoruchko, 2012; Jensen and Jensen, 2013). The ordinary Kriging method was used for interpolating the apparent resistivity values and the groundwater depth in the study area. The digital elevation model (DEM) was used to extract the elevation value at the VES locations of the geophysical survey which is needed for constructing profiles. In this study, ASTER-GDEM-v.2 scene was analyzed using ArcGIS for this purpose. (iii) Quantitative interpretation of vertical electrical soundings (VES)
Figure 3 Stratigraphic Column of the Study Area (modified after EGSMA, 1993).
Figure 4
In order to determine the subsurface layer parameters (resistivity and thickness), the manual interpretation technique was utilized by matching the plotted field curves with two layers master curves and the generalized Cagniard graphs (Koefoed, 1960; Orellana and Mooney, 1966). The obtained results were introduced to the IPI2WIN software (Bobatchev et al., 2001) as initial models to compute the final models.
Location map showing VES and profiles distribution.
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
Application of Electrical Resistivity and GIS for and Groundwater Exploration
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tive high resistivity values which may be referred to the existence of a compacted limestone while the western parts have a relatively low resistivity values reflecting the existence of a probable clay layer.
Results and discussion (i) Iso-Apparent maps Iso-Apparent maps (Fig. 5) shows that the surface layer is characterized by high resistivity values which may be attributed to the surface unconsolidated quaternary deposits. At AB/2 = 8 m, the resistivity of the northwestern and northeastern parts of the study area tend to decrease due to the partial saturation of water. Generally, the resistivity values tend to decrease in the whole study area with depth as a result of the subsurface saturation with water. At AB/2 = 300 m, the southeastern part of the study area is characterized by a rela-
(ii) Geoelectrical cross-sections The results of VES’s interpretation revealed 5–6 subsurface layers. The geoelectrical cross-section No. 1 (Fig. 6) is located at the most western part of the study area with a total length of about 26 km. It consists of four VES’s named 1, 2, 3 and 4. This cross-section shows that the subsurface section consists of five geoelectrical units. The first unit is composed of surface
AB/2 = 8m
AB/2 = 10m
AB/2 = 25m
AB/2 = 30m
AB/2 = 65m
AB/2 = 500m
Figure 5
AB/2 = 300m
AB/2 = 1000m
Iso-apparent resistivity maps.
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
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Figure 6
Geoelectrical cross-section for profile 1.
Quaternary wadi deposits with thickness ranging from 1.8 m to 3.5 m and the resistivity values ranging from 226 Ohm.m. to 2732 Ohm.m. The second geoelectrical unit is composed of limestone or chalk with flint of Lower Eocene (Egma Formation) with thickness ranging from 9.2 m to 12.8 m and resistivity values ranging between 21 Ohm.m. and 82 Ohm.m. It covers the ground surface at VES 2, and is not detected at the most southern part of this profile. The third geoelectrical unit is formed from Paleocene Esna shale with thickness ranging from 15.6 m to 166.5 m and resistivity values ranging from 8.9 Ohm.m. to 20 Ohm.m., and not detected at the most southern part of this profile. The fourth geoelectrical unit is Nubian Sandstone of Malha Formation (Lower Cretaceous) with depth ranging from 3.5 m to 182 m and its resistivity values ranging from 35 Ohm.m. to 113 Ohm. m. This Nubian Sandstone represents the main aquifer in the study area where its thickness at the geoelectrical cross-section No. 1 increases toward the southern part of this profile (Fig. 6). This thickness ranges from 20.8 m at the northern part of this profile to 200.5 m to the south. The fifth geoelectrical unit is composed of claystone of Naqus Formation with depth ranging from 46 m to 349 m and its resistivity values ranging from 3 Ohm. m. to 13 Ohm.m., its depth increases toward the southern part of this profile specially at VES 3. It extends to the maximum depth of penetration. Structurally, this profile is affected by two probable faults. The first fault (F1) is located to the south of VES 2 with down thrown side toward the southern direction, while the second fault (F2) is located to south of VES 3 with down thrown side toward the northern direction. These two faults form a graben structure which reflects that the central part represents the deepest part of Malha Formation. Geoelectrical cross-section No. 2 (Fig. 7) is located at the central part of the study area with total length of about 20.9 km. It consists of four VES’s named 8, 9, 10 and 11. This cross-section shows that the subsurface section consists of two geoelectrical units. The first unit is composed of surface Qua-
ternary wadi deposits; its thickness ranges from 1.6 m to 25 m and the resistivity values range from 220 Ohm.m. to 39680 Ohm.m. covering the ground surface of this profile. The second geoelectrical unit is composed of Nubian Sandstone of Malha Formation (the main aquifer) with depth ranging from 1.6 m to 25 m and its resistivity values ranging from 16.5 Ohm.m. to 62.3 Ohm.m. This unit extends to the maximum depth of penetration. Structurally, this profile is affected by two probable faults. The first fault (F3) is located to the northwest of VES 9 with down thrown side toward the northwest direction, while, the other fault (F4) is located to the northwest of VES 18 with down thrown side toward the southeast direction. These two faults form a horst structure which reflects that the central part is characterized by shallow depth for the Malha Formation. Geoelectrical cross-section along profile 3 (Fig. 8) is located at the eastern part of the study area with a total length of about 19.2 km. It consists of four VES’s named 13, 14, 15 and 17. This cross-section shows that the subsurface section consists of four geoelectrical units. The first unit is composed of surface Quaternary wadi deposits with thickness ranging from 8.8 m to 30.9 m and the resistivity values ranging from 177 Ohm.m. to 2068 Ohm.m. The second geoelectrical unit is composed of Nubian Sandstone of Malha Formation (the main aquifer) with depth ranging from 8.8 m to 30.9 m and its resistivity values ranging from 14.1 Ohm.m. to 71.2 Ohm. m. The base of this unit extends to depth ranging from 31.2 m to 274. The third geoelectrical unit is composed of claystone of Naqus Formation with depth of 31.2 m and resistivity value of 2.7 Ohm.m. It has been detected at VES 13. The fourth geoelectrical unit is the basement rocks represented by Pre-Cambrian Granite. It is located at the deepest parts in this profile with resistivity values ranging from 3524 Ohm.m. to 25462 Ohm.m. The depth to the basement rocks is ranging from 60.1 m to 274 m. Structurally, this profile is affected by two probable faults. The first fault (F4) is located to the south of VES 13 with down
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
Application of Electrical Resistivity and GIS for and Groundwater Exploration
Figure 7
Geoelectrical cross-section for profile 2.
Figure 8
Geoelectrical cross-section for profile 3.
thrown side toward the southern direction, while, the other fault (F5) is located to the north of VES 17 with down thrown side toward the northern direction. These two faults form a graben structure which reflects that the central part is deeper for the Malha Formation. Geoelectrical cross-section along profile 4 (Fig. 9) is located at the northern part of the study area with a total length of about 30 km. It consists of seven VES’s named 5, 6,7, 11, 12, 13 and 16. This cross-section shows that the subsurface section consists of four geoelectrical units. The first unit is composed of surface Quaternary wadi deposits with thickness ranging from 0.6 m to 8.9 m and resistivity values ranging from 309 Ohm.m. to 4746 Ohm.m. The second geoelectrical unit is composed of Nubian Sandstone of Malha Formation (the main aquifer) with depth ranging from 0.6 m to 8.9 m and resistivity values ranging from 22.9 Ohm.m. to 133 Ohm.m.
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This unit extends to the maximum depth and its thickness ranging from 14.2 m to 283 m. The third geoelectrical unit is composed of claystone of Naqus Formation with a depth ranging from 14.2 m to 283 m and its resistivity values ranging from 2.7 Ohm.m. to 9.4 Ohm.m. It has not been detected at VES 7 and VES16. The fourth geoelectrical unit is the Granitic PreCambrian basement rocks. It is located at the deepest parts in this profile with resistivity values ranging from 970 Ohm. m. to 18841 Ohm.m. Structurally, this profile is affected by two probable faults. The first fault (F3) is located to the east of VES 11 with down thrown side toward the eastern direction, while the other fault (F4) is located to the west of VES 13 with down thrown side toward the western direction. These two faults form a horst structure which reflects that the central part is characterized by shallower depth for the Malha Formation.
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
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Figure 9
Geoelectrical cross-section for profile 4.
The true resistivity of the water bearing layer decreases toward the eastern parts of the study area (Fig. 10). This may be attributed to the saltwater intrusion from the Gulf of Aqaba. The depth of groundwater increases toward the western and southeastern parts, while it decreases in the northern parts of the study area as shown in Fig. 11. Conclusion The central part of the area under investigation is characterized by high elevation with drainage system collecting the water from wadi El Arish to the central part of the study area. Eighteen VES’s were applied to provide reasonable results and clear the picture about the subsurface formations. IsoApparent maps show that the surface layer is characterized by high resistivity values which may be attributed to the surface unconsolidated quaternary deposits. Generally, the resis-
Figure 10
tivity values tend to decrease in the whole study area with depth as a result of the subsurface saturation with water. At AB/2 = 250 m, the southeastern part of the study area is characterized by a relative increase in the resistivity values which may be attributed to the existence of a compacted limestone while the western parts have a relatively low resistivity values reflecting the existence of a probable clay layer. The results of VES’s interpretation revealed 5–6 subsurface layers. The geoelectrical cross-sections show that the subsurface section consists of six geoelectrical units. The first unit is composed of surface Quaternary wadi deposits with thickness ranging from 0.6 m to 30.9 m and the resistivity values ranging from 177 Ohm.m. to 39680 Ohm.m. The second geoelectrical unit is composed of limestone or chalk of Lower Eocene (Egma Formation). It is located at the extremely western part of the study area, with thickness ranging from 9.2 m to 12.8 m and resistivity values ranging between 21 Ohm.m. and
True resistivity map of the water bearing layer.
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
Application of Electrical Resistivity and GIS for and Groundwater Exploration
Figure 11
9
Depth map of the groundwater.
F F
F
F F
F
F
Down Figure 12
Up
Sketch map for faults directions.
82 Ohm.m. It covered the ground surface around of VES 2, and is not detected at the extreme southern part of this profile; it extends to a depth ranging from 1.8 m to 3.5 m. The third geo-electrical unit is composed of Paleocene Esna shale, also not detected at the study area with exception at profile 2, its thickness ranges from 15.6 m to 166.5 m and resistivity ranges from 8.9 Ohm.m. to 20 Ohm.m. This layer has not been detected at the extremely southern part of this profile, its depth ranges from 9.63 m to 15.5 m. The fourth geoelectrical unit is composed of Nubian Sandstone of Malha Formation (Lower Cretaceous) with depth ranging from 0.5 m to 8.9 m and its resistivity values ranging from 14 Ohm.m. to 133 Ohm.m. This layer represents the main aquifer in the study area with thickness ranging between 14.2 m and 283 m. The fifth geoelectrical unit is composed of claystone of Naqus Formation with depth ranging from 14.2 to 349 m and its resistivity values ranging from 2.7 Ohm.m. to 13 Ohm.m., sometimes, it is extends to the maximum depth of penetration. The sixth geoelectrical unit
is composed of Basement rocks. It is characterized by resistivity ranging from 970 Ohm.m. to 25462 Ohm.m. and depth ranging from 60.1 m to 283 m. This unit is detected at eastern part of the study area. Structurally, the study area is affected by sets of faults (Fig. 12) trending mainly NE-SW (Aqaba Trend). References Abdel-Gawad, G.I., El Qot, G.M., Mekawy, M.S., (2006): Cenomanian-Turonian Macrobiostratigraphy of Abu Darag Area, Northern Galala, Eastern Desert, Egypt, Intern. Conf. Geol. Arab World (GAW8), Cairo Univ., Giza, Egypt, p. 553–568. Bhattacharyya, D.P., Dunn, L.G., 1986. Sedimentologic evidence for repeated pre-cenozoic vertical movements along the Northeast Margin of the Nubian Craton. J. Afr. Earth Sci. 5 (2), 147–153. Bobatchev A., Modin, I., Shevnin, V. (2001): IPI2WIN V. 2 for VES data interpretation. Dept. of Geophysics, Geological Faculty, Moscow State University, Russia.
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
10 Conoco, Coral., 1987. Geological map of Egypt, scale 1:500,000-NH 36 SE-South Sinai. The Egyptian General Petroleum Corporation, Cairo, Egypt, Egypt. Egyptian Geological Survey and Mining Authority (EGSMA), (1993): Geological and geophysical studies for groundwater exploration on Nukhl area, central Sinai. Internal report No. 49/93, 24p. ESRI, 2003. Using ArcGIS Geostatistical Analyst. Environmental Systems Research Institute, Redlands, CA, USA. ESRI, 2010. ArcGIS Geostatistical Analyst. Environmental Systems Research Institute, Redlands, CA, USA. Ghoubachi, S.Y. (2013): Contribution to the hydrogeology of the Lower Cretaceous aquifer in east Central Sinai, Egypt, Journal of King Saud University – Science, Vol. 25, pp. 91–105. Hamouda, A.Z., 2006. Seismic hazard of Eastern Mediterranean. J. Acta Geophys. 54 (2), 163–173. Hamouda, A. Z., (2009a): Recent evaluation of the assessment seismic hazards for Nuweiba, Gulf of Aqaba. Arab J. Geosc., 10.1007/ s12517-009-0096-3. Hamouda, A.Z., 2009b. A Reanalysis of the AD 365 Tsunami Impact along the Egyptian Mediterranean Coast. Acta Geophys. 58 (4), 1– 18. Hamouda, A.Z., 2010. Worst scenarios of tsunami effects along the Mediterranean coast of Egypt. Mar. Geophys. Res. 31, 197–214. Hamouda, A.Z., 2011. Assessment of seismic hazards for Hurghada. Nat Hazards, Red Sea, Egypt. 10.1007/s11069-011-9767-y. Hossein, Z.E.M., 1980. Geophysical study on abu Hamath – Nakhl – Darag area, central of Sinai a. R.E. (MSc.). Ain Shams Univ., Egypt, p. 98p. Jakosky, J.J., (1961): Exploration geophysics. Tiya New Beach Calif, Techs. 1, 2 and 6. Jensen, J.R., Jensen, R.R., 2013. Introductory Geographic Information Systems. Pearson, Toronto. Keller, G.V., 1967. Application of resistivity method in mineral and groundwater exploration programs. Geophys. Surv. Can. 26, 51– 66. Khalifa, N. & Abdel-Halim, N., 2013.An Evaluation of the GIS Industry in Egypt. International Conference on Information Technology and Computer Systems Engineering ITCSE, Johannesburg, South Africa. Koefoed, O., 1960. A generalized cagniard graph for interpretation of geoelectrical sounding data. Geophys. Prospect. 8 (3), 459–469. Kora, M and Adel Genedi (1995): Lithostratigraphy and Facies Egypt, Erlangen, 223–236. Krivoruchko, K., 2012. Empirical Bayesian kriging.ArcUser, Fall 2012.. Massoud, U., (2005): Geophysical studies for groundwater exploration in El-Bruk area, north central Sinai, Egypt. Ph.D. Thesis, Fac. of Science, Minufiya Univ., Egypt, 130p.
M.I.I. Mohamaden et al. Medhat, M.M., 2011. Lithostratigraphy and biostratigraphy of the upper cretaceous succession of Southeastern Sinai, Egypt. Egypt. J. Petrol. 20, 89–96. Mohamaden, M.I.I., 2005. Electric Resistivity Investigation at Nuweiba Harbour of Aqaba, South Sinai, Egypt. Egypt. J. Aquat. Res. 31 (1), 58–68. Mohamaden, M.I.I., 2008. Groundwater exploration at Rafah, Sinai Peninsula, Egypt. Egypt. J. Aquat. Res. 35 (2), 49–68. Mohamaden, M.I.I., Abu Shagar, S., 2008. Structural Effect on the Groundwater at the Arish City, North eastern Part of Sinai Peninsula, Egypt. Egypt. J. Aquat. Res. 35 (2), 31–47. Mohamaden, M.I.I., Abu Shagar, S., Abdallah, Gamal A., 2009. Geoelectrical Survey for Groundwater Exploration at the Asyuit Governorates, Nile Valley, Egypt. J. King Abdulaziz Univ., Marine Sci. 20, 91–108. Orellana, E., Mooney, H.M., 1966. Master table and curves for vertical electrical sounding data. Geophys. Prospect. 8 (3), 459–469. Said, R., 1981. The geological evaluation of the River Nile. Springerverlag, New York, p. 174p. Santos, F.A.M., Sultan, S.A., Represas, P., El Sorady, A.L., 2006. Joint inversion of gravity and geoelectrical data for groundwater and structural investigation: application to the northwestern part of Sinai, Egypt. Geophys. J. Int. 165, 705–718. Shaaban, M.A., 1980. Geophysical contribution to the groundwater of north Central Sinai. J. Geol. 24 (1–2), 151–164. Shalaby, A.A., Seiam, E., 2012. Structural constraints on the groundwater regime of the Cretaceous aquifers in Central Sinai, Egypt. J. Afr. Earth Sci. 75, 37–56. Sultan, S.A., Khalil, M.A., Masoud, U.S., Hassaneen, A.Gh., ElShayeb, H.M., Osman, S.Sh., 2006. Characterization of the groundwater Aquifers using combined modelling of VES – TEM data IN el-Bruk area, Central Sinai, Egypt. J. Nat. Res. Inst. Astron. Geophys. 5 (1), 1–28. Sultan, A.S., Mekhemer, H.M., Santos, F.M., 2009a. Groundwater exploration and evaluation by using geophysical interpretation (case study: Al Qantara East, North Western Sinai, Egypt), Arab. J. Geosci. 2, 199–211. Sultan, A.S., Mohameden, M.I.I., Santos, F.M., 2009b. Hydrogeophysical study of the El Qaa Plain, Sinai, Egypt. Bull. Eng. Geol. Environ. 68, 525–553. Sultan, S.A., Mekhemer, H.M., Santos, F.A.M., AbdAlla, M., 2009c. Geophysical Measurements for Subsurface Mapping and Groundwater Exploration at the Central Part of the Sinai Peninsula, Egypt. Arab J. Sci. Eng. 34 (1A), 103–119. Sultan, A.S.A., Sabet, H.S., Gaweish, W.R., 2015. Integrated geophysical interpretation for delineating the structural elements and groundwater aquifers at central part of Sinai Peninsula, Egypt. J. Afr. Earth Sci. 105, 93–106.
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
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Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt M.I.I. Mohamaden *, H.M. El-Sayed, A.Z. Hamouda National Institute of Oceanography and Fisheries, Alexandria, Egypt Received 24 August 2016; revised 12 October 2016; accepted 31 October 2016
KEYWORDS El-Themed; Sinai Peninsula; Malha Formation; VES
Abstract The study area is located at south central part of Sinai Peninsula at El-Thamed area. Geoelectrical resistivity method was used by measuring eighteen vertical electrical soundings using the Schlumberger configuration with total current electrode separation ranging between 3 m and 4000 m in order to investigate the deep groundwater aquifer and to delineate the subsurface structures of this area. The geoelectrical cross-sections show that the subsurface section consists of six geoelectrical units. The first unit is Quaternary deposits with thickness ranging from 0.6 m to 30.9 m and the resistivity values ranging from 177 Ohm.m. to 39680 Ohm.m. The second geoelectrical unit is composed of Egma Formation, with thickness ranging from 9.2 m to 12.8 m and the resistivity values ranging between 21 Ohm.m. and 82 Ohm.m. The third geo-electrical unit is composed of Paleocene Esna shale, also not detected at the study area with exception at profile 2, its thickness ranges from 15.6 m to 166.5 m and resistivity range from 8.9 Ohm.m. to 20 Ohm.m. This layer has not been detected at the extremely southern part of this profile, its depth ranges from 9.63 m to 15.5 m. The fourth geoelectrical unit is composed of Nubian Sandstone of Malha Formation (Lower Cretaceous) with depth ranging from 0.5 m to 8.9 m and its resistivity values ranging from 14 Ohm.m. to 133 Ohm.m. This layer represents the main aquifer in the study area with thickness ranging between 14.2 m and 283 m. The fifth geoelectrical unit is composed of claystone of Naqus Formation with depth ranging from 14.2 to 349 m and its resistivity values ranging from 2.7 Ohm.m. to 13 Ohm.m., sometimes, it is extends to the maximum depth of penetration. The sixth geoelectrical unit is composed of Basement rocks. It is characterized by resistivity ranging from 970 Ohm.m. to 25462 Ohm.m. and depth ranging from 60.1 m to 283 m. This unit is detected at the eastern part of the study area. Structurally, the study area is affected by sets of faults trending mainly NE-SW (Aqaba Trend). Ó 2016 National Institute of Oceanography and Fisheries. Hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
* Corresponding author. E-mail address: [email protected] (M.I.I. Mohamaden). Peer review under responsibility of National Institute of Oceanography and Fisheries. http://dx.doi.org/10.1016/j.ejar.2016.10.007 1687-4285 Ó 2016 National Institute of Oceanography and Fisheries. Hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
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Introduction The study area lies between latitudes 29.246607°N and 29.532753°N and longitudes 33.988647°E and 34.674099°E with an area of about 2111.8 km2 (Fig. 1a). It is suffering from water shortage which is essential for domestic use and agricultural activities. The vertical electrical sounding (VES) method is used to provide reliable information about the shallow subsurface layers. The electrical resistivity method is a favorable geophysical tool which is commonly used for groundwater exploration. It provides beneficial information about the subsurface lithology and structures (Jakosky, 1961; Keller, 1967). Many authors used the geoelectrical tool for investigation of groundwater or the structure affecting the groundwater flow such as Mohamaden (2005, 2008), Mohamaden and Abu Shagar (2008), Mohamaden et al. (2009), Santos et al. (2006) and Sultan et al. (2009a). Other geoelectrical studies have been performed around the study area such as Hossein (1980), Shaaban (1980), Massoud (2005) and Sultan et al. (2006, 2009b, 2015). It is concluded that the groundwater aquifer is affected by various geologic structures trending in the of NE–SW and NW–SE directions. The main aims of the present study are to explore the Nubian Sandstone aquifer, evaluating the affecting structures and controlling the geometry of the aquifers configuration. Hydrogeological setting The hydrogeological evaluation of the main aquifer in east Central Sinai is Malha sandstone aquifer (Lower Cretaceous)
Figure 1
with high hydraulic parameters and good water quality (Shalaby and Seiam, 2012) . The groundwater of Lower Cretaceous aquifer exists under confined conditions (Ghoubachi, 2013). The top surface of the Lower Cretaceous dips steeply toward the southwest direction. The average sand percent of the penetrated aquifer attains 54%. The groundwater flow direction of Lower Cretaceous aquifer is concentric to the center of study area related to the influence of the graben block which controlled by the fault-fold patterns. The general hydraulic gradient ranges from 0.0011 to 0.0028. The average effective porosity and transmissivity and hydraulic conductivity of the Lower Cretaceous aquifer are 17.3%, 416 m2/day and 1.4 m/day, respectively (Ghoubachi, 2013; Shalaby and Seiam, 2012). They increase toward the northeast direction with increasing of the sand percentage. The groundwater salinity increases coinciding with groundwater flow. The groundwater salinity of the Lower Cretaceous aquifer is brackish water and varies from 2510 to 5256 ppm (Ghoubachi, 2013). Geologic setting The central part of the study area is characterized by relatively low elevation with drainage system collecting the rain water from the surrounding parts of the study area (Hamouda, 2006). The study area is located nearly to the active tectonics region (Gulf of Aqaba) which is characterized by left lateral strike slip fault. The recent main major earthquake sequences for their foreshocks and aftershocks from the period from 1983 to 1996. The three characteristics of the main earthquake sequence have been discussed; i.e. epicenters and hypocenters
(a) Location map showing the study area; (b) Digital elevation model of Sinai.
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
Application of Electrical Resistivity and GIS for and Groundwater Exploration distribution of foreshocks and aftershocks, mechanisms of rupture process of movement, variation of stress drops in space and time domains, heterogeneous structures in the crust, and occurrence times of earthquakes (Hamouda, 2009a,b, 2011). The swarm seismicity along the central part of the Gulf of Aqaba, may be related to the effect of active tectonic process in this area that affect both the shallow and deep crusts. Also, it may be associated with the actual effect of mantle upwelling at the crustal thickness in this area (Hamouda, 2010). The main surface geology was described in the geological map of Sinai with scale 1:500,000 (Fig. 2). According to different studies on this area (Said, 1981; Bhattacharyya and Dunn, 1986; EGSMA, 1993; Kora and Genedi, 1995; Abdel-Gawad et al., 2006; Sultan, 2009b,c; Medhat, 2011), the subsurface stratigraphic units were described (Fig. 3)as follows: Quaternary Deposits; Most of the area is covered by Pleistocene alluvium deposits. Egma Formation; It is composed of chalky limestone of Lower Eocene. Esna Formation; It is composed of Paleocene marly shale. Suder Formation; It is composed of Upper Cretaceous chalky limestone intercalated with very thin bands chert with some marls and argillaceous limestone streaks of Maastrichtian age. Duwi Formation; It is composed of Campanian carbonate alternated with clastic. Matullah Formation; It represents the limestone of Coniacian–Santonian age. It is composed of basal shale followed by sandstone, marls, fossiliferous limestone and nonfossiliferous sandstone. Wata Formation; It is composed of Turonian-Coniacian dolomitic limestone with sandstone and shale intercalation. Galala Formation; It is composed of fossiliferous marl, dolomitic limestone, with a few shale siltstone interbeds.
Figure 2
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Malha Formation; It is formed from Lower Cretaceous nonfossiliferous sandstone intercalated with mudstone. Naqus Formation; It is formed from medium to coarse grained Sandstone. The basal units inter finger with Araba Formation. Araba Formation; It is composed of Cambrian sandstone and sandy claystone. Basement Rocks; It is Granitic Pre-Cambrian basement rocks. Materials and methods (i) Geoelectrical data In this study, eighteen VES’s (covering the study area) were performed in 2014 using Syscal-Pro instrument. Schlumberger configuration was used with total current electrode separation ranging between 3 m and 4000 m. The main aim is to detect the Nubian Sandstone aquifer in addition to the geologic structures in the study area (Fig.4). The geoelectrical parameters have been correlated by the geology obtained from previous work. (ii) Geographic information system Geographic information system (GIS) is a powerful tool that can help to overlay maps with different thematic data and facilitate map integration and analysis (Khalifa and AbdelHalim, 2013). It was used to build a geodatabase containing the study area and the field measurements in order to generate contour maps showing the spatial variation of the measured apparent resistivity values and the groundwater depth in the study area. The obtained data have been analyzed using the geostatistical analyst tools in ArcGIS software by examining the data
Geological Map of the study Area (modified after Conoco, 1987).
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
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M.I.I. Mohamaden et al. using the exploratory spatial data analysis (ESDA) which is a set of tools that allow graphically exploring the data distribution, looking for outliers, looking for global trends and examining the spatial autocorrelation (ESRI, 2003). Each parameter of the measured data was examined by ESDA tools such as histogram and QQPlot to determine whether it is normally distributed or not and to determine the suitable type of data transformation if needed. The presence of global trends was also checked in each parameter using trend analysis tool which provides a three dimensional perspective of the data. The semivariogram tool was used to explore the spatial autocorrelation of the measured data (ESRI, 2003). Based on the ESDA data examination, the suitable interpolation method has been chosen for each parameter. Kriging method is one of the most common geostatistical interpolation methods. It is a probabilistic predictor which uses the least square linear regression algorithms to estimate the value of a continuous attribute in any unmeasured location using the values of the surrounding measured points (ESRI, 2010; Krivoruchko, 2012; Jensen and Jensen, 2013). The ordinary Kriging method was used for interpolating the apparent resistivity values and the groundwater depth in the study area. The digital elevation model (DEM) was used to extract the elevation value at the VES locations of the geophysical survey which is needed for constructing profiles. In this study, ASTER-GDEM-v.2 scene was analyzed using ArcGIS for this purpose. (iii) Quantitative interpretation of vertical electrical soundings (VES)
Figure 3 Stratigraphic Column of the Study Area (modified after EGSMA, 1993).
Figure 4
In order to determine the subsurface layer parameters (resistivity and thickness), the manual interpretation technique was utilized by matching the plotted field curves with two layers master curves and the generalized Cagniard graphs (Koefoed, 1960; Orellana and Mooney, 1966). The obtained results were introduced to the IPI2WIN software (Bobatchev et al., 2001) as initial models to compute the final models.
Location map showing VES and profiles distribution.
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
Application of Electrical Resistivity and GIS for and Groundwater Exploration
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tive high resistivity values which may be referred to the existence of a compacted limestone while the western parts have a relatively low resistivity values reflecting the existence of a probable clay layer.
Results and discussion (i) Iso-Apparent maps Iso-Apparent maps (Fig. 5) shows that the surface layer is characterized by high resistivity values which may be attributed to the surface unconsolidated quaternary deposits. At AB/2 = 8 m, the resistivity of the northwestern and northeastern parts of the study area tend to decrease due to the partial saturation of water. Generally, the resistivity values tend to decrease in the whole study area with depth as a result of the subsurface saturation with water. At AB/2 = 300 m, the southeastern part of the study area is characterized by a rela-
(ii) Geoelectrical cross-sections The results of VES’s interpretation revealed 5–6 subsurface layers. The geoelectrical cross-section No. 1 (Fig. 6) is located at the most western part of the study area with a total length of about 26 km. It consists of four VES’s named 1, 2, 3 and 4. This cross-section shows that the subsurface section consists of five geoelectrical units. The first unit is composed of surface
AB/2 = 8m
AB/2 = 10m
AB/2 = 25m
AB/2 = 30m
AB/2 = 65m
AB/2 = 500m
Figure 5
AB/2 = 300m
AB/2 = 1000m
Iso-apparent resistivity maps.
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Figure 6
Geoelectrical cross-section for profile 1.
Quaternary wadi deposits with thickness ranging from 1.8 m to 3.5 m and the resistivity values ranging from 226 Ohm.m. to 2732 Ohm.m. The second geoelectrical unit is composed of limestone or chalk with flint of Lower Eocene (Egma Formation) with thickness ranging from 9.2 m to 12.8 m and resistivity values ranging between 21 Ohm.m. and 82 Ohm.m. It covers the ground surface at VES 2, and is not detected at the most southern part of this profile. The third geoelectrical unit is formed from Paleocene Esna shale with thickness ranging from 15.6 m to 166.5 m and resistivity values ranging from 8.9 Ohm.m. to 20 Ohm.m., and not detected at the most southern part of this profile. The fourth geoelectrical unit is Nubian Sandstone of Malha Formation (Lower Cretaceous) with depth ranging from 3.5 m to 182 m and its resistivity values ranging from 35 Ohm.m. to 113 Ohm. m. This Nubian Sandstone represents the main aquifer in the study area where its thickness at the geoelectrical cross-section No. 1 increases toward the southern part of this profile (Fig. 6). This thickness ranges from 20.8 m at the northern part of this profile to 200.5 m to the south. The fifth geoelectrical unit is composed of claystone of Naqus Formation with depth ranging from 46 m to 349 m and its resistivity values ranging from 3 Ohm. m. to 13 Ohm.m., its depth increases toward the southern part of this profile specially at VES 3. It extends to the maximum depth of penetration. Structurally, this profile is affected by two probable faults. The first fault (F1) is located to the south of VES 2 with down thrown side toward the southern direction, while the second fault (F2) is located to south of VES 3 with down thrown side toward the northern direction. These two faults form a graben structure which reflects that the central part represents the deepest part of Malha Formation. Geoelectrical cross-section No. 2 (Fig. 7) is located at the central part of the study area with total length of about 20.9 km. It consists of four VES’s named 8, 9, 10 and 11. This cross-section shows that the subsurface section consists of two geoelectrical units. The first unit is composed of surface Qua-
ternary wadi deposits; its thickness ranges from 1.6 m to 25 m and the resistivity values range from 220 Ohm.m. to 39680 Ohm.m. covering the ground surface of this profile. The second geoelectrical unit is composed of Nubian Sandstone of Malha Formation (the main aquifer) with depth ranging from 1.6 m to 25 m and its resistivity values ranging from 16.5 Ohm.m. to 62.3 Ohm.m. This unit extends to the maximum depth of penetration. Structurally, this profile is affected by two probable faults. The first fault (F3) is located to the northwest of VES 9 with down thrown side toward the northwest direction, while, the other fault (F4) is located to the northwest of VES 18 with down thrown side toward the southeast direction. These two faults form a horst structure which reflects that the central part is characterized by shallow depth for the Malha Formation. Geoelectrical cross-section along profile 3 (Fig. 8) is located at the eastern part of the study area with a total length of about 19.2 km. It consists of four VES’s named 13, 14, 15 and 17. This cross-section shows that the subsurface section consists of four geoelectrical units. The first unit is composed of surface Quaternary wadi deposits with thickness ranging from 8.8 m to 30.9 m and the resistivity values ranging from 177 Ohm.m. to 2068 Ohm.m. The second geoelectrical unit is composed of Nubian Sandstone of Malha Formation (the main aquifer) with depth ranging from 8.8 m to 30.9 m and its resistivity values ranging from 14.1 Ohm.m. to 71.2 Ohm. m. The base of this unit extends to depth ranging from 31.2 m to 274. The third geoelectrical unit is composed of claystone of Naqus Formation with depth of 31.2 m and resistivity value of 2.7 Ohm.m. It has been detected at VES 13. The fourth geoelectrical unit is the basement rocks represented by Pre-Cambrian Granite. It is located at the deepest parts in this profile with resistivity values ranging from 3524 Ohm.m. to 25462 Ohm.m. The depth to the basement rocks is ranging from 60.1 m to 274 m. Structurally, this profile is affected by two probable faults. The first fault (F4) is located to the south of VES 13 with down
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
Application of Electrical Resistivity and GIS for and Groundwater Exploration
Figure 7
Geoelectrical cross-section for profile 2.
Figure 8
Geoelectrical cross-section for profile 3.
thrown side toward the southern direction, while, the other fault (F5) is located to the north of VES 17 with down thrown side toward the northern direction. These two faults form a graben structure which reflects that the central part is deeper for the Malha Formation. Geoelectrical cross-section along profile 4 (Fig. 9) is located at the northern part of the study area with a total length of about 30 km. It consists of seven VES’s named 5, 6,7, 11, 12, 13 and 16. This cross-section shows that the subsurface section consists of four geoelectrical units. The first unit is composed of surface Quaternary wadi deposits with thickness ranging from 0.6 m to 8.9 m and resistivity values ranging from 309 Ohm.m. to 4746 Ohm.m. The second geoelectrical unit is composed of Nubian Sandstone of Malha Formation (the main aquifer) with depth ranging from 0.6 m to 8.9 m and resistivity values ranging from 22.9 Ohm.m. to 133 Ohm.m.
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This unit extends to the maximum depth and its thickness ranging from 14.2 m to 283 m. The third geoelectrical unit is composed of claystone of Naqus Formation with a depth ranging from 14.2 m to 283 m and its resistivity values ranging from 2.7 Ohm.m. to 9.4 Ohm.m. It has not been detected at VES 7 and VES16. The fourth geoelectrical unit is the Granitic PreCambrian basement rocks. It is located at the deepest parts in this profile with resistivity values ranging from 970 Ohm. m. to 18841 Ohm.m. Structurally, this profile is affected by two probable faults. The first fault (F3) is located to the east of VES 11 with down thrown side toward the eastern direction, while the other fault (F4) is located to the west of VES 13 with down thrown side toward the western direction. These two faults form a horst structure which reflects that the central part is characterized by shallower depth for the Malha Formation.
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Figure 9
Geoelectrical cross-section for profile 4.
The true resistivity of the water bearing layer decreases toward the eastern parts of the study area (Fig. 10). This may be attributed to the saltwater intrusion from the Gulf of Aqaba. The depth of groundwater increases toward the western and southeastern parts, while it decreases in the northern parts of the study area as shown in Fig. 11. Conclusion The central part of the area under investigation is characterized by high elevation with drainage system collecting the water from wadi El Arish to the central part of the study area. Eighteen VES’s were applied to provide reasonable results and clear the picture about the subsurface formations. IsoApparent maps show that the surface layer is characterized by high resistivity values which may be attributed to the surface unconsolidated quaternary deposits. Generally, the resis-
Figure 10
tivity values tend to decrease in the whole study area with depth as a result of the subsurface saturation with water. At AB/2 = 250 m, the southeastern part of the study area is characterized by a relative increase in the resistivity values which may be attributed to the existence of a compacted limestone while the western parts have a relatively low resistivity values reflecting the existence of a probable clay layer. The results of VES’s interpretation revealed 5–6 subsurface layers. The geoelectrical cross-sections show that the subsurface section consists of six geoelectrical units. The first unit is composed of surface Quaternary wadi deposits with thickness ranging from 0.6 m to 30.9 m and the resistivity values ranging from 177 Ohm.m. to 39680 Ohm.m. The second geoelectrical unit is composed of limestone or chalk of Lower Eocene (Egma Formation). It is located at the extremely western part of the study area, with thickness ranging from 9.2 m to 12.8 m and resistivity values ranging between 21 Ohm.m. and
True resistivity map of the water bearing layer.
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
Application of Electrical Resistivity and GIS for and Groundwater Exploration
Figure 11
9
Depth map of the groundwater.
F F
F
F F
F
F
Down Figure 12
Up
Sketch map for faults directions.
82 Ohm.m. It covered the ground surface around of VES 2, and is not detected at the extreme southern part of this profile; it extends to a depth ranging from 1.8 m to 3.5 m. The third geo-electrical unit is composed of Paleocene Esna shale, also not detected at the study area with exception at profile 2, its thickness ranges from 15.6 m to 166.5 m and resistivity ranges from 8.9 Ohm.m. to 20 Ohm.m. This layer has not been detected at the extremely southern part of this profile, its depth ranges from 9.63 m to 15.5 m. The fourth geoelectrical unit is composed of Nubian Sandstone of Malha Formation (Lower Cretaceous) with depth ranging from 0.5 m to 8.9 m and its resistivity values ranging from 14 Ohm.m. to 133 Ohm.m. This layer represents the main aquifer in the study area with thickness ranging between 14.2 m and 283 m. The fifth geoelectrical unit is composed of claystone of Naqus Formation with depth ranging from 14.2 to 349 m and its resistivity values ranging from 2.7 Ohm.m. to 13 Ohm.m., sometimes, it is extends to the maximum depth of penetration. The sixth geoelectrical unit
is composed of Basement rocks. It is characterized by resistivity ranging from 970 Ohm.m. to 25462 Ohm.m. and depth ranging from 60.1 m to 283 m. This unit is detected at eastern part of the study area. Structurally, the study area is affected by sets of faults (Fig. 12) trending mainly NE-SW (Aqaba Trend). References Abdel-Gawad, G.I., El Qot, G.M., Mekawy, M.S., (2006): Cenomanian-Turonian Macrobiostratigraphy of Abu Darag Area, Northern Galala, Eastern Desert, Egypt, Intern. Conf. Geol. Arab World (GAW8), Cairo Univ., Giza, Egypt, p. 553–568. Bhattacharyya, D.P., Dunn, L.G., 1986. Sedimentologic evidence for repeated pre-cenozoic vertical movements along the Northeast Margin of the Nubian Craton. J. Afr. Earth Sci. 5 (2), 147–153. Bobatchev A., Modin, I., Shevnin, V. (2001): IPI2WIN V. 2 for VES data interpretation. Dept. of Geophysics, Geological Faculty, Moscow State University, Russia.
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007
10 Conoco, Coral., 1987. Geological map of Egypt, scale 1:500,000-NH 36 SE-South Sinai. The Egyptian General Petroleum Corporation, Cairo, Egypt, Egypt. Egyptian Geological Survey and Mining Authority (EGSMA), (1993): Geological and geophysical studies for groundwater exploration on Nukhl area, central Sinai. Internal report No. 49/93, 24p. ESRI, 2003. Using ArcGIS Geostatistical Analyst. Environmental Systems Research Institute, Redlands, CA, USA. ESRI, 2010. ArcGIS Geostatistical Analyst. Environmental Systems Research Institute, Redlands, CA, USA. Ghoubachi, S.Y. (2013): Contribution to the hydrogeology of the Lower Cretaceous aquifer in east Central Sinai, Egypt, Journal of King Saud University – Science, Vol. 25, pp. 91–105. Hamouda, A.Z., 2006. Seismic hazard of Eastern Mediterranean. J. Acta Geophys. 54 (2), 163–173. Hamouda, A. Z., (2009a): Recent evaluation of the assessment seismic hazards for Nuweiba, Gulf of Aqaba. Arab J. Geosc., 10.1007/ s12517-009-0096-3. Hamouda, A.Z., 2009b. A Reanalysis of the AD 365 Tsunami Impact along the Egyptian Mediterranean Coast. Acta Geophys. 58 (4), 1– 18. Hamouda, A.Z., 2010. Worst scenarios of tsunami effects along the Mediterranean coast of Egypt. Mar. Geophys. Res. 31, 197–214. Hamouda, A.Z., 2011. Assessment of seismic hazards for Hurghada. Nat Hazards, Red Sea, Egypt. 10.1007/s11069-011-9767-y. Hossein, Z.E.M., 1980. Geophysical study on abu Hamath – Nakhl – Darag area, central of Sinai a. R.E. (MSc.). Ain Shams Univ., Egypt, p. 98p. Jakosky, J.J., (1961): Exploration geophysics. Tiya New Beach Calif, Techs. 1, 2 and 6. Jensen, J.R., Jensen, R.R., 2013. Introductory Geographic Information Systems. Pearson, Toronto. Keller, G.V., 1967. Application of resistivity method in mineral and groundwater exploration programs. Geophys. Surv. Can. 26, 51– 66. Khalifa, N. & Abdel-Halim, N., 2013.An Evaluation of the GIS Industry in Egypt. International Conference on Information Technology and Computer Systems Engineering ITCSE, Johannesburg, South Africa. Koefoed, O., 1960. A generalized cagniard graph for interpretation of geoelectrical sounding data. Geophys. Prospect. 8 (3), 459–469. Kora, M and Adel Genedi (1995): Lithostratigraphy and Facies Egypt, Erlangen, 223–236. Krivoruchko, K., 2012. Empirical Bayesian kriging.ArcUser, Fall 2012.
M.I.I. Mohamaden et al. Medhat, M.M., 2011. Lithostratigraphy and biostratigraphy of the upper cretaceous succession of Southeastern Sinai, Egypt. Egypt. J. Petrol. 20, 89–96. Mohamaden, M.I.I., 2005. Electric Resistivity Investigation at Nuweiba Harbour of Aqaba, South Sinai, Egypt. Egypt. J. Aquat. Res. 31 (1), 58–68. Mohamaden, M.I.I., 2008. Groundwater exploration at Rafah, Sinai Peninsula, Egypt. Egypt. J. Aquat. Res. 35 (2), 49–68. Mohamaden, M.I.I., Abu Shagar, S., 2008. Structural Effect on the Groundwater at the Arish City, North eastern Part of Sinai Peninsula, Egypt. Egypt. J. Aquat. Res. 35 (2), 31–47. Mohamaden, M.I.I., Abu Shagar, S., Abdallah, Gamal A., 2009. Geoelectrical Survey for Groundwater Exploration at the Asyuit Governorates, Nile Valley, Egypt. J. King Abdulaziz Univ., Marine Sci. 20, 91–108. Orellana, E., Mooney, H.M., 1966. Master table and curves for vertical electrical sounding data. Geophys. Prospect. 8 (3), 459–469. Said, R., 1981. The geological evaluation of the River Nile. Springerverlag, New York, p. 174p. Santos, F.A.M., Sultan, S.A., Represas, P., El Sorady, A.L., 2006. Joint inversion of gravity and geoelectrical data for groundwater and structural investigation: application to the northwestern part of Sinai, Egypt. Geophys. J. Int. 165, 705–718. Shaaban, M.A., 1980. Geophysical contribution to the groundwater of north Central Sinai. J. Geol. 24 (1–2), 151–164. Shalaby, A.A., Seiam, E., 2012. Structural constraints on the groundwater regime of the Cretaceous aquifers in Central Sinai, Egypt. J. Afr. Earth Sci. 75, 37–56. Sultan, S.A., Khalil, M.A., Masoud, U.S., Hassaneen, A.Gh., ElShayeb, H.M., Osman, S.Sh., 2006. Characterization of the groundwater Aquifers using combined modelling of VES – TEM data IN el-Bruk area, Central Sinai, Egypt. J. Nat. Res. Inst. Astron. Geophys. 5 (1), 1–28. Sultan, A.S., Mekhemer, H.M., Santos, F.M., 2009a. Groundwater exploration and evaluation by using geophysical interpretation (case study: Al Qantara East, North Western Sinai, Egypt), Arab. J. Geosci. 2, 199–211. Sultan, A.S., Mohameden, M.I.I., Santos, F.M., 2009b. Hydrogeophysical study of the El Qaa Plain, Sinai, Egypt. Bull. Eng. Geol. Environ. 68, 525–553. Sultan, S.A., Mekhemer, H.M., Santos, F.A.M., AbdAlla, M., 2009c. Geophysical Measurements for Subsurface Mapping and Groundwater Exploration at the Central Part of the Sinai Peninsula, Egypt. Arab J. Sci. Eng. 34 (1A), 103–119. Sultan, A.S.A., Sabet, H.S., Gaweish, W.R., 2015. Integrated geophysical interpretation for delineating the structural elements and groundwater aquifers at central part of Sinai Peninsula, Egypt. J. Afr. Earth Sci. 105, 93–106.
Please cite this article in press as: Mohamaden, M.I.I. et al., Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt. Egyptian Journal of Aquatic Research (2016), http://dx.doi.org/10.1016/j.ejar.2016.10.007