Indonesian Journal on Geoscience Vol. 8 No. 3 December 2021: 359-369 INDONESIAN JOURNAL ON GEOSCIENCE Geological Agency Ministry of Energy and Mineral Resources Journal homepage: h p://ijog.geologi.esdm.go.id ISSN 2355-9314, e-ISSN 2355-9306 Vertical Electrical Sounding Exploration of Groundwater in Kertajati, Majalengka, West Java, Indonesia Gumilar Utama Nugraha1, Boy Yoseph Cahya Sunan Sakti Syah Alam2, Andi Agus Nur2, Pulung Arya Pranantya3, Lina Handayani1, Rachmat Fajar Lubis1, and Hendra Bakti1 Research Center For Geotechnology, Indonesian Institute of Sciences, Indonesia 2 Faculty of Geological Engineering, Padjadjaran University, Indonesia 3 Research Center For Water Resources, Ministry of Public Works and Housing, Indonesia G 1 Corresponding author: gumi001@lipi.go.id / gumilar15001@mail.unpad.ac.id Manuscript received: December, 9, 2019; revised: January, 17, 2020; approved: October, 29, 2020; available online: August, 13, 2021 IJ O Abstract - Continuously increasing population and progressive infrastructural development in the region of Kertajati International Airport, Indonesia, emphasize the need to develop a sustainable water supply network. Airport facilities require sufficient water resources, which can be obtained from surface water and groundwater. Groundwater exploration can provide necessary information for assessing water resources. The purpose of this study is to analyze the configuration of aquifers in the studied area. A Schlumberger array was used to carry out twelve vertical electrical soundings (VES) with AB/2 electrode spacing ranging from 1.5 m to 150 m. IPI2win software was used to qualitatively interpret the VES results and it suggested the presence of three distinct lithological units interpreted as clay, alluvial sand, and a Lower Quaternary formation. In general, resistivity values in the studied area can be divided into five resistivity categories: very low resistivity with values ranging from 1 Ωm to 10 Ωm, low resistivity with values ranging from 10 Ωm to 50 Ωm, medium resistivity with values ranging from 50 Ωm to 100 Ωm, high resistivity with values ranging from 100 Ωm to 200 Ωm, and very high resistivity with values > 200 Ωm. The geo-electric interpretation revealed three geo-electric layers: topsoil (1 - 144 Ω m), sand (1 - 298 Ω m), and clay (1 - 82 Ω m). Aquifers in the studied area are lithologically composed of sand. Clay is the dominant lithology in the studied area, so the presence of aquifers in this area is very limited, and thus the supply of groundwater is also limited. The exploitation of groundwater must be limited and controlled to maintain the sustainability of groundwater in the studied area. Keywords: vertical electrical sounding, aquifer, groundwater, geo-electric layers © IJOG - 2021 ­ How to cite this article: Nugraha, G.U., Alam, B.Y. C.S.S.S., Nur, A.A., Pranantya, P.A., Handayani, L., Lubis, R.F., and Bakti, H., 2021. Vertical Electrical Sounding Exploration of Groundwater in Kertajati, Majalengka, West Java, Indonesia. Indonesian Journal on Geoscience, 8 (3), p.359-369. DOI: 10.17014/ijog.8.3.359-369 Introduction Background Groundwater is a highly valuable natural resource (Song et al., 2012) and an essential geological agent in the transport of mass and energy within the earth (Llamas, 1987), providing a wide variety of ecological and social services (Houben and Weihe, 2010). The advantages of groundwater over other sources of water have been emphasized in literature (Bayewu et al., 2018). A high percentage of water users worldwide rely substantially on groundwater (Reilly et al., 2008). Demand for this resource has increased significantly throughout the world due to population growth, socio-economic development, technological and Indexed by: SCOPUS 359 Indonesian Journal on Geoscience, Vol. 8 No. 3 December 2021: 359-369 most frequently used electrical resistivity tool in groundwater studies, as it can give information about subsurface rocks and structures at depths useful for water exploration (Araffa et al., 2015). It is also comparatively less expensive than other methods, and its methodology is simple. The VES technique is based on the fact that the subsurface layer can only transmit current because of the presence of water, since the rock itself is considered an insulator (Anomohanran, 2015). The VES technique is thus widely used to explore groundwater resources (Hafeez et al., 2018; Mohamaden et al., 2009), and has therefore been chosen to analyze aquifer configurations in this study. G climatic changes (Alcamo, 2007). Despite its advantage of easy accessibility, surface water is often polluted by anthropogenic activities, making groundwater a desirable option to satisfy our demand for quality water (Anomohanran, 2015). The continuous increase in population and the progressive infrastructural development in Kertajati area emphasize the need to develop a sustainable water supply network. Airport facilities require sufficient water resources, which surface water and groundwater are often used to fulfill. Groundwater exploration can provide necessary information for assessing water resources. The purpose of this study is to analyze the configuration of aquifers in the area of Kertajati Airport. Kertajati Airport is the second largest airport in Indonesia, located in the Majalengka Regency, northeastern part of West Java Province, approximately 68 km east of Bandung City. The urgent need for groundwater has driven the application of appropriate geophysical and hydrogeologic exploration techniques (Anudu et al., 2011) to locate areas of high and reliable groundwater potential or to characterize seasonal changes in near-surface aquifers (Webb et al., 2011). A geophysical investigation is a powerful tool for exploring subsurface geology and collecting information about subsurface layers and structures (El-Sayed, 2010). Various geophysical techniques or applications have been employed in groundwater exploration in many parts of the world, including magnetic resonance sounding (MRS), remote sensing, geographic information systems, seismic refraction, and electrical resistivity, among others (Kamble et al., 2012). The electrical resistivity method has been extensively used for groundwater aquifers mapping (Massoud et al., 2015), investigating aquifer vulnerability (Sørensen et al., 2005), and freshwater/saline water studies (Khalil, 2010). The electrical resistivity survey method is one of the oldest geophysical exploration techniques and has been extensively employed in environmental, engineering, hydrological, archaeological, and mineral exploration surveys (Reynolds, 2011). Vertical electrical sounding (VES) has been the IJ O Geological and Hydrogeological Settings The geology of the studied area is composed of Lower Quaternary sedimentary rocks (Qos) and Holocene alluvium deposits (Qa) (Figure 1). The Lower Quaternary sedimentary rocks extend across almost all of the studied area and consist of tuffaceous sandstone, sand, tuffaceous silt, clay, conglomerate, and tuffaceous breccia containing pumice, which crop out in Kertajati Village in the form of conglomerates, and in Pasiripis Village in the form of coarse sand. The weathering of these rocks produces residual soils which include clays subject to swelling (Hasibuan et al., 2009) . Holocene-aged alluvium (Qa) deposits occur in the southeastern part of the studied area, as a result of flood deposition from the Cimanuk River. This alluvium consists of clays, silts, sands, and gravels which has been mainly deposited by Holocene streams (Hasibuan et al., 2009). The studied area has a widespread medium aquifer consisting of undifferentiated sandstones and tuffs, with groundwater flowing through the pore spaces in the media (IWACO-WASECO, 1990). A geoelectrical survey using VES was conducted on November 2015. The electrical resistivity of the studied area was measured using a GL-4100 Earth Resistivity meter. A Schlumberger array was used to carry out 12 VES with AB/2 electrode spacing ranging from 1.5 m to 150 m (Figure 2). These stations are referred to as MJL-01 - MJL-12. The geo-electrical method 360 Vertical Electrical Sounding Exploration of Groundwater in Kertajati, Majalengka, West Java, Indonesia (G.U. Nugraha et al.) 108 6’0” E o 108 12’0” E o 108o9’0” E 108 15’0” E 108 18’0” E o 6 33’0” S o o 6 33’0” S 108 3’0” E o o N 3 4.5 6 6 36’0” S 6 36’0” S 0 0.75 1.5 Legend: o o Lithology Qa Alluvium: clays, silts, sands, gravels. Mainly deposits of Holocene Streams. Qos Qos o 6 42’0” S o Qa 6 42’0” S 6 39’0” S 6 39’0” S Qos Tuffaceous sandstones, sands, tuffaceous silts, clays, conglomerate, tuffaceous breccia containing pumice, as revealed in Kertajati Village in the form of conglomerates and Pasiripis Village in the form of coarse sand o o G Study area 108 3’0” E o 108 6’0” E 108 9’0” E o o 108 12’0” E o 108 15’0” E o 108 18’0” E o Figure 1. Geological map of the studied area. VES station MJL-05 and the geological data obtained from well TW-88. The measured vertical electrical soundings were interpreted qualitatively and quantitatively to build a geo-electrical model, which was initiated using all available data about the geologic and hydrogeologic settings. The data were calculated to obtain the apparent resistivity and thickness values, which were again used in the computerized interpretation to obtain the true resistivity and thicknesses of the various layers encountered. The interpretation of geo-electrical resistivity data from the twelve VES curves was conducted by converting the values of AB/2 and ρa into a multilayer model. The quantitative interpretation has been applied to determine the correlation between the geo-electrical parameters obtained from station MJL-05 and geological information from drilled hole TW-88 (Figure 3). The initial models have been constructed using the available geologic data from the existing boreholes. IPI2 win is a programme provided by Moscow State University, Russia, to produce quantitative interpretations of the geo-electrical sounding curves. It is an inverse modeling programme for interpreting resistivity sounding fi IJ O was adopted in this study, because it is a useful tool for ascertaining the subsurface geology of an area (Tizro et al., 2012). VES data interpretation aims to determine the true resistivities and thicknesses of the successive strata below the different stations, utilizing measured eld curves (El-Gawad et al., 2018). The apparent resistivity (ρa) values were obtained from the voltage (mV) and current (mA) read from the resistivity meter and its calculated corresponding geometric factor (Zohdy, 1975). A VES station, MJL-05, was located beside a borehole with known lithologic logs to serve as parametric measurements, which were helpful in interpreting the VES data (El-Gawad et al., 2017). The lithology data obtained from well TW-88, which were drilled by the Groundwater Development Project (P2AT), Ministry of Public Works, Republic of Indonesia, were used to calibrate the geo-electrical models obtained from the apparent resistivity curves. Figure 3 shows the correlation between geo-electrical parameters of well TW-88 and the geology obtained from station MJL-05. Figure 3 shows the correlation between geo-electrical parameters measured at 361 Indonesian Journal on Geoscience, Vol. 8 No. 3 December 2021: 359-369 108 10’0”E 108 12’30”E o 120 0’0”E o 10 0’0”N 140 0’0”E o o Indonesia o 10 0’0”S o 108 17’30”E o 100 0’0”E A’ TW132 calibration well 106 0’0”E 107 0’0”E o 6 0’0”S o o MJL-05 C o MJL-02 6 2’30”S TW137 N MJL-10 B G Sumedang Regency o 7 0’0”S Central Java MJL-06 TW141 TW145 TW136 MJL-09 o Majalengka Regency West Java o MJL-08 TW135 8 0’0”S o 6 40’0”S B’ TW142 o 6 7’30”S o 6 7’30”S TW-147 TW164 TW133 TW215 MJL-07 109 0’0”E o DKI Jakarta Banten MJL-04 TW144 108 0’0”E 6 40’0”S o MJL-11 C’ o o 6 35’0”S 108 15’0”E o MJL-03 o o 6 32’30”S o 6 32’30”S 108 7’30”E o 6 35’0”S 108 5’0”E o 6 2’30”S 108 2’30”E 0 1 2 6 4 8 o o km VES Points A 108o2’30”E 108o5’0”E 108o7’30”E Cross section lines MJL-12 Borthilogy events 108o10’0”E 108o12’30”E 108o15’0”E 108o17’30”E Figure 2. Location map of sampling sites in the studied area. Lithology Log Project: Location: VES Point ID: Kertajati VES Kertajati TW88 Client: Geophysicist: Electrode Array: GumilarUtamas TW88 Easting: Northing: Longitude: 188374 9264764 Elevation: Datum: Total Depth: 66 WGS 84 155 Lithology Well Construction cover IJ O Interpreted VES MJL5 100 ρ a Depth(m) 0 10 cement 20 10 screen 30 casing casing screen 40 casing 50 AB/2 1 1 10 100 1000 Weather: Shinny Equipment Latitude: Date: 15 Nov 2015 Well Point TW 88 Description Top soil: mixing sand, clay, and silt fine sand light brown clay fine sand dark brown clay fine sand light brown clay screen fine sand casing grey clay 60 70 80 N ρ h d Alt 1 54 0.75 0.75 -0.75 2 1 0.883 1.63 -1.633 3 15.1 2.81 4.44 -4.443 4 1 9 13.4 -13.44 5 7 90 100 screen 110 casing coarse sand light brown clay 120 130 140 150 160 screen coarse sand casing brown-green clay screen coarse sand screen coarse sand ? Figure 3. Corelation between lithological data and the interpreted results of vertical electrical sounding (VES) station MJL5. data in a layered earth (1-D) model. In order to perform this step, sounding curves were entered 362 as apparent resistivity versus spacing (AB/2) for the Schlumberger soundings. The results of geo- Vertical Electrical Sounding Exploration of Groundwater in Kertajati, Majalengka, West Java, Indonesia (G.U. Nugraha et al.) electric survey were used to establish the depth of the aquifer layer and to construct a geo-electric section for the studied area. These results were then used to describe the geological framework for the studied area (Tizro et al., 2012; Anomohanran, 2015). The pseudosections and geoelectrical resistivity sections were obtained from the quantitative interpretation of the VES data. Table 1. Vertical Electrical Sounding Point Locations VES Points Results Lat Easting Northing Z (m) MJL1 108.1786 -6.62436 188005 9266890 69 MJL2 108.1297 -6.6795 182632 9260756 66 MJL3 108.1781 -6.5405 187904 9276171 40 MJL4 108.1586 -6.62777 185793 9266500 69 MJL5 108.1817 -6.64369 188368 9264752 66 MJL6 108.1987 -6.65247 190249 9263791 68 MJL7 108.1067 -6.64422 180059 9264646 74 MJL8 108.1259 -6.6592 182193 9263000 66 MJL9 108.1483 -6.66887 184677 9261944 66 MJL10 108.1677 -6.68682 186837 9259970 66 MJL11 108.0999 -6.59537 179275 9270048 40 MJL12 108.169 187017 9254166 65 -6.73927 G Twelve VES measurements were conducted at locations around the area of West Java International Airport, Kertajati Subregency, Majalengka Regency, West Java Province (Table 1). Resistivity values in the studied area can be divided into five resistivity categories: very low resistivity with values ranging from 1 Ωm to 10 Ωm, low resistivity with values varying from 10 Ωm to 50 Ωm, medium resistivity with values ranging from 50 Ωm to 100 Ωm, high resistivity with values between 100 Ωm and 200 Ωm, and very high resistivity categories with values > 200 Ωm. Table 2 shows the details of resistivity and the thickness for each layer as inferred from resistivity inversion using IPI2win software. The inversion result was interpreted qualitatively and quantitatively using the geological and lithological information from Hasibuan et al. (2009) and drill hole section from the Groundwater Development Project (P2AT) by the Ministry of Public Works, Republic of Indonesia, as Lon IJ O described in the previous section. The number of units was interpreted as three to seven resistivity layers. These layers have true resistivities ranging between 1 and 298 Ω m, with various thicknesses. The VES interpretation revealed three layers: topsoil (1 - 144 Ω m), sand (1 - 298 Ω m), and clay (1 - 82 Ω m). A detailed description for each station can be seen on Table 3. Groundwater At MJL-01, the aquifer layer was interpreted lithologically as a sand layer at a depth range of 5 - 14 m, with an aquifer resistivity value of 31 Ωm. At MJL-02, the aquifer layer was interpreted lithologically as a sand layer at a depth range of 13 - 40 m, with an aquifer resistivity value of 133 Ωm. At MJL-03, the aquifer layer was estimated to lie at a depth range of 2 - 71 m, with an aquifer re- Table 2. Resistivity and Thickness of Each Layer VES ID MJL1 MJL2 MJL3 MJL4 MJL5 MJL6 MJL7 MJL8 MJL9 MJL10 MJL11 MJL12 Resistivity (ρ) Ωm Thickness (h) m ρ1 ρ2 ρ3 ρ4 ρ5 ρ6 ρ7 h1 h2 h3 h4 h5 h6 h7 141 1 45 22 54 1 1 42 3 1 5 5 14 5 8 82 1 13 4 9 19 8 1 42 31 1 13 8 15 1 2 41 1 1 33 1 14 133 247 298 1 6 7 27 10 1 33 34 1 7 1 1 2 5 258 - 233 - 1 3 1 3 1 1 1 1 1 1 1 1 1 3 2 2 1 1 4 8 1 1 7 1 3 7 69 5 3 18 18 91 3 2 15 3 9 27 79 12 9 130 127 12 8 128 10 24 98 137 83 21 135 64 118 - 48 - 363 Indonesian Journal on Geoscience, Vol. 8 No. 3 December 2021: 359-369 Table 3. VES Interpretation and Their Inferred Lithologies MJL1 MJL2 MJL3 MJL4 MJL5 MJL6 Resistivity (Ohm-m) Layer 1 Layer 2 Layer 3 Layer 4 Layer 5 Layer 6 Layer 7 Layer 1 Layer 2 Layer 3 Layer 4 Layer 1 Layer 2 Layer 3 Layer 4 Layer 1 Layer 2 Layer 3 Layer 4 Layer 5 Layer 1 Layer 2 Layer 3 Layer 4 Layer 5 Layer 1 Layer 2 Layer 3 Layer 4 Layer 1 Layer 2 Layer 3 Layer 4 Layer 1 Layer 2 Layer 3 Layer 1 Layer 2 Layer 3 Layer 4 Layer 5 Layer 1 Layer 2 Layer 3 Layer 4 Layer 5 Layer 6 Layer 1 Layer 2 Layer 3 Layer 4 Layer 1 Layer 2 Layer 3 Layer 4 Layer 5 141 14 31 14 34 5 233 1 5 1 133 45 8 13 247 22 82 8 298 1 54 1 15 1 7 1 13 1 6 1 4 2 7 42 9 41 3 19 1 27 1 1 8 1 10 1 258 5 1 33 1 5 42 1 33 2 Thickness (m) 1 1 3 9 24 64 48 3 3 7 27 1 2 69 79 3 2 5 12 98 1 1 3 9 137 1 1 18 130 1 4 18 127 1 8 91 1 1 3 12 83 1 1 2 8 21 118 1 7 15 128 1 1 3 10 135 IJ O MJL7 No of Layers MJL8 MJL9 MJL10 MJL11 MJL12 sistivity value of 247 Ωm. At MJL-04, the aquifer layer was estimated to lie at a depth range of 5 - 9 m, with an aquifer resistivity value of 298 Ωm. At MJL-05, the aquifer layer was estimated to occur at a depth range of 13 - 150 m, with an aquifer resistivity value of 7 Ωm. At MJL-06, the aquifer layer was estimated to exist at a depth range of 2 - 20 m, with an aquifer resistivity value of 6 Ωm. At MJL-07, the aquifer layer was estimated to 364 Depth (m) Inferred Lithology 1 2 5 14 38 102 150 3 6 13 40 1 2 71 150 3 5 9 22 120 1 2 4 13 150 1 2 20 150 1 5 23 150 1 9 100 1 2 5 17 100 1 2 4 12 32 150 1 8 23 150 1 2 5 15 150 Top Soil Top Soil Sand Clay Sand Clay Sand Top Soil Clay Clay Sand Top Soil Top Soil Clay Sand Top Soil Clay Clay Sand Clay Top Soil Sand Clay Clay Sand Top Soil Top Soil Clay Sand Top Soil Clay Clay Sand Top Soil Clay Sand Top Soil Top Soil Clay Clay Sand Top Soil Top Soil Clay Sand Clay Sand Top Soil Clay Sand Clay Top Soil Top Soil Clay Sand Clay G VES No. occur at a depth range of 5 - 23 m, with an aquifer resistivity value of 7 Ωm. At MJL-09, the aquifer layer was estimated to appear at a depth range of 5 - 17 m, with an aquifer resistivity value of 1 Ωm. At MJL-10, the aquifer layer was estimated to lie at a depth range of 4 - 12 m, with an aquifer resistivity value of 258 Ωm. At MJL-11, the aquifer layer was estimated to occur at a depth range of 4 - 12 m, with an aquifer resistivity value of 33 Vertical Electrical Sounding Exploration of Groundwater in Kertajati, Majalengka, West Java, Indonesia (G.U. Nugraha et al.) Aquifer Resistivity 350 300 MJL 4; 298 Ωm 250 MJL 10; 258 Ωm MJL 3; 247 Ωm 200 IJ O Resistivity (Ω m) the aquifer in the studied area (Dobrin and Savit, 1988; Kearey and Brooks, 1991; Reynolds, 1997; Telford et al., 1990; Tiab and Donaldson, 2012). Figure 6a shows a sand layer thickening towards the north. The existence of this continuous layer shows that this layer is part of the hydrogeological system in the studied area. The impermeable zone of the groundwater system in the studied area was dominated by the presence of a clay layer which acts as an aquiclude layer in the studied area. Aquiclude layers may store water easily, but do not transmit the groundwater easily (Fetter, 2001; Freeze and Cherry, 1979; Harter, G Ω. At MJL-12, the aquifer layer was estimated to exist at a depth range of 5 - 15 m, with an aquifer resistivity value of 33 Ωm. The detailed summary of aquifer resistivity is described in Figure 4. The values of aquifer resistivity in the studied area are very diverse (Figure 5). This is consistent with previous studies that measured the resistivity values of sand layer aquifers (Maiti et al., 2011; Obiora and Ibuot, 2020; Reynolds, 1997; Telford et al., 1990). Differences in the degree of compaction and also the physical properties of the sand within the aquifer layer can cause very significant differences in the resistivity values of 150 MJL 7; 7 Ωm MJL 2; 133 Ωm MJL 6; 6 Ωm 100 MJL 12; 33 Ωm MJL 8; 41 Ωm MJL 5; 7 Ωm 50 MJL 9; 1 Ωm MJL 1; 31 Ωm 0 MJL 11; 33 Ωm Figure 4. Aquifer resistivity chart of studied area. Aquifer Resistivity (ohm meter) 20 60 100 140 180 220 260 300 Figure 5. Aquifer resistivity map of studied area. 365 Indonesian Journal on Geoscience, Vol. 8 No. 3 December 2021: 359-369 A a MJL 12 5806.8 m MJL 10 MJL 4 6612.9 m A’ MJL 9898.7 m B b MJL10 MJL8 2695.0 m B’ MJL 60 50 40 50 30 40 20 30 10 20 0 10 -10 0 -20 -10 -30 -40 -20 -50 -30 -60 -40 -70 -90 2999.1 m 70 60 -80 MJL9 2926.1 m Lithology -50 Clay Clay -60 Lithology Sand Top soil 20000 c Top soil -70 -100 0 -110 C MJL 6 Sand 2112.3m MJL 5 -80 0 MJL 4 3112.3m 2000 7421.1 m 4000 6000 8000 C’ MJL 50 40 30 20 10 0 -10 -20 -30 -40 -50 -60 -70 IJ O -80 G 60 -90 Lithology Clay Sand -100 0 -110 5000 Top soil 10000 Figure 6. Cross-sections of 12 measured points in the studied area. (a). A - A cross-section; (b). B - B cross-section; (c). C - C cross-section. (Cross-section lines are presented in Figure 2). 2003). The clay layer can be classified as an aquiclude layer (Freeze and Cherry, 1979; Fetter, 2001; Lopez-Gunn et al., 2011; Singhal and Gupta, 2010), while the sand layer can both store and transmit groundwater, acting as an aquifer (Freeze and Cherry, 1979; Fetter, 2001; Wal, 2010). The pattern distribution of sand in cross-section 1 tends to follow the elevation of the studied area. A layer of sand that is thick enough to serve as an aquifer is found at the MJL-10 VES station, but nevertheless does not have the potential to be an aquifer, because it is present only locally and noncontinuously. Groundwater may be present in this layer but is not sustainable, because it does not have a continuous water supply. Figure 6b shows a layer of sand that is thick enough to act as an aquifer, with a small lens from the clay layer. In this cross-section, the sand layer functions as an aquifer layer and the clay layer functions as an 366 aquiclude. Figure 6c shows that the sand layer is continuous towards the northwest. The clay layer dominates in almost all cross-sections, and the aquifer potential is found in the sand layer. Figures 6a and 6b show that the clay layer predominates in all studied areas. Due to the dominance of the clay layer compared to the sand layer, the presence of aquifers in the studied area is very limited. With limited aquifer layers, the groundwater supply in the studied area is also limited (Fetter, 2001; Lopez-Gunn et al., 2011; Ramsar, 2006). Figure 6 shows the geometry of the aquifer, which suggests that groundwater cannot be exploited excessively if the sustainability of groundwater in the studied area is not to be maintained. IWACO-WASECO (1990) states that in the studied area, there is an aquifer with medium potential. Resistivity values indicate that clay layers dominate the studied area. Vertical Electrical Sounding Exploration of Groundwater in Kertajati, Majalengka, West Java, Indonesia (G.U. Nugraha et al.) Conclusions IJ O G Twelve VES measurement points were conducted around the area of West Java International Airport, Kertajati Subregency, Majalengka Regency, West Java Province. In general, resistivities in the studied area can be divided into five categories from very low resistivity to very high resistivity. Aquifer resistivities falling into all of these categories are found in the studied area. The aquifer resistivity values for each VES station are 31 Ωm for MJL1, 133 Ωm for MJL2, 247 Ωm for MJL3, 298 Ωm for MJL4, 7 Ωm for MJL5, 6 Ωm for MJL6, 7 Ωm for MJL7, 41 Ωm for MJL8, 1 Ωm for MJL9, 258 Ωm for MJL10, 33 Ωm for MJL11, and 33 Ωm for MJL12. In general, aquifers in the studied area are lithologically composed of sand. The sandy aquifer layer was typically found at relatively shallow depths of less than 20 m, although at a few sites the aquifer extended deeper. 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