Geoelectrical Cross-sections Research Articles

Application of remote sensing and electrical resistivity technique for delineating groundwater potential in North Western Nigeria

Improving the living condition of residents of Palladan and Basawa community requires access to drinking water. The main objectives of this paper are to identify suitable groundwater zones for productive drilling and to assess groundwater mineralization in the coastal aquifers of the study area. Geographic Information Systems (GIS) and Analytical Hierarchy Process (AHP) were used in the methodology to generate the groundwater potential map. Slope, landcover/land use, lineament density, rainfall, soil cover and drainage density were taken into account to characterize the groundwater potential zones. Weights were assigned to the various parameters and their characteristics according to their impact on groundwater recharge. The groundwater potential map was classified into five zones namely: poor, fair, moderate, good, excellent. Based on the lineament density map, the distribution of these lineaments reveals the degree of porosity or permeability in each area and, consequently, its groundwater potential. Aeromagnetic data filtering permits the construction of a structural map that illustrates various geophysical lineaments that are known to be fault systems in the research area. These faults are the main routes via which groundwater seeps into the subsurface and granitoid-type magnetic rocks intrude into the basement. The research region is badly fractured/failed and made up of four lithologic units, including the aquifer layer (clayey sands in the cracked basement) with thicknesses varying from 12–55 m, according to the vertical electrical sounding (VES) applications. According to geoelectric cross-sections, the subsurface structures are made of granitic rocks that are surrounded by normal faults that trend both NW and NE. It is believed that groundwater flows into the hard rock aquifers in the studied locations through these notable geological features, such as faults and fractures. Two phenomena are responsible for the mineralization of water: a process of interaction between water and rock; and a process of salinization resulting from natural phenomena or anthropic activities. The present study could guide hydrogeological investigations and groundwater resource management planning in the study area.

Geometric Characterization of the Mateur Plain in Northern Tunisia Using Vertical Electrical Sounding and Remote Sensing Techniques

The Mateur aquifer system in Northern Tunisia was examined using data from 19 water boreholes, 69 vertical electrical sounding (VES) stations, and a Sentinel-2 satellite image. Available boreholes and their corresponding logs were compared to define precisely the multi-layer aquifer system, including the Quaternary and Campanian aquifers of the Mateur plain. Quantitative interpretation and qualitative evaluation of VES data were conducted to define the geometry of these reservoirs. These interpretations were enhanced by remote sensing imagery processing, which enabled the identification of the Mateur plain’s superficial lineaments. Based on well log information, the lithological columns show that the Quaternary series in the Ras El Ain region contains a layer of clayey, pebbly, and gravelly limestone. Additionally, in the Oued El Tine area, a clayey lithological unit has been identified as a multi-layer aquifer. The study area, exhibiting apparent resistivity values ranging between 20 and 170 Ohm·m, appears to be rich in groundwater resources. The correlation between the lithological columns and the interpreted VES data, presented as geoelectrical cross-sections, revealed variations in depth (8–106 m), thickness (10 to 55 m), and resistivity (20–98 Ohm·m) of a coarse unit corresponding to the Mateur aquifer. Twenty-three superficial lineaments were extracted from the Sentinel-2 image. Their common superposition indicated that both of them are in a good coincidence; these could be the result of normal faults, creating an aquifer system divided into raised and sunken blocks.

Geoelectric Investigation for Groundwater in Imo State University Campus and Environs using Direct Current Electrical Resistivity Method

Eighteen, vertical electrical soundings (VES), were carried out in Imo State University and Environs to delineate the potential site for groundwater. Data were acquired using ABEM SAS 300 resistivity meter. Schlumberger array and maximum electrode spread of 700m were adopted. Data were interpreted with IP2WIN software. Contour maps were done using Sulfer 20 software. Geoelectric cross-sections constructed along three profile lines delineated subsurface stratification. Sediments consist of sequence of sandstone/gravel, silty sand/sand and clay with geology representing the Benin Formation. Groundwater was delineated within the zone interpreted to be sand with quartz making up more than 95% of all grains. Resistivity of aquifer varies across study area and ranges from 159Ωm, observed around Library and Information Department (VES 11) to 100000Ωm recorded at IMSU Plaza (VES 10). Depth to water table also varied across study area with higher values of 150m and 130m observed at College of Health Science (VES 3) and Behind Old ETF (VES 4). A relatively shallow aquifer is delineated behind Senate Building and Okwu-Uratta with water table at depths of 23.5m and 26.5m. The transmissivity values are moderately high except at some locations. The variation in longitudinal conductance and transverse resistance values show that part of the study area such as Aso Rock, Female Hostel, Law Faculty and IMSU Plaza are underlain by relatively resistive (low longitudinal conductance) aquifer material. Distribution of hydraulic conductivity and electrical conductivity values indicates that in some of the VES points, the values are fairly constant. This could be seen as areas with similar geologic settings and water quality. Storativity of study area ranges from 0.00003 at VES 1 and 12 to 0.00028 at VES 4. Study area shows a good prospect for groundwater development, except at Library and Information Department, where the zone delineated is an aquitard.

Shallow and deep geothermal water sources identification in Unai geothermal field, Gujarat, India with applications of Magnetotelluric (MT)

The aim of this study is to conduct and examine the results of a Magnetotelluric (MT) survey in Unai, Gujarat, India for geothermal prospect identification. At Unai, the data was acquired, processed, and interpreted in the form of 2D and 3D MT surveys. Data were acquired at 56 stations in uniformly spaced profiles along the ENE-WSE direction (geological strike direction) with a station spacing of 2 km. Qualitative and quantitative data understanding has been done for geothermal prospect identification. Deep and shallow 1D and 2D models of electrical resistivity were made, which suggests the presence of a geothermal aquifer. This is corroborated by polar and skew tipper diagrams. The one-dimensional Occam models and two-dimensional conjugate gradient models confirm the presence of a low resistivity anomaly near the surface ranging from the depth of 100–700 m. This suggests the presence of a shallow geothermal zone. Apart from the shallow geothermal prospect, this study also delineates a deep conductive body which may be attributed to a matured geothermal reservoir. For a better understanding of the prospect geoelectrical cross sections are analysed from a depth of 10 m to 15 km. The MT cross-sections show the presence of geological features such as a series of faults. These faults form horst and graben in nature and may act as a good trap for the shallow reservoirs.

Delineating of Groundwater Aquifer Potential Using Vertical Electrical Sounding (VES) Methods in Giriloyo, Wukirsari Village, Imogiri District, Bantul Regency, Special Region of Yogyakarta

The geophysical investigation in Giriloyo, Wukirsari Village, has defined the groundwater potential zones. The research region underwent a geophysical examination utilizing the electrical resistance method, which comprised the vertical electrical sounding (VES) technique and the Schlumberger array system. The study area is surrounded by common rock types such as lava, tuff, agglomerate, and alluvial. In the study region, five lines were explored. Data for subsurface resistivity were gathered with an Oyo McOhm type 2115. IPI2win, a piece of computer software that analyzes data and automatically interprets apparent resistivity, was used to examine the data. The VES data showed the varied nature of the subsurface geological sequence. The geoelectrical cross-sections along the profile of (VES 2-3-4-1) show an aquifer, which stretches from the southeast towards the northwest part of the basin. Tuff is seen to have formed shallow aquifers due to the top weathered part at VES-2 and 3, while Quartz chlorite calcite (VES-4) and Plagioclases (VES-1) are devoid of shallow aquifers. The higher-elevation lithological areas recharge the low-elevation aquifer zones. At VES 2 and 3, relatively low resistivity values (< about 100 Ωm) have been observed. A field observation at these locations reveals that these lithologies are highly fractured with a weathering profile of up to 10 m. Thus, these are the sites where groundwater potential zones can be marked (figure 4). The high resistivity (about 3162 Ωm regions is observed extending at the VES-4; this may be due to the least weathered Quartz chlorite calcite at high elevation. VES-1 is also located on the plagioclase and shows a slight resistivity zone, which could be considered a groundwater recharge zone. This profile shows the high possibility of groundwater potential due to the zone of lineaments.

Assessment of groundwater aquifer using geophysical and remote sensing data on the area of Central Sinai, Egypt

The study aims to assess groundwater resources in Sinai's central area using remote sensing, geoelectric, and well-logging data, utilising techniques for modelling hydrogeological frameworks and evaluating desert regions' groundwater potential. Its utilized satellite image sources, soil maps, and geological maps to map the effects of various factors on groundwater potentiality recharge, dividing it into five zones. Eighteen deep VES stations were used to examine the upper part of the groundwater aquifer in Central Sinai, Egypt, comparing it with available borehole information (Well-1, and JICA-1) to establish subsurface geology and hydro-geology positioning. Borehole data, VES interpretation results, hydro-geophysical maps, and four geoelectrical cross-sections were used to visualize the rearward expansion of eight lithological units, groundwater-bearing sections, and aquifer-filled thicknesses. From interpretation data output reveal three zones with significant recharge and storage potential, including two groundwater aquifers. The shallow aquifer has a saturation thickness of the fractured limestone of 35–250 m, while the deep aquifer Nubian sandstone is detected at depths ranging from 660–1030 m. NW–SE and NE–SW faults likely recharge conduits connecting shallow and deep aquifers, providing sites with acceptable groundwater potential for living, agriculture, and development in Sinai.

Applying Geophysical and Hydrogeochemical Methods to Evaluate Groundwater Potential and Quality in Middle Egypt

The El-Minia district is a location of interest for future urban development. Using hydrochemistry and electrical resistivity studies, this work aimed to evaluate the groundwater potentiality and it’s suitable for various uses. The groundwater potential in the study area was evaluated based on 24 VESs (vertical electrical soundings), and its quality was determined based on the analyses of 57 groundwater samples. EC (salinity index), Na% (salt hazard), SAR (ratio of sodium adsorption), chloride risks, SSP (soluble sodium percentage), MH (magnesium hazard), and other indicators were used to determine whether the collected water samples were suitable for irrigation. Four layers in the study area are mentioned in the geoelectrical cross-sections that have been constructed. The first is made up of silt and clay from the Nile River, while the second is made up of sandy clay, which has a resistivity range of 15 to 32 Ohm.m and a range thickness of 2 to 68 m. Dry limestone makes up the third layer; its resistivity ranges from 1222 to 3000 Ohm.m and its thickness varies between 75 and 95 m. The Eocene aquifer in the research area is represented by the final layer, which has a thickness of more than 250 m and resistivity values that range from 602 to 860 Ohm.m. Most groundwater samples that were collected are safe for drinking; however, none of them are fit for home usage because of their extreme hardness. According to the SAR and US diagram, RSC, KR, and PI, most groundwater samples from the Pleistocene and Eocene aquifers are fit for irrigation.

Geological-geotechnical investigations of the historical Diriyah urban zone in Riyadh, Saudi Arabia: an integrated approach

One hundred seventy geotechnical boreholes, two geo-seismic profiles of multichannel analyses of surface waves (MASW), and two geoelectrical cross-sections of electrical resistivity tomography (ERT) were carried out in the historical Diriyah urban zone. The borehole samples were analyzed for the geotechnical parameters of the standard penetration test (SPT N-value), the rock quality designation (RQD), and compressive strength (CS). Moreover, P- and S-wave velocities have been calculated. The measured SPT N-value has been corrected to amend the N60 parameter. According to the corrected N60, type, lithological, and soil profiles were divided into five distinct subsurface layers. It is indicated, for all recorded depths, these sediments become denser with depth where the values of N60 increase from 5 to 88 downward. According to grain size distribution, the major part of soil sites is composed of sand and varies from low to medium compressibility. The estimated RQD values range from 5 to 100 indicating rocks with significant variations in their geotechnical and physio-chemical characteristics. Furthermore, the compressive strength varies widely between 152.3 and 1,104.2 kg/cm2, which represents diverse geodynamic behavior under civil engineering constructions. Besides, the range of soil stiffness is indicated by the Shear-wave velocity (Vs) for soil layers, which varies from 171.3 to 456.2 m/s. According to the findings of the MASW profiles, the shear wave velocity is shown to be decreasing in MASW profile 1 between depths of 8 and 14 m, where the values range from 1,000 to 1,500 m/s, indicating a weak zone filled with secondary materials. But line 2 shows how the shear wave velocity decreased from depths of 5 m–11 m, where values ranged from 1,000 to 1,500 m/s, thus indicating a weak zone. The low resistivity zones in ERT cross-sections, which are found at the same depths in MASW profiles, are well associated with these findings. It can be concluded that there are a number of weak zones with varying depths, shapes, and dimensions found in the historical Diriyah urban zone’s near-surface deposits that civil engineers, urban planners, and urban developers should consider before undertaking any construction or developmental work involving civil engineering.

GEOELECTRICAL ASSESSMENT OF GROUNDWATER POTENTIAL OF KEANA AREA NORTHCENTRAL NIGERIA

This work was undertaken to unravel the hydro geophysical characteristics of Keana metropolis Nasarawa State, northcentral Nigeria. This study aims to assess and determine the sustainability of groundwater resources in Keana Town by using geoelectric techniques to collect data and analyze subsurface characteristics that can assist identify suitable sites for groundwater extraction. Once accomplished, it will give useful information for groundwater resource management and contribute to Keana’s long-term growth. Fifteen (15) Vertical Electrical Sounding (VES) data with a maximum electrode spacing of (AB/2) of 200 meters were acquired using the Schlumberger electrode configuration. The VES data were interpreted using the conventional partial curve matching technique to obtain initial model parameters, which were used as input for computer iterative modelling using the IPI2WINTM software. The study revealed three (3) to six (6) geo-electric layers with underlying indurated sandstone and shale beds in some areas. In the study area, the apparent resistivity of the aquifer ranges from 32.4 to 407 m, with a depth ranging from 30 to 120m. Information extracted from iso-resistivity models and geoelectric cross sections revealed sandy strata with an exception around the northern portion i.e., around Federal Government Girls College Keana (FGGC) where a thick layer of shale is envisaged, extending to over 150 m depth with an average apparent resistivity value of 35Ω m. Thus, making the section fair to poor groundwater potential. However, this research has aided in delineating the groundwater potential of the area into three distinct zones.

Remote sensing and geophysical methods for delineating groundwater resources in schists hard rocks of the Adamawa Yadé Domain, Cameroon

The combination of remote sensing and geophysical techniques is a practical approach for mapping environmental hydrogeological setting and delineating groundwater zones. This paper applies an integrated approach to identify and extract the subsurface structures that act as conduits for the groundwater flow in the highly deformed area of the Adamawa region. Remote sensing data through the lineament’s extraction technique highlights topographic lineaments along which rivers flow in the area. The distribution of these lineaments according to the lineament density map indicates the degree of permeability or porosity of each region and thus the capability in terms of groundwater potential. The filtering of aeromagnetic data enables to produce a structural map showing various geophysical lineaments interpreted as the fault systems of the study area. These faults are the main conduits through which magnetized rocks of granitoid type intruded into the basement and groundwater flows to the subsurface. Local application of the vertical electrical sounding (VES) shows that the study area is highly fractured/faulted and composed of multiple lithologic units including two aquifer layers (clayey sands and fractured schists) with thickness ranging from 5 to 15 m and from 34 to 82 m, respectively. Geoelectric cross-sections reveal that the subsurface structures consist of horsts, followed by a progressive subsidence depicted by the NE-trending faults towards the southern depression and grabens bounded by NW- and NE-trending normal faults. These prominent structures (faults, fractures, and grabens) are considered as the conduits for the groundwater flow into hard rock aquifers of the study area.

Groundwater resource evaluation using geoelectrical resistivity survey in the Ghard El-Hunishat area of New Delta project province, North Western Desert, Egypt

The present study aims to assess the groundwater resources in the Ghard El-Hunishat area, North Western Desert, Egypt, as it is part of the national agricultural reclamation mega-project (New Delta). This involves defining the groundwater-bearing zones and estimating their thicknesses and depths, outlining their lateral extents, besides trying to estimate the aquifer groundwater quality. To achieve these objectives, geoelectrical resistivity measurements with a total of thirty-eight vertical electrical soundings (VES) distributed along seven profiles have been carried out using the Schlumberger configuration. VES data were acquired at a maximum electrode spacing (AB/2) of 1000 m. The interpreted data have been correlated and calibrated with the available borehole lithological information in the study area to minimize the uncertainty of the interpreted models. Data analysis and interpretation revealed that the subsurface stratigraphic sequence consists of five geo-electrical layers; the fourth one represents the saturated Moghra aquifer unit, where its resistivity ranges between 25 and 78 Ω m, and its thickness ranges from 116 to 172 m, while the depth to the top of this layer ranges from 99 to 168.5 m. The interpreted layer parameters were used to generate geo-electrical cross-sections, and then these sections were presented in the form of a 3D fence diagram showing the lateral and vertical extents of the subsurface geological succession in the study area. Contour maps were also created, showing the spatial distribution of the saturated aquifer parameters. The current research findings can contribute to a better understanding of subsurface geological situations and assess the suitability of the investigated area for anticipated agricultural and urban developments, as well as water management for related activities.

Three-dimensional magnetotelluric signatures and rheology of subducting continental crust: Insights from Sikkim Himalaya, India

3D inversion of broad band MT data present variation of electrical signatures across the subducting Indian crust in Sikkim Himalaya. The vertical and horizontal geoelectric cross-sections are dominated by north-east dipping conductive zones. Two high conductivity zones (4–8 Ω m) at a depth of 5–18 km in Lesser Himalayan Domain (LHD) are explained by conductive mineral assemblage associated with abundant low saline and entrapped fluids. Another conductive feature (6–16 Ω m) in Main Himalayan Thrust Zone close to Main Himalayan Thrust ramp could have arisen from entrapment of CO2-H2O fluids and fluids released by metamorphic reactions. The high conductive anomaly (4–10 Ω m) at a depth of 5–16 km in Greater Himalayan Sequence (GHS) is caused by the presence of partial melts/aqueous fluids derived by present day fluid-absent melting of leucogranite source rocks. A combination of leucogranite intrusion, shear heating, and radiogenic heat production (4–17 μW/m3) are the heat sources for inferred partial melting. Though, the constrained melt fractions of 1.4–3.8% in GHS are lower than the estimation in south Tibet that might be due to the less intrusion of leucogranites. The obtained moderate viscosities of (104.19-105.49 Pa.s) from empirical relation with low melt and fluid fractions of 5–6 wt% in high conductive zone suggest viscous/ductile deformation and weakening mid-crust beneath northern Sikkim Himalaya. However, the estimated values of melt fractions and viscosities at mid-crustal depth of GHS are insufficient to develop a melt channel to flow southward between Main Central Thrust-1(MCT-1) and South Tibet Detachment (STD) envisaged by channel flow model.

Geophysical studies to delineate groundwater aquifer in arid regions: A case study, Gara Oasis, Egypt

Groundwater is an important factor in establishing new urban communities, especially in coastal arid and semi-arid regions. Egypt is one of the world's driest countries, with hyper-arid territory accounting for 86% of the total area and arid and semi-arid terrain accounting for the rest. The present work aims to demonstrate the powerful integration of geophysical techniques to assess groundwater potentiality and suitability in Gara Oasis (GO), which describes a good example of Egypt's strategic southern extension of its arid north-western coast. Geophysical methods, including electrical resistivity and aeromagnetics, were used to evaluate groundwater resources. The study region reduced to pole total magnetic intensity map is subjected to digital filters that include derivatives, analytic signal, and tilt angle. The possible structures controlling the shallow and deep aquifers are delineated and integrated with geoelectric results. Moreover, two magnetic tomography sections are constructed to show the subsurface distribution of magnetic susceptibilities and formation boundaries. Ten vertical electric soundings (VESs) are measured and used in this study to construct four geoelectrical cross-sections. According to the results, Gara's commonly calculated subsurface resistivity model comprises six major resistivity layers. The 5th layer, in particular, is composed of Fractured dolomitic Limestone and represents a possible promising shallow aquifer. Moreover, as evidenced by various magnetic data filters, the shallow (Miocene carbonate) and deep (Nubian sandstone) aquifers are structurally controlled and regulated by a system of faults or contacts. These contacts trends NW–SE, E–W, and NE–SW as common trends emerged from the total derivative and tilt maps. Results suggest that the central part (N–S zone) together with the western side of Gara, have the most notable aquifer possibility demanded future improvement strategies.

Employing Geophysical Techniques to Detect and Assess Groundwater Pollution at El-Akader Landfill North Jordan

A geophysical study was conducted for the El-Akader landfill to determine its impact on groundwater, which is located along the northern road of Jaber International Road, north Jordan, which covers an area of 0.806km2. it was commissioned in 1981 to be the only municipal landfill at north Jordan and it is considered the second-largest landfill in the country. A geoelectrical survey was conducted in the study area using the Vertical Electrical Sounding and an electromagnetic survey using the Transit Electromagnetic. Upon analyzing the 42 TEM loops and performing geoelectrical cross-sections, landfill leachate is found to be concentrated below the dumping site and its surroundings and would infiltrate down to about 200 m below land surface. The results of the Vertical Electrical Sounding revealed that the depth of groundwater to be around 300 m with a resistivity less than 5-ohm.m. It also indicates that the leachate is moving mainly vertically, which confirms the TEM results. Contaminants are detected in water samples collected from several nearby wells which indicates a horizontal movement of the landfill leachate which would have been penetrated down through inferred faults deep fractures detected in the area.

Identification of Groundwater Bearing Zones Using Geoelectrical and Electromagnetic Techniques at Tourah Area, South of Cairo - Egypt

The complex geology of Tourah area, south Cairo is a serious challenge for groundwater exploration, where the risk of unsuccessful groundwater drilling excavation for industrial purposes is well dressed, raising the need for better geophysical subsurface detection and characterization approaches in terms of water bearing and aquitard zones. Datasets from the study area were acquired using integrated geophysical techniques comprising of one Dimensional Vertical Electrical Soundings (1D VES) and one Dimensional Transient Electromagnetic (1D TEM) as well as two-Dimensional Electrical Imaging (2D ERI) which was restricted to the available spreading space as well as subsurface infrastructure noise. The results of 1D VES and 1D TEM soundings detected three to five geoelectric layers used to generate geoelectrical cross sections and maps of resistivity, thickness, and depth to water bearing zone. Moreover, the 2D ERI inversion profiles were able to image the first three layers and the depth of the water bearing zone [A] with significantly greater resolution due to their higher lateral and vertical resolutions compared to the traditional 1D VES and TEM interpolated cross section. The integration of the three geophysical methods displayed a smooth distribution of both marly limestone and fractured shaly limestone and claystone bands water bearing zones [A and B]. Resistivity values of the water bearing zone [A] ranges from 0.1 to 24 Ω m, with average thickness of 4 to 12 m, and depth to water of 1.5 to 13.6 m. In addition, [zone B] is the main water bearing zone of fractured shaly limestone and claystone bands (2 to 14 Ω m) which is detected at deep depth of 40 and 75 m. Two normal fault systems inferred from 1D interpretation are considered responsible for local recharging of the main Eocene aquifer over the study area. In conclusion, the outlined water bearing thickness as well as limited sources of groundwater recharge indicate that these water bearing zones may not provide a sustainable supply for the industrial development purposes in the future.

Use of geoelectrical resistivity method for detecting near-surface groundwater potential zones at Riyadh city, Saudi Arabia

Six profiles of the two-dimensional multi-channel electrical resistivity tomography (ERT) were conducted at the northwest part of Riyadh city using the SYSCAL Pro system with a dipole–dipole configuration to detect the near-surface water-bearing potential zones. The ERT field measurements use a series of regularly placed electrodes to measure the electrical resistivity along the profile. The results of the inverse models are displayed as cross-sections of the true resistivity distribution of the subsurface with depth along with each profile. The two-dimensional (2-D) inversion results of the electrical resistivity data indicate three geoelectric zones; 1st zone of low resistivity values (<100 Ω.m), representing two groundwater-bearing potential zones from top to bottom as follows; the 1st one extends downwards to 10- and 15-meters depth, while the 2nd zone spreads between 15- and 30-meters depth, 2nd zone with resistivities ranging from 100 to 1000 Ω.m, which represent the highly fractures limestone; the 3rd zone with resistivities greater than 1000 Ω.m reflecting compacted limestone rocks. It is noticed also some of the low resistivity pockets are isolated through the subsurface geoelectrical cross-section indicating the presence of voids and/or cavities. Based on these results, the investigated area is considered as one of the promising zones for groundwater supply in Riyadh city and its future urbanization expansion projects. This can be accessed by drilling wells down to a depth of 50 m for groundwater extraction.

Multi-criteria ground water potentiality mapping utilizing remote sensing and geophysical data: A case study within Sinai Peninsula, Egypt

Groundwater demand has dramatically increased due to the swift demographic explosion, especially in arid areas, where groundwater is considered the main source for all purposes. Thus, this research integrates climatological, lithological, structural, topographical, hydro-morphological, and geoelectrical data to explore groundwater potential zones in the central part of Sinai Peninsula, Egypt using the GIS-based Analytic Hierarchy Process (AHP). Seven thematic layers of soil moisture, rainfall, normalized difference vegetation index, drainage density, lineament density, slope, and land use/land cover were built from different remote sensing data sets. The eighth layer represents a high-resolution lithological map of the study area, constructed utilizing the power of the support vector machine over Sentinel 2 data and accurately assessed with a previously published geological map. Ground Water Potentiality Map (GWPM) was constructed and highlighted four main areas as promising zones. Comprehensive geoelectrical analysis was executed through seventeen deep vertical electrical soundings (VESs) using Schlumberger configuration, isoresistivity mapping, and geoelectric cross-sections along five different profiles. 3D view of the studied area's subsurface geological and structural pattern with groundwater flow direction specification, and adequate aquifer characterization, revealed four main geoelectrical units. Geoelectrical data results reasonably coincided with remote sensing data findings in highlighting three freshwater potential zones. Furthermore, the study strongly recommends integrating low-cost remote sensing datasets in narrowing the zone to be intensively investigated using further costly geophysical approaches or drilling test boreholes.

Near-surface groundwater exploration using the geoelectrical resistivity method: A case study of Wadi Nisah, Riyadh, Saudi Arabia

In desert regions like Saudi Arabia, groundwater exploration is critical for drinking, household, and agricultural purposes. The purpose of this study is to use Vertical Electric Sounding (VES) to assign near-surface groundwater sources in the Wadi Nisah area of central Saudi Arabia. Twenty VES stations were installed in the central part of Wadi Nisah, with a maximum half current electrode separation (AB/2) of 100 m, utilizing a Syscal R2 resistivity-meter with Schlumberger electrode design. The interpretation of these VES's revealed five geoelectric layers, the first of which is formed of dry sand with greater resistivity values and has a depth of around 3 m. The groundwater-bearing aquifer is represented by the fifth layer, which is the deepest, with depths ranging from 37.8 to 52.25 m below the surface and resistivities ranging from 47 Ω-m to 115.3 Ω-m. Six geoelectrical cross-sections were also mapped to show the lateral and vertical heterogeneities of the underlying lithology in the study area. These findings suggest that the groundwater bearing layer is a hydrologically promising zone capable of delivering optimal groundwater yield for drinking and agricultural use in the study area; the VES technique is a useful tool for identifying groundwater prospective zones.

Using the magnetotelluric method to study the deep structure of the Sai Gon river fault in the vicinity of Ho Chi Minh City

This paper presented the study of the two magnetotelluric profiles crossing the Saigon river fault. The first one was 13.5 km long consisting in 8 stations extending from Cu Chi district, Ho Chi Minh city to Ben Cat district, Binh Duong province, and the second was 11.7 km long including 7 stations in Nhon Trach district, Dong Nai province, Vietnam. The data were recorded in the period range 0.002‒259 s using the GEPARD-4 instrument. Because of the influence of the equatorial electrojet (EEJ) on magnetotelluric soundings in this region, only data in the period range shorter than about 1 s for the analysis were used. The resistivity data of both TE and TM modes were used for inversion using the MT2DinvMatlab software. Firstly, data were inverted down to a depth of 10 km to obtain the main electric features of the region. The results showed that on both profiles, the resistivity cross-sections showed a 3-layer geoelectric structure in which the top low resistivity layer had a thickness of about 2 km, the resistive intermediate layer was about 6‒7 km thick, and the underlying low resistivity layer. On these cross-sections, the Saigon river fault could not be observed. Then data were inverted down to 3 km to obtain more detailed information to determine the location and dip direction of the Saigon river fault. The geoelectric cross-sections of 3 km depth showed that for the Cu Chi‒Ben Cat profile, the Saigon river fault corresponded to the low resistivity region below the stations CB5 and CB6, and for the Nhon Trach profile, the river fault Saigon would be related to the low resistivity region below the stations NT3 and NT4. The obtained results confirmed the existence of the Saigon river fault, with the location and its continuous extension from the Cu Chi‒Ben Cat area, through Thu Duc city to Nhon Trach district of Đồng Nai province.

Geoelectrical Survey for Evaluation of Groundwater Potential Within the Basaltic Terrain of Chikotra River Basin, Maharashtra (India)

Geoelectrical data was acquired using Wenner array over 23 sites with constant electrode separation of 70 m over Chikotra Basin, Dist. Kolhapur, Maharashtra (India). The spatial variation maps of resistivity at depths from 2 to 70 m were plotted using Inverse Distance Weighted (IDW) technique for interpolation in ArcGIS 10.5 to obtain a comprehensive subsurface hydrogeological representation of the study area. High resistivity (&gt;140 Ωm) up to 20m depth, indicative of massive basalts is deciphered towards the NE part of the study area, while the NW sector reveal low resistive (up to 40 Ωm) feature at shallow depths due to fractured basalts, thus conducive for groundwater exploration. Alluvium deposits and columnar jointed basalts in the central part depicts as EW trending conductive (&lt; 30 Ωm) feature suggesting prospective groundwater zone. Low resistivity (6-50 Ωm) from shallow to deeper depths (up to 70m), in the southern region can be identified as potential aquifer system. Longitudinal geoelectric cross-sections are generated over four profiles to identify the lateral and vertical variation in geology and groundwater potential zones. The western and central part of the northern profile (A-A') is highly resistive with resistivity of the order of 80-140 Ωm constituting compact basalts and thus devoid of water. Low resistive zone (30 Ωm) in the eastern part suggests groundwater at shallow depths. Low resistivity zones ranging from 10-50 Ωm is observed at different depth levels over the central profile (B-B') which can be tapped for groundwater exploitation. Several sites over profiles C-C' and the southern-most D-D' suggest promising aquifer zones. Because defining prospective groundwater zones in hard rock terrain is difficult, it’s crucial to look into a river basin’s hydrogeological arrangement early on in the planning process.