Geoelectric Units Research Articles

Geoelectric analysis for groundwater potential assessment and aquifer protection in a part of Shango, North-Central Nigeria

Groundwater is vital for sustainable development, and this study addresses potable water challenges in Shango, North-Central Nigeria. The main goal is to identify optimal sites for new wells and boreholes, utilizing geological and geo-electrical attributes from existing boreholes and wells. Vertical Electrical Sounding (VES) assessed groundwater potential, aquifer protection, and overburden corrosivity. Sixteen VES stations were probed using Schlumberger array with a maximum current electrode spacing (AB/2) of 200 m using a resistivity meter. The data were interpreted using an automatic computer inversion program, IPI2WIN. The VES results revealed five subsurface geo-electric units, with depths to the aquifer ranging from 58 to 68 m, each exhibiting distinct characteristics contributing to the lithological variability of the research area. Hydraulic conductivity ranged from 0.465 to 0.534 m/day, while transmissivity varied from 9.589 m2/day to 26.029 m2/day across different VES points. Regions exhibiting thick layers and low resistivity values indicate high longitudinal conductivity. Furthermore, areas with low protective capacity are susceptible to the risks of pollution and contamination stemming from leaks and waste sites. The study revealed that all VES points are in practically non-corrosive zones, making them suitable for burying underground tanks with extremely low deterioration rates. Based on geoelectrical characteristics, the study area was divided into three groundwater potential zones: low, medium, and high. These findings provide valuable insights into the groundwater potential and protective capacity of the Shango area, while emphasizing on the vulnerability of these regions and highlighting the pressing need for appropriate preventive measures to safeguard against potential environmental hazards.

Groundwater potential of subsurface geo-electrical units in part of River Niger Floodplain, Jebba, Nigeria

Groundwater potential of subsurface geo-electrical units in part of River Niger Floodplain, Jebba, Nigeria

Investigation of Groundwater Occurrences Along the Nile Valley Between South Cairo and Beni Suef, Egypt, Using Geophysical and Geodetic Techniques

Water is becoming one of the most critical strategic challenges for any country. Egypt has numerous water resources, the most notable being the Nile River. Egypt must seek alternative resources because the development of an Ethiopian dam has reduced the Nile's water flow. Underground water is a source of available water. Therefore, it is necessary to understand the variables governing the flow of subsurface water in Egypt. The primary objective of this study is to examine the hydrological water flow along the Nile Valley between southern Cairo and Beni Suef, Egypt. Applying integrated geophysical and geodetic methods can improve our understanding of the hydrological regime. Fault and stress regimes have a direct effect on underground water flow. Aeromagnetic data were used to determine the main faults in the study area, and four geoelectrical long profiles were measured crossing the Nile Valley. Global navigation satellite system (GNSS) measurements observed along geodetic points covered the study area. The magnetic results show that two faults hit the area, both of which have a pronounced magnetic pattern in the ENE–WSW direction, and two faults in the NW–SE direction. For the geoelectrical results, we observed that the second geoelectrical unit represents the main groundwater aquifer in this region, and it is regulated in the NW–SE direction. The obtained GNSS results demonstrate that compression forces in the south and north influence the hydrological system in the Nile Valley. Faults detected from geological maps and magnetic observations are also influenced by compression forces from the north and south, while the middle section displays tension forces. This geodynamic regime causes the water to flow toward the Nile Valley in the Southwestern of the study regions, whereas water flows outside the Nile Valley in the northeastern part.

Integrated Geophysical Approach of Groundwater Potential in Wadi Ranyah, Saudi Arabia, Using Gravity, Electrical Resistivity, and Remote-Sensing Techniques

In order to cope with the rise in human-caused demands, Saudi Arabia is exploring new groundwater sources. The groundwater potential of Wadi Ranyah was studied using a multi-dataset-integrated approach that included time-variable gravity data from the Gravity Recovery and Climate Experiment (GRACE), vertical electrical sounding (VES), and time-domain-electromagnetic (TDEM) data with other related datasets to examine the variations and occurrence of groundwater storage and to define the controlling factors affecting the groundwater potential in Wadi Ranyah in southwestern Saudi Arabia. Between April 2002 and December 2021, the estimated variation in groundwater resources was −3.85 ± 0.15 mm/yr. From 2002 to 2019, the area observed an average yearly precipitation rate of 100 mm. The sedimentary succession and the underlying fractured basement rocks are influenced by the structural patterns that run mainly in three different trends (NW, NE, and NS). The sedimentary cover varies from 0 to 27 m in thickness. The outputs of the electrical sounding revealed four primary geoelectric units in the study area: on top, a highly resistant geoelectrical unit with a resistivity of 235–1020 Ω.m, composed of unsorted, loose, recent sediments; this is followed by a layer of gravel and coarse-grained sands with a resistivity of 225–980 Ω.m; then, a water-bearing unit of saturated sediments and weathered, fractured, basement crystalline rocks with a resistivity of 40–105 Ω.m, its depth varying from 4 to ~9 m; and then the lowest fourth unit composed of massive basement rocks with higher resistivity values varying from 4780 to 7850 Ω.m. The seven built dams store surface-water runoff in the southwestern part of the wadi, close to the upstream section, in addition to the Ranyah dam, as the eighth one is located in the middle of the wadi. The subsurface NW- and NS-trending fault lines impede the groundwater from flowing downstream of the wadi, forming isolated water-bearing grabens. Minimal surface runoff might occur in the northern part of the wadi. The combined findings are beneficial because they provide a complete picture of the groundwater potential of Wadi Ranyah and the controlling structural patterns. Using this integrated technique, the groundwater potential in arid and semiarid regions can now be accurately assessed.

Application of Geoelectric Technique in Groundwater Protection of Quaternary Aquifer in Wadi El Natrun, Egypt

Qualitative and quantitative interpretations of the accessible geoelectrical resistivity data were conducted in the area located to the west of Nile Delta on both sides of the Cairo-Alexandria desert road, between latitudes 30.190816° and 30.745892° N and longitudes 29.797607° and 30.702070° E, in the northern Western Desert of Egypt. The study area is covered by thick sedimentary exposures ranging from the Miocene to the Quaternary period. Geological factors such as lithology and geological structures significantly influence the groundwater in the study area. The Quaternary, Pliocene, and Miocene eras make up the majority of strata in the study region that require water.
 The study conducted twenty-three vertical electrical resistivity soundings using the Schlumberger array to define the shallow subsurface geological inferences and investigate the possibilities of finding underground water accumulations and its contamination with clay lenses. The examination of the obtained electric resistivity values revealed the segmentation of the examined section into five geoelectrical units with lateral variations in thicknesses, lithologies, and features. The five geoelectrical units had different compositions, with the first surface unit consisting of silt clay and relatively high resistivity sands and gravels that have been altered laterally. After the surface unit, resistivity ranges from relatively modest to high. Intercalation of sand and clay occurs in the second unit, followed by lenses of relatively medium-resistance coarse sand and clay in the third and fourth units, possibly forming an aquifer, and finally relatively low-resistance sand and clay in the fifth unit.
 Due to the haphazard drilling of hundreds of water wells, significant hydrogeological and environmental issues, such as soil salinization, water head decline, and groundwater salinity deterioration, have occurred. These issues have attracted significant expenditures in the field of land reclamation, both on small and large-scale projects. The study area is divided into five main geoelectrical layers observed along this cross area, as follows:
 The first surface geoelectrical layer (layer A) is characterized by relatively high resistivity ranging from 8.21 to 595.3 Ohm.m. The thickness of this layer varies from 2.1 to 8.86 m. This layer represents the dry surface cover of the area and consists of gravel, sand, and silt clay.
 The second geoelectrical layer (layer B) represents the dry layer lying above the water-bearing formation. It generally consists of sand and clay intercalation. The resistivity of this layer varies from 3.49 to 91.18 Ohm.m, and the thickness of this layer ranges from 17.13 to 38.3 m.
 The third geoelectrical layer (layer C1) is the water-bearing formation that generally consists of coarse sand and clay. The resistivity of this layer varies from 4.41 to 37.5 Ohm.m, and the thickness ranges from 10.38 to 54 m.
 The fourth geoelectric layer (layer C2) represents the lower part of the water-bearing formation. It consists of clayey sand and clay. The resistivity of this layer varies from 1.83 to 30.1 Ohm.m, and the thickness ranges from 17.78 to 31.35 m.
 The last geoelectric layer (layer D) represents the lower layer of investigation, consisting mainly of clay. The resistivity of this layer is generally low, varying within a narrow range of 26.7-39.8 Ohm.m.
 Finally the current study highlights the necessity of conducting in-depth geomorphological assessment studies before developing new reclamation projects, in addition to soil and water assessment.

Geoelectrical Characterization of Coastal Aquifers in Agbado-Ijaye, Lagos, Southwestern Nigeria; Implications for Groundwater Resources Sustainability

Water is a natural resource; its availability depends on climatic and geological conditions, and it is invariably controlled by human activities. Agbado-Ijaye lies within a coastal area, where local communities have been facing incessant water shortages, especially during the dry season. This study investigated the groundwater-bearing geological unit(s) using hydrogeophysical techniques in the coastal environment. The electrical resistivity technique, involving vertical electrical sounding (VES) and two-dimensional (2D) electrical resistivity imaging via Wenner array electrode configuration, was used to characterize the geoelectric distribution. Twenty VES stations were investigated and current electrodes (AB/2 m) spacing expanded from 1–200 m; four 2D electrical resistivity imaging traverses having a length of 200 m each and interelectrode spacing of 10 m (level 1) to 60 m (level 6) was adopted. Four geoelectric units were delineated, namely: topsoil (15–251 Ωm), clayey (28–100 Ωm), clayey sand (125–190 Ωm) and sandy (205–876 Ωm) with thicknesses ranging from 0.7–1.3 m, 4.1–19.0 m, 2.6–15.6 m and undefined depth, respectively. The 2D imaging sections also detected similar geoelectric layers, corroborating the VES-derived sections. The inverted sections delineated two different aquifers: the shallower low-yield aquifer comprising sandy clay/clayey sand units with a maximum depth of about 5.5 m. This layer is adjudged to be the continental plain sand of the Benin Formation. The deeper high-yield aquifer with a maximum depth of 30.4 m is a beach sand unit that belongs to the Tertiary Alluvium of the Dahomey Basin. The study showed that hydrogeophysical investigation is vital in exploring, developing, and managing coastal groundwater resources.

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.

Applications of Electromagnetic Induction and Electrical Resistivity Tomography for Digital Monitoring and Assessment of the Soil: A Case Study of Al-Ahsa Oasis, Saudi Arabia

Al-Ahsa Oasis is one of the main and oldest agricultural centers in Saudi Arabia and one of the largest natural oases in the world. It is the largest irrigated agricultural oasis worldwide. The cultivated area is about 12,000 hectares in the region of Al-Ahsa. Groundwater was considered the main water source, if not the only source, for the different purposes of Al-Ahsa Oasis. However, due to groundwater depletion from these aquifers, treated wastewater is currently used to meet the shortage of irrigation water at Al-Ahsa Oasis. Today, several problems affect the agricultural productivity at Al-Ahsa Oasis, and modern geophysical techniques could contribute effectively to solving these problems; such problems are increasing soil salinity and the existence of a hardpan layer in some parts of the Al-Ahsa oasis. The soil texture is considered a critical factor to be taken into consideration. Therefore, the objectives of this study were to evaluate the effectiveness of modern geophysical techniques to study the agricultural aspects of Al-Ahsa oasis. Ten profiles of 2-D electrical tomography using SuperSting R8/IP 8 channel multielectrode resistivity and IP imaging system with 112 electrodes at one-meter spacing were implemented. Moreover, twenty electrical conductivity profiles were measured of 2240 points using EM38-MK2 at vertical mode with transmitter–receiver coils of 0.5 and one meter spacing. The results indicated that the salinity variation along the measured profiles was changed vertically and laterally due to the changes in the soil type, texture, moisture content, sabkha, and the whole oasis. Analysis and interpretation of the interpreted resistively tomograms of the ten 2-D profiles indicate remarkably the different geoelectric units of different hydrogeological conditions and soil texture across the oasis. These results will be of good utility for farmers, development sectors, and research institutions, especially in agriculture development studies, at Al-Ahsa Oasis, to ensure the sustainability of agriculture in this important historical Oasis.

Geophysical Investigation of Groundwater Potentials of the Nanka Sand in Obosi and Its Environs, Anambra State Nigeria

Geophysical investigation for Groundwater which entails the use of vertical electrical sounding (VES) methods was carried out in parts of the Idemili area of Anambra State, Nigeria. Geologically the study area falls within the Nanka Sand, belonging to the Ameki Group in the Tertiary Niger Delta Basin. The investigation intends amongst others to assess the groundwater potential of the area, find out the existence of possible aquifer(s) within the area, and estimate the possible depth of a borehole. 15 VES stations were established at the site using Ohmega System Tetrameter and Schlumberger electrode configuration with current electrode spacing (AB/2) of 350 meters. The geologic parameters, such as the number of geo-electric layers, the thickness of the geo-electric units, and their resistivities were interpreted from the VES curves. A qualitative assessment of the curves shows that a model with 5 layers would sufficiently model the field curves. The thickness value ranged from 0.1 to 86 m, the resistivity ranged from 258 to 13,258 Ωm, and the depth ranged between 1.2 and 109 m. Quantitative interpretation of field curves involved inversion with appropriate parameters using Zond Res1D software.

Application of Electrical Resistivity Method to Site Characterisation for Construction Purposes at Institute of Agriculture Research and Training Moor Plantation Ibadan

This research was carried out within Institute of Agriculture Research and Training Moor Plantation Ibadan, Southwestern Nigeria, with the aim to ascertain suitability of the proposed site for building construction and usage. The geophysical investigation involved three electrical resistivity techniques; Vertical Electrical Sounding (VES) using the Schlumberger configuration, 2D ERT and 2-D electrical imaging using Dipole-dipole electrode configuration. Two traverses were established E–W direction cutting across geologic strike with a distance of 80 m and of varying inter-traverse spacing. Eight (8) VES stations were occupied covering the entire study area for layer stratification and geoelectric parameters. The results were qualitatively and quantitatively interpreted and are presented as sounding curves and geoelectric sections. The 2-D imaging gave information on the subsurface characteristic in the area with generally low apparent resistivity indicating low competence material. The results obtained from the VES delineate three geoelectric units which comprise of the topsoil, weathered layer and fresh basement. The results from the VES were used to determine the second order parameters. The entire results correlate well with one another showing that all the techniques used were complemented. This study has further justified the need for geophysical site investigation as pre-condition before any construction to avoid problems of differential settlement. In determining of foundation material, topography elevation, clay content and the depth of weak zones should be put into consideration, since the depth of the weak zone is appreciably high.

Evaluation of near-surface groundwater aquifers through integrated geophysical and geodetic measurements

Extensive geophysical and geodetic measurements were carried out to evaluate the groundwater aquifer, trace the basement relief, as well as detect the igneous intrusions and structural elements (mainly faults) that affect the occurrence of groundwater in the study area. The fieldwork included resistivity sounding, a geomagnetic survey, and Global Positioning System measurements. The magnetic results showed the presence of a group of main faults in East-west trend at the western part of the area and major fault at the northern part of the area of NW-SW trend. The findings also showed the presence of two igneous rock intrusions located in the middle of the eastern part of the valley. Pronounced differences in the depths of basement rocks have been identified, ranging between 0 and 900 m from the surface. Both high horizontal movements and high shear strain rates have been found to be concentrated at the southeast of the study area and it was noted that high stress was accumulated along the main observed faults and at the main groundwater aquifers. The geoelectrical results confirmed the presence of two aquifers; a shallow aquifer (Quaternary aquifer) that narrows northwards and a Nubian sandstone aquifer, which considered the main aquifer. The Nubian sandstone aquifer carries groundwater in the region, which overlies the last geoelectric unit represented by the basement complex layer and geological structures affecting the potential availability of groundwater in the study area, as proved by the geomagnetic survey and stress accumulation.

Geophysical assessment of open dumpsite nearby Khamis Mushait industrial zone, Southwestern Saudi Arabia

Vertical electrical soundings, seismic refraction tomography, and ground magnetic measurements were taken or conducted close to an open dumpsite near Khamis Mushait, southwestern Saudi Arabia, which is characterized by shallow groundwater conditions. Structurally, intersected series of north- to northwest-trending faults affect the area. A new urban expansion and the Khamis Mushait industrial zone are close to the open dumpsite. This study evaluates the potential for leachate intrusion into groundwater aquifers. The results of electrical soundings reveal four geoelectric units: the topsoil, weathered layer, partly weathered/fractured basement, and fresh basement bedrock. At the dumpsite, relatively low resistivity values that are less than 30 Ωm characterize the topsoil, weathered layer, and partly weathered/fractured basement because of conductive leachate from the dumpsite. Besides, the results of ground magnetic data indicate that the deformation of varying intensities affects the dumpsite area, resulting in fractures developing in the N–S, NE–SW, NW–SE, and, to a lesser extent, E–W directions. Moreover, geoseismic tomographic models illustrate a low P-wave velocity zone corresponding to a low resistivity zone, and a NE–SW fault was identified from geoseismic cross-sections. Finally, these fractures and faults could become contaminant pathways for shallow aquifers around the dumpsite. To minimize the impact of such leachate, from a dumpsite, on groundwater quality and the environment in general, the dumpsite must be properly designed, constructed, and managed using engineering principles.

Geo-electric assessment for groundwater potential at permanent site of Waziri Umaru Federal Polytechnic, Birnin Kebbi, Kebbi State North Western, Nigeria

Vertical Electrical Soundings (VES) afford fast and economical measurements used in geophysical exploration. VES was used for groundwater exploration at the permanent site of Waziri Umaru Federal Polytechnic, Birnin Kebbi. Eighteen (18) Vertical Electrical Sounding (Schlumberger array, maximum AB/2 distance 100 m) were performed, data were acquired using ABEM terrameter (SAS 300c), to determine the geoelectric units in the subsurface stratigraphy as well as to delineate groundwater potential in the area via electrical resistivity soundings. Field data collected was analyzed using computer software (IPI2win) which gives an automatic interpretation of the apparent resistivity in ohm-meter. Data was interpreted in terms of the resistivity and thickness of subsurface layers. Results indicates that three to five (3-5) distinct layers in the study area namely; top soil which is mainly sand, clayey sand/loose sand, sandy clay/fine sand and clay unit were delineated. The result also revealed that water bearing formation exists in the third layer in some identified VES locations i.e VES 3, VES5, VES13 and VES14 with very good aquifers, with thickness and corresponding resistivity values of 40.5, 37.5, 45.8, 60 m and 173, 148, 222 and 432 Ωm respectively. The electrical resistivity data, therefore gives reasonable accurate results that can be used to understand stratigraphy and sedimentary configuration in ground water exploration.

Innovative Hydrogeophysical Approaches as Aids to Assess Hungarian Groundwater Bodies

The Hungarian water management plan has lately identified 185 groundwater bodies based on the concepts given by the European Water Framework Directive. Achieving and maintaining the good quantitative and chemical status of these groundwater bodies is of primary importance. It is demonstrated how innovative hydrogeophysical methods can be applied successfully to assess the Hungarian or other international groundwater bodies. By applying geoelectric methods, horizontal layering or large uniform rock units can be well characterized by Wenner–Schlumberger array, also enabling accurate depth determination of the shallow groundwater table. Horizontal variations in the rock type or its state can be well described by dipole–dipole array or, even better, by the newly developed quasi-null arrays. Their joint application may be very straightforward to investigate different aquifer types by giving high-resolution resistivity images as input for hydrogeological modeling. In the identification of porous formations, multivariate statistical interpretation of wireline logs using cluster analysis allows reliable lithological separation of potential aquifers. Their clay content is estimated by robust factor analysis, while their hydraulic properties are directly derived from the resistivity log. For a more effective interpretation, a combination of surface and borehole geophysical methods can be recommended for meeting challenges in hydrogeology and groundwater management.

Delineation of sinkhole in evaporite deposits using electrical resistivity survey: a case study of southern Kohat Plateau, Pakistan

Vertical electrical sounding (VES) is a non-destructive geophysical technique which provides fast subsurface lithological investigations and it is widely used in exploration of water, mineral resources, and its characterization. The present study work has been focused on subsurface imaging over evaporite deposits in Bahadarkhel area, Karak, Pakistan where multiple VES points along three profile lines have been acquired using Schlumberger electrode configuration to delineate subsurface lithology and structure of the area. The VES curves have been modeled and interpreted which resulted in true resistivities, depths, and thicknesses of layers. These VES points have been stacked along their respective profile lines for pseudosections and resistivity cross section preparation. Five distinct geoelectrical units have been identified depending upon their true resistivity values. Iso-resistivity 3D surfaces at 30 m and 60 m depths have been generated using the interpreted data which exhibits salt diapiric structure and dissolution of salt at depth by the action of infiltrating water from nearby ephemeral stream. Dar-zarrouk parameter calculations yield transverse resistance, longitudinal conductance, and anisotropy maps which infer that the area is mostly covered with rock salt and the presence of clay beds and calcareous sediments increases the resistivity values.

Hydrogeophysical investigation at El Moghra Area, North Western Desert, Egypt

El Moghra area, in the western desert of Egypt, is an important part of the national reclamation project (1.5 million acres—6.07 × 109 m2), which depends on the groundwater of El Moghra Formation (MF), the main aquifer in this area. Moghra Oasis and its surroundings are characterized by vast areas of good soil, which are favorable for agricultural development. In this respect, ambitious plans and successful programs are urgently required. Thirty-one vertical electrical sounding stations (VES’s) were measured in El Moghra. The results of quantitative interpretation of such stations and well logging data indicate that the subsurface stratigraphy of the investigated area consists of six geo-electrical units where the main aquifer is represented by the fourth and sixth units intercalated with a clay unit (fifth unit). Thirteen boreholes of depth reaching 200 m are drilled in the study area. The hydrochemical analyses for collected samples indicate that the salinity of the groundwater in the Moghra area increases with depth. The result of the pumping test for boreholes indicates that the efficiency of the wells is ranging from 65 to 96% of the average value of 84.5%. The aquifer has transmissivity which represents a highly potential aquifer.

Modelling aquifer parameters using surficial geophysical techniques: a case study of Ovwian, Southern Nigeria

Vertical electrical sounding (VES), pumping test and grain size distribution techniques have been used to model the hydraulic parameters in Ovwian, Nigeria. Twenty-two depth soundings were carried out with a maximum current electrode separation of 400 m to delineate the aquifer layers while the pumping test and grain size distribution procedures were conducted by drilling two boreholes where thirteen representative soil samples were collected at an interval of 3.048 m. The field data obtained from the resistivity sounding were modelled using the Win Resist software and the results when correlated with borehole log identified five geoelectric units made up of the topsoil, clayey sand, sandstone, fine grain sand and coarse grain sand. The sands of the third and fourth geologic layers constitute the aquiferous units with depth which varied between 6 and 42 m while the aquifer resistivity ranged between 100 and 2100 Ωm. The pumping test was analysed using the Copper Jacob method and the results revealed that the hydraulic conductivity and transmissivity of the aquifer from the reference well are 30.467 m/day and 495.072 m2/day, respectively. These results together with results from the vertical electrical soundings were used to model the hydraulic conductivity and transmissivity values for the area. This showed that the hydraulic conductivity of the area ranged from 28.595 to 38.435 m/day, with a mean value of 30.757 m/day while the transmissivity ranged from 185.697 to 1310.636 m2/day, with a mean of 495.752 m2/day. The grain size distribution analysis also revealed the hydraulic conductivity value of 1.46–171.94 m/day with an average of 38.880 m/day, while transmissivity ranged from 23.725 to 2794.025 m2/day with an average values of 631.738 m2/day. The close approximations of the results revealed the reliability of the VES, pumping test and grain size distribution analysis in the estimation of aquifer hydraulic parameters for groundwater resource development. Analyses of the results obtained in this study suggest that the aquifer is prolific and highly permeable with a high degree of rechargeability.

Lithologic modeling using VES method for subsurface structure delineation with geological constraints, eastern margin of Chiang Mai Basin and southwestern margin of Mae On Depression, San Kamphaeng District, Chiang Mai Province, northern Thailand

We conducted a vertical electrical sounding (VES) survey over the Quaternary sediments covering a transitional region between the eastern part of the Chiang Mai rift basin and the Mae On Depression, northern Thailand and constructed 1D lithologic subsurface models for delineating geological structures of the underlying basement rocks. Thirteen VES stations were collected and divided into northern and southern sub-parallel alignments trending WSW-ENE across the high magnetic contrast zone. We employed a Schlumberger array with the maximum half current electrode separations around 465–500 m, using the ABEM Terrameter SAS4000 resistivity meter. The VES data were inverted using EarthImager™ 1D program. We classified four geoelectric units composed of (1) very-low-resistivity saturated sediments (17–39 Ωm), (2) low-resistivity unsaturated sediments (33–581 Ωm), (3) medium-resistivity sedimentary rocks (57–110 Ωm), and (4) high-resistivity mafic volcanic rocks (176–804 Ωm). Shallow zones of the geoelectric models were interpreted as sediment fill with layered strata with variable resistivity because of different water saturation and clay content. The sediment fill thickens westward to the Chiang Mai rift basin. Deeper zones of higher resistivity are interpreted as the underlying basement rocks. These basement rocks show contrasting resistivities with the western part modeled as clastic sedimentary rocks of sandstone and the eastern part as mafic volcanic rocks. Geological observation evidence of westward-dipping faults and chronostratigraphic results integrated with the 1D lithologic models and drilled well information support a structural model of a reverse fault trending SW-NE between the Permian volcanic and Carboniferous sedimentary basements. This structure is part of the Chiang Mai-Chiang Rai Suture Zone associated with the eastward subduction model during the Permo-Triassic Indosinian Orogeny in northern Thailand.

Evaluating the groundwater potential of coastal aquifer using geoelectrical resistivity survey and porosity estimation: A case in Ota, SW Nigeria

Geoelectrical resistivity sounding surveys was carried out at two locations (A and B) in the new CanaanCity residential estate of Canaan land Ota, Ogun state in order to locate possible targets for groundwater explorations. A total of twelve (12) vertical electrical soundings were conducted using the Schlumberger array configuration. The interpretations of the VES curves revealed five to six geoelectrical layers at location A which comprises VES1-7. The geoelectric units consist of the topsoil, sandy clay, lateritic clay, confining bed (clayey sand), and main aquifer (sand). The top of the aquifer in this part of the study area is between 40 m and 83.5 m. Likewise, a total of five to seven layers of geoelectrical units were delineated at the location B portion of the study site (VES 8–12) similar to location A with an addition of the shale unit that was interpreted to be that of the Akimbo Formation of the Dahomey Basin. The depth to the top of the productive aquifer within location B is in the range of 40–112.4 m. The delineated basal shale layer is impermeable, serving as the base seal rock for the confined aquifer system. The estimated porosity values range from 28% to 74%, indicating that the highly porous aquifer system in the area is the coastal plain sands mixed with the alluvium sand of the Benin Formation of Dahomey Basin. The study revealed the complexity of the productive aquifer system in the area and its undulating topography.

Integrated geophysical investigation for mapping of manganese-iron deposits at Wadi Al Sahu area, Sinai, Egypt—a case study

This study used data from an investigation into the mapping of manganese-iron (Mn-Fe) mineralization, located within the Um Bogma formation. The ore takes the form of patchy isolated bodies or lenses in the three members of the Um Bogma formation located in East Sinai, Egypt. Magnetic, resistivity, and induced polarization (IP) surveys were applied at the Wadi Al Sahu area to delineate the mineralized ore bodies in terms of depth and extension. The quantitative interpretation of magnetic data was carried out using the 2D analytical signal. The results of the magnetic interpretation indicated that the depths of such ore deposits range from − 2 to − 20 m, and the shape of the magnetized units (assumed to be manganese-iron ore) is lenticular and of small size ranging from 20 to 100 m in width. Three dipole-dipole geo-electrical traverses were carried out along the anomalous sites, the traverse locations selected from the constructed magnetic maps of the study area, and the resistivity and IP measurements along with them. The results of the resistivity and IP inversion indicate that there are conductive and chargeable bodies at a depth that indicate the shape of small Mn-Fe lenses being present and conform to the shape of the Mn-Fe ore mineralization. Integration between the magnetic and geo-electrical data is made to lessen the non-uniqueness problem in geophysical prospecting. In this case, we used electrical resistivity and induced polarization models to delineate the boundaries between different geo-electric units, and these boundaries were used as interfaces between layers with different magnetic susceptibility for magnetic modeling to perform magnetic data inversions.