Geoelectrical Resistivity Survey Research Articles

Aquifer Mapping Using Geo-Electrical Resistivity Survey for Seepage Mitigation in Kuwil Kawangkoan Dam, North Minahasa, North Sulawesi, Indonesia

Abstract The dam built in an area with a productive aquifer system has potential seepage, influenced by groundwater presence. Seepage can cause instability in the main dams or slopes around the dam. An initial assessment of subsurface geological conditions needs to be done to identify groundwater potential as information in mitigating seepage potential in the dam. Kuwil Kawangkoan Dam is located in the Manado groundwater basin with a high groundwater potential. The 2D electrical resistivity approach with the Wenner configuration was applied in this study. Geoelectric data was acquired on 12 lines spread across the dam area. The measurement results show a resistivity value of less than 300 Ωm, indicating the layer is composed of unconsolidated pyroclastic sediments in the form of sand–gravel. This layer has a depth of around 35 m from the surface. The lithology found is dominated by tuff lapilli with pumice fragments that have the potential as an aquifer.

A Quantitative interpretation of salt water mixture in the shallow aquifer through the geoelectrical resistivity data

The main problem of groundwater in coastal areas is the intrusion of saltwater into freshwater aquifers. This study aims to predict the amount of saltwater content in aquifers polluted by intro-sea saltwater. In this study, an attempt is made to provide a direct correlation approach for resistivity measurements with the physical characteristics of groundwater. A 2D resistivity survey with the Wenner configuration have been carried out in the coastal area. The geoelectrical resistivity survey is about 3 km from the shoreline. The chemical measurement was done on freshwater, seawater and fresh-seawater mixture, which the mixture was consisted of 25%, 50% and 75% of seawater content. The results showed that the resistivity below 5 ohm.m indicated the presence of seawater with a concentration of more than 50% mixed with fresh water. In general, it can be seen that the decrease in resistivity appears to decrease exponentially with increasing seawater content in the aquifer.

A preliminary groundwater investigation using geoelectrical resistivity survey in the Bengkalis Island, Indonesia

Groundwater resources are one of the natural resources that need to be preserved. The main problem of groundwater in coastal areas is the intrusion of seawater into the groundwater aquifer. The problem will be even more complex when the land is covered by peat soil. The purpose of this study was to investigate the potential of groundwater in the western part of Bengkalis Island. Geoelectrical resistivity data was taken with the Schumberger configuration with the increase in the electrode distance being varied to obtain accurate measurements. Groundwater samples were measured to obtain the physical character of the groundwater. The results show that groundwater close to the shoreline has been contaminated by the presence of seawater intrusion. However, in areas that are a bit far from the shoreline, the shallow aquifer groundwater conditions are still not contaminated by seawater. It can be concluded that the presence of seawater in the aquifer is caused by the trapping of seawater in the aquifer during sediment deposition in the past.

Subsurface Analysis Using Microtremor and Resistivity to Determine Soil Vulnerability and Discovery of New Local Fault

Microtremor and geoelectrical resistivity surveys have been conducted in areas where the April 10, 2021, earthquake of 6.1 Mw caused the most damage. Wirotaman Village, Malang Regency, was one of the regions with the most extensive damage. This study aims to investigate the seismic vulnerability and subsurface conditions that result in severe damage at the research location. This study's Horizontal to Vertical Spectral Ratio Analysis (HVSR) curve was derived from the recorded microtremor signal in the frequency domain. The frequency parameter and amplification factor obtained from the curve are used to determine the seismic vulnerability index. In addition, a geoelectrical resistivity study with a dipole-dipole configuration was conducted at the site with the most extensive damage. The results of this study show the correlation between the results of the HVSR curve analysis and geoelectrical resistivity in determining the seismic vulnerability of an area. The results indicated that the high seismic vulnerability index value ranged from Kg= 12.0 to 18.0, with the most severe damage concentrated in the Southwest at SA 05 and SA 06. Based on the results of the geoelectrical survey, information was obtained that several points of damage to buildings at SA 05 (red circle) were on the same line, where this condition was associated with the possibility of new faults at that location. This microtremor and geoelectric resistivity investigation reveals thick sedimentary deposits with a high seismic vulnerability index and low resistivity. This study's findings can be utilized as a guide for micro zonation studies in research areas. This research contributes to the surrounding community in the form of disaster mitigation, where construction must avoid local fault positions that have been found to reduce the level of damage when natural geological disasters occur. Doi: 10.28991/CEJ-2023-09-09-014 Full Text: PDF

Landslide Soil Failure Parameters Characterization Using Geoelectrical Resistivity Methods in Uruagu, Nnewi, Anambra State, Nigeria

Electrical Resistivity Imaging (ERI) and Vertical Electrical Sounding (VES) were deployed over Uruagu landslide area. The main purpose of the geoelectrical resistivity surveys was to characterize the landslide failure parameters in order to identify the soil failure mechanisms. Ten profiles of 2D Electrical Resistivity Imaging (ERI) measuring 200 m each, and thirty Vertical Electrical Sounding (VES), with three VES along each profile, were executed. Nine of the ten profiles were executed within the landslide site while one profile was executed in a residential street as a control profile. Four soil samples were also taken for physical and geotechnical laboratory index analysis. The PASI resistivity meter was used for the geoelectrical resistivity measurements. The Wenner-Schlumberger array was deployed for the ERI with a minimum electrode spacing of 10 m. The Schlumberger array was deployed for the VES with a maximum current spacing of 130 m. ERI resistivity data analysis involved inversion using RES2DINV software package involving mean model residual and construction of iso-apparent resistivity contour maps. VES resistivity data analysis involved calculated parameters from plotted field data on log-log graph then used as initial models in an iterative forward modeling WinResist software package. The results of the ERI and VES for the control profile reveal that the subsurface strata are originally composed of silty clay of resistivity values (16.7 – 60.9) Ωm, clayey silty sand having resistivity values (116 – 800) Ωm and sandstone layer with resistivity values (>814 Ωm). The ERI and VES results for the devastated landslide site reveal counteraction material of resistivity values (>814 Ωm), colluvia and regoliths (116 - 300 Ωm) and variably wet weathered sandstones of resistivity values (<60.9 Ωm). The laboratory results revealed the landslide site is majorly composed of silty sandy clay, silty clay, sandy silty clay and sandstones as the pre-landslide existing lithologies. The natural water content ranges from 10.6% to 14.0%. The liquid limit ranges from 44.0% to 46.0%, the plastic limit ranges from 15.0% to 17.0% and the plasticity index from 28.0% to 29.1%. The geophysical and laboratory results revealed consistency in the lithological units in agreement to the characteristic geology of the study area. The landslide site has high gully slope gradients and collects large volume of floods during intense rainy season. These soils during intense rainfall, imbibe more water, following their high plasticity, slid along the sandstone to activate the soil failure.

Landslide Soil Failure Parameters Characterization Using Geoelectrical Resistivity Methods in Uruagu, Nnewi, Anambra State, Nigeria

Electrical Resistivity Imaging (ERI) and Vertical Electrical Sounding (VES) were deployed over Uruagu landslide area. The main purpose of the geoelectrical resistivity surveys was to characterize the landslide failure parameters in order to identify the soil failure mechanisms. Ten profiles of 2D Electrical Resistivity Imaging (ERI) measuring 200 m each, and thirty Vertical Electrical Sounding (VES), with three VES along each profile, were executed. Nine of the ten profiles were executed within the landslide site while one profile was executed in a residential street as a control profile. Four soil samples were also taken for physical and geotechnical laboratory index analysis. The PASI resistivity meter was used for the geoelectrical resistivity measurements. The Wenner-Schlumberger array was deployed for the ERI with a minimum electrode spacing of 10 m. The Schlumberger array was deployed for the VES with a maximum current spacing of 130 m. ERI resistivity data analysis involved inversion using RES2DINV software package involving mean model residual and construction of iso-apparent resistivity contour maps. VES resistivity data analysis involved calculated parameters from plotted field data on log-log graph then used as initial models in an iterative forward modeling WinResist software package. The results of the ERI and VES for the control profile reveal that the subsurface strata are originally composed of silty clay of resistivity values (16.7 – 60.9) Ωm, clayey silty sand having resistivity values (116 – 800) Ωm and sandstone layer with resistivity values (>814 Ωm). The ERI and VES results for the devastated landslide site reveal counteraction material of resistivity values (>814 Ωm), colluvia and regoliths (116 - 300 Ωm) and variably wet weathered sandstones of resistivity values (<60.9 Ωm). The laboratory results revealed the landslide site is majorly composed of silty sandy clay, silty clay, sandy silty clay and sandstones as the pre-landslide existing lithologies. The natural water content ranges from 10.6% to 14.0%. The liquid limit ranges from 44.0% to 46.0%, the plastic limit ranges from 15.0% to 17.0% and the plasticity index from 28.0% to 29.1%. The geophysical and laboratory results revealed consistency in the lithological units in agreement to the characteristic geology of the study area. The landslide site has high gully slope gradients and collects large volume of floods during intense rainy season. These soils during intense rainfall, imbibe more water, following their high plasticity, slid along the sandstone to activate the soil failure.

A Systematic Approach of Optimal Land-Use Planning by Applying Geo-Environmental Techniques: A Case Study

This article demonstrates the capabilities and integrity of the environmental geological and geophysical techniques for planning the suitability of the extension of Helwan city for construction and engineering purposes. The geological and topographical mapping were utilized as well as environmental geophysical techniques (seismic refraction, ground penetrating radar (GPR), and resistivity soundings) for optimal land-use planning. The seismic refraction profiles were conducted to evaluate the geotechnical characteristics of the bedrock, GPR was applied to define the main subsurface reflectors, and the geoelectrical resistivity survey was used to identify the subsurface stratigraphic sequence and the distribution of main structural elements impacting the investigated area. The integrated results and findings of the environmental geological and geophysical survey inferred two major distinctive subsurface layers: a thin surface layer represented by highly weathered limestone, with an average thickness of 3 m, and a bottom layer equivalent to the bedrock composed of hard limestone. In addition, GPR performed an analysis of two remarkable subsurface layers, which supported the generated model of other geophysical surveying techniques. Finally, all the geological and various geophysical techniques were integrated and merged to generate the optimal land-use plan of the extension of Helwan city for construction and engineering purposes and to avoid high-risk areas to reserve the sustainability of the new urban communities.

Dolines Phenomenon Determination Using by Geological and Geoelectrical Resistivity Survey Approach in Bedoyo Village, Ponjong Subdistrict, Gunung Kidul Regency

Gunung Kidul Regency is a highland consisting of carbonate rocks dominantly. Bedoyo village in Ponjong sub district has a lot of dolines, but in the summer season, the dolines become dry and could not be water storage. Geological mapping is included in geomorphological, rock observation, structural mapping also petrographical analysis in the laboratory. A Geophysics survey is to observe the subsurface rock distribution laterally and vertically with dipole-dipole configuration. The resistivity method is to determine the resistivity value for the depth of fewer than 40 meters with the length of electrodes of about 250 meters. The result of the geological and geophysical analysis is to review the dolines phenomenon that could not be a shallow aquifer. It is caused by the subsurface condition beneath the dolines consisting of carbonated rocks with poor porosity, lenses of impermeable tuffaceous claystone, and igneous rock. Those rock basements have a moderate to poor porosity in the aquifer. The less opportunity to be a good aquifer if the deeper rock is an impermeable igneous rock. An alternative geophysical survey is needed to observe the deeper rock vertically.

Assessment of seawater ingress in the coastal aquifers of south Andaman Island, India

Seawater ingress is a widespread environmental issue posing threat to the fresh groundwater reserves of the coastal aquifers of Andaman and Nicobar Islands (ANI) particularly after the great Indian Ocean Tsunami 2004, and the comprehensive investigations of seawater ingress in this region are relatively uncommon. In this context, the spatial distribution and vertical movement of seawater ingress in the coastal and catchment areas were mapped using geo-spatial techniques and the extensive geoelectrical resistivity surveys (96 vertical electric soundings (VES) and profiling) along and across the identified and affected coastlines. The geoelectrical surveys unravels very low resistivity formations (≤10 Ω m) at varying depths interpreted as the lateral and vertical intrusion of seawater. The hydro-chemical and other physical analyses of groundwater samples reveal critical concentrations of the different major elements and other physical parameters like TDS, pH as well the EC above its permissible limit for drinking water standards. The integrated approach allows to delineate the site specific hydrogeological setting including the saline/fresh aquifer geometry (transition zone) and stratigraphic−geomorphological reconstruction of coastal aquifers. Further, various assessment parameters including very low formation resistivity, surface manifestation of salt tolerant plants, high chloride concentration, low formation factor and high ionic strength were employed to infer the various levels of contamination. The present study show that impact of seawater intrusion is intense in sedimentary formations than Ophiolite suite and needs site specific mitigation measure to prevent further deterioration of aquifer health.

Geophysical and contamination assessment of soil spatial variability for sustainable precision agriculture in Omu-Aran farm, Northcentral Nigeria

The spatial and temporal variability of soil properties (fluid composition, structure, and water content) and hydrogeological properties employed for sustainable precision agriculture can be obtained from geoelectrical resistivity methods. For sustainable precision agricultural practices, site-specific information is paramount, especially during the planting season. An integrated one-dimensional (1D) and two-dimensional (2D) electrical resistivity survey have been adopted to characterize the subsoil parameters and delineate the aquifer unit of large farm areas, especially in precision agricultural practices. Also, contamination assessment reveals the soil quality status of farmlands. This study aims to determine the site-specific soil parameters of a commercial farm in Omu-Aran, Northcentral, Nigeria. The subsoil features from the geoelectrical resistivity surveys indicate 3 to 4 distinctive lithology to a depth of 43.4 m into the subsurface of the farm. The ID (Vertical Electrical Sounding) and 2D resistivity inversion models results have revealed the heterogeneity nature of the topsoil, also known as the stone zone comprising of reworked clayey soil and sandy gravelly soil, the weathered/saprolite zone (gravelly sandy/sandy soil), the fractured basement and the fresh basement rock. Contamination factor (Cf), pollution load index (PLI) and Nemerow integrated pollution index (NIPI) were used to assess the contamination index on the farmland. Toxic elements such as arsenic, cadmium, chromium, cobalt, lead, manganese, nickel, and zinc have low to moderate contamination in the farm. The depth of investigation (≤3m) covers the upper root zone of significant crops grown in the area. The findings can assess soil contamination, delineate basement features, subsoil variability, soil profiling, and determine the subsoil hydrological properties.

Lenggong Valley – Revisit Our National Treasure

Lenggong Valley was incepted as UNESCO World Heritage Site in 2012 for its marvellous cultural value. However, the status will be in peril if the valley is left neglected and nothing is done. The area is renowned for the discovery of prehistoric human settlement. Numerous studies and researches have been conducted at Lenggong Valley to increase the scientific knowledge of the surrounding areas for further conservation and development. Toba ash deposit from volcanic eruption in Sumatra, Indonesia and possible meteorite impact were also discovered within the valley. Geoelectrical resistivity survey have been conducted to determine the thickness of Toba ash. The results were correlated with borehole log from the Department of Mineral and Geoscience Malaysia (JMG), that shows the Toba ash layer is around 10 m in depth and presents low resistivity range of values (<100 Ωm). Water geochemical analysis at one of the known water spring shows the surface temperature is 27.6 °C, with a pH value of 7.47. Truth be told, Lenggong Valley has a diversity of archaeological sites and geosites that can be established as a geopark and a group of committee will be materializing it in year 2021 or 2022.

Isotope hydrogeochemical models for assessing the hydrological processes in a part of the largest continental flood basalts province of India

Continental Flood Basalts (CFB) occupy one fourth of the world’s land area. Hence, it is important to discern the hydrological processes in this complex hydrogeological setup for the sustainable water resources development. A model assisted isotope, geochemical, geospatial and geophysical study was conducted to understand the monsoonal characteristics, recharge processes, renewability and geochemical evolution in one of the largest continental flood basalt provinces of India. HYSPLIT modelling and stable isotopes were used to assess the monsoonal characteristics. Rayleigh distillation model were used to understand the climatic conditions at the time of groundwater recharge. Lumped parameter models (LPM) were employed to quantify the mean transit time (MTT) of groundwater. Statistical and geochemical models were adopted to understand the geochemical evolution along the groundwater flow path. A geophysical model was used to understand the geometry of the aquifer. The back trajectory analysis confirms the isotopic finding that precipitation in this region is caused by orographic uplifting of air masses originating from the Arabian Sea. Stable isotopic data of groundwater showed its meteoric origin and two recharge processes were discerned; (i) quick and direct recharge by precipitation through fractured and weathered basalt, (ii) low infiltration through the clayey black cotton soil and subjected to evaporation prior to the recharge. Tritium data showed that the groundwater is a renewable source and have shorter transit times (from present day to <30 years). The hydrogeochemical study indicated multiple sources/processes such as: the minerals dissolution, silicate weathering, ion exchange, anthropogenic influences etc. control the chemistry of the groundwater. Based on the geo-electrical resistivity survey, the potential zones (weathered and fractured) were delineated for the groundwater development. Thus, the study highlights the usefulness of model assisted isotopic hydrogeochemical techniques for understanding the recharge and geochemical processes in a basaltic aquifer system.

Identification of Seawater Intrusion in Kota Lama Semarang and Surrounding Based on Geoelectrical Resistivity Survey

Kota Lama Semarang is a tourism potential that causes a high demand for groundwater, which can cause seawater intrusion. Seawater intrusion can affect groundwater quality and soil conditions. This research aimed to determine the depth and distribution of seawater intrusion in the Kota Lama Semarang and surrounding. The research used electrical resistivity tomography (ERT) and vertical electrical sounding (VES). Geoelectrical resistivity surveyed consist of 4 ERT lines and 3 VES lines with a line length was 100 to 160 m. Lines were scattered north and south of the Kota Lama to determine the distribution of seawater intrusion. Inversion processing used Progress for VES and Res2DInv for ERT. The content of chloride as well in Kota Lama was measured as supporting data. At this location it was estimated that it has 3 layers: top soil, sand and sandy clay. The sand layer at a depth of 3 to 11 m was the layer affected by seawater intrusion. Seawater intrusion on the north side was higher than on the south side. This was indicated by the lower resistivity value of the groundwater layer on the north side. The resistivity value of the groundwater layer on the north side was 0.96 Ωm while the south side was 3.76 Ωm. This result was appropriate to the chloride content which indicates a higher concentration on the north side of the Kota Lama Semarang.

Groundwater potential zones identification in Purwobinangun, Pakem, Sleman, D.I. Yogyakarta using vertical electrical sounding (VES)

Water is crucial part in tourism development. However, not all locations have good and accessible groundwater resources. Ngepring Vineyard in Purwobinangun Village, Pakem District, Sleman, Yogyakarta face this problem. Ngepring vineyard is a developing tourism area at southern mountainside of Merapi which is one of geotourism destination in Indonesia. In its development, there were obstacles to fulfill the water supply for tourism and locals’ daily use. This research aims to determine groundwater potential zone and recommend a drilling point for a new well. Geoelectric resistivity survey conducted to evaluate subsurface condition by measuring and interpretating rock resistivity properties. Schlumberger Vertical Electrical Soundings (VES) configuration used with a maximum spacing from the center point as far as 250 meters with three VES were measured in study area along two N-S profiles perpendicular to one E-W profile. As the results, there is a sand layer at approximately 80m depth interpreted as aquifer. This result can be used as a preliminary study used to determine potential location for a new water resource in Ngepring vineyard.

Investigation of Aquifer Zone in Tambakromo Village, Ponjong Subdistrict, Gunung Kidul Regency, Yogyakarta, Indonesia

The presence of surface water is always being a primary issue in Gunung Kidul regency. An aquifer investigation would support groundwater exploration. The research area is located in Tambakromo village, Ponjong subdistrict, Gunung Kidul Regency, Daerah Istimewa Yogyakarta Province. The aim of this research is about geological and subsurface conditions based on geological data and geoelectrical resistivity methods. By resistivity value interpretation, the position, depth, and thickness of aquifer could be determined. The purpose of this research is to identification of geological conditions that supported being aquifer rock. The method in this research is used geological mapping combined with petrographic analysis. The geophysics method is used to identification of aquifer in research area. Three locations were selected to acquisition geoelectrical resistivity survey. In Grogol village, there is no aquifer based on resistivity values of more than 10000 ohmmeters (andesitic breccia). An akuifuge is interpreted there in andesitic breccia instead of the presence of aquifer. The tuffaceous is interpreted as lapillistone that contained the glass with resistivity value of 43.63 and 340.11 ohmmeters. The Garon and Sumberejo village have aquifer at depth of 50 to 80 meters with a thickness of 13 to 70 meters. The type of aquifer in both area is included an unconfined aquifer, specifically located in between the limestone rock layer and andesitic breccia. By regional stratigraphic correlation, tuffaceous lapillistone is interpreted as derived from Semilir Formation. In addition, the presence of aquifer in research area could recommend for local people and government to reduce the drought disaster.

Gravity Analysis for Subsurface Characterization and Depth Estimation of Muda River Basin, Kedah, Peninsular Malaysia

Gravity survey is one of the passive geophysical techniques commonly used to delineate geological formations, especially in determining basement rock and the overlying deposit. Geologically, the study area is made up of thick quaternary alluvium deposited on top of the older basement rock. The Muda River basin constitutes, approximately, of more than 300 m of thick quaternary alluvium overlying the unknown basement rock type. Previous studies, including drilling and geo-electrical resistivity surveys, were conducted in the area but none of them managed to conclusively determine the basement rock type and depth precisely. Hence, a regional gravity survey was conducted to determine the thickness of the quaternary sediments prior to assessing the sustainability of the Muda River basin. Gravity readings were made at 347 gravity stations spaced at 3–5 km intervals using Scintrex CG-3 covering an area and a perimeter of 9000 km2 and 730 km, respectively. The gravity data were then conventionally reduced for drift, free air, latitude, Bouguer, and terrain corrections. These data were then consequently analyzed to generate Bouguer, regional and total horizontal derivative (THD) anomaly maps for qualitative and quantitative interpretations. The Bouguer gravity anomaly map shows low gravity values in the north-eastern part of the study area interpreted as representing the Main Range granitic body, while relatively higher gravity values observed in the south-western part are interpreted as representing sedimentary rocks of Semanggol and Mahang formations. Patterns observed in the THD anomaly and Euler deconvolution maps closely resembled the presence of structural features such as fault lineaments dominantly trending along NW-SE and NE-SW like the trends of topographic lineaments in the study area. Based on power spectral analysis of the gravity data, the average depth of shallow body, representing alluvium, and deep body, representing underlying rock formations, are 0.5 km and 1.2 km, respectively. The thickness of Quaternary sediment and the depth of sedimentary formation can be more precisely estimated by other geophysical techniques such as the seismic reflection survey.

Geoelectrical and Geotechnical Characterization of Different Types of Soil in Ede, Osun State, Nigeria

Geoelectrical and geotechnical investigations were carried out to characterize soils from different locations in Ede, Osun State, Nigeria for engineering purposes. Wenner electrode configuration technique was deployed in carrying out the geoelectrical survey of about 40m for each profile. The data analysis was approached by plotting the apparent conductivity against electrode spacing (s) and the result was interpreted. The geoelectrical resistivity survey revealed locations 1 and 2 with resistivity values of 25.01-419.22ohm-m (conductivity 0.002 - 0.194 (ohm-m)-1and 5.5-1246.57 ohm-m (conductivity = 0.0002 - 0.001 (ohm-m)-1) respectively could be classified as clay. Sample 3 recorded a resistivity value of 1.00- 22,787.39 ohm-m (conductivity= 0.00004- 1.00 (ohm-m)-1) thus, was classified as silt/sand respectively. Soil from the said different locations in Ede, Nigeria, were tested in the Laboratory for certain properties like Atterberg limits, specific gravities, sieve analysis, compaction test, etc and the results showed that samples 1, 2 and 3 have specific gravity values of 2.50, 2.13 and 2.40 respectively and could therefore be referred to as organic soil. Samples 1, 2 and 3 have maximum dry density (MDD) of 1.45g/cm3­, 1.92g/cm3, 1.95g/cm3 and optimum moisture content (OMC) of 15.40%, 13.36% and 9.61% respectively. The analysis conducted in this study revealed that the soil type found in Ede, Nigeria could be classified as silt-clay, sandy clay, clay and sand.Keywords- Electrical conductivity, Characterization, Compaction, Plasticity, Wenner array.

Application of Vertical Electrical Sounding for Groundwater Investigation in the Premises of the Sabaragamuwa University of Sri Lanka

Growing social, as well as development activities in the premises of Sabaragamuwa University of Sri Lanka (SUSL) and its surroundings, have reformed the natural landscape of the area. Consequently, water demand is increasing. Therefore, an understanding of the subsurface geology and their potential as beneficial aquifers help to overcome the impending water demand because surface water scares in the area. In view of assessing the groundwater potential of the area, an initial study was conducted using topographic and satellite maps followed by a geo-electrical resistivity survey, consisting of vertical electrical sounding (VES) and electrical profiling. Results revealed three subsurface layers in most places. The resistivity of the topsoil layer is ranging between about 50 to 2800 Ωm and the average thickness between 1 m to 15 m. The second layer is characterized by resistivity between about 16 to 9760 Ωm. The resistivity of the third layer ranges from about 2 to 5600 Ωm, and extending to a depth of more than 100 m. Most of the curves were identified as K type. The rest of the curves were H, Q, and A types. Out of 18 VES points, nine locations were identified as possible locations for groundwater abstraction. Groundwater could be located at a depth of between 25 to 60 m. Resistivity data indicate that the regolith mostly forms the aquifers in the area along with some weathered rock aquifers at depth. Most of the points close to or at valleys were found to be deep aquifers. Considering all the geological, structural, and morphological features, nine locations were identified as most convincing and could be recommended for test drilling.

Geophysical and Contamination Assessment of Soil Spatial Variability for Sustainable Precision Agriculture in Omu-Aran Farm, Northcentral Nigeria

The Spatial and temporal variability of soil properties (fluid composition, structure and water content) and hydrogeological properties employed for sustainable precision agriculture can be obtained from geoelectrical resistivity methods. For sustainable precision agricultural practices, site-specific information is paramount, especially at the planting season. An integrated one-dimensional (1D) and two-dimensional (2D) electrical resistivity surveys have been adopted to characterize the subsoil parameters and delineate the aquifer unit of large farm area, especially in precision agricultural practices. Also, contamination assessment reveals the soil quality status of farmlands. This study aims to determine the site-specific soil parameters of a commercial farm in Omu-Aran, Northcentral, Nigeria. The subsoil features from the geoelectrical resistivity surveys indicate 3 to 4 distinctive lithology to a depth of 43.4 m into the subsurface of the farm. The ID (Vertical Electrical Sounding) and 2D resistivity inversion models results have revealed the heterogeneity nature of the topsoil also known as the stone zone comprising of reworked clayey soil and sandy gravelly soil, the weathered/saprolite zone (gravelly sandy/ sandy soil), the fractured basement and the fresh basement rock. Contamination factor (Cf), pollution load index (PLI) and Nemerow integrated pollution index (NIPI) were used to assess the contamination index on the farmland. Toxic elements such as arsenic, cadmium, chromium, cobalt, lead, manganese, nickel, and zinc have low to moderate contamination in the farm. The depth of investigation (≤ 3m) covers the upper root zone of significant crops grown in the area. The findings can assess soil contamination, delineate basement features, subsoil variability, soil profiling, and determine the subsoil hydrological properties.

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.