Electrical Resistivity Survey for Predicting Aquifer at Onicha-Ugbo, Delta State, Nigeria (original) (raw)
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Discovery Scientific Society, 2023
Assessment of groundwater yielding region using geophysical investigation was carried out to identify possible potential aquifer using Vertical Electrical Sounding (VES) method and 2-Dimensional method in Kajola town, Ondo State. The Schlumberger array configuration was used for acquiring data for VES and Wenner array for 2-D methods. Seven (7) Vertical Electrical Soundings and Ten (10) 2-D images were obtained. VES data acquired from the study area were processed using iteration software WINRESIST. Also, the 2-D data acquired were analysed, processed and inverted using a software called RES2DINV to obtain the 2-D resistivity structure. Varying anomalous features along each profile were delineated from the distribution of areas of high, low and moderate resistivity. The model also exhibits gradational change in resistivity with depth, and with varying subsurface topographies. VES results clearly indicate that the depth of the aquifers are 8.9m, 12.5m, 16.5m, 22.7m, 16.5m, 7.8m and 8.0m for VES 1, VES 2, VES 3, VES 4, VES 5, VES 6 and VES 7 locations respectively. Thus, the average depth to aquifer is at the depth range between 13m and 20m. The geologic layer of this aquifer zone is characterized by structural features like fractures and pore spaces that enhance groundwater permeability and storage.
In this study, data obtained with the aid of an ABEM Terameter (SAS 300C), from twenty-five Vertical Electrical Soundings (VES) stations in Kutunku, with maximum half-current electrodes spacing AB/2, of 170m and maximum half-potential electrodes spacing MN/2, of 7.5m for most of the profiles, were analysed with IPI2Win software. The analysis indicated 3 to 5 geo-electric layers where the former was predominant and the lithologic units were interpreted to consist of sandy top soil, clay/clayey sand, lateritic sand, compact laterite, weathered/fractured basement and fresh basement. Layer resistivity ranges were 1. 95 -1360Ωm, 0.4 -1723Ωm, 7.7 -180000Ωm and 71 -44878Ωm for the first, second, third and fourth layers respectively. In the same vein, layer depth ranged from 0. 6 -4.3m, 1.1 -47.3m, 3.9 -56.9m and 31.1m to undetermined depth. The second layer in most of the profiles showed conductive zones with low resistivity values ranging from 0.403Ωm to 151Ωm. In most of the profiles, the third layer manifested as the last layer, predominantly with high resistivity readings of the order of 10 3 Ωm to 10 5 Ωm with unknown depths suspected to be fresh basement rocks. In the few profiles where four geo-electric layers were detected, with the exception of VES 18, the resistivity values (in Ωm), obtained for the last layer, were of the order of 10 3 and above, with unknown depth suspected to be fresh basement rocks. Amongst the second, third and fourth layers, the second layer mostly constitute the aquifer unit in the area with weathered/fractured basement rock type. The stations of highest groundwater potential were found to be VES 2, VES 5, VES 8, VES 14, VES 21, VES 24 and VES 25 because of the thicknesses of the layers interpreted as weathered or fractured zones which ranged from 25m to 55m.
Groundwater Investigation Using Geoelectrical Method: A Case Study of the Western Region of Cameroon
Journal of Water Resource and Protection, 2013
A geoelectrical survey using the electrical resistivity method was carried out in some villages in the western region of Cameroon to investigate the sub-surface layers and evaluate the characteristics of aquifers. The direct current electrical resistivity method was utilized for the present study. Applying the Schlumberger array, a total of twenty four (24) Vertical Electrical Soundings (VES) were conducted. Quantitative and qualitative interpretations of data were carried out to determine the nature and thickness of the aquifer zone combined with existing litho-logs aided correlation of geoelectric sections to litho-logs. Four to five geoelectric layers were delineated from the survey area. The first layer which is the topsoil has resistivity values ranging from 6-949 Ωm and the thickness is between 0.2-4.2 m. The second layer which is made up of clay and laterite has resistivity values ranging between 9-1862 Ωm and thickness range from 1.0-16.4 m. The third and fourth geoelectric layers are made up of clay and granite/basalts with thickness varying from 2.2-39.5 m which corresponds to an aquifer horizon. Resistivity values of the aquifer ranges from 10 to 70,506 Ωm. The resistivity map drawn from these measurements shows the presence of a low resistivity zone which indicates the reflection in the direction of ground water from northeast to southwest with the recharge concentrated to the south of the study area. This study has revealed for this area, an average depth of the aquifer of 32 m with the average thickness of the aquifer being 22 m. The geoelectric sections of some VES stations demarcated corroborate very well with the geological description of the area.
SEG Technical Program Expanded Abstracts 2018
A knowledge of hydrogeophysical parameters of aquifers is essential for groundwater resource assessment, development and management. Traditionally, these parameters are estimated using pumping test carried out in boreholes or wells; but this is often costly and time consuming. Surface geophysical measurements can provide a cost effective and efficient estimates of these parameters. In the present work, geoelectrical resistivity data has been used to characterize and evaluate the aquifer potential at Covenant University, Ota, southwestern Nigeria. Some thirty-five vertical electrical soundings (VESs) were conducted using Schlumberger array with a maximun half-current electrode spacing (AB/2) of 240 m. The geoelectrical parameters obtained were used to estimate longitudinal conductance and transverse resistance of the delineated aquifer. Both the longitudinal conductance and transverse resistance, which qualitatively reflects the hydraulic properties of the aquifer, indicate that the aquifer unit is characterized with high values of hydraulic parameters; consequently a good groundwater potential. Thus, groundwater resource development and management in the area can be effectively planned based on these parameters.
American journal of water resources, 2014
Geophysical study of the Northeastern part of Owo was conducted to investigate the geoelectric characteristics of its aquiferous units and its implication on groundwater potential of the area. Vertical electrical sounding method was employed and Schlumberger configuration was adopted. Thirty-two points were sounded along three different sections of the town namely; Idasen, Okedogbon and Express (Figure 1). Six different subsurface lithologic units were established namely; lateritic topsoil, clay, sand, quartzite, weathered/fractured basement and, basement. The curve types range between simple H, K, HA, HK, KH to complex, HKH, KHA and KHK. The topsoil, clay, sand and weathered basement materials are characterised with relatively low resistivity values while the quartzite ridge materials are characterized with high resistivity values. The average resistivity and thickness values for the topsoil are 220 Ωm and 2.0 m respectively. Clay was encountered across Okedogbon and Express area of the town and the average resistivity and thickness values of 34 Ωm and 6.0 m respectively. Sand was encountered across the entire study area with average resistivity and thickness values of 115 Ωm and 11.0 m respectively. Quartzite was encountered in all the locations with average resistivity and thickness values of 611 Ωm and 11.0 m respectively. Weathered/fractured basement was encountered across the three sections with average resistivity and thickness values of 86 Ωm and 12.0 m respectively. Basement is relatively deep in the study area and the average resistivity and depth values to the top of basement are 878 Ωm, and 24 m respectively. Overburden thickness was established across the area with an average value of 20 m. The overburden materials with the fractured basement constitutes aquiferous units within the study area though the sand and weathered basement units are largely responsible for the groundwater potential. The groundwater potential of the area is moderate with Express area having the highest potential.
Earth Science Research, 2016
Vertical electrical sounding was done at 47 points using an ABEM 1000 Terrameter and a set of cables that could probe up to a depth of 500m. Resistivity was determined in two sites located in the district of Douala III (Bomkoul and Ngoma) 6 km west of the main town on the left bank of the Wouri River. The choice of these neighbourhood is as a result on the one hand, the presence of clay deposits from which sections have helped to configure resistivity data with those of geoelectric sections, and on the other hand, by the ability to extend the measuring device over great distances without being hindered by urbanization. The depths of investigation range from a minimum of 30 m and a maximum of 120 m. The results show a wide variability in resistivity values throughout the study area; it may be related to the high variability of facies described on sections by diggers. This variability may be due to the complexity of deposits recorded in the Douala sedimentary basin and also because of the presence of water in both sandy and clay sediments due to climate. The suggested resistivity is between 20 and 600ohm.m for clays and greater than 1000 ohm.m for sand. Given the weak thickness of some layers, the cancellation phenomena that affect very thin layers between two layers of different geoelectric properties of the latter have been observed, thus assigning to clay layers, sand resistivity.
2021
Well-drilling for groundwater exploration is often costly, thus it is imper- ative to avoid drilling dry borehole and low-yield borehole. Geoelectrical soundings were conducted in the new Canaan-City residential estate of Canaan land Ota, Ogun state. The results of VESs from the study area revealed five to six layers of five geoelectrical units which consist of the Topsoil, Sandy clay, Lateritic clay, confining bed (clay) and Main aquifer (sand). The depth to the top of the main aquifer is in the range of 40–112.4 m. The research has further revealed that the aquifer architecture in this area is complex with undulating topography of the depth to the main aquifer. Geophysical investigations are therefore recommended in this area for groundwater exploration to be able to drill into the actual main aquifer in the area.
A geoelectrical study for groundwater prospect in a physiographic area of Oke-Igbede in Ikare-Akoko, southwestern Nigeria was undertaken, with specific objective of evaluating the weatheredfractured basement components. Thirty five (35) Schlumberger soundings were acquired with ABEM SAS 1000 Resistivity Meter. The electrode spacing (AB/2) was varied from 1-75 m with maximum spread length of 150 m. Results revealed three to four distinct subsurface geologic/geoelectric layers, comprising clayey / sandy topsoil, weathered basement/fractured basement and fresh basement, with resistivity and thickness values of 33-410 m ohm-m and 0-2.5 m; 17-961 m and 0-32.8 m and; infinity ohm-m and thickness respectively. The depth to bedrock varied from 0.1-33.5 m indicating a series of uneven basement topography constituting varying thicknesses of the heterogeneous regoliths. The weathered-fractured column is generally sandy with average resistivity of 252 ohm-m, thin with average value of 11.0 m across the area. Fairly thick columns of pockets of basement depressions found particularly towards the northwestern part constituted the aquifer unit(s) with tendencies to yield appreciable quantity of groundwater to wells and boreholes. The diminishing groundwater prospect in the area may be attributed to the general thin nature of the regoliths and limited fractures at deeper depth beyond 30 m. The weathered-fractured components with thicknesses not less than 30 m may be considered as first order priority sites, while others with thicknesses less 30 m are outside choices. It can, therefore, be concluded that the groundwater potential of the study area is feasible with the weatheredfractured components of the basement being considered the targets for groundwater prospect for sustainable domestic water supplies in the area.
IOSR journal of applied geology and geophysics, 2017
An integrated use of geo-electrical resistivity soundings and hydrogeologic methods were employed in the investigation for groundwater resource,evaluation and development around Obu-Okpella, nearBuacement factory, Southwestern Nigeria. The study area is underlain by Basement Complex rocks which consist of migmatites, granite gneiss and pegmatites.A total of 35 vertical electric soundings (VES) and four exploratory boreholes were carried out in the study. The geo-electric resistivity sounding datawere interpreted using IXD interpexsoftware and the VES interpretation revealed 4 geo-electric layers/lithologic units from the geo-electric parameters. The geo-electric layers are-(1) Topsoil from 0 to 2.5m, (2) weathered basement from 3.3 to 49m, (3) Slightly weathered/Fresh basement from 5m to ∞, (4) Fractured basement (≥5 to 150m) and are characterised by resistivity value range of 14 to 297 ohm-m, 16 to 98 ohm-m, >1000 ohm-m and < 50 to 31056 ohm-m respectively. Four exploratory boreholes numbered BH1, BH2, BH3, and BH4 were drilled on VES 1, 17, 18 and 31 to a depth of 180, 150, 58 and 110m respectively. The VES interpretation and boreholelithologic logs were well correlated. The main aquifer is in the deep and highly fractured basement rocks with average depth of 50-150m. The pumping test results for the boreholes number BH1, BH2, BH3 and BH4 were 0.8l/s, 1.87l/s, 1.2l/s and 1.7l/s respectively with very maximum dynamic water level of <10m.Transitivity value of the aquifer for BH1, BH2, BH3 and BH4 are 2.58m 2 /day, 21.43 m 2 /day, 55.62 m 2 /day, and 37.98 m 2 /day respectively indicates that the lithostrata constituting the aquifer is fair in transmitting the groundwater. With a volume of 12,000 l/day, 97,000 l/day, 91,000 l/day and 51,840 l/day for BH1, BH2, BH3 and BH4, the total volume of water for the four boreholes is 253,560 l/day.
Asian Journal of Geological Research, 2019
Inadequate potable water supply remains one of the challenges of residents of Bosso Estate in Minna Metropolis, Niger State, Nigeria owing to the Basement Complex terrain underlying the area. Rapid increase in population in the area over the years, which is due to its proximity to Federal University of Technology Minna (Bosso Campus) and the nation’s capital city (Abuja) among others. This has led to increase in the demand for potable water supply for domestic use since public water supply by government is inadequate. Consequently, in a quest to seek for Groundwater as a reliable source of water supply for domestic need, various abortive boreholes have been drilled without proper geophysical survey. This has led to loss of valuable time, energy and money. Therefore, Geoelectrical investigation using Schlumberger array was carried out with a view to delineate zones with good groundwater occurrence. A locally made Terrameter (resistivity meter) of high precision was used for data acquisition. Schlumberger array was used to obtain geophysical data at ten (10) VES stations in the area. Field data obtained were analysed and interpreted using Win RESIST and Surfer Software which gives an automatic interpretation of the apparent resistivity data. Results from the interpretation revealed these curve types: the HK, H KH and A whereas three to four (4) geoelectric layers which consist of Topsoil layer, Lateritic clay, Weathered/fractured basement and Fresh basement. Fractured/weathered basement has resistivity values ranging from 35.5 to 841.62 Ωm and thickness variation of 13.5 to 48.5 m. This weathered /fractured layer constitutes the aquifer zones in the area. The fresh basement has resistivity values as high as 7336 Ωm and above. The groundwater potential in the study area was classified into high, medium and low/non groundwater potentially occurring zones. High groundwater potential zones were found at VES station 01, 02, 03, 04, 07 and 08 corresponding to the North-Eastern, Central and North-Western parts. This survey revealed aquifer zones having thickness ranging from 20 to 40 m and depth to bedrock ranges from 8.7 to 55 m. A recommended minimum depth for drilling borehole in the study area is about 46 to 60 m. The study however recommends an integrated geophysical method for future groundwater exploration in the area.