scholarly journals Hydrogeological appraisal of basement and sedimentary terrain in Ogun state using Geoelectrical methods

2020 ◽  
Vol 8 (1) ◽  
pp. 95
Author(s):  
Aladeboyeje Adegoke Ige ◽  
Coker Joseph Olakunle ◽  
Agbasi Okechukwu Ebuka ◽  
Inyang Namdie Joseph

The coverage of the groundwater potential was estimated using the geometry calculator, the potential groundwater zones were validated using geophysical surveyed points of some selected locations in Abeokuta and Ewekoro. Generally, the result of the study shows that the higher the aquifer thickness and depth the better the groundwater potential. In the basement part of the study area (Abeokuta), the Northwestern region is characterized by increase in overburden thickness (28.1 m at VES-9), weathered layer resistivity (546 Ω m at VES-7) and longitudinal conductance unit (0.193 S at VES-3 and 0.218 S at VES-7), reflecting high aquifer potentials. In this regard, the Northeastern part of the study area can be categorized as good groundwater potential; moving towards the Southwestern part from the northern, groundwater potentiality changes from good to moderate while the Southwestern/ central part is categorized as area with poor groundwater potential. In the Sedimentary part of the study area (Ewekoro), the northcentral region is characterized by increase in overburden thickness (93 m at VES-10), longitudinal conductance unit (3.644 S at VES-6), reflecting high aquifer potentials. In this regard, the northcentral part of the study area can be categorized as good groundwater potential; moving towards the northeastern part of the study area, groundwater potentiality changes from good to moderate while the southwestern part is categorized as area with poor groundwater potential. The area showed very good protective capacity at VES’s 2, 3, 4, 5, 7 and 8; making 60% of the VES stations. Good protective capacity is observed at VES 1 and 6, making 15% of the VES stations in the town. The excellent protective capacity is observed at VES 9 and 10; making 15% of the study area.   

2020 ◽  
Vol 4 (2) ◽  
pp. 99-102
Author(s):  
Johnson C. Ibuot ◽  
Moses M. M. Ekpa ◽  
Doris O. Okoroh ◽  
Aniefiok S. Akpan Emmanuel T. Omeje

Geoelectric survey employing Vertical Electrical Sounding (VES) was carried out in order to assess the groundwater repositories. A total of seven soundings were obtained with their layer resistivity, thickness and depth within the maximum electrode separation. The geoelectric parameters obtained were used to estimate the Dar-Zarrouk parameters (longitudinal conductance and transverse resistance), hydraulic conductivity and transmissivity. The result shows the aquifer resistivity ranging from 77.14 to 784.76 Ωm, with thickness ranging from 28.78 to 80.04 m. The longitudinal conductance have values ranging from 0.071 to 0.825 Ω-1 while the values of hydraulic conductivity and transmissivity range from 1.087 to 5.881 m/day and 60.180 to 374.031 𝑚2/day respectively. The contour maps generated show the variation of these parameters across the subsurface, and areas with poor protective capacity were delineated. The results also delineate the groundwater potential of the study area as moderate, while the corrosivity rating indicates non-corrosive and slightly corrosive.


Author(s):  
Dian Darisma ◽  
Ferdy Fernanda ◽  
Muhammad Syukri

Lam Apeng is a village with a majority of people living as farmers, which causes the need of water for agriculture is increasing. The water demand in this area continues to increase as the population increases, for various purposes. The objective of this study is to determine the distribution of the groundwater layer using the electrical resistivity method and to determine groundwater potential using hydraulic parameters. This research is conducted using 2 measurement line with a length of each line is 112 meters and distances of each electrode is 2 meters. The data invert using Res2Dinv software to obtain 2D subsurface lithology subsurface. At line 1, the aquifer (sand) layer is located in the second layer with a rock resistivity value of 12 Ωm - 18.6 Ωm at a depth of 8 m - 18 m. At line 2, the aquifer (sand) layer is also located in the second layer with a resistivity value of 4.6 Ωm - 18 Ωm at a depth of 5 m – 12 m. Based on the interpretation of the two measurement lines, it can be concluded that the type of aquifer in the research site is a semi unconfined aquifer. In this study, hydraulic parameters (hydraulic conductivity, longitudinal conductance, transverse resistance, and transmissivity) was calculated based on the resistivity value and the thickness of the aquifer layer. The average resistivity of the aquifer layer used is 15.3 Ωm and 11.3 Ωm, respectively for line 1 and line 2, indicating that the aquifer was moderately corrosive. Longitudinal conductance values are 0.65 Ω-1 and 0.62 Ω-1 which indicated moderate protective capacity. The transmissivity values are 6.78 m2/dayand 4.77 m2/day, which indicates that the designation in this area is low and the groundwater potential is local or only for personal consumption.


2021 ◽  
Vol 20 (1) ◽  
pp. 171-182
Author(s):  
S.A. Adekoya ◽  
H.T. Oladunjoye ◽  
J.O. Coker ◽  
O.A. Adenuga

The study presented the results obtained from estimation of the depth to the bsement bedrock (overburden thickness) in Olabisi Onabanjo University, Ago-Iwoye using two configurations of electrical resistivity methods. The study was aimed to delineate the stratigraphy and thicknesses of the subsurface layer present in the study area for comprehensive study of the lithostratigraphic information of the area. Vertical Electrical Sounding (VES) and 2-D Horizontal Electrical Profiling (HEP) techniques were used to obtain 1-D and 2-D subsurface resistivity images of the study area. The VES data were plotted manually on the Bi-log graph. The curve obtained was partially curve – matched to obtain the layer resistivities and thicknesses for further iteration. The 2-D resistivity imaging data were analyzed and processed to obtain the inverted (true) resistivity image. From the results, five (5) VES type curves weredelineated. These includes H, HA, QH and KH type. The geoelectric sections and 2-D resistivity images showed three to four geoelectric layers. These layers are topsoil/laterite, weathered basement, partly weathered/fractured basement and fresh basement. The study showed that materials with resistivity values that ranged between 10 and 298 Ωm and 152 and 589 Ωm representing clayey weathered layer and partly weathered/fractured basement were delineated beneath some sounding points. The clayey and weathered layer are indicative of soil formations that are inimical to foundation of civil engineering structure. Likewise, they can serve as reservoir for groundwater potential (if the porosity and permeability are high). Due to this, detailed lithostratigraphic evaluation through petrophysical analysis is encouraged for the purpose of mapping and correlation of the rock units before embarking on any engineering construction in the study area. The study concludes in providing assistance to subsequent research on the stratigraphic related studies in the area. Keywords: Geo-electric , Stratigraphy, Lithology, Layer,


2021 ◽  
Vol 47 (2) ◽  
pp. 520-534
Author(s):  
Ayodele Kehinde Olawuyi

Hydrogeophysical study involving the use of Vertical Electrical Sounding (VES) was carried out in part of the basement complex rocks of Ilorin, central Nigeria, with the aim of determining its geoelectric parameters and groundwater potential. A total of thirty (30) VES were carried out using Schlumberger electrode configuration, with half electrode separation (AB/2) varying from 1m to 100m. Information on the subsurface lithologies, overburden thickness and aquiferous layers were obtained from the different VES locations in the study area. From the quantitative interpretations of the data collected, using the method of curve matching with the Orellana-Mooney master curves and 1-D forward modeling with WinResist 1.0 version software, three to five lithologic units were identified in the study. These include: the topsoil, sandy/lateritic clay/laterite, the weathered basement, the fractured basement and the fresh bedrock which are predominantly of the ‘KH’ curve type (30%), followed by ‘H’ type (26.7%), other type curves include ‘QH’ (16.7%), ‘HKH’, ‘HA’ and ‘A’ (6.7% each) and KQ and KQH (3.3% each). The weathered layer and the fractured basement constitute the main aquifer units. The aquifers are of generally low resistivity values (mostly below 100 Ω-m). The depths to dry bedrock at the chosen VES locations vary from 2.7 to 62.7 m with a mean value of 13.02 m in the study area. The geoelectrical interpretations of data obtained in these areas have permitted the delineation of the study area into low and moderate groundwater potential zones. This study is expected to assist in future planning for groundwater resources. Keywords: Hydrogeophysical, Basement Complex, Groundwater, Electrical Soundings, Weathered, Fractured


Author(s):  
A. Olajide ◽  
S. Bayode ◽  
T. Fagbemigun ◽  
A. Oyebamiji ◽  
J. Amosun ◽  
...  

Groundwater potential and aquifer protective capacity of the overburden unit was evaluated in part of Iju, Akure North, Ondo State using integrated geophysical methods involving Very Low Frequency Electromagnetic (VLF-EM) profiling and Vertical Electrical Sounding (VES). Four major traverses were established of varying length extents. The VLF-EM measurements were taken along the four major profiles of 10 m station interval.Forty two (42) Vertical Electrical Soundings were also conducted with half electrode spacing varying between 1 and 100 m and interpretation was done using the partial curve matching techniques and computer aided iteration. Five subsurface geological units were identified from geoelectric sections, consisting of the top soil, lateritic, weathered, partly weathered and fresh basement layers consecutively. For the first layer, resistivityranges between 23 and 323 Ωm with values of thickness ranging between 0.5 and 2.2 m. The resistivity and thickness of the second (lateritic) layer range from 132 to 430 Ωm and 1.6 to 4 m respectively. The resistivity of the weathered layer ranges from 4 to 94 Ωm and variable thickness between 10 and 24.4 m. The fourth layer has a resistivity value range of 65 to 120 Ωm and thicknesses between 20 and 30 m. The basement bedrock (fifth layer) has resistivity values between 770 and 820 Ωm. The depth to bedrock ranges from 1.8 to 31 m. The geophysical data and the basement aquifer delineated were then used to evaluate the hydrogeological setting and aquifer protective capacity of the study area. The observation from the results shows that close to 70 % of the study area falls within the zones of low groundwater potential, 25 % falls within medium potential zones while only 5 % make up the high potential zones. 75 % of the study area constituted the weak to poor protective capacity zones.  


2021 ◽  
Vol 11 (4) ◽  
Author(s):  
A. A. Alabi ◽  
S. A. Ganiyu ◽  
O. A. Idowu ◽  
A. F. Ogabi ◽  
O. I. Popoola

AbstractWater is essential for livelihood, development, and industrial growth. Its exploration in sufficient quantity is required where it does not freely occur on the surface. This research was aimed to delineate aquifer regions and provide information on the subsurface lithology of Moloko-Asipa Southwestern Nigeria. A combination of eight traverses investigated with very low frequency electromagnetic (VLF-EM) method at 5 m constant sampling interval and ten vertical electrical sounding (VES) were carried out in the survey. Measurements from the VLF-EM survey were processed with Karous and Hjelt filtering to give the resistivity contrast across the selected profiles. The VES data processing involved an automatic approximation of the initial resistivity and thickness of the geoelectric layers with IPI2Win and further filtering by WinResist iteration. Estimation of Dar-Zarrouk parameters was also employed to investigate the aquifer protective capacity of the area. The processed VLF-EM results showed the geology of the area to an average depth of 25 m. The geoelectric section of the VES data revealed minimum of 3 layers from sandy top soil to weathered layer and fresh basement with an average resistivity values of 1,816, 926 and 17,503 Ωm, respectively. The integration of VLF-EM and VES in the investigation revealed that the potential for groundwater exploration in the study area is poor due to the thin nature of the weathered layer and its shallow depth to basement. The aquifer protective capacity of the area was likewise inferred to be poor.


2021 ◽  
Vol 8 (12) ◽  
pp. 411-417
Author(s):  
Adediran Olanrewaju Adegoke ◽  
E. Rotimi Olafisoye ◽  
Oluwatoyin Ologe

Electrical resistivity method was used to carry out hydrogeophysical study in order to evaluate the groundwater potential of Igarra Comprehensive High School, Akoko Edo Local Government, Nigeria. The vertical electrical sounding technique (VES) was adopted for the resistivity method. A total of eighteen electrical soundings were conducted across the area using the Schlumberger electrode array with AB/2 varying from 1 to 65 m. After the data acquisition, interpretation was carried out qualitatively and quantitatively and the results were presented as sounding curves, tables, charts, maps and geoelectric sections. The generated geoelectric layers from the sounding curves revealed four geologic layers: the topsoil, the weathered layer, the partially weathered/fractured basement and the fresh basement with their resistivity values ranging from 129.1 to 956.4 -m, 6.8 to 1491.1 -m, 261.3 to 776.6 -m and 1515.6 to 2653.5 -m respectively. The overburden thickness in the study area varies from 5.5 to 23.5 m. The groundwater potential map enabled in the classification of the study area into: low, medium and high groundwater potential area. About 85% of the study area falls within the low groundwater potential rating while about 10% constitutes the medium groundwater potential rating and the remaining 5% constitutes high groundwater potential rating. Keywords: Groundwater, overburden, electrical resistivity, basement, geoelectric sounding.


2020 ◽  
Vol 66 (3) ◽  
pp. 199-209
Author(s):  
J.O. Aina ◽  
O.O. Adeleke ◽  
V. Makinde ◽  
H.A. Egunjobi ◽  
P.E. Biere

AbstractHydrogeological assessment of groundwater resources was carried out with a view to evaluate the potential of the aquifers to provide portable water supply and access the distribution of electrical parameters of hydrogeologic units in some areas in Odeda, Ogun State, Nigeria. A geophysical survey using vertical electrical sounding (VES) with the Schlumberger electrode array, with half-current electrode spacing (AB/2) varying from 1 to 132 m was carried out at 30 different stations in the study area. The VES data were interpreted qualitatively and quantitatively. Three-to-five sub-surface layers consisting of topsoil, weathered layer consisting of clay, sandy clay, clayey sand and sand layers, and fractured/fresh basement were delineated. Layer resistivities and thicknesses obtained on the curves within the study area showed one main aquifer type, which is the fractured basement. The longitudinal unit conductance (ranging from 0.049720 to 1.4520000 mhos) of the study area aided the protective capacity to be rated into good, moderate and weak. About 33% of the study area falls within the weak protective capacity, 57% falls within the moderate protective capacity and 10% falls within the good protective capacity.


2020 ◽  
Vol 4 (2) ◽  
pp. 102-104
Author(s):  
Johnson C. Ibuot ◽  
Moses M. M. Ekpa ◽  
Doris O. Okoroh ◽  
Aniefiok S. Akpan Emmanuel T. Omeje

Geoelectric survey employing Vertical Electrical Sounding (VES) was carried out in order to assess the groundwater repositories. A total of seven soundings were obtained with their layer resistivity, thickness and depth within the maximum electrode separation. The geoelectric parameters obtained were used to estimate the Dar-Zarrouk parameters (longitudinal conductance and transverse resistance), hydraulic conductivity and transmissivity. The result shows the aquifer resistivity ranging from 77.14 to 784.76 Ωm, with thickness ranging from 28.78 to 80.04 m. The longitudinal conductance have values ranging from 0.071 to 0.825 Ω-1 while the values of hydraulic conductivity and transmissivity range from 1.087 to 5.881 m/day and 60.180 to 374.031 𝑚2/day respectively. The contour maps generated show the variation of these parameters across the subsurface, and areas with poor protective capacity were delineated. The results also delineate the groundwater potential of the study area as moderate, while the corrosivity rating indicates non-corrosive and slightly corrosive.


2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Olayiwola G Olaseeni ◽  
Ajibola Oyebamiji ◽  
Oluwaseun Olaoye ◽  
Bosede Ojo ◽  
Ayokunle Akinlalu

This study aimed at evaluating the potential for groundwater development in the eastern part of Ado-Ekiti, Southwestern Nigeria using Vertical Electrical Sounding (VES). Data were acquired with ABEM SAS 300 and processed through partial curve matching techniques and assisted with 1-D forward modelling. Geoelectric parameters were determined from the VES interpreted result. Seven (7) different VES type curves (H, A, HA, KH, HK, QH and HKH) indicating inhomogeneity of the subsurface layer beneath the study area were observed. Weathered layer resistivity map having values ranging from 3.2 – 272 Ωm, overburden thickness of value vary between 0 and 28m and  bedrock relief values range from 360 – 480 m were delineated. It was estimated from the result that the northwestern and southeastern part which constituted about 15%of the study area possess high groundwater potential while the remaining 85% of the study area exhibit low/moderate potentials for yielding substantial water. Hence, the groundwater potential rating of the area was considered generally low.Keywords- Geoelectric, Groundwater potential, Overburden thickness, Vertical Electrical Sounding


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