Curve Matching Technique Research Articles

Aquifer delineation in parts of Akwa-Ibom State, Southern Nigeria using Resistivity Survey

In line with Sustainable Development Goals (SDG 6.6), aquifer delineation in parts of Akwa-Ibom State, Southern Nigeria was carried out using resistivity survey. The areas covered in the study included Uyo, Itu and Ibiono Ibom. Electrical resistivity technique was applied to obtain data from the subsurface layers. The study utilized a Signal Averaging System (SAS) 1000 Terrameter, four stainless steel electrodes, four reels of cable, geologic hammer, a measuring tape and a Global Positioning System (GPS). A SAS 1000 Terrameter was used in measuring the resistivity of the materials within the subsurface. Electric current was transmitted into the ground from the Terrameter using current electrodes while the potential difference between the current electrodes was measured. A total of four (4) stainless steel electrodes were used: two (2) current electrodes which transmitted electric current into the ground and two (2) potential electrodes from which the potential difference was measured between the current electrodes. Four reels of cable were used to link the electrodes and the Terrameter. The cable served as conductor of electric current into the ground. A total of four geologic hammers were used in sending the electrodes into the ground and in making them to be firmly fixed. A 100-m measuring tape was used to determine the intervals between the current electrode and potential electrode. A total of nine (9) ERT data points were obtained, processed and interpreted. The data obtained from the field were processed and also interpreted from curve matching techniques together with computer-aided software called Interplex 1-D. Deeper aquifers free from surface contamination and suitable for groundwater development are encountered at depth ranges of 90 m to 120 m, 70 m to 130 m, 80m to 160m and 70 m at Uyo, Itu, Ibiono Ibom and Ibesikpo respectively. The depths to aquifer, thicknesses and resistivity values were 1.086-445m, 1.086-248m and 0.114-8,132 Ωm, and 1.45-378m, 1.45-348m and 203-5,229Ωm, and 1.345-863.8m, 1.345-422.5m and 202.5-445.3Ωm, and 1.464-66.61m, 1.464-41.99m and 90.85-695.4Ωm in Uyo, Itu, Ibiono Ibom and Ibesikpo Asutan respectively. Borehole drilling within the locations where survey was carried out should target the depths of the delineated aquifers is recommended.

Geoelectrical Evaluation of Contamination in and around Ori-Ile Battery Wastes Dumpsite in Ibadan, Southwestern Nigeria

Geoelectrical surveys involving vertical electrical sounding (VES) and 2D resistivity imaging were integrated to assess subsurface contamination by heavy metals in and around Orile Battery Waste Dumpsite, Kumapayi in Ibadan, Southwestern Nigeria. The objectives are to determine the lateral and vertical variations of resistivity/conductivity in and around the dumpsite, determine the nature and thickness of the overburden, determine the depth to bedrock, and delineate subsurface zones of anomalously high conductivity/low resistivity which may have resulted from contamination by heavy metals. Thirty-three VES stations were occupied using the Schlumberger electrode array with electrode spacing (AB/2) varied from 1 m to 100 m. The 2D resistivity survey was carried out along six East–West trending traverses established across and around the dumpsite using the Dipole-Dipole electrode array with station spacing of 10 m and expansion factor, n=1-5. The VES data were quantitatively interpreted using initial partial curve matching technique and 1D forward modelling while the dipole-dipole data were interpreted using 2D inversion procedures. The geoelctric sections delineated three layers comprising topsoil with layer resistivity ranging from 18 Ωm to 264 Ωm and thickness varying from 0.4 m to 1.4 m, weathered layer with resistivity and thickness ranging from 1 Ωm to 219 Ωm and 0.6 m to 9.4 m respectively, and weathered/fractured/fresh bedrock with resistivity ranging from 132 Ωm and 6500 Ωm. The 2D inverted resistivity sections revealed anomalous resistivity lows suggesting contamination at depths ranging from 5 m to 10 m beneath the traverses. The contamination zones are characterized by resistivity values less than 10 Ωm. The study revealed that the soil beneath the study area has been contaminated by the battery wastes. The suspected fractures and relatively shallow water table observed in the study area may have predisposed the groundwater to contamination which could constitute serious health risk to the inhabitants. It is recommended that geochemical analysis for heavy metals be conducted on the soil and groundwater from wells in the study area to assess the level of contamination.

Application of surface geophysical investigations and pumping test data analysis for better characterization of aquifer hydraulic parameters, Upper Awash Sub-Basin, Central Ethiopia

Study regionUpper Awash River Sub-basin in central Ethiopia Study focusThe research aimed to estimate aquifer parameters and conduct resistivity modeling in the study area. Data were collected from 890 Schlumberger Vertical Electrical Soundings (VES) points strategically distributed across six selected zones. The VES data were analyzed using computer modeling and curve-matching techniques to interpret the resistivity responses of the geological formations. This analysis provided insights into the subsurface characteristics and identified potential aquifer zones. New insights for the regionThe interpreted curves from the VES data and Root Mean Square (RMS%) values ranging from 0.36 % to 1.67 %, indicating a good fit between observed and modeled data. Resistivity modeling and geoelectrical sections were produced along specific lines, visualizing subsurface structures and confirming the resistivity responses of the geological formations. To determine aquifer parameters, the Dar-Zarrouk parameters were calculated from the interpreted curves, yielding crucial information about hydraulic properties such as hydraulic conductivity (K) and transmissivity (T). Hydraulic conductivity values ranged from 1.1 m/day to 21.7 m/day, while transmissivity values ranged from 144.3 m²/day to 2763.3 m²/day. Validation against borehole pumping test data showed strong correlations: R² = 0.9873 for transmissivity and transverse resistance, and R² = 0.9352 for hydraulic conductivity and resistivity. These findings enhance the understanding of the complex volcanic aquifer characteristics in the Upper Awash River Sub-basin, aiding sustainable groundwater management and development in the area.

Assessment of groundwater vulnerability using GOD index and Dar Zarrouk parameters: A case study of OAUSTECH main campus, Okitipupa, Ondo State

Groundwater is essential for efficient management of groundwater to prevent the deterioration of its quality. The objective of this study is to evaluate the vulnerability of the primary campus of (Olusegun Agagu University of Science and Technology) OAUSTECH in Okitipupa, Ondo State, Nigeria. This was done by analysing the GOD index and the Dar Zarrouk parameters of conductance and transverse resistance. A total of 24 Vertical Electrical Sounding (VES) data points were gathered, with AB/2 values varying from 200 to 225. These data points were then analysed utilising partial curve matching and computer iteration techniques to determine geoelectric characteristics, including resistivity and thickness. The computed characteristics, longitudinal conductance and transverse resistance, suggest that the aquifer's ability to defend against contamination in the research area is generally insufficient. The longitudinal conductance values range from 0.02 to 0.6, with most values below 0.1. Using the GOD method, the study shows that the GOD index value varies from 0.2 to 0.6, with an average of 0.325, suggesting a moderate to high level of vulnerability in the groundwater. The association between the GOD index and longitudinal conductance results in a 60 % accuracy in predicting groundwater susceptibility. This research emphasises that the groundwater within the main campus of OAUSTECH is moderately to highly vulnerable.

APPLICATION OF ELECTRICAL RESISTIVITY METHOD FOR SAFETY EVALUATION OF ASEJIRE DAM IBADAN, SOUTHWESTERN NIGERIA

Dam construction provides economic importance to the environs through, water supply and flood control. Post-construction investigation is however necessary for maintenance stability to avoid irreversible environmental changes. In view of this, horizontal resistivity profiling and vertical electrical sounding (VES) were conducted along the embankments and the downstream of Asejire dam to determine its integrity. The methods used were horizontal resistivity profiling and vertical electrical soundings conducted along the embankments and the downstream. Thirty-one VES and Dipole-Dipole Profiling were occupied along the embankments and downstream using Resistivity meter at 20 m intervals for both the VES and Dipole-Dipole. The Dipole-Dipole data were inverted into 2-D Resistivity Images using DIPPRO™ 4.0 Inversion Software while the VES data were quantitatively interpreted using the partial curve matching technique and Winresist 1.0 Version Software. Results of dipole-dipole image and geo-electric section identified three geo-electric layers; comprising topsoil presumably clayey sand and laterites with resistivity and thickness between 59-760m and 0.7-5.2m respectively. The second layer is weathered layer attributed with clay/clayey sand having resistivity and thickness 18-766m and 3.1-36.7 m. The third layer suspected to be fresh bedrock with resistivity range 121-3672m and 18-766 m thick. The Dipole-Dipole results displayed resistivity less than 500m in the first layer with structural evidence of discontinuous observables, but the underlying sequences displayed no indicative of structural weakness. This significant features play a major role in seepage processes from the dam, therefore lithological composition obtained from these results shows the dam has a good integrity.

ASSESSMENT OF SUBSOIL CORROSIVITY USING GEOELECTRIC LAYER PARAMETERS AT ILERE COMMUNITY NEAR AKURE, SOUTHWESTERN NIGERIA

ASSESSMENT OF SUBSOIL CORROSIVITY USING GEOELECTRIC LAYER PARAMETERS AT ILERE COMMUNITY NEAR AKURE, SOUTHWESTERN NIGERIA

PROTECTIVE CAPACITY ASSESSMENT OF A SHALLOW AQUIFERAT THE EASTERN PART OF ADO-EKITI, SOUTHWESTERN NIGERIA

Vertical Electrical Soundings (VES) survey has been undertaken at the eastern part of Ado-Ekiti, southwestern Nigeria to assessthe aquifer protective capacity of the overburden units of the area. The Schlumberger electrode array was adopted with a maximumcurrent electrode spread (AB) of 300 m.Thirty-six(36) VES points wasoccupied and processed through a partial curve matching technique and 1-D forward modelingcomputer-assistedsoftware.The interpretation revealed H, A, KH and HA-type curves and threemajor geoelectric layers overlying the resistive basement. The groundwater potential and overburden protective capacity maps were prepared. The groundwater in the area was categorized into high, medium and low groundwater potential zones. About 80% of thestudy area falls within the moderate/low groundwater potential zone while the remaining 20% constituted the high groundwater potential zone (Agric Olope area). Hence, thegroundwater potential rating of other areas is considered to be low. The values of longitudinal conductance (ranging from 0.01 to 2.01 mhos) of the area enabled the overburden units to be rated into good, moderate and weakprotective capacity. About 75% of the area falls within the good/moderate rating while 25% constitutes the weak/poorprotective capacity rating (Agric Olope area), suggesting that the groundwater around Agric Olope isvulnerable to contamination.

Mapping of Aquifer Characteristics and Reservoir Protective Capacity Variation in Obafemi-Owode Local Government Area, Ogun State South-West Nigeria

Variation of Aquifer potential characteristics and its impacts on the groundwater subsurface protection of the aquiferous zone using electrical resistivity method was carried out at Obafemi-Owode Local Government Area, Ogun State South-West Nigeria with the principal purpose of assessing and rating aquifer protective capacity of the overburden units in the area. Twenty seven (27) vertical electrical sounding (VES) were conducted using Schlumberger configuration with the maximum electrode spacing of 100m at each point using Allied OMHEGA Resistivity meter. The data were interpreted using partial curve matching techniques and computer iteration program using WINRESIST. Parameters such as aquifer resistivity, aquifer thickness, overburden thickness, bedrock resistivity, reflection coefficient and longitudinal unit conductance were calculated and used for evaluating the groundwater yields and vulnerability of the aquiferous zone to contaminant seepages. The range of reflection coefficient is found to be between 0.02 and 0.98 while that of the protective capacity is between 0.00135 and 0.510. Groundwater potentials of the area were categorized as being high (overburden thickness 13m and reflection coefficient less than 0.8); medium (overburden thickness 13m and with reflection coefficient 0.8) and low (overburden thickness < 13m and reflection coefficient. Also, the study area shows a very poor, poor, and moderate protective capacity rating. Seven (7) VES stations have very poor protective capacity, eighteen (18) VES stations shows poor protective capacity and only two (2) VES stations shows a moderate protective capacity rating. Since the illustration the longitudinal conductance revealed the impermeability of the confining layers which is generally ˂ 1.0 Siemens; values ˃1.0 Siemens which indicates zones in which the confined aquifer is subject to protection by the overlying formation materials; these revelations in the study area were possible indications that the groundwater quality status may have been impaired which necessitated the urgent need for the groundwater to be randomly...

PRELIMINARY ASSESSMENT OF GROUNDWATER POTENTIAL ZONES IN AYEDE-EKITI, EKITI STATE, SOUTHWESTERN NIGERIA USING ELECTRICAL METHODS

An electrical resistivity survey was conducted at different locations within Ayede Ekiti, Ekiti State, Southwestern Nigeria. This is aimed at evaluating groundwater potential zones and aquifer properties within the study area. Data were acquired at four (4) different locations using the vertical electrical sounding method by employing the Schlumberger array configuration. This study utilizes resistivity data processed with IPI2win software to analyze the subsurface geology of a basement complex region. The result of the study showed that qualitatively, three major curve types (A, HA, and H) were observed. Varying curve types, predominantly A curves, were observed across the research area, with notable groundwater potential indicated by H and HA curve types at select points. Through curve matching techniques, three to four distinct geo-electric layers were identified, while the quantitative interpretation resulted in deducing layers with different resistivity and thickness values for each VES(s) of the study area. It was deduced that the VES 2 and 3 zones are connected to a high output of groundwater. However, VES 1 and 4 are characterized by low groundwater potential. This research contributes valuable insights for geological mapping and groundwater resource assessment in complex basement terrains of the study area.

Geo-electrical investigation for characterizing the shallow Quaternary aquifer parameters and vulnerability to contamination: a case study from semi-arid Khanasser Valley region, Syria

Abstract Schlumberger configuration was used to carry out 34 vertical electrical sounding (VES) measurements for estimating and characterizing the shallow Quaternary aquifer parameters and its vulnerability to surficial contamination in the region of Khanasser Valley, Northern Syria. The data of VES are interpreted by the curve matching technique (CMT) and WinResist software package to get one dimensional (1D) geoelectrical solution model for each study VES point. The electrical conductivity (EC), total dissolved solids (TDS), porosity (Ø%), the overburden protective capacity (OPC), and the corrosion (Corr) of the study aquifer were revealed by parameters of longitudinal conductance and transverse resistance of Dar-Zarrouk results. The protective capacity for the shallow Quaternary aquifer is classified as 56% poor, indicating high vulnerability to contamination, 5.9% weak, 14.7% moderate, 20.6% good, and 2.9% excellent. The ratings of corrosivity for the study region are classified as 26.5% slightly corrosive (SC), 61.8% moderately corrosive (MC), 5.9% very strongly corrosive (VSC), and 5.9% practically noncorrosive (PNC).

GEOELECTRICAL ASSESSMENT OF GROUNDWATER POTENTIAL OF KEANA AREA NORTHCENTRAL NIGERIA

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

Assessment of groundwater potential of the Obafemi Awolowo University Estate, Southwestern Nigeria

Assessment of the groundwater potential of the OAU Estate involving digital image processing of Landsat 8 imagery, and geophysical and hydrogeological investigations were carried out. Landsat 8 imagery was processed to produce hydrolineament map. Topographic parameters including drainage density and slope gradient were derived from SPOT DEM using ArcGIS 10.3 software, and used to generate drainage density and slope gradient maps. The lithology of the study area was extracted from existing geological map. One hundred and four Vertical Electrical Sounding data were analyzed quantitatively using partial curve matching technique and computer assisted 1-D forward modelling and the results used to generate overburden thickness and coefficient of anisotropy maps. The hydrolineament, drainage density, slope gradient, lithology, overburden thickness and coefficient of anisotropy maps were developed into thematic maps and used to generate the groundwater potential map. The groundwater potential of the study area was classified as low- (61%), moderate- (32%) and high- (7%) with corresponding yields of < 0.5 L/s, 0.5 L/s – 1.5 L/s and > 1.5 L/s, respectively.

Subsurface Integrity Assessments of a Proposed Plaza Building at Oniru Lekki, Lagos, South-western Nigeria, Using Geoelectrical and Geotechnical Methods of Investigations

Subsurface integrity assessment for building foundation using geophysical and geotechnical methods was carried out at Oniru, Eti- Osa, Lagos State. A total of twenty-five Vertical Electrical Sounding (VES), five 2-D Resistivity Imaging Survey traverses and two borings with Standard Penetration Test (SPT) were carried out at the study site. The acquired data were processed quantitatively using partial curve matching and computer iteration technique to generate the geoelectric sections, the 2-D model and the SPT logs. The VES results revealed five to six geologic units corresponding to topsoil, clayey sand, sandy clay, clay/peat, and sand while the 2-D resistivity structure corresponds with the VES result. The borehole log reveals sand layers having an N-value of 22-30 which is indicative of medium-dense, brown (medium to fine) sand with occasional gravels from depth 1.50 - 7.50m. The borehole log information correlates well with the VES/2-D result. For the sand layer which connotes dense, grey (medium to fine) sand with occasional gravels from a depth 7.50 – 15.75m with N-value ranging from 26–30m. The study analysis shows that the proposed building could be placed on the dense sand at depth 7.50 – 15.75m, this, however, should depend on the proposed load, length, and breadth of the proposed building. This study has provided useful information about the subsurface condition for engineering structure and zone suitable for the proposed foundation.

Application of Vertical Electrical Sounding in Mapping Lateral and Vertical Changes in the Subsurface Lithologies: A Case Study of Olbanita, Menengai Area, Nakuru, Kenya

Much study has been done in the study area linking Vertical Electrical Sounding (VES) interpreted results to lithologies in the subsurface though only tend to indicate the vertical changes with the aim of mapping the occurrence of groundwater aquifers. Several boreholes have been drilled in the study area, though not much has been done to compare the vertical and lateral lithologic changes in the study area. This research is based on VES modelled geoelectric layers compared from point to point and using borehole logs as control data to establish inferences of certain lithology in the subsurface. The inversion of each VES curve was obtained using an AGI Earth Imager ID inversion automated computer program and resistivities and thicknesses of a geoelectric model were estimated. The analyzed VES data interpretation achieved using the curve matching technique resulted in mapping the subsurface of the area as portraying H-type; ρ1 > ρ2 ρ3, K-type; ρ1 ρ2 > ρ3, A-type; ρ1 ρ2 ρ3, Q-type; ρ1 > ρ2 > ρ3, representing 3-Layer subsurface and subsequently a combination of HK, HA and KHK types of curves representing 4-Layer and 5-Layer in the subsurface. The analysis further deployed the use of the surfer software capabilities which combined the VES data to generate profiles running in the west-east and the north-south direction. A closer analysis of the curve types indicates that there exists a sequence showing a shifting of the order of arrangement between the west and the east fragments which incidentally coincides with VES points 8, 9 and 10 in the West-East profiles. The lateral change is noted from the types of curves established and each curve indicates a vertical change in the subsurface. Control log data of lithologies from four boreholes BH1, BH2, BH3 and BH5 to show a qualification that different resistivity values portent different lithologies. Indeed, an analysis at borehole BH3 lithologies is dominated by either compacted rocks or soils, insinuating a scenario of compression experienced in this part of the subsurface which confirmed compression of subsurface formations. A correlation of the VES curve types and their change from one point to another in the study area are evident. This change supported by the surfer generated profiles from the modeled VES data show that there exists and inferred fault line running in the north-south in the area. The inferred fault line by VES mapping, is magnificently outlined by the geological map. There is exuded evidence from this study that the application of VES is able to help map the lateral and the vertical changes in the subsurface of any area but the evidence of the specific lithologies has to be supported by availability of borehole log control data. The VES data was able to enumerate vertical layering of lithologies, lateral changes and even mapping vertical fault line in the study area.

Geoelectrical Sounding to Identify Sub-surface and Groundwater State at Village Banauli, Singrauli District, Madhya Pradesh, India

Electrical resistivity (Geoelectrical) methods are well-known and common techniques for investigating the groundwater potential zone. These methods are economically viable and have the highest resolving power compared with other geophysical methods. A total of fifteen Vertical electrical soundings were conducted in the village of Banauli, located in Singrauli district in Madhya Pradesh, India. Vertical electrical sounding was carried out using Schlumberger electrode configuration with the maximum current electrode (AB) spacing of 200 m and potential electrode (MN) spacing of 10 m. For interpretation of measured resistivity, the Partial curve matching technique was used to calculate the layer parameters (resistivity and thickness) and further depict the depth section of the profile. In this study, the maximum five-layer model is obtained, and most curves are of HAK types. The first layer has a mean resistivity value of 12.41 Ωm and a mean thickness of 0.94 m. The second layer has mean resistivity of 7.93 Ωm and a mean thickness of 4.79 m. The third layer has a mean thickness value of 10.55 m and a mean resistivity value of 16.54 Ωm. The fourth layer has a mean resistivity value of 20.17 Ωm and a mean thickness of 9.20 m, and finally, the fifth layer, the bedrock, has a higher mean resistivity value of 59.92 Ωm. Thus, the obtained results may be used for identifying the drilling site for the groundwater potential zone.

Geo-electrical investigation of ground water potential using vertical electrical sounding

Groundwater potential assessment using the vertical electrical sounding (VES) technique was carried out at Ekiti state Southwestern, Nigeria with a view to solving the problem of incessant failure of groundwater boreholes in the study area. A total of 10 VES were carried-out using Schlumberger electrode configuration. The data was interpreted quantitatively using the partial curve matching and computer iteration techniques to generate the first order geoelectric parameters. The borehole lithological log was used to constrain the conventional VES interpretation. The VES results aided by the borehole lithological log reveal four distinct subsurface geologic layers which correspond to Top soil, Lateritic clayey sand, Sand, Sandstone and Consolidated sandstone. The analysis shows that sands at the upper layer within the depth of 2.3 - 76.2 m are unsaturated while sands at depth not less than 100 m in some sampling points are saturated and denote the aquifer units in the study area. Boreholes/deep wells could be cited at these points at depth interval 80 - 100 m. This study has provided an insight to the subsurface condition of the aquifer systems and delineated areas for probable groundwater development in Ekiti State.

Determination of Aquifer Parameters by Using Aqtesolv-software

Several aquifer properties regulate groundwater inflow/outflow to any area, and determination of propertieslike hydraulic conductivity (K), transmissibility and storativity (S) is essential to ascertain the sustainablewell yield. In situ estimation of these properties/parameters is accomplished by conducting pumpingtests. Aquifer parameter tests deliver vital information to resolve regional and local groundwater flowconcerns. In both the confined and unconfined aquifers, there are numerous methods for the determinationof aquifer parameters. In the present research, ten pumping tests were conducted at different geologiclocations in the hardrock region-dominated watershed to estimate aquifer properties. Method “Papadopulos-Cooper (P)” was considered a reference, and “AQTESOLV (Aquifer Test SOLver)” software methods whichinclude (Theis method, Cooper and Jacob (C) method, Neuman (N) method and Tartakovsky-Neuman (T)method) were utilized for the estimation of aquifer properties. Results revealed that T values calculatedusing the P-C method varied from 105.1 square meters per day to 322 square meters per day. However, Tvalues estimated employing AQTESOLV ranged from 122 to 300 square meters per day. All approachesusing the software gave T values that were found to be strongly correlated with the P-C method (Curvematching technique).

Investigation of Layer Thickness and Groundwater Potentials in Federal University Gusau and Its Environs, Zamfara State, Nigeria

The groundwater potential and layer thickness were investigated using vertical electrical sounding (VES) method. A total number of 40 vertical electrical sounding VES points were used for the investigation using Schlumberger array and data obtained were analyzed using curve matching and computer iteration techniques. The data revealed a 3-layer (A, KA and H Curve type) and 4-layer (A and H-curve type). In the 3-layer system, the apparent resistivity of the first layer ranged from 18.90 Ωm to 183.20 Ωm with a corresponding thickness of 0.7 m to 14.8 m. The second layer has apparent resistivity value ranged from 13.50 Ωm to 423.80 Ωm with a corresponding thickness in the range of 4.5 m to 14.7 m while the third layer has resistivity values ranging from 1156.40Ωm to 3732.70 Ωm with an infinite depth. For the four (4) layered model curves, first layer’s resistivity ranged from 29.50 Ωm to 244.70 Ωm, with a corresponding thickness ranging from 0.8 m to 13.0 m. The resistivity of the second layers ranged between 25.2 Ωm to 183.4 Ωm with a corresponding thickness ranging from 8.0 m to 14.2 m. The third layer resistivity ranged from 119.4 Ωm to 586.7 Ωm with a corresponding thickness ranging from 8.1 m to 20.4 m. The forth layer has a resistivity value ranging from 1318.3 Ωm to 3240.9 Ωm with an infinite depth. An integration of both isopach and iso-resistivity maps for both the 3- layer model curves and 4- layer model curves indicates that most of the northwest parts of the study area have low apparent resistivity values and thick overburden while, the southern portion has a little higher resistivity values and shallow overburden, an indication of poor groundwater potential. Future boreholes in the area should reached an expected depth of 50 m to 70 m depth

Geoelectrical Assessment of Groundwater Potential within Zamfara and its Environs, Northwestern Nigeria

Groundwater potential assessment was carried out within Zamfara environs, Northwestern Nigeria using geoelectrical technique with a view of solving the problem of incessant failure of boreholes in the study area. A total of one hundred and eighty-three (183) vertical electrical soundings (VES) were used to identify potential groundwater bearing zones capable of sustaining economic development of the study area. Two hydrogeological units were investigated (basement rock units and sedimentary rock unit), using Omega resistivity meter Model No. 122, to measure and record the resistance of the subsurface by Schlumberger configuration. The data obtained were interpreted quantitatively and qualitatively using the partial curve matching and computer iteration techniques to generate the first order geoelectric parameters. Generally, the VES result from the basement rock units revealed, four geoelectric layers which correspond to lateritic top soil, weathered basement (clay), partially fractured layer/fractured layer and fresh basement. The weathered/fractured layer was identified as the water bearing layer, within the basement rock units of the study area. From geospatial analysis of both weathered thickness/fracture thickness layers, South and Northeastern part tends to be the most prospective area with the best hydrogeologic conditions for borehole siting within the basement rock units. Consequently, three geo-electric layers were delineated from VES result obtained from Gundumi formation, which correspond to sandy clayey top/gravelly sandy top soil, second layer are mostly silty-clay/compacted sandstone/sandy gravel layers, the third layer were majorly saturated sandstone in some instances silty clay. However, the aquiferous layer is saturated sandstone/sandy gravel layer. The Dar Zarrouk result revealed excellent groundwater potential within the Gundumi formation. The values of coefficient anisotropy obtained from Gundumi rock units range from 0.44 to 3.79, which implies moderate saturation of groundwater. This is an indication that the aquifers of the Gundumi formation is more promising and it can be tap for both domestic and agricultural uses.&#x0D; Keywords: Vertical electrical sounding; Fractured layer; Saturated Sandstone; Basement rock units; Gundumi formation

Geophysical investigation of groundwater potential and aquifer protective capability in selected communities within Cape Coast municipality, Ghana

Application of VES geophysical technique to investigate the groundwater potential and the aquifer protective capability has been carried at Cape Coast Municipality, Ghana. The geology of Cape Coast is mainly made of the Secondian formation and the Eburnean Plutonic Suite. Twenty (20) VES points were selected after the profiling, and Schlumberger array was applied for the conduction of the VES. The PASI Resistivity Terrameter was used, and the maximum current electrode spacing (AB/2) was 100 m. Partial curve matching technique and computer iteration technique were applied in the interpretation data using WINRESIST software. The thematic maps of the parameters were generated to display their spatial variations using Surfer Golden software by the application of appropriate variograms depending on their range of values. The study revealed the presence of three to six layers curve types which include HKH (45%), QH (20%), HA (10%), KH (5%), QHKH (5%), A (5%), AKH (5%) and KHKH (5%) in the study area. The layers include topsoil (31.00–9135.00 Ω m), weathered layer (2.35–60,801.00 Ω m), fractured basement (4.39–32,431.00 Ω m), and fresh basement (59.40–22,521.00 Ω m). About 70% of the resistivities are less than 600 Ω m indicating the possibility of a fractured formation with high potential groundwater storage. The other 30% recorded high bedrock resistivities values of possible massive crystalline granitic rock with a limited fracture. Reflection coefficient and longitudinal conductance were calculated using appropriate equations and parameters. The values of the reflection coefficient ranged from 0.215606 to 0.997049. The study revealed that 20% of the total VES points have high groundwater potential, 65% showed medium potential, 5% showed low potential, while 10% showed very low potential. The study revealed poor (20%), moderate (35%), good (30%), and very good (15%) protective capacity ratings in the area. The technique has been effective in revealing the groundwater potential and the aquifer protective capability of the area. The aquiferous zone of the Secondian formation falls within the range of 17–43 m of depth with a borehole yield of 210–240 l/m. The successful borehole in the granitic rocks shows a low yield of 10 l/m with a water-saturated zone within 20–48 m of depth.