Groundwater Identification Using the Geoelectric Method (Electrical Resistivity TomographyERT) For the Utilization of Mining Areas

Groundwater Identification Using the Geoelectric Method (Electrical Resistivity Tomography/ERT) For the Utilization of Mining Areas

PATTERN OF ELECTRICAL RESISTIVITY IN REGOLITH AQUIFER AND THEIR IMPLICATION FOR GROUNDWATER MANAGEMENT IN ILORIN METROPOLIS, NIGERIA

Groundwater development in basement complex terrains is largely dependent on the occurrence and characteristics of the regolith aquifer, making geophysical investigation a vital precursor to borehole siting. This paper examines the pattern of electrical resistivity in the regolith aquifer of Ilorin metropolis, Kwara State, Nigeria. Forty (40) Vertical Electrical Sounding (VES) points were established across the study area to delineate subsurface lithological layers, determine resistivity patterns, and estimate weathering depth. The resistivity data were processed and interpreted using computer iteration techniques, while an aquifer potential index was used to evaluate groundwater potential. The findings reveal a geo-electric sequence of five lithological layers, comprising topsoil, lateritic layer, clayey soil, weathered basement, and fresh basement, with resistivity curve types identified as H, K, A, and Q. The regolith aquifer, represented by the weathered basement, recorded resistivity values ranging from 3.57Ωm to 297Ωm, while weathering depth varied from 3.30 m to 31.28 m, with both parameters showing higher values in the south-western and north-eastern parts of the study area. Analysis indicated that 45% of the study area exhibited optimum weathering and groundwater potential, whereas correlation analysis revealed a weak inverse relationship (r = -0.361) between regolith resistivity and aquifer potential, suggesting that resistivity alone is insufficient predictor of groundwater yield. The study concludes that the regolith aquifer constitutes the principal groundwater reservoir in the study area. Recommendations include the adoption of pre-drilling geophysical surveys as a mandatory practice and the prioritization of boreholes in zones identified with optimum aquifer potential.

Identification of Subsurface Lithology Using the Vertical Electrical Sounding Geoelectric Method in The Kuta Area, Central Lombok, West Nusa Tenggara

The Kuta region is one of the most developed tourism areas in the Central Lombok Regency. This development impacts the population that continues to increase in the area, thereby influencing the increasing need for groundwater. However, the study area tends to be dry, especially in the dry season and rainfall is very low. This is quite difficult for residents to find good aquifers for groundwater exploration. From this, subsurface lithology identification is carried out to determine the lithology of the subsurface layers to obtain potential aquifers. The method used is geoelectric vertical electrical sounding which is carried out at two location points with a track length of 500 meters and a spacing of 10 meters. From the analysis of the 1D resistivity curve produced in this survey, information on subsurface lithology at the measurement point, consisting of layers of clay, sandstone, and breccia, was obtained. At the MR-1 line there is sandstone lithology at a depth of 53-84.3 meters which is thought to have the potential to be an aquifer, while at the MR-2 line, the presence of sandstone lithology is at a depth of 67.5-110 meters. Therefore, this measurement location shows the prospect of the existence of an aquifer which is characterized by a layer of sandstone which is a rock with good porosity and permeability  

Hydrogeophysical investigation for groundwater development in the crystalline terrain of Ohagainyi area of Lokoja, North-Central, Nigeria

Electrical Resistivity Imaging on Limestone Formation for Aquifers Identification in Poguwatu Village, Central Sumba

Poguwatu Village in Central Sumba Regency is a dry area characterized by low rainfall and dominated by carbonate rocks, resulting in limited surface water availability and posing a persistent challenge for groundwater exploration. This study presents the first subsurface investigation using the Dipole-dipole resistivity geoelectrical method to characterize aquifer-bearing rock conducted in Poguwatu Village, West Cendana. This method has the ability to identify the conductor zone related to the saturation area where the water accumulated. Measurements were conducted along 5 survey lines, where each line has 620 m length, except Line 5 extending to 880 m, with 10 m electrode spacing. The measured data calculate in apparent resistivity value and then invert to true resistivity using least-square inversion processes. The result yielded RMS errors ranging from 17.7% to 24.8%. The inversion results identified four rock units based on resistivity values, sandy limestone saturated with saline water (< 2.0 Ωm), marl (2.0–32.0 Ωm), fractured or sandy limestone (32.0–128.0 Ωm), and compact limestone (>128.0 Ωm). A seepage with thickness ± 2 m was identified on Line 2 within the fractured/sandy limestone, bounded below by an impermeable marl. Compact limestone, with very low porosity and permeability, dominates in most of the study area and functions as an aquifuge, a finding corroborated by a dry borehole on Line 5 that failed to yield groundwater. These results indicate limited groundwater potential across Poguwatu Village, and further investigation into alternative water sources from surrounding areas is recommended for the community's water supply.

Deployment of Electrical Resistivity Method for Evaluation of Sustainable Groundwater Resources in Lapai, Niger State, Nigeria

Groundwater accessibility in basement complex terrains is governed by the hydraulic properties of weathered and fractured aquifer systems. Despite growing demand driven by rapid urbanisation, systematic hydrogeophysical characterisation of such aquifers remains limited across central Nigeria. This study deployed the Schlumberger vertical electrical sounding (VES) technique using the SYSCAL Pro resistivity meter (IRIS Instruments, France) at twelve stations to evaluate the groundwater potential of Lapai, Niger State, underlain by the migmatite-gneiss basement complex. Acquired data were processed through partial curve-matching and computer-assisted iterative inversion to determine subsurface resistivity distribution, aquifer depth, and groundwater prospectivity. All interpreted VES curves exhibit the H-type configuration (ρ₁ > ρ₂ < ρ₃), confirming a three-layer subsurface model. The uppermost lateritic layer ranges in thickness from 2 to 6 metres. The second layer, with resistivity values of 60–140 Ωm occurring at depths of 2–23 metres, is interpreted as a saturated weathered basement aquifer. The third layer represents fresh, locally fractured basement encountered at depths of 30–60 metres, constituting a secondary aquifer target. The study concludes that sustainable groundwater development is technically feasible through boreholes drilled to approximately 70 metres, targeting both the weathered and fractured basement aquifer units.