Aim/objectives: This research is geared towards integrating Vertical Electrical Soundings (VES) and Electrical Resistivity Tomography (ERT) profiles constrained with geoelectric sections and borehole logs to assess the vulnerability of the aquifer units employing Aquifer Vulnerability Indexing (AVI) method. Method: The dataset used in this study comprises of fifty VES, five ERT profiles surveyed in parts of Enugu north in Enugu state, two geoelectric sections and three borehole logs. The computer and manual interpretation of VES resistivity data using WinResist software gave values of resistivity, depth and thickness of each geoelectric layer using half current electrode spacing of 1.0 to 450.0 m and maximum current electrode spacing of 900 m. 2D imaging data from the measured field resistance values were processed using RES2DINV×32 version 3.71.115 software. The geoelectrical sections show the variation of resistivities with depth along transcent lines. The geohydraulic parameters were also estimated. Finding: Interpreted VES data revealed five to six geoelectric layers and fundamental parameters generated were used to estimate the values of hydraulic conductivity (σ) and hydraulic resistance (C) of the covering layers ranging from 0.010 to 0.769 mday −1 and 40.47 to 8292.0 day −1 respectively. This research revealed high hydraulic conductivity in the western part implying good groundwater potential with moderate to high protective capacity while areas with low hydraulic conductivity correspond to areas with high resistivity indicating little or no pore space and total devoid of water. The hydraulic resistance quantifies groundwater vulnerability using AVI and reveals that the area of study is characterized by low to high AVI with moderate AVI dominanting. Originality and novelty: The estimated geohydraulic properties from resistivity data and their spatial spread are promising and could increase the depth of knowledge on groundwater vulnerability within and around the study area.

The aeromagnetic data of Nsukka area was interpreted qualitatively and quantitatively. Standard Euler deconvolution, Source Parameter Imaging (SPI), Forward and Inverse modeling techniques were employed in quantitative interpretation with the aim of determining depth/thickness of the sedimentary Basin, magnetic susceptibilities and type of mineralization prevalent in the area. Oasis montaj 6.4.2 software and potent Q 4.10.07 software were employed in the data analysis. Forward and inverse modeling estimated depths for profiles 1, 2, 3, 4 and 5 were 1644, 2285, 1972, 2193 and 1200 m respectively, with respective susceptibility values of 0.0031, 0.0073, 1.4493, 0.0069 and 0.0016 which indicate dominance of iron rich minerals like limonite, hematite, pyrrhotite and pyrite, and forms lateritic caps on sandstones. Results from SPI estimated depth ranges from 151.6 m (outcropping and shallow magnetic bodies) to 3082.7 m (deep lying magnetic bodies). Depths of shallow magnetic sources resulting from lateritic bodies in the outcrops within the study area as estimated by Euler depths for the four different structural index (SI = 0.5, 1, 2, 3) ranges from 7.99 to 128.93 m. 35 to 150 m depth are good potential water reservoirs for Nsukka and environs. Depths of 1644 to 3082.7 m show sufficiently thick sediments suitable for hydrocarbon accumulation.

Airborne geophysical (aeromagnetic and gravity) data of Nsukka area was interpreted qualitatively and quantitatively with the aim of determining the susceptibilities of rock types, depth/mass of the anomalous bodies, possible cause of the anomalies and type of mineralization prevalent in the area. The estimated depths from forward and inverse modeling of aeromagnetic data for profiles 1, 2, 3, 4 and 5 were 1200m, 1644m, 1972m, 2193m and 2285m respectively. The respective susceptibility values were 0.0031, 0.0073, 1.4493, 0.0069 and 0.0016. These indicate dominance of iron rich minerals like limonite, hematite, pyrrhotite, and pyrite and forms lateritic caps on sandstones. SPI depth result ranges from 151.6m minimum (shallow magnetic bodies) to 3082.7 m maximum (deep lying magnetic bodies). Euler depths for the four different structural index (SI = 0.5, 1, 2, 3) ranges from 7.99 to 128.93m which are depths of shallow magnetic sources resulting from lateritic bodies in the outcrops in the study area. From the gravity data interpretation, Euler depth estimation reveals that depth to anomalous bodies ranges from 89.13 to 2296.92m. Density of the causative body obtained from modeling results for profile 1 was 1498kg/m3, which is in the range of clay material and the depth was about 923m. From models 2, 4 and 5, the densities of the causative bodies were 3523, 4127 and 3707kg/m3, while depths to the surface were about 604, 815 and 1893m respectively. These density ranges correspond to that of ironstone. From model three, the density of causative body obtained was 2508kg/m3, located at a depth of about 268m below the surface. This work has shown that Nsukka area is underlain by thick strata of shales, sandstones and ironstones, which together are suitable for ceramic production, and sufficiently thick sediments suitable for hydrocarbon accumulation.

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The effect of dumpsite leachate on groundwater at the Ezeani-Obimo community was performed by employing Schlumberger and Wenner configurations for four vertical electrical sounding (VES) and four electrical resistivity tomography (ERT). Four geoelectric layers were obtained and characterized by KH, AK, KH, and QH curve types. The first layer, second and third layer has resistivity values ranging from 21.2 to 7026.0  with thickness and a depth ranging from 0·5-31.6 m. The fourth layer has resistivity values ranging from 105.9 to 3355.4  with undefined thickness and depth values harboring all the aquifer units in the study area. Aquifer resistivity and thickness values vary from 105.9 to 3355.4  and 6.6 to 27.1 m while aquifer conductivity ranges from 0·0003 to 0·0094  increasing towards the E-W direction. The longitudinal conductance and transverse resistance values vary from 0.0024 to 0.0623  and 698.94 to <br /> 27178.7  respectively. 2D ERT profiles show low resistivity in the eastern direction and a lateral spread of low resistivity value indicates that leachate flow is moving away gradually from the dumpsite to its outside environment. This study revealed that the layers harboring the aquifer in the area are significantly affected as a result of dumpsite leachate that accumulates on the surface. This result is beneficial for waste managers to take mitigation measures to prevent the risk of total contamination of the groundwater in the area in the nearest future.