An integration of remote sensing, geographical information system (GIS) and 2D resistivity techniques was used to evaluate the groundwater potential of Obafemi Owode local government area (LGA) in Ogun State, southwestern Nigeria. A composite Landsat 7 image was used to produce land use and lineament of the study area. Advanced space-borne thermal emission and reflection radiometer (ASTER) data were used to generate slope and drainage density. The study adopted modified drastic model for groundwater potential, integrating six parameters which are land use, lineament density, slope, drainage density, geology and soil map. The contribution of each theme to groundwater potential was weighted and ranked using ArcGIS 10.2 software. The groundwater potential zone of the study area delineated five distinct zones which include very high (196.39 km 2), high (334.64 km 2), moderate (481.76 km 2), low (298.46 km 2) and very low (95.73 km 2). Eight zones were delineated for further study. A total of 4.8 line km of 2D resistivity profiles were investigated in one of the designated zones labeled "area D" based on the groundwater potential map. Pole-dipole and dipole-dipole arrays used reveal five geoelectric layers within the study area. The 2D inverse models of resistivity variation with depth suggest the occurrence of potential carbonate and silicate aquifers. To verify the interpreted results within the "high" groundwater potential zone, a well was drilled on traverse 1. A potential water-bearing aquifer was encountered at a depth of 75 m. The groundwater potential map of the study area was tested with five existing wells, and the result was impressive. The outcomes from this study show that the high potential zones would play a key role in future expansion of drinking water and irrigation development in the study area.

Electrical resistivity sounding was employed to delineate different water bearing layers and their architectural parameters. Sixty Vertical Electrical Soundings (VES) were obtained in the built-up area of Olabisi Onabanjo University campus to map out variations in subsurface resistivity, which was used to determine aquifer parameters favourable for groundwater development. Interpretation of electrical sounding data helps in determining the resistivity and thickness of aquifers, aquifer and overburden thicknesses and depth to the basement. We employ a lithology-based hydrogeological model with definite boundary to classify the apparent resistivity. In this model, range of electrical resistivity values were assigned to different layers based on field observation and knowledge of the geology of the area. In all, five litho-units were delineated besides the topsoil, which are: clay with resistivity range of 25-53 Ωm; clayey sand/sandy clay with resistivity range of 122-440 Ωm; weathered layer with 62-119 Ωm; fractured basement with 208-667 Ωm and resistivity above 720 Ωm were taken as fresh basement. From the initial lithologic-based model, we developed 2D model that conceptualized aquifer architecture and bedrock topography along the major traverses obtained in the area. Also, Isopac map reveals that the overburden is thicker in the western half while the 2D model and structural map clearly show undulating bedrock topography made up of bedrock ridge with elevations of 127.0-170.0 m and bedrock depressions with elevation of 97.0-123 m. Derived Geo-electric parameters revealed that aquifer quality increases as we move northward, though recommended aquifers cut across all the area survey. Based on the study, we recommended VES stations with good overall qualities to be developed to productive water-supply tube wells.

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