Abstract
In this study, an integrated remote sensing and geophysical (aeromagnetic and geo-electric) methods was employed to assess the potential of groundwater in a basement complex terrain of Okene and its environs, Southwestern, Nigeria. Landsat imagery acquired over the study area was processed in the Geographic Information Systems (GIS) environment to delineate the surface lineaments, drainage networks and their orientations. Aeromagnetic data over the area were analyzed and its derivative maps were interpreted to further map the structures and the geology in the subsurface; depths to magnetic sources were determined using spectral analysis. Vertical Electrical Sounding (VES) of geo-electric method was interpreted to map the subsurface geology layers. The results of the integrated data were correlated with borehole yield data of the area for effective interpretation. Delineated lineaments from the azimuth, frequency plot showed dominant trends in the NE-SW and NNE-SSW directions. Radial average power spectrum revealed the depth to magnetic sources between 100 and 2500 m and the interpreted VES data characterized the area into three to four subsurface layers. In correlating the results with borehole yield data, the zones with high lineament density and low/negative magnetic anomaly were categorized as high groundwater potential zones while areas with low lineament density and high/positive magnetic anomaly as low groundwater potential zones. This study will guide efficiently subsequent groundwater drilling program in the study area.
Highlights
Groundwater is one of the most valuable natural resources on the earth surface and serves as one of the main sources of drinking water
In typical basement complex areas such as the study area, the occurrence of groundwater in recoverable quantity as well as its circulation is controlled by geological factors i.e. faults, joints and fracture zones [2] [3]
The delineation of these features is very essential for better understanding of the subsurface geology of these areas in term of their groundwater potential
Summary
Groundwater is one of the most valuable natural resources on the earth surface and serves as one of the main sources of drinking water. In Okene and its environs, the delineation of geologic features i.e. faults, joints and fracture zones of their low permeability rocks is a challenging task as numerous unsuccessful boreholes have been drilled within these areas Their inhabitants depend solely on surface water from few available streams and hand dug wells for their domestic use, and such sources are highly vulnerable to pollution. In this work geophysical methods comprising aeromagnetic and electrical resistivity combined with remote sensing technique are used with the objectives of delineating structures/lineaments i.e. faults, fractures, joints/shear zones associated with the study area, determining their trend/pattern, drainage network, depth to magnetic sources and geoelectric parameters of subsurface layers in order to evaluate the study area groundwater potential
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