Application of remote sensing, GIS and geophysical techniques for groundwater potential development in the crystalline basement complex of Ondo State, Southwestern Nigeria

Abstract

Remotely sensed and electrical resistivity data were employed to develop the groundwater potential of the hard-rock terrain of Ondo State, Southwestern Nigeria. Administrative map, Landsat ETM +, Aster DEM were acquired and processed to produce geomorphological map, lineament and lineament-intersection density maps. Electric sounding and groundwater yield data were also acquired. The electric sounding data were interpreted quantitatively. Aquifer thickness and coefficient of anisotropy were generated from geoelectric parameters (resistivities and thicknesses) deduced from the interpreted results of the electric sounding data. All these maps were reclassified into hydro-thematic maps and combined using weighted linear combination function in ArcGIS 10.5 software to develop a composite groundwater potential map. Groundwater yield data were used to establish the reliability of the groundwater potential map derived from the remotely sensed and geophysical data interpretation. Erosional and depositional landforms were identified in the area and these included: residual hill (677–980 m.a.s.l), pediment (452–677 m.a.s.l), pediplain (226–452 m.a.s.l) and pediplain with alluvium (74–226 m.a.s.l). The lineament density ranged from 0.00 to 69.48 km/km2. The lineament-intersection density ranged between 0.00 and 72.92 km/km2. The aquifer thicknesses varied from 0.2 to 79 m. The aquifer types identified from the study were the weathered layer (WL), weathered/fractured (unconfined) (W/F(u)), weathered/fractures (confined) (W/F(c)), weathered/fractured (unconfined)/fractured (confined) (W/F(u)/F(c)) and fractured confined aquifer (F(c)). The coefficient of anisotropy (coa) values ranged from 1.0 to 2.88 units. Four distinct groundwater potential zones: very low, low, moderate and high zones were identified. However, the study concluded that the groundwater potential rating of the study area was low to moderate.