Aquifer characterization and subsurface geology of the Ewohimi–Ewatto–Igueben–Ubiaja Axis Edo State Nigeria

An integrated geophysical, geological, and hydrogeological study was conducted along parts of the Ewohimi–Igueben–Ubiaja axis in Edo State, Nigeria, to characterize the aquifer systems and delineate zones of groundwater occurrence. Vertical electrical soundings, geological mapping, and correlation of borehole logs were used to delineate a multi-aquifer system comprising perched, unconfined, semi-confined, and confined aquifers at depths ranging from 30 to 300 m. Six to nine geoelectric layers were identified, consisting mainly of clay, sand, lignite, and sandstone units. Lignite horizons encountered at depths of 20–143 m were found to contribute to circulation losses and pipe clogging during drilling operations. Pumping tests yielded transmissivity values of 8.626–35.564 m²/day and discharge rates of 17.33–44.6 m³/h, confirming the productivity of the deeper aquifers. Groundwater contour and stream hydrograph analyses indicated baseflow contributions exceeding 70%, demonstrating active groundwater–surface water interactions. The study provides improved understanding of the subsurface stratigraphy and groundwater dynamics of the area and establishes a scientific basis for sustainable groundwater exploration and management.