Geophysical Investigation of Groundwater Potential at Alhudahuda College, Zaria Using Very Low Frequency Electromagnetic (VLF-EM) Method

Abstract

Geophysical investigation of groundwater potential at Alhudahuda College, Zaria, Kaduna State, Nigeria, was carried out using the Very Low Frequency Electromagnetic (VLF-EM) method in response to persistent water scarcity and recurrent borehole failure within the school. The study area is situated within the Nigerian Basement Complex, where groundwater occurrence is predominantly controlled by weathered and fractured crystalline formations. Five traverses were established across the area, and VLF-EM measurements were acquired in vertical mode to delineate subsurface conductive structures associated with groundwater accumulation. The acquired data were processed using Fraser and Karous–Hjelt filtering techniques to enhance anomaly resolution and generate pseudo-sections representing subsurface current density distribution. Interpretation of the filtered data revealed several conductive zones across the profiles with depths extending to approximately 15 m, indicative of potential aquiferous formations. Profiles 3 and 5 exhibited relatively homogeneous conductive responses, while Profiles 2 and 5 revealed distinct fractured zones suggestive of enhanced groundwater potential. High positive peaks in the in-phase component and corresponding high current density values were interpreted as conductive anomalies associated with groundwater-bearing zones, whereas low current density regions represented resistive formations with limited groundwater potential. Two principal prospective groundwater targets were identified along Profiles 2 and 5 and are recommended as suitable locations for borehole development. The results confirm the effectiveness of the VLF-EM method in delineating subsurface conductive structures and provide reliable guidance for groundwater exploration in basement complex terrains.