Assessment of Aquifer Protective Capacity in a Basement Terrain: A Case Study of the Federal University of Technology Akure, Southwestern Nigeria, Using Geoelectric and Geologic Parameters

Background and Objective: Groundwater resource vulnerability in crystalline basement terrains is a growing concern due to limited natural filtration capacity. This study aimed to assess the aquifer protective capacity in part of the Federal University of Technology, Akure (FUTA) to identify zones with varying levels of groundwater protection and enhance sustainable groundwater development. Materials and Methods: A total of 25 vertical electrical soundings (VES) were conducted using the Schlumberger array with a maximum half-current electrode spread of 65 m. Data interpretation revealed 3 to 4 geoelectric layers: Topsoil, laterite/weathered layer, partially fractured basement and fresh basement. The interpretation also revealed the layer parameters (resistivity and thickness values). Dar-Zarrouk parameters were subsequently calculated to evaluate aquifer protective capacity. These parameters were integrated in a GIS environment using a weighted sum overlay analysis. Results: The topsoil resistivity ranged from 24 to 444 Ωm (thickness: 0.2-3.3 m), the weathered layer from 54 to 506 Ωm (thickness: 0.9-25.9 m) and the fractured basement from 89 to 320 Ωm. The resulting aquifer protective capacity map identified five protective zones: very low, low, moderate, high and very high. About 56% of the area falls under very low to low protection, 16% under moderate protection and 28% under high to very high protection, with higher protection zones mainly in the northern region. Conclusion: The study provides a comprehensive assessment of aquifer vulnerability across FUTA and demonstrates the utility of integrating geoelectrical and GIS techniques. The dominance of low protective capacity zones highlights the need for strategic groundwater management. Future work should include hydrochemical validation and seasonal monitoring to refine the protective capacity assessment.