Abstract
Electrical resistivity data acquired in one hundred and ten (110) locations using vertical electrical sounding method of Schlumberger array have been used to study the hydrogeological properties and groundwater storage potential of bedrock aquifers in an area covered by Geological Sheet 223 Ilorin, Nigeria. The aim of the study was to identify productive aquifer zones for citing boreholes for community water supply. The data acquired were processed and interpreted using auxiliary curve matching and computer automation method to delineate the different geo-electric layers, their resistivities, thicknesses, and depths. Geo-electrical layers were interpreted to their equivalent geological layers using borehole lithological logs from the study area. Then, the hydraulic conductivity, transmissivity, fracture contrast, reflection coefficient were estimated and plotted in the form of 2D maps to describe the spatial variations of these parameters in the area. The results of the study revealed the presence of three to five geo-electric layers. The geo-electric layers, from top to the bottom, corresponds to the topsoil layer, lateritic layer, weathered rock layer, fractured rock layer, and the fresh basement rock. Lateritic and/or fractured rock layers were not delineated in some places. The weathered and fractured rock layers, where present, correspond to the aquifer units. The thickness of the fracture aquifer ranges from 0.6 to 33.6 m while the thickness of the weathered aquifer ranges from 1.4 to 49.3 m. The transmissivity, T , and hydraulic conductivity, K , range from 3 to 1200 m2/day and 1 to 48 m/day, respectively. The reflection coefficient and fracture contrast map showed the presence of water-bearing fractures and shared some similarities with T and K maps. A mathematical model for predicting groundwater potential, {text{GW}}_{text{P}} , of weathered aquifer in the basement complex terrain was proposed in this study. The consistencies between the overall groundwater potential map and aquifers parameters distributions maps suggest the appropriateness of the proposed mathematical model for predicting groundwater potential of weathered rock in the basement complex area of Nigeria. The western, northwestern, and central parts of the study area, having {text{GW}}_{text{P}} greater than 0.6 (60%), were recommended for groundwater development through boreholes drilled to a depth ranging between 75 and 100 m.
Highlights
Climate change is anticipated to affect groundwater availability throughout Africa than it was previously forecast
vertical electrical sounding (VES) results show that the study area is underlain by three to five distinct geo-electric layers (Fig. 2a)
The interpretation showed that the five geo-electric layers correspond to the topsoil layer, lateritic layer, weathered rock layer, fractured rock layer, and fresh basement rock, respectively
Summary
Climate change is anticipated to affect groundwater availability throughout Africa than it was previously forecast. In hard rock terrain, changes in aquifer storage, due to groundwater withdrawal can be substantial and significant because the aquifers have limited extent, are not interconnected and poorly recharge (Healy et al 2007; Raji et al 2019; Raji and Abdulkadir 2020a, b). This is why groundwater scarcity is common in the basement rock terrain. Crystalline rocks are generally impervious to fluid except when it’s decomposed by weathering, or fractured, jointed, and faulted by tectonic activities. The knowledge of the spatial distribution of hydraulic properties of rocks is essential for the prediction of groundwater availability, recharge, and yield in bedrock aquifers (Scanlon and Cook 2002; Ezeh 2011; Raji 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
