Use of geo-electric data in the determination of groundwater potentials and vulnerability mapping in the southern Benue Trough Nigeria

Geo-electric parameters (resistivity, depth and thickness) and hydraulic parameters including transmissivity (T) and hydraulic conductivity(K) were estimated using Vertical Electrical Sounding (VES) data . VES technique employing Schlumberger electrode configuration was carried out in 47 locations with a maximum electrode spacing of 1000 m. The spatial distribution of Longitudinal Conductance (S) was used to delineate groundwater across the study area into various categories of vulnerability to contamination sources using the primary geo-electric parameters. Primary geo-electric parameters such as resistivity, thickness, and depth measured were used to determine the longitudinal conductance ( S) , transverse resistance (TR), hydraulic conductivity (K) and transmissivity (T). The estimated aquifer geometrical and hydraulic characteristics across the study area revealed values ranging from 10.74 to 3240 Ωm, 0.000252–0.06734 mhos, 5.89–198 m, 3.3–186.2 m, 0.00153–2.136 Ω −1 , 52.896–162,701.56 Ωm 2 , 0.00573–12.96 m/day, and 0.0358–650.80 m 2 /day for aquifer resistivity, conductivity, depth, thickness, longitudinal conductance, transverse resistance, hydraulic conductivity and transmissivity, respectively. The decrease in resistivity with depth shows that the clay/shale composition across the study area generally increases with depth. Findings from the study revealed that the NE and SW parts of the study area showed more prospects of groundwater potential when compared to other parts of the study area. Overall, the groundwater potentials of the study area range from low to high with the areas that are underlain by sandy lithologies in the NE and SW sections being more prolific. Aquifer vulnerability analysis of the study area using the longitudinal conductance values revealed that 45%, 37%, and 28% of the study area fell within the moderate, weak, and poor categories based on aquifer protective capacity rating. The findings of the present study have therefore helped to delineate the groundwater potentials and vulnerability of the study area. Graphical abstract