Aquifer Characterisation Using Vertical Electrical Sounding in Parts of Nasarawa State, Nigeria: Resistivity, Thickness and Overburden Mapping

                @article{CRSIJ26000405,
                  author = {Paul Amade EMMANUEL , Olugbenga Tajudeen ADEEKO, Ado Umar FAROUQ},
                  title = {Aquifer Characterisation Using Vertical Electrical Sounding in Parts of Nasarawa State, Nigeria: Resistivity, Thickness and Overburden Mapping},
                  journal = {Cosmo Research and Science International Journal},
                  year = {2026},
                  volume = {2},
                  number = {2},
                  pages = {489-503},
                  issn = {3108-1584},
                  url = {https://cosmorsij.com/published/CRSIJ26000405.pdf},
                  abstract = {Groundwater in the Precambrian Basement Complex of Nasarawa State is governed by strong lithological and structural heterogeneity, so reliable aquifer characterisation is essential if groundwater development is to be sustainable. With that in mind, this study set out to evaluate the geo electrical characteristics of selected basement-complex locations in the state and consider what they imply for groundwater occurrence, using Vertical Electrical Sounding with the Schlumberger configuration. Four soundings were acquired at each site, three investigation points and one control station, with current-electrode half-spacing (AB/2) ranging from 1 to 150 m and potential-electrode half-spacing (MN/2) from 0.5 to 15 m. The interpreted resistivity data were then used to characterise the subsurface and to derive the Dar–Zarrouk parameters: longitudinal conductance (S), transverse resistance (T), longitudinal resistivity (ρL), transverse resistivity (ρT), and the coefficient of anisotropy (λ). The results reveal substantial spatial variability in subsurface electrical properties. Mean longitudinal conductance ranges from 0.182 to 0.344 S, with Angwa Adamu Kugbaru and Tudun Wada classified as having weak protective capacity, while Auta Balefi, Nasarawa-Toto, Keffi, Lafia Site 1, and Lafia Site 2 show moderate protective capacity. Mean transverse resistance varies markedly, from 2,801.25 Ωm² at Auta Balefi to 427,876.25 Ωm² at Lafia Site 2, reflecting pronounced differences in layer resistivity and thickness. The coefficient of anisotropy ranges from 1.188 at Auta Balefi to 11.918 at Lafia Site 2, indicating significant directional variability and subsurface heterogeneity at some locations. The exceptionally high anisotropy and transverse-resistance values at Keffi, Lafia Site 1, and Lafia Site 2 are treated cautiously, since they are strongly influenced by the very high resistivity assigned to deeper layers. In conclusion, the investigated basement terrain is highly heterogeneous, with weak-to-moderate groundwater protective capacity and substantial spatial variation in subsurface electrical structure. The study underscores the value of combining VES-derived Dar–Zarrouk parameters with lithological, structural, borehole, and hydrogeological information for reliable aquifer evaluation and sustainable groundwater development in basement-complex environments.},
                  keywords = {Aquifer characterization; Basement Complex; Vertical Electrical Sounding; Schlumberger array; Dar–Zarrouk parameters; protective capacity; anisotropy; groundwater; Nasarawa State; hydro geophysics},
                  month = {September}
        }