GROUNDWATER POTENTIAL AND VULNERABILITY STUDIES OF PARTS OF AGO IWOYE, SOUTHWESTERN NIGERIA USING ELECTRICAL RESISTIVITY METHOD

Abstract

Groundwater resources exploration within the Olabisi Onabanjo University campus, Ago–Iwoye was done with the
aim of determining groundwater potential zones and the vulnerability of the aquifer in the area. Forty-one (41) Vertical
Electrical Sounding (VES) were established using the Schlumberger array configuration with current electrode
spacing varying from 1-100 m. The interpretation was done using partial curve matching and computer iteration
technique with the aid of WinResist 1.0TM software programme. Parameters such as overburden thickness, basement
resistivity, reflection coefficient and longitudinal conductance were derived. The geoelectric interpretation revealed
that the area is underlain by three basic lithological layer grouping; topsoil (14 Ωm–316.2 Ωm), weathered layer (28
Ωm–302 Ωm) and basement rock (245 Ωm–986 Ωm). The resistivity curve types obtained were H and HK with
percentage of 90%, and 10% respectively. The overburden thicknesses range between 5m–25m and reflection
coefficient between 0.70–0.90. Groundwater potential of the area revealed that the eastern part was low, the western
part was moderate while the central part showed high groundwater potential. The longitudinal conductance values
range from 0.08–0.43 indicating weak to moderate protective capacity which suggest high vulnerability rate of
groundwater in the study area.