Abstract

A multi-criteria model (GRTER), created as G (geology), R (resistivity), T (thickness of the aquifer), E (elevation) and R (bedrock relief) and groundwater occurrences (G), general lithology of the overlying strata (O) and depth to aquifer units (D) termed GOD index, were employed towards delineating the groundwater potential and aquifer vulnerability of Ilere Town, Ondo State, Southwestern Nigeria. Hydrogeologic measurement of fifty-two (52) wells, by measuring the column of water and static water level of all tested wells, was performed so as to identify groundwater flow direction. Thirty (30) Vertical Electrical Sounding (VES) data were acquired and the results displayed as tables, charts, and maps. The maps developed using the measurements of aquifer resistivity and thicknesses were further used to create the groundwater potential map. The results attest to a good correlation between maps of the bedrock relief and groundwater potential zones and indicate that the north-central and the south-eastern parts are the recharge zones, with elevation values ranging between 365m and 390m; while the north-western and the south-western regions are the discharge zones, with elevation values that vary from 325m to 360m. The GOD map shows area of vulnerability range: 0.0 - 0.1 (insignificant), 0.1 - 0.3 (low), 0.3 - 0.5 (medium) and 0.5 - 0.7 (high). This map, therefore, suggests that the groundwater potential and aquifer vulnerability index of Ilere town is moderate.