DELINEATION OF SHALLOW FLOODPLAIN AQUIFERS FOR IRRIGATION PURPOSES OVER A FLOODPLAIN AT AULE, AKURE SOUTHWESTERN NIGERIA

Abstract

Geophysical investigation involving the use of Electrical Resistivity method using Modified Wenner Array Configuration has been adopted for shallow groundwater potential evaluation over a floodplain at AULE, Akure southwestern Nigeria for irrigation purposes. The research presents the result from the quantitative interpretation of forty eight vertical electrical sounding (VES) obtained from the survey area which has helped in the identification of aquiferous units and has provided an understanding of aquifer characteristics especially the thickness and depth to fractured zones which are required for locating points with high potentials for groundwater occurrence. The Vertical Electrical Sounding technique result delineated three to six (3-6) subsurface geologic layers (top soil, clay, clay, weathered layer, partly weathered layer and bedrock) with different depth ranges (0.04m to 10.0m). The lithology of the subsurface strata is mainly clay (expansive clay) which justifies the dominance of low resistivity values and explains why the runoff water via flood doesn’t infiltrate the soil. The overburden thickness and aquifer resistivity were used in classifying the groundwater potential of the study area. Areas having moderate overburden with thickness between 5m and 10m with weathered layer above 4 Ωm such as VES 1, 3, 13, 28, 32, 39, 40, 41, 43 and 44 are delineated to be promising sites for shallow wells.