Hydrolithological Investigation for Near-Surface Aquifers Within Lekki Peninsula, Lagos, Southwestern Nigeria

Abstract

This study is aimed at investigating the near-surface aquifers within Lekki Peninsula, Lagos, Southwestern Nigeria. Thirty-one (31) Vertical Electrical Sounding (VES) data were acquired using the Schlumberger array with current electrode spacing, which varies between 1 and 400m. The VES data were quantitatively interpreted, and the final layer parameters obtained were used to generate 2D geoelectric sections. Litho-logs acquired within the Lekki Peninsula were used to correlate the geoelectric sections to understand the nature and depth of groundwater contained in each aquiferous zone. The lithologies delineated in the study area include the topsoil (fill and/or sand) with resistivity value, which varies between 39 and 1535Wm as well as layer thickness from 0.5 to 5.5m; second layer of wet clay/sandy clay (saturated with brackish water) with resistivity value, which varies between5 and 163Wm as well as layer thickness from 1.5 to 10m; third layer of clayey sand/sand (saturated with freshwater) with resistivity value, which varies between 10 and 898Wm as well as layer thickness value from5 to 34m; and fourth layer of clay (saturated with saline water) with resistivity value, which varies between 1 and 9Wm. Isolated sand bodies (probably unsaturated zone) with resistivity value, which varies from 648 to 3560 Wm, were delineated beneath VES stations 24, 25, 29 and 30. The study concludes that the topsoil (sand/fill), unsaturated zone (conglomerate), silty mud layer (brackish/ freshwater saturated), and sand layer (saline water-saturated) constitute the aquifers and water quality within Lekki Peninsular. The inhabitants of the study area are, therefore, advised to avoid absurd usage of water to reduce the pumping rate and intrusion into the saline water formation.