Geoelectric sounding for the determination of groundwater conditions around Iwaya area of Lagos, Nigeria

Abstract

High apparent resistivity contrasts between the saturated freshwater zones and apparent low resistivity of the saturated seawater intrusion were measured on eleven vertical electrical soundings field curves using the Schlumberger electrode array in Iwaya area of Lagos. The field measurements were inverted to subsurface layers.

The results of the interpretation revealed four to five geoelectric layers. Resistivity maps were constructed at depths of 6m, 10m, 15m and 40m. Resistivities of between 4 and 20Wm indicated areas of seawater intrusion with average depth range of 6m. Trough like pattern of the resistivity map at 6m depth indicate the shape of the seawater plume. Resistivities higher than 100Wm indicate areas of freshwater zone at an average depth of 10m.