Abstract

Geophysical investigation in part of Tombia, Degema L.G.A of Rivers State has been successfully carried out. Electrical resistivity method using the Wenner electrode configuration was undertaken in order to explore for freshwater depth for borehole drilling and to evaluate areas within the subsurface where the saltwater intrudes into the freshwater zones. The resistivity values were taken along three survey lines with survey one and three having excellent aquifer properties. The aquifer depths for survey one are located at 40m (131.2ft), 80m (262.4ft), 140m (459.3ft) and 175m (574.1ft) with resistivity values of 376.4 Ωm, 521.9 Ωm, 528.4 Ωm and 460.9 Ωm respectively; the aquifer depth for survey two is located at depth 50 – 60m (164ft – 196.8ft) with resistivity value of 404.1 Ωm; while the aquifer depths for survey three are located at depth 80 – 100m (262.4ft-328ft) and 160m (524.8ft), with resistivity values of 498.6 Ωm and 410.5 Ωm respectively. The aquifers from the 2D contour maps have shown high resistivity properties which indicate the presence of freshwater in the soil layers. The zone in the 2D contour map where the fresh water intrudes that salt water occur at survey line two at depth 20m to 40m and depth 82m to 95m.

Key words: Geophysical investigation, Electrical resistivity method, Survey, Aquifer, 2D contour map