Resistivity Methods in Hydro-Geophysical Investigation for Groundwater in Aghalokpe, Western Niger Delta

Abstract

A combined surface and subsurface resistivity investigation was conducted in Aghalokpe with a view to providing adequate information about the subsurface layers, groundwater potential and quality of the area. Twelve (12) Schlumberger depth soundings and one (1) single-point resistance logging were carried out in the study area. Four subsurface layers were delineated from the investigation. The first layer is the top soil and has resistivity values ranging from 92-1009.1 ohm-m and thickness between 0.8-1.6m. The second layer composed of clay and sand has resistivity values varying from 61.9-1571.2 ohm-m and thickness ranging from 1.3-16.1m. The third and fourth geoelectric layers with resistivity values ranging from 414.8-4091.1 ohm-m diagnostic of fine and medium to coarse grained sands constitute the aquifer unit and occur at an average depth of 10.8m and extend beyond 63.8m. The result of the water quality based on total dissolved solids computed from the single-point resistance log showed that the groundwater in the upper part of the aquifer may not be potable because of TDS concentration above the lower limits of general acceptability of 500 ppm. But at the depth of 18-50m, the quality of the groundwater seems to be potable.

KEY WORDS: Potable Water, Geoelectric, Resistivity, Formation Factor, Electrical Conductivity