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ABSTRACT: a natural and instantaneous geophysical method for groundwater investigation in volcanic formations of Kibumba area has been developed. A geophysical evaluation using Electrical Resistivity method for groundwater investigation was carried out which involved the utilization of Vertical Electrical Sounding (VES) technique with Schlumberger array system. The study area is located within the igneous rocks, sedimentary, and metamorphic. The data acquired from twelve (12) VES stations using ABEM terrameter (SAS 1000) was tabulated in a table which shows the resistivity, the thicknesses and the number of layers for each VES station. The data was analysed using computer inversion software called INTERPEX1D, which yield an automatic interpretation of the apparent resistivity. The VES results revealed heterogeneous nature of the subsurface geological sequence. The geological profile sequence in the study area includes the topsoil (clay and fragments rocks and/or boulders formations of basalt), weathered layer (and/or fractured basalt) and fresh basement. The value for topsoil ranges from 10 Qm to 1500 Qm with thickness varies from 0.3 m to 10 m. The weathered layer (and/or fractured basalt) resistivity ranges from 100 Qm to 2000 Qm and thickness of 3 m to 20 m. The fresh basalt or bedrock basement ranges in value from 30 Qm to 3000 Qm with an unknown thickness due to the volcanic formation in the study area. However, the bedrock depth of all the VES stations from the earth's surface could range from 1 m to 34 m. Based on the result of VES data, the proper area for making boreholes would be VES Kibumba 2, VES Kibumba 5 and VES Kibumba 9.
KEYWORDS: Vertical Electrical Sounding (VES), Groundwater potential aquifers, topsoil, weathered layer, fractured basalt layer, fresh basalt.
1Introduction
Groundwater exploration is becoming increasingly important for D.R.Congo due to an ever-increasing demand for water; especially in areas like Kibumba with absent or inadequate surface water supplies. Already, ten percent of the world's population is affected by chronic water scarcity and this is likely to rise to one-third by about 2025 (WHO, 1996).
The problem of gaining...