APPLICATION OF GEOPHYSICS FOR GROUNDWATER EVALUATION IN HARDROCK: CASE STUDY: KITUI FAULT ZONE

Abstract

The lack of access to potable water in Kitui has resulted to severe droughts causing poverty, famine and high infant mortality rates, which has risen to 9.8% and life expectancy is declining steadily. The fact that the basement system is hard Precambrian rock, ground water tends to be more localized and thus sustainable wells cannot be dug on a trial and error basis. The aim of this project was to evaluate groundwater potential located in the concealed fractured /faulted zones which act as groundwater storage and conduits, using magnetic and geoelectrical geophysical techniques. A terrameter was used to collect resitivity data and subsequently determine the subsurface layer resistivity anomalies using Wenner profiling and resistivity sounding inversion software, IP2WIN. Proton precession magnetometer was used to measure the total magnetic field intensity of the earth and 2D Euler deconvolution software was used to model the disintegrated basement. Magnetic surveys showed distinct magnetic anomalies signifying sudden disruption of the basement rock which occur due to faulting. Resistivity surveys also showed low resistivity anomaly at points of significant magnetic anomaly. This suggests groundwater potential in the inferred fault.