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.

Key words: groundwater elevation, geophysical techniques, magnetic field, sounding inversion software, resistivty