Die Evaluasie van geofisiese grondwatereksplorasie-tegnieke in die gebied rondom Witbank Mpumalanga

Abstract

A number of boreholes in different litostatigraphic units, which occur in a 50km. radius around Witbank, were studied by the use of applicable geophysical techniques. The boreholes were studied and characterised by means of the direct current resistivity technique, the magnetic technique, the frequency domain electromagnetic technique, slug tests and one pump test. The different geophysical techniques are evaluated against the parameters of effective characterising of the geo-electric layers in die substratum, estimating the yield of a borehole from a sounding curve, defining vertical structures, instrument sensitivity with regard to artificial noise and the influence of anisotropy on the obtained sounding curve. Ground water indicators, which can indicate potential borehole sites, are discussed. These include abnormalities visible on aerial photos, field irregularities and geobotany. The study has made recommendations concerning the desirability of using different geophysical techniques in a certain geological area and the essence of geophysical information on the estimation of borehole yield and/or borehole depth.