VERTICAL ELECTRICAL RESISTIVITY SOUNDING FOR GROUNDWATER IN BISHINI AREA OF KADUNA STATE

Groundwater occurrence in Bishini area of Kaduna state was investigated using Electrical resistivity method for the purpose of sitting viable borehole. A total of twenty-seven (27) vertical electrical soundings (VES) using Schlumberger electrode array were acquired with a maximum electrode separation of AB/2=150 m, using the ABEM Terrameter SAS 300C. Interpreted sounding curves revealed predominant of Three to five electro-stratigraphic units were delineated in the study area, namely: the topsoil (indurated laterite), lateritic clay, weathered basement rock, fractured basement rock and fresh basement. The weathered and / fractured basement rocks constitute the aquiferous zones with the weathered layer aquifer (63%) predominant while the weathered/fractured (unconfined) aquifer (7.4%) was least represented. The first two layers have variable resistivity of between 76 and 22938Ω-m. Weathered basement with average resistivity and thickness values of 211.52Ω-m and 16.4m respectively was encountered in all the sounding locations with exception of VES 23 and VES 26. Weathered/fractured basement was encountered in six locations with resistivity and depth to the top of fracture basement ranging from 77 - 977Ω-m and 5 -14m respectively. The weathered layer (5 ? 37m overburden thickness) and weathered/fractured basement (20 ? 62m overburden thickness) found within basement depressions constitutes the main aquiferous units. The geo-electric sections in the N-S, NW- SE and NE-SW directions revealed VES 9, VES13, VES 19 and VES 21 as sounding locations that could be drilled. VES 21 that was fractured with resistivity of 977Ω-m and overburden thickness of 62m was considered most suitable for borehole drilling provided there is no drop in volume of water as drilling progresses