DETERMINATION OF POTENTIAL GROUNDWATER SITES USING GEOLOGICAL AND GEOPHYSICAL TECHNIQUES IN THE CROSS-RIVER STATE, SOUTHEASTERN NIGERIA

Radar images, aerial photographs, geoelectrical studies (vertical elec trical sounding, VES and horizontal resistivity profiling, HRP), geolo gical logs based on exploratory drilling and the local surfacial geolo gy have been employed for groundwater investigations in the Cross Rive r Sate, southeastern Nigeria. Results from the study show that areas w ith high lineament frequency and a thick regolith should be targeted f or groundwater investigation within the crystalline basement complex t errains, whereas in the sedimentary areas the target areas are determi ned by the lithology and stratigraphical sequence. Using the results o f this study there is an increase in the number of successful borehole s drilled in the area from 35% to 92%. It is also observed that remote ly sensed, geoelectric and exploratory drilling data are adequate for delineating the surface and near-subsurface hydrogeology of the area. (C) 1998 Elsevier Science Limited.