Safe and sustainable development of groundwater resources is a key element of the Millennium Development Goals (MDGs). Pursuant to this, surface geophysics involving the Vertical Electrical Sounding (VES) technique was deployed to determine subsurface rock types and their thicknesses with the aim of delineating depths to potable groundwater in parts of Udi – Ezeagu area of Southeastern Nigeria. The terrain rises from as low as 61.0 meters in Mgbagbu-Owa to 457.0 meters in Abia as a dome-shaped hill with highly indented ridges and gullies. Underlying the study area are three conformable geologic formations namely the Lower Maastrichtian Mamu Formation, loose and cross-bedded Upper Maastrichtian Ajali Sandstone and the Danian Nsukka Formation. Geoelectric data indicate multiple layer curves which were interpreted as successions of lateritic topsoil, clay, shale, siltstone and sandstone which is consistent with the known lithologies of the three identified geologic formations in the area. An isopach map of overburden thickness to saturated horizons shows that the target aquifer, commonly the saturated Ajali Sandstone can be sufficiently accessed at depths of 180.0 meters around communities central to the cuesta and gets shallower from the slopes towards the plains where it is almost 85.0 meters yielding a symmetric profile indicative of a probable recharge around the cuesta and a radial drainage at the foothills giving rise to the Ajali and Nyaba rivers in the southwest and southeast axes respectively. It is expected that the results of this study will impact positively on the quest for sustainable development of water resources and form baseline data for the mitigation and management of some of the geotechnically-induced environmental challenges in the area.
