ASSESSMENT OF PARTS OF UGBOMORO FOR AQUIFER DEPTH USING VERTICAL ELECTRICAL SOUNDING (VES)

ABSTRACT The study investigates the geological and hydrogeological characteristics of the sedimentary terrain in the Anambra Basin, Southern Nigeria, focusing on Campanian-Maastrichtian sediments. The terrain is predominantly composed of sandstone, shale, and siltstone, correlated with the Mamu Formation and Ajali Sandstone Formation. These units are influenced by historical transgressions and regressions, affecting sedimentary facies and depositional environments. Geophysical prospecting conducted at eighteen locations identified two distinct.aquifer systems: a shallow perched aquifer at depths of 40-80 meters and a deep aquifer extending from 120 meters downward. The shallow aquifer is predominantly confined, while the deep aquifer is mostly unconfined. An interlayer of shale and sandstone with clay/mud intercalations was analyzed for geoelectric interpretation. The study highlights the absence of a regionally extended aquiferous zone or water table, suggesting the need for site-specific geophysical borehole logging before installation of screens and casing. For reliable groundwater extraction, direct rotary drilling to an average depth of 180 meters is recommended, with an emphasis on considering regional flow direction and employing an integrated geophysical approach to detect highly consolidated or intrusive bodies, particularly at specific VES points. These findings provide valuable insights for groundwater development in the region and underscore the importance of tailored geophysical assessments in aquifer management and exploration.