Integrated Geophysical and Hydrogeological Assessment of Groundwater Potential in Selected Urban Towns of Anambra State, Nigeria

Abstract

Groundwater remains the primary source of potable water in many urban centres of southeastern Nigeria, yet its potential, quality, and sustainability are often poorly understood. This study aimed to evaluate the groundwater potential and aquifer characteristics of selected urban towns. Groundwater remains the primary source of potable water in many urban centres of southeastern Nigeria, yet its potential, quality, and sustainability are often poorly understood. This study aimed to evaluate the groundwater potential and aquifer characteristics of selected urban towns such as Oba, Ojoto, Alor, Oraukwu, Nnobi, Awka-Etiti, and Nnewi in Anambra State, Nigeria, to support sustainable water resource management. Specific objectives were to delineate aquifer zones, determine hydraulic properties, and assess groundwater potential and variability using integrated geophysical and hydrogeological methods. Forty - nine Vertical Electrical Sounding (VES) stations were investigated using the Schlumberger array, complemented with 22 archived datasets from Rural Water Supply and Sanitation Agency (RUWASSA), Anambra State. Inversion modelling using Interpex IX1D and IPI2Win software generated layered resistivity models that defined subsurface lithologies and aquifer geometry. Thirty-five pumping test datasets were analysed to estimate the transmissivity (T) and hydraulic conductivity (K). Results showed the hydrological setting of the study area is a deltaic–fluvial–alluvial system, reflecting a transition from marine deposits at depth to continental alluvial sediments upwards. This depositional evolution has resulted in a multi- layered aquifer system composed of sandy and sandstone formations interbedded with clayey units. The aquifer types ranged from unconfined to confined in the area. Hydraulic conductivity ranged from 0.013 to 40.54 m/day, and transmissivity from 0.73 to 2,716 m²/day, indicating significant spatial variability. Three groundwater potential zones were delineated: shallow, pollution-prone aquifers at 80 – 150 m elevation; productive, middle aquifers at 150 – 220 m; and deep, confined aquifers above 220 m with excellent water quality. The study concludes that integrated VES and pumping test methods provide a reliable, cost-effective framework for urban groundwater evaluation. It recommends prioritising high-transmissivity zones for water supply, enforcing aquifer protection in vulnerable areas, and establishing long-term groundwater monitoring and management frameworks for sustainable utilisation.