Geophysical and hydrogeochemical assessments of groundwater quality conditions for domestic and irrigation purposes

A sustainable supply of freshwater for human, environment and economic development is a pressing global challenge. Groundwater resource in the Niger Delta region of southern Nigeria is under increasing pressure arising from population growth and increasing economic activities. This study therefore aims at assessing groundwater quality for domestic and irrigation purposes in parts of the Niger Delta region using an integrated approach, which combines geophysical and hydrogeochemical techniques. Integration of vertical electrical sounding (VES) data with groundwater samples from local boreholes in the area, supplemented with borehole lithologic data, yields a multi-scale dataset that is not common in previous studies in the region. The subsurface is shown to consist of three to four poorly sorted sandy strata with slight clay intercalations. The aquifer layer occurs at depths of 0.9 to 44.1 m and exhibits significant heterogeneity. Aquifer vulnerability to contamination varies from low to moderate while aquifer protective capacity is mostly poor. Domestic water quality is also mostly poor, suggesting the need of treatment before usage. Irrigation suitability varies from very poor to excellent and NaCl water type predominates, reflecting both natural geochemical processes and anthropogenic influences. These outcomes provide important insights into the current groundwater conditions in the area, and the reported methodology and dataset combination reported here provide a novel perspective to groundwater quality studies in the region. The generated aquifer vulnerability, protective capacity and groundwater quality categorizations maps offer a practical tool for policymakers and water managers to prioritize interventions in the area. The classification of irrigation suitability assists farmers to select crops that are compatible with the local water conditions and provides guidance for agricultural planning in the area. The integrated approach can be employed in regions of similar geology for the formulation of efficient and sustainable groundwater management and utilization schemes.