Aquifer potentials and vulnerability studies in Northern parts of Anambra State, SE Nigeria

Abstract

Geophysical and geologic feld mapping data were used to model and estimate groundwater potentials and aquifer vulner ability in parts of Awka North Local Government Area of Anambra State, SE Nigeria. The Vertical Electrical Sounding VES technique of the Resistivity Method was employed to acquire feld data used to estimate aquifer potentials, while the Aquifer Vulnerability Index AVI method was used to model and characterize aquifer vulnerability. Results from the interpretations of the VES data showed that the area is underlain by Topsoil, sandstone, clayey sandstone, and shale lithologies at various horizons and depths. The target aquifers are water-saturated sandstone units. The average depth to the aquifer (and overburden thickness) in the study area is 50.8 m. Depth to the aquifer increases southwards suggesting deeper aquiferous units towards the southern parts of the study area. Average aquifer thickness and transmissivity are 14.81 m and 396.85 m2/day, respectively, and their values also increase towards the south. Aquifer potential classifcation based on aquifer transmissivity suggests moderate-high aquifer potentials in the study area. Estimated Aquifer Protective Capacity APC and Aquifer Vulnerability models gave moderate–good APC and moderate-high vulnerability, respectively. These models, which are a consequence of the overburden thickness and lithologies, have implications for groundwater quality and aquifer quality conservation. Groundwater conservation and exploitation are important elements in the sustainable development of groundwater resources in the study area. The results of the groundwater potentials, APC, and aquifer vulnerability analysis, therefore, suggest that groundwater exploitation schemes should target the southern parts of the study area where these parameters of interest are more favorable. Also, proper waste disposal management schemes designed with regard to the underlying geology/hydro geology should be put in place in the study area since the aquifer is vulnerable to pollution.