Assessment of Aquifer Vulnerability to Pollution in Selected Part of Oji River Town, Enugu State Using Drastic Model

Abstract

Aquifer vulnerability assessment could be defined as the degree of assimilation capacity of an area to contaminant from surrounding surface above the aquifer. In this study, intrinsic vulnerability of aquifer in selected part of Oji River was evaluated using DRASTIC model in framework of GIS environment. An additional objective is to use sensitivity analysis to evaluate the effect of each DRASTIC parameter on the final vulnerability map. The results show that the study area is characterized by three vulnerability zones: Very low vulnerability‟ (risk index <90), „Low vulnerability‟ (risk index 90 - 120) and „Moderate‟ (risk index 120 - 160). The area is dominantly of low vulnerability while very low and moderate vulnerability occur in patches. The DRASTIC index value indicates that the aquifer system in the study area is relatively protected from contamination on the groundwater surface, but no area was free from contamination risk because of continuous modification of the earth and urbanization. A protective measure must therefore be put in place before exploiting the aquifer and before comprehensive agricultural activities begin in the area to mitigate the contamination risks in the moderate vulnerability zones.