Modeling assessment of groundwater vulnerability to contamination risk in a typical basement terrain case of vulnerability techniques application comparison study

Groundwater vulnerability to contamination risk is increasing daily due to human activities in the environment and increasing load on these precious resources. The groundwater underlying the Akure metropolis in southwestern Nigeria was assessed by the development of the DRASTICLYS model. The assessment results of the groundwater vulnerability were compared to the results of the conventional DRASTIC model generated. The analytical hierarchy process was employed to determine the weights of the model to adapt the model to the study area which can make the approach applicable in other areas. The DRASYICLYS model result showed moderate to high contamination risk in the central and eastern portions of the study area, while the DRASTIC model result showed moderate to high contamination in the eastern flank of the study area. The developed DRASTICLYS model is a modification of the conventional DRASTIC model in which three new parameters were imputed into the DRASTIC model namely lineament density, borehole yield and longitudinal conductance. The results were validated by conducting water chemistry analysis and statistical analysis on the groundwater. The efficiency of the developed DRASTICLYS model against the conventional DRASTIC model using water chemistry data was shown to be 95% and 90%, respectively. The statistical analysis using standard deviation carried out on the water sample superimposed on the developed DRASTICLYS and conventional DRASTIC models showed a correlation of 78% and 74%, respectively. The result shows that the DRASTICLYS model has better accuracy than the DRASTIC model. The analyzed results were able to zone the study area to groundwater vulnerable potential zones. The developed models will serve as a guide for planners and policymakers in the area for groundwater resources management and protecting the aquifer from pollutants.