Local Scale Groundwater Vulnerability Assessment with an Improved DRASTIC Model

The rapid increase in demand and consumption of groundwater in the past few decades has imposed colossal pressure on the stakeholders responsible for groundwater management. Assessment of groundwater vulnerability and knowledge about hydrogeological settings are crucial for a particular region, especially at a local scale, to manage groundwater resources effectively. The present study aimed to develop a modified DRASTIC model to demarcate groundwater vulnerability zones based on experimental analysis of field samples to make the model more feasible at local scale. Four techniques were implemented in this study to determine groundwater vulnerability zones: (a) DRASTIC; (b) DRASTIC–AHP (analytic hierarchy process); (c) Modified DRASTIC; (d) Modified DRASTIC–AHP. The best groundwater vulnerability model was determined based on validation results with groundwater nitrate concentration. The comparative assessment showed that the Modified DRASTIC–AHP outperformed the other models. More than 50% of the study area was classified as ‘high’ (33.06%) and ‘very high’ (21.31%) groundwater vulnerability zones. The vulnerability map shows that high vulnerable zones dominate in the northwestern part and in some portions of the floodplain near central part of the study area. The results of this study envision that inclusion of experimentally derived parameters can be used to modify the conventional DRASTIC model and obtain better results at local scale.