Uncontrolled urbanization and industrial growth are increasing the vulnerability of groundwater to pollution. Vulnerability assessment has become a key element for the areas which are more susceptible to anthropogenic pollution. This study focuses on evaluating the vulnerability of the Rachna Doab aquifer to pollution through the comparison of five GIS based models i.e., DRASTIC, Pesticide DRASTIC, Modified DRASTIC, Modified Pesticide DRASTIC, and DRASTICA. Models were calibrated using measured values of electrical conductivity (EC), total dissolved solids (TDS), and nitrate concentration. The DRASTICA model exhibited the highest coefficient of determination ( \({R}^{2}\) ) values of 0.72 and 0.75 for nitrate concentration and EC, respectively. Among the pesticide-based models, the Modified Pesticide DRASTIC model demonstrated high ( \({R}^{2}\) ) values of 0.64 and 0.67 for EC and TDS, respectively. Map removal sensitivity analysis indicated that parameters such as hydraulic conductivity, impact of vadose zone and aquifer media have less significance in the DRASTICA model. The study also incorporated an improved weight-based approach by using single parameter sensitivity analyses to enhance the correlations between water quality parameters and the DRASTICA index, which improved to 0.76 for nitrate concentration and 0.80 for EC. DRASTICA identified high and very highly vulnerable zones, covering 46.6% and 12.3% of total area, respectively. The Modified Pesticide DRASTIC model identified 75.5% of the area as falling within the high to very high vulnerability zones. The identified vulnerable zones should be prioritized in future groundwater pollution control and preservation efforts to safeguard water resources in the Rachna Doab region.
