<p>Groundwater is a vital resource for providing fresh water to various sectors, including domestic use, agriculture, and industry. In urban environments, particularly megacities, the quality and quantity of groundwater are critical issues exacerbated by rapid population growth and urban sprawl. This is notably evident in Kolkata, India, where approximately 52% of the population relies on groundwater on a daily basis. This study utilizes an adapted DRASTIC model to evaluate groundwater vulnerability in Kolkata, integrating LULC, PD, and LR factors to enhance the standard assessment framework. This modification enables a more comprehensive understanding of local environmental conditions, which in turn influence the vulnerability of groundwater resources. To minimize human subjectivity in the assessment process, the AHP assigns weights to the eight parameters considered in the model. This approach ensures a more objective evaluation of groundwater vulnerability. The study also correlates the resulting groundwater vulnerability index with groundwater quality indicators, particularly nitrate, fluoride, and pH levels, to validate the effectiveness of the modified model. The correlation between DRASTIC scores and measured indicators concentration is significantly improved after incorporating the modified models, indicating a stronger relationship between LULC changes and groundwater quality. The findings reveal contamination in the groundwater aquifer, primarily driven by alterations in land use and shallow groundwater depths. Given the reliability of the modified DRASTIC AHP model, this research recommends its use for initial groundwater vulnerability assessments by stakeholders and policymakers, providing a valuable tool for informed decision-making in managing urban water resources.</p>