A dynamic DRASTIC-based approach for multi-hazard groundwater vulnerability mapping

This study advances the DRASTIC groundwater vulnerability assessment framework by integrating a multi-hazard groundwater index (MHGI) to account for the dynamic impacts of diverse anthropogenic activities and natural factors on both groundwater quality and quantity. Incorporating factors such as population growth, agricultural practices, and groundwater extraction enhances the framework's ability to capture multi-dimensional, spatiotemporal changes in groundwater vulnerability. Additional improvements include refined weighting and rating scales for thematic layers based on available observational data, and the inclusion of distributed recharge. We demonstrate the practical utility of this dynamic DRASTIC-based framework through its application to the agro-urban regions of the Irrigated Indus Basin, a major groundwater-dependent agricultural area in South Asia. Results indicate that between 2005 and 2020, 54% of the study area became highly vulnerable to pollution. The MHGI revealed a 13% decline in potential groundwater storage and a 25% increase in groundwater-stressed zones, driven primarily by population growth and intensive agriculture. Groundwater vulnerability based on both groundwater quality and quantity dimensions showed a 19% decline in areas of low to very low vulnerability and a 6% reduction in medium vulnerability zones by 2020. Sensitivity analyses indicated that groundwater vulnerability in the region is most influenced by groundwater recharge (42%) and renewable groundwater stress (38%). Validation with in-situ data yielded area under the curve values of 0.71 for groundwater quality vulnerability and 0.63 for MHGI. The framework provides valuable insights to guide sustainable groundwater management, safeguarding both environmental integrity and human well-being.