Assessing groundwater vulnerability in Karnataka using the DRASTIC model and GIS-based spatial analysis

Abstract Groundwater is a critical resource for domestic, agricultural, and industrial needs across Karnataka, India, yet rising extraction pressures, land use change, and emerging contamination risks highlight the need for region specific vulnerability assessment. This study applies the DRASTIC model within a Geographic Information System to evaluate groundwater vulnerability based on seven hydrogeological parameters: depth to water table, net recharge, aquifer media, soil media, topography, vadose zone impact, and hydraulic conductivity. High resolution spatial datasets were processed to generate parameter layers, which were weighted and combined to produce the DRASTIC vulnerability index. The index ranges from approximately seventy to one hundred ninety across the state, with high vulnerability zones concentrated in the northern and central districts, including Vijayapura, Kalaburagi, and Belagavi, while lower vulnerability occurs in the southern and western regions. Approximately 11.00% of Karnataka falls in the high vulnerability category, 86.44% in the moderate category, and 2.56% in the low category. Sensitivity analysis using Map Removal Sensitivity Analysis shows that depth to water, net recharge, and vadose zone properties exert the strongest influence on the vulnerability outcome. The findings underscore the value of GIS based DRASTIC assessment for guiding groundwater protection, prioritizing monitoring, and supporting sustainable land and water management across Karnataka.