An integrated approach to groundwater potential-vulnerability mapping using AHP and DRASTIC

Groundwater in semi-arid regions is increasingly stressed by intensive abstraction and contamination, while aquifer productivity and intrinsic vulnerability are commonly evaluated separately. This study investigates whether structured integration of groundwater potential and intrinsic vulnerability can provide a more reliable basis for sustainable groundwater management in the Halabja-Khwrmal area, northeast Iraq. Groundwater potential was delineated using the Analytical Hierarchy Process (AHP) applied to seven hydrogeological and environmental factors, whereas intrinsic vulnerability was assessed using the standard DRASTIC model. Both indices were independently validated prior to integration. Receiver Operating Characteristic (ROC) analysis based on 430 well discharge records yielded an Area Under the Curve (AUC) of 0.751, indicating acceptable discrimination of productive zones. Regression between DRASTIC index values and measured nitrate concentrations showed a strong positive relationship (R² = 0.797), supporting vulnerability reliability. Cross-classification of the validated ordinal groundwater potential and vulnerability indices generated nine Potential-Vulnerability zones, where highly productive areas largely coincide with low intrinsic vulnerability. High groundwater potential occupies 49.24% of the basin, while high intrinsic vulnerability covers 20.65%, with limited spatial overlap between highly productive and highly vulnerable conditions. The class-preserving integration prevents compensatory masking between productivity and susceptibility and provides a transparent spatial framework for regulated abstraction and priority protection. The proposed Potential-Vulnerability framework offers a transferable spatial basis for groundwater management in hydrogeologically variable semi-arid aquifer systems.