Spatial assessment of surface water vulnerability through MCDM and open-source data

Given the crisis of surface and groundwater shortages, coupled with the impact of human activities on the quality of surface water resources in watersheds, many rivers have suffered significant damage in recent decades. This issue underscores the importance of managing both water quality and quantity to achieve sustainable development. Assessing the risk of water pollution and zoning vulnerable areas can provide valuable information for controlling and reducing pollution. In this study, the Babolroud watershed was divided into five sub-basins to assess its vulnerability. Influential pollution factors were identified, and the necessary data were obtained from open-source resources. Thematic maps for each factor were prepared, and the factors were scored and weighted using expert opinions through a combination of the Analytic Hierarchy Process and Weighted Linear Combination methods. To examine the interrelationships between factors and identify the most prominent ones, the Decision-Making Trial and Evaluation Laboratory analysis was employed. The resultant vulnerability map shows that sub-basins A1 and A2 have high vulnerability. Decision-Making Trial and Evaluation Laboratory model results show that industrial activities have the highest priority and are considered the key factor. Based on the decision-making model presented in this study, the derived policies focus on preventing the establishment of industrial centers and the expansion of agriculture in high-risk areas, as well as mandating industries to install wastewater treatment systems.