Integrating hydrodynamic modeling and multi-criteria analysis for process-based risk assessment of organic pollutants

This study develops a novel quantitative risk assessment framework to evaluate the environmental impact of Olive Mill Wastewater (OMW) pollution on surface water resources in the Keritis watershed, Western Crete. Unlike prior OMW assessments that relied on qualitative indicators or single-factor analysis, this research integrates Multi Criteria Analysis (MCA) with physically based hydrological modeling to enable quantitative, sub-catchment scale risk mapping. Risk is assessed through two core components: magnitude (encompassing spatial and temporal pollution dimensions) and probability (integrating hazard occurrence, receptor exposure, and harm likelihood). Eleven criteria, including population vulnerability, precipitation, pollutant dilution potential, and lagoon conditions, were normalized and weighted via the Analytic Hierarchy Process (AHP). The methodology classified sub-catchments into five risk tiers using natural breaks, revealing significant spatial variability. Key findings identified sub-catchments 4, 5, and 9 as high-to-moderate risk zones for human health, while sub-catchments 5 and 6 faced elevated risks for NATURA sites. The analysis underscores the critical role of flow path length and dilution capacity in mitigating risks. Specific evidence-based management strategies are proposed to support EU Water Framework Directive alignment, balancing ecological preservation with socio-economic needs in olive oil-dependent regions.