Modelering van saliniteit in het Schelde-estuarium onder huidige en toekomstige klimaatcondities

Estuarine salinity dynamics are critically linked to freshwater availability, ecosystem stability, and socio-economic resilience in coastal regions. Saltwater intrusion (SWI) — the landward encroachment of saline water into rivers and aquifers — poses escalating risks under climate change, threatening drinking water supplies, agricultural productivity, and industrial operations globally. Low-lying estuaries like the Scheldt River in Northwestern Europe are particularly vulnerable due to their exposure to sea level rise (SLR), intensified droughts, and tidal amplification. The Scheldt Estuary, a vital waterway supporting densely populated regions in Belgium and the Netherlands, has experienced worsening SWI in recent decades. Compounding these challenges, climate projections indicate SLR and freshwater discharge (Q) reduction in summer for the Scheldt Basin, which could permanently alter salinity regimes and amplify SWI's socio-environmental impacts. This PhD dissertation addresses these gaps by rigorously evaluating three modeling paradigms, including data-driven, physically-based, and conceptual approaches, for SWI simulation in the Scheldt Estuary, while developing integrative frameworks to enhance predictive accuracy and decision relevance. The study is motivated by four urgent questions: (1) How do existing models perform in replicating observed salinity dynamics under baseline and extreme conditions? (2) How will climate-driven perturbations alter SWI's longitudinal extent and temporal variability? (3) Can hybrid ensembles mitigate individual model weaknesses to improve reliability during climate change? (4) How can modeling strategies be optimized for stakeholder-specific needs, from real-time forecasting to long-term planning?