Supplementary information files for "High-performance modelling of urban non-point-source pollutant dynamics: a full-process approach"

Supplementary files for article "High-performance modelling of urban non-point-source pollutant dynamics: a full-process approach"Non-point-source pollutants (NPSPs) are a major cause of urban water quality degradation. Effective management requires an understanding of pollutant dynamics across spatial scales. Existing storm water quality models are often based on empirical or hydrological approaches, which have limited capacity to represent flow-pollutant interactions and particle-facilitated dynamics in complex urban environments. Physically based models provide a more realistic description, but their applications are constrained by high computational costs and detailed data requirements. This study presents a high-performance, GPU-accelerated hydrodynamic-particle-based water quality model to simulate the full dynamics of wash-off, deposition, and transport of urban particulate-based NPSPs at high spatial resolution. The initial pollutant mass and particle size distribution (PSD) fields were derived from a physics-informed Random Forest build-up model trained on literature-reported data. The model was validated using two monitored events in a road catchment near Paris, achieving NSEs of 0.86 for runoff and 0.67 for pollutant fluxes. Sensitivity analyses revealed a strong dependence on the single particle mass (Pm), with simulation accuracy becoming stabilised beyond 50 particles per grid. Application to a real-world urban case study confirmed the framework's efficacy in reproducing flood inundation and NPSP propagation. The analysis further underscores that a resolution finer than 5 m is necessary for reliable simulations in complex urban settings. The particle-tracking capability enabled spatio-temporal pollutant source identification. This framework presents a valuable tool for scientists, policymakers, and environmental practitioners to advance urban water quality management.© The Author(s), CC BY 4.0