Unraveling small-scale coastal processes in a shallow lake through GPU-Accelerated modelling

Shallow lakes in semi-arid environments are highly dynamic systems where wind forcing drives circulation, sediment redistribution, and shoreline reshaping. However, resolving the fine-scale morphodynamic processes governing the lacustrine systems over annual time scales remains computationally challenging. In this study, we perform a full-year (2025) morphodynamic simulation of Gallocanta Lake (NE Spain) forced by semi-hourly wind records. The model couples the two-dimensional (2D) shallow-water equations with a sediment transport formulation, allowing the simultaneous evolution of the free surface and lakebed morphology. To assess the impact of spatial resolution, simulations are conducted using multiple grid sizes ranging from coarse representations of the basin to high-resolution meshes capable of resolving geomorphological features generated in the lake shoreline at a detailed scale features of the littoral zone. The computational demands of year-long simulations at fine resolution are addressed through Graphics Processing Unit (GPU) acceleration. Results reveal a strong resolution dependency in both hydrodynamic and morphodynamic patterns. While coarse grids reproduce large-scale circulation structures and general trends in sediment redistribution, high-resolution simulations capture localised circulation cells, shear-stress hotspots, and short littoral sedimentary structures that remain unresolved at lower resolutions.