Integration of a cellular automata to simulate snow cover with the Snowmelt Runoff Model to assess impacts of climate change on streamflow in a Mediterranean snow-dominated catchment

Mountain snowpacks are key components of surface water resources as snowmelt significantly contributes to streamflow and serves as essential indicators of climate change and variability. Accurate estimation of snowmelt-induced streamflow and assessment of its potential response to climate change are therefore essential for effective water resources planning and management. This study presents a new coupled modeling framework that integrates a cellular automata model (CAM) to simulate snow cover area (SCA) with the Snowmelt Runoff Model (SRM) to simulate daily streamflow. The model was applied to assess the impacts of climate change and associated uncertainty on SCA and streamflow in a Mediterranean mountainous catchment. Four local climate scenarios were developed from an ensemble of nine downscaled Regional Climate Models (RCMs), assuming two warming levels for Spain (1.5 ºC and 3.0 ºC). The CAM–SRM framework was calibrated and validated using precipitation and temperature data from the AEMET 5 km gridded product for the period 2000–2020. Under future climate conditions, the model projects a substantial decrease in SCA and a two-month shorter snow season in warmer scenarios. An earlier onset of peak flows is also expected, along with a projected decline in mean annual streamflow of 19.4 – 32.9 %. These results indicate significant changes in the hydrological regime driven by climate change. The proposed modeling framework proves effective for reproducing snowmelt-driven streamflow dynamics in snow-dominated catchments and offers valuable insights for future water resources planning and management in mountainous regions.