Linking Model Parameter Sensitivities With Hydrological Process Behavior Along Elevation Gradients in Alpine Terrain

Abstract Analyzing process interactions in hydrological systems typically requires catchment‐scale hydrological models, where greater model complexity enhances the representation of physical process behavior but also poses challenges related to parameter equifinality. To investigate process interactions in a snow dominated alpine headwater catchment, we have analyzed spatial and temporal parameter sensitivities of the fully distributed, physically based Water Balance Simulation Model WaSiM. We focused on the role of model structural parameters and the interaction between a variety of processes including evapotranspiration (ET), snowmelt, and soil moisture on sub‐daily (1 hr) as well as seasonal scales. Utilizing process specific performance metrics, we evaluated parameter equifinality, process affiliation and ‐interaction. Parameters of the pre‐known dominant processes (snow and energy‐balance) show the highest sensitivities across processes, but their magnitude varies across scales, seasons and elevations. Parameters of less dominant processes (ET, soil water dynamics) showed generally lower sensitivities and higher temporal and spatial variations. However, the results show a pronounced shift in parameter dominance on ET during dry‐down events. While under moist conditions, energy and temperature related parameters are dominant, structural soil parameters gain importance as dry‐day sequences lengthen. Similar patterns emerge along elevation gradients at the seasonal scale, where soil parameters gain importance in high elevation areas that frequently dry out. The analysis of parameter sensitivities thus allows the spatial and temporal investigation and validation of interactions between catchment processes with limited influence on the overall water balance and is therefore an important step in the development of future‐proof models.