Integrating a Global Glacier Model into Local Hydrological Modelling: Impacts on Future Water Availability

The cryosphere in mountain areas serves as a critical water resource, supplying melt water to downstream communities in spring as well as summer months for irrigation and human consumption. Effects of climate warming on the cryosphere and therefore melt water availability are expected to be substantial for many mountain ranges worldwide. An accurate representation of glacier processes is thus crucial to predict future water availability in catchments that are currently at least partially glacier-covered. Hydrological models often focus on meltwater-streamflow transformation processes occurring in non-glacierized areas with sometimes an overly simplified representation of glacier dynamics and melt. This can lead to uncertainties in streamflow predictions, especially in highly glacierized catchments and for longer time horizons. Coupling a glacier model with a hydrological model can address some of these uncertainties by a more accurate representation of glacier-related processes including ice melt and changes in glacier extent, which are essential to quantify streamflow changes under a transient climate. This study couples the global glacier model GloGEM with the semi-distributed hydrological modelling framework Raven to enhance the representation of these glacier dynamics. The implemented one-way coupling (from the glacier model to the streamflow model) aims to reduce uncertainties and improve predictions of streamflow and water availability under transient climate conditions. The relevance of using a global-scale glacier model for local-scale hydrological modelling is evaluated in 15 glaciated catchments in Switzerland. Initial results indicate that the coupled model enhances streamflow predictions and provides a more accurate representation of glacier melt contributions to streamflow. These improvements influence model parameters, particularly snow-related ones, which previously compensated for deficiencies in the modelled glacier melt, thereby leading to changes in snowmelt contributions to streamflow. This study assesses how these shifts in glacier and snowmelt contributions under future climate scenarios impact water availability.