Hydrological response of catchments to declining snow and ice storage

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The ongoing and projected climate change will progressively reduce the seasonal (snow) and semi-permanent (glaciers, permafrost) storage of frozen water in mountain and other cold climate catchments. These cryospheric changes could drastically modify the nivo-glacial river regime of these catchments, redefining new risk levels (drought, floods) as well as freshwater-derived ecosystems services (e.g. agriculture culture irrigation, hydroelectricity production). This 5-year research program aims to study the impact of climate variability on the cryosphere and related meltwater contribution to catchment hydrology using a combined observational-modelling approach. The program will pursue three objectives: (1) to estimate climate change impacts on meltwater fluxes from glacierized mountain catchments; (2) to test the ability of snow models to simulate spatio-temporal snow dynamic; (3) to assess the ability of simple hydrological models to predict complex hydrological systems in future climates. Two experimental catchments with different topography, climate and cryospheric storage will be studied for this purpose: the Rapel River in Chile (Mediterranean climate, partly glacierized) and the Matawin River in Canada (snow dominated, continental-humid climate). Our proposed methodological approach will (1) use glacio-hydrological models as a learning tool to better constrain the dominant processes in the catchment, and (2) quantify the climate sensitivity of these processes in order to provide a physical understanding of potential future changes. Results from sensitivity analyses can be easily communicated to water managers and applied to the continuously refining climate projections. A distributed SNow Observing System (SNOS) will be deployed in one catchment (Matawin) to study the spatio-temporal variability of snow accumulation and meltwater runoff generation, and to provide an observational basis for model testing. Are simple hydrological models able to extrapolate beyond the present climate conditions? This ongoing problem in hydrology will be addressed by challenging common conceptual hydrological models to reproduce synthetic river discharge data generated by a 'virtual catchment' with different boundary conditions (climate, topography). A spatially-distributed, physically-based hydrological model will be used as a virtual catchment platform. We expect the results generated by this research program to bring both practical valuable information for water managers seeking adaptive strategies as well as theoretical advances in the field of snow and ice hydrology (ability of models to simulate present and future snow and ice hydrology).