Nivo-glaciological changes in Alpine catchments: impacts on hydrological regimes and aquatic ecosystems

The rapid evolution of glaciers and snow cover in mountain areas reflects the impacts of climate change on these regions. The decrease of the water stock in solid form induces irreversible changes on the hydrological regimes of alpine rivers and affects their ecological functioning. In addition, there are numerous anthropogenic pressures, mainly due to the use of water in mountain areas (artificial snow, water supply, agriculture, hydropower production, tourism). To better understand the consequences of glacial retreat and snow cover changes on water resources and help decision makers, we have set up a modeling chain composed of a dynamic glacier module, based on the ALPGM glaciological model (Bolibar et al., 2020), as well as the J2000 semi-distributed hydrological model (Branger et al., 2016) running at daily time step. In the present contribution, this modelling chain is applied to 3 catchments of the French Northern Alps characterized by contrasting ranges of altitudes and glacier cover. The evolution of hydrological regimes over the last sixty years is first examined using meteorological reanalysis products adapted to the Alpine regions (SPAMZ; Gottardi, 2009 and S2M; Vernay et al., 2021). Then, we envisage hydrological projections until 2100 from regionalized climate projections (Verfaillie et al., 2017) according different greenhouse gas emission scenarios. We also study of the evolution of evapotranspiration as a function of altitude to characterize its impact on the catchment’s water balance. The ALPGM-J2000 modelling chain allows us to discriminate the contributions of different inputs to the riverflow (glacial melt, snow melt, precipitation runoff), highlighting the shift in time of the parts of the catchment under glacial or more nival influence. We illustrate the use of this modelling chain through the production of indicators to characterize the impacts of glacier melt on aquatic ecosystems at different temporal scales, with particular emphasis on the relationship between changes in hydrological conditions and changes in aquatic invertebrate habitat.

References : https://cloud.univ-grenoble-alpes.fr/index.php/s/Gz9iLzd9ZRtrTjt