Water and energy transfer modeling in a permafrost-dominated, forested catchment of Central Siberia: The key role of rooting depth

To quantify the impact of evapotranspiration phenomena on active layer dynamics in a permafrost-dominated forested watershed in Central Siberia, we performed a numerical cryohydrological study of water and energy transfer using a new open source cryohydrogeology simulator, with two innovative features: spatially distributed, mechanistic handling of evapotranspiration and inclusion of a numerical tool in a high- performance computing toolbox for numerical simulation of fluid dynamics, OpenFOAM. In this region, the heterogeneity of solar exposure leads to strong contrasts in vegetation cover, which constitutes the main source of variability in hydrological conditions at the landscape scale. The uncalibrated numerical results reproduce reasonably well the measured soil temperature profiles and the dynamics of infiltrated waters revealed by previous biogeochemical studies. The impacts of thermo-hydrological processes on water fluxes from the soils to the stream are discussed through a comparison between numerical results and field data. The impact of evapotranspiration on water fluxes is studied numerically, and highlights a strong sensitivity to variability in rooting depth and corresponding evapotranspiration at slopes of different aspect in the catchment.