Evaluation of soil layer discretization in HYPE to analyse water balance components for Nelson Churchill River Basin under changing climate

Abstract:

Hydrological models are essential tools to analyse the cold region's processes, such as permafrost, seasonally frozen soil, and snow cover, which are widely distributed across Canada. Frozen soil and permafrost processes play key roles in runoff generation by restricting the infiltration during the frozen state, and thawing during the melting phase. Therefore, the representation of these processes in hydrologic models is critical for model projections under climate change, and hence for reducing the uncertainty associated with the freshwater runoff. In this research, the frozen soil infiltration is incorporated in the HYPE model, and the output variables such as soil temperature and soil moisture are validated with field observations across the Nelson Churchill River Basin (NCRB). Further improvement in the model is integrated by discretizing the conventional 3-soil layer scheme of HYPE to finer soil layer discretization up to 5 sub-layers for each soil layer. This allows the model to execute soil-water balance calculations at each discretized soil layer, for better simulation of such components and runoff generation. The modified HYPE-NCRB model will be used to project climate change impacts on soil moisture, soil temperature, and implications on model uncertainty associated with the projection of streamflow. A suite of 14 GCMs and 2 RCP (RCP 4.5 and RCP 8.5) scenarios representing 87% of the variability of 154 climate scenarios will be used for this purpose. The study could be beneficial to access the impact of climate change and degrading permafrost on infrastructures and ecosystems of this region.