Jardine, T., Carriere, G., Strickert, G., McKay, K., Mohammadiazar, A., Carriere, R., Lindenschmidt, K., Sabokruhie, P., Brinkmann, M., Gutwin, C., Carriere, A., Patrick, R., Reed, M., Steelman, T., Abu, R., Doig, L., Crane, J., McKay-Carriere, L., Carriere, R., MacKenzie, D., Carriere, S., Lento, J., Monk, W., Razavi, S., Duffy, A., and Lin, L. (2023) Long-term decline in the health of the Saskatchewan River Delta, and potential restoration solutions. Society for Canadian Aquatic Sciences, February 22, Montreal, QC.

The melt of seasonal snowcovers in cold regions provides downstream regions with a critical supply of freshwater, impacting ecosystems and human society such as agricultural, industrial, and municipal users. Late lying snowpacks can persist into early summer in mountain headwaters and can maintain streamflow through periods of low precipitation. They also support mountain glaciers. The spatial heterogeneity of these late-lying snowpacks is high and stems from energetic differences (slope and aspect), mass transport (blowing snow and avalanching), and precipitation variability. The amount of water stored in these snowcovers and the impact of climate change on these late-lying snowcovers remain uncertain in high mountain regions. Although airborne LiDAR observations can quantify end-of-winter snowdepths, large scale application of airborne LiDAR remains limited due to high costs. Large-scale modelling of these regions has been problematic due to coarse spatial resolutions in models that removed key land-surface features (e.g., ridges) and poor or non-existent representation of key cold-regions processes. Snowdrift-resolving models (1 m – 250 m spatial scales) have been proposed as a way forward to accurately simulate snowcover heterogeneity. However, these spatial scales can be computationally intractable for large extents. A solution, next-generation, multi-scale land surface models allow for large reductions in computational elements (98%+) whilst preserving critical land-surface heterogeneity. In this work, the multi-scale Canadian Hydrological Model (CHM) was applied to simulate end of winter snowcovers at snowdrift resolving scales across the Canadian Cordillera (1.3 million km2) driven with forcing from the Environment Canada High Resolution Deterministic Prediction System (HRDPS) at 2.5 km. The model outputs were compared to indices of snow persistence using Sentinel and Landsat imagery to evaluate its skill in predicting late lying snowpacks. This work is the first large extent application of a deterministic, non-calibrated comprehensive snow redistribution and ablation model that includes a rigorous quantification of cold regions processes at snowdrift resolving scales (50 m). Such an approach presents a direction for calculating the impact of climate change on snowcovers and water supply and for prediction of water supply, droughts, and floods.

AOSM2022 Next gen core modelling First Author: C.B. Marsh; Centre for Hydrology, University of Saskatchewan Additional Authors: V. Vionnet[2], K.R. Green [3] , R.J. Spiteri [3], Z. Lv [1], J.W. Pomeroy [1]; [1] Centre for Hydrology, University of Saskatchewan; [2] Meteorological Research Division, Environment and Climate Change Canada; [3] Numerical Simulation Lab, University of Saskatchewan