https://doi.org/10.1002/hyp.70608

Yassin, Fuad; Pomeroy, John W.; Pietroniro, Alain; Davison, Bruce; Elshamy, Mohamed; Tesemma, Zelalem (2026) Sensitivity of Large-Scale Hydrological Predictions to Precipitation Phase Partitioning Methods Under a Changing Climate, Hydrological Processes, https://doi.org/10.1002/hyp.70608

Accurate partitioning of precipitation into rain and snow remains a major source of uncertainty in hydrological projections for cold regions. This study quantifies how four precipitation phase-partitioning formulations influence simulated precipitation phase, snow storage and streamflow response in the Saskatchewan River Basin under historical (1981–2010) and late-century (2071–2100) climate conditions. Simulations were conducted under naturalised conditions, with all reservoir regulation, irrigation and water-management abstractions deactivated to isolate the effect of phase-partitioning choice, using the MESH land-surface hydroloical model forced with CanRCM4 climate projections spanning 1950 to 2100. Three empirical temperature-based methods (single-threshold, linear-transition and polynomial) and one physically based psychrometric formulation were evaluated using diagnostic variables including total precipitation, snow and rain fractions, annual maximum snow water equivalent (SWE), runoff, peak discharge and streamflow timing metrics. Late-century projections showed increases in total precipitation of 19%–30% and declines in snowfall fraction of 25%–34% across landforms. Reductions in annual maximum SWE ranged from approximately 5%–13% in the cordillera and foothills to 13%–19% in the plains. Inter-method spreads in projected SWE were small in colder landforms (