Macro-HyProS: A new macro-scale hydrologic processes simulator for depression-dominated cold climate regions

This study introduces a new Macro-scale Hydrologic Processes Simulator (Macro-HyProS), tailored for cold climate regions and depression-dominated terrains. Macro-HyProS is a grid-based hydrologic model of a unique structure to deal with hydrologic complexities in depression-dominated cold climate regions. The model runs on a daily time step and incorporates a LEGO-fashion horizontal layout to account for sub-grid land use heterogeneity. On the vertical layout, each grid consists of different bands, each of which is responsible for simulating specific hydrologic processes. Macro-HyProS employs improved methodologies to account for snow accumulation and ablation, depressions, and frozen ground condition. The Red River of the North Basin (RRB) was selected to highlight the capabilities of Macro-HyProS in describing the spatiotemporal complexities associated with depression-dominated cold climate regions. Results indicated that the model provided a satisfactory performance, having the Nash-Sutcliffe efficiency coefficients of 0.56 and 0.72 in the calibration and validation periods, respectively. The modeling results accentuated the impacts of frozen ground, snowmelt, and depressions in the generation of surface runoff over the basin. On average, the RRB experienced 145 days of frozen or partially frozen ground conditions per year, which coincided with early spring rainfall and snowmelt events. Due to the widespread frozen ground conditions over the basin, up to 60% of the generated snowmelt on specific days contributed to surface runoff, whereas infiltration had a smaller portion. Also, the results revealed that the depression-dominated areas acted as "regulators" of surface runoff, particularly in early springs. Macro-HyProS provides spatiotemporal simulations of various hydrologic processes to facilitate a better understanding of macro-scale hydrologic trends.