A Modified SWAT Model to Simulate Soil Water Content and Soil Temperature in Cold Regions: A Case Study of the South Saskatchewan River Basin in Canada

Soil water content (SWC) and soil temperature are important hydrologic state variables. Accurate model simulation is critical in regimes cold regions dominated by spring snowmelt. In this study, we developed a combined physically-based energy-balance rain-on-snow (ROS) module for the Water Assessment Tool (SWAT) applied it to South Saskatchewan River Basin (SSRB). We calibrated SWAT base (SWAT-B) modified (SWAT–M) using daily measured SWC hydrological response unit (HRU) years 2015 2020. The results of sensitivity analysis SUFI-2 technique SWAT-CUP indicated that eight parameters have most significant (p < 0.5) effect on streamflow, moisture, Statistics SWAT-B SWAT-M streamflow models revealed new improved Nash-Sutcliffe efficiency (NSE) from 0.39 0.71 0.42 0.76 calibration validation, respectively. statistics SWAT-simulated showed data were better fit with versus output. Furthermore, values exceeded output field measurements, thus, range was observations. tended underestimate season, while significantly winter. This simulated freeze-thaw cycles captured influence snow cover surface ice-water content. Spatial across SSRB predicted more lower western part than SWAT-B, higher eastern region.