Impacts of seasonally frozen ground on streamflow recession in the Red River of the North Basin

The projected rising temperatures due to climate change can alter the frozen ground's duration and thickness in the cold regions of the Northern Hemisphere, leading to changes in surface and subsurface contributions to streamflow. The initial step in understanding the impacts of the changing climate on the hydrologic response of the cold climate watersheds is to investigate the effects of the cold climate processes (e.g., freeze-thaw processes) on watershed response. However, complexities associated with the spatiotemporal data collection of cold climate processes have limited the capabilities of hydrologic models in simulating cold climate watershed responses. This study aims to evaluate the impacts of seasonally frozen soil on the streamflow recession in the Red River of the North Basin (RRB). To the best of our knowledge, this study is one of the first attempts to quantify the impacts of frozen soil on the storage-discharge relationship of the RRB. We define a set of hypotheses to evaluate how cold climate processes influence the surface and subsurface flow paths and affect the linearity/non-linearity of the storage-discharge relationship in spring and summer. The results confirmed that the cold climate processes control the recession behavior of the RRB. It was found that the streamflow discharge is linearly related to the storage during spring, whereas during summer, the relationship was less linear. Statistical analyses revealed that the antecedent winter soil temperature and snowpack control the seasonal dynamics of hydrograph recession. Particularly, results indicated a more linear storage-discharge relationship for antecedent winters characterized by colder soil temperatures and larger snowpack. These findings highlight the importance of the cold climate hydrologic processes in cold climate basins such as the RRB.