Investigating River Ice Breakup Patterns and Snow and Ice Affected Spring Streamflow
Creators: Chen, Yuzhuang
Publisher: name: University of Alberta Library
Year: 2022

<p>Both the observed and projected temperature in Canada increase faster than the global temperature, which has extensive implications on snow and river ice breakup regime, and then can greatly affect the timing and magnitude of snow and ice affected spring streamflow. This research is to expand our knowledge of river ice breakup timing through collecting and analyzing scientific data describing and driving such events, and simulating snow and ice induced spring streamflow through the development and application of the physics-based hydrologic and river ice models.<br>
The biggest challenge of large-scale spatial and temporal analyses of river ice breakup timing across Canada is there are no long-time and uniform river ice breakup timing records. This study used the date of last ‘B’ symbol in the discharge record as breakup timing and constructed a long-term (1950-2016) and uniform river ice breakup timing dataset using nearly 200 hydrometric stations form Water Survey of Canada HYDAT database. It provides a way for researchers to construct the river ice breakup timing database and investigate the breakup timing trends under historical climate change. The spatial-temporal variations of breakup timing over terrestrial ecozones and five selected river basins of Canada were investigated based on the constructed long-term data record. The links between the discovered patterns and climatic drivers (e.g., air temperature, snowfall and rainfall), as well as elevation and anthropogenic activities were also analyzed. An overall earlier breakup trend was observed across Canada and the spring air temperature was found to be the main driver behind it. However, the most pronounced warming trends across Canada was observed in winter. Spring warming trend was not as strong as winter warming and even became weak in some periods. Other factors, such as snowfall, rainfall, elevation and flow regulation, also contributed to changes of river ice breakup in various ways. Their combined effects made river ice breakup patterns display evident spatial and temporal differences. In addition to providing evidence of climate changes in Canada, the findings can provide theoretical support in modelling breakup processes.<br>
The choice of proper input data and suitable calibration scheme is challenging in hydrologic modeling of higher-latitude watersheds with their unique hydro-climatic conditions. Based on the hydrologic model SWAT (Soil and Water Assessment Tool) and the calibration tool SWATCUP, this study revisited various climate data and calibration schemes, and developed a multi-objective calibration framework that can automatically eliminate unrealistic snow parameters combinations and calibrate Snow Water Equivalent (SWE) and streamflow simultaneously in a large cold region watershed, the Peace River Basin (PRB) in western Canada. It demonstrated that the proposed multi-objective calibration framework can effectively limit the uncertainty of snow-related parameters and significantly improve the simulation of snow-affected spring streamflow in the PRB. The evaluating workflow developed in this study can provide insights in modelling cold region watersheds and calibrating the hydrologic models.<br>
Modelling snow and ice affected streamflow in cold region rivers is challenging. Ignoring the streamflow from the ungauged zones/subbasins of a river basin in preparing inflow boundaries for river ice modes could add further challenges and uncertainties. This study firstly attempted to combinedly use the river ice model River1D with the hydrologic model SWAT model to investigate the impacts of ungauged subbasin streamflow on peak flow simulation under open water and rive ice breakup conditions in the PRB. Ungauged subbasin streamflow in each inflow boundary was estimated by both simple drainage-area ratio (DAR) method and the sophisticated hydrologic model. Compared with DAR method, the hydrologic model was proved to be a promising and robust tool for estimating ungauged subbasin streamflow for the river ice model. The results showed that ungauged subbasins of the PRB can greatly affect the peak flow simulation for both open water and river ice breakup events, especially for flood events. The peak flow simulation was significantly improved when the ungauged subbasin streamflow was properly considered and/or estimated. The findings can contribute to open water and river ice breakup flood simulation, and water resources planning and management in the PRB. The hydrologic and river ice modelling framework developed in this study can be applied into other cold region watersheds to explore the effects of the ungauged subbasins and/or forecast snow and ice induced flood events.</p>