Author(s): Ge Yang; Yuntong She; Wenming Zhang
Linked Author(s): Wenming Zhang, Yuntong She
Keywords: Water quality cold region long-term
Abstract: Urban rivers in cold regions face unique water quality challenges which are compounded by the complex interactions of environmental, anthropogenic, and climatic factors. The discharge of sanitary and industrial wastewater into rivers impacts instream water quality. The seasonal formation of ice cover can significantly alter river hydrodynamics, thereby affecting many water quality processes. Despite its significance, river water quality under ice-covered conditions remains understudied as compared to the open water seasons. Understanding the full spectrum of water quality throughout the year is essential for comprehensive river management. In this study, one-dimensional and two-dimensional modeling of water quality in the North Saskatchewan River (NSR) during open water and ice-covered periods was performed using the Environmental Fluid Dynamics Code (EFDC+). The study reach encompasses different land uses and pollutant inputs, and serves a large population and several important industry facilities. Each year the study reach is ice-covered for almost half of a year. Water quality variables considered include algae and various components of nitrogen (e. g., ammonia/ammonium (NHx), nitrate/nitrite (NOx) and total nitrogen (TN) ), phosphorus (e. g., total phosphorus (TP) and particulate organic phosphorus) and carbon (e. g., dissolved organic carbon (DOC) and refractory particulate organic carbon). The EFDC+ model was calibrated and validated using historical observed data from 2000 to 2021. The model has good performance in hydrodynamics and water quality simulation under both open water and ice-covered conditions. The spatial and temporal variability of the water quality variables along the study reach were assessed based on the model. The impacts of pollutant loadings from industrial facilities, tributaries, stormwater outfalls and combined sewer overflows on river water quality were assessed. The effects of ice cover on the pollutant transport were investigated. Additionally, the changes of water quality due to human activities and industrial activities over the 22 years were discussed. This study provides insights for river water quality monitoring and management in cold regions.
Year: 2025