Sensitivity Analysis of Dissolved Oxygen in Cold Region Rivers Through Numerical Modelling

This is the authors' abstract. We don't add key points for this paper.

Dissolved oxygen (DO) is one of the most critical water quality constituents in cold region rivers. Harsh winter conditions pose significant challenges for DO sampling, making numerical modeling a valuable tool for gaining insights into DO concentrations during winter. Sensitivity analysis is essential for understanding the relative importance of the model parameters to the DO concentrations; however, such studies are rare. This study conducted a DO sensitivity analysis in the Lower Athabasca River, Canada, using a water quality model with ice effects in the MIKE HYDRO River. The simulated flow, water level, water temperature and DO concentrations closely matched observed values along the study reach. A bidirectional perturbation analysis was conducted to assess the sensitivity of DO concentrations to 14 model parameters. The results indicate that photosynthesis and respiration are the two most influential processes affecting river DO under winter conditions despite lower biomass activity compared to open-water conditions. A distinct seasonal pattern was observed for most parameters, with DO sensitivity during winter ice-covered periods being significantly higher than in summer open-water conditions. The study provides valuable insights for the development of integrated water quality and ice models for cold region rivers.