Impact analysis of short-term air temperature changes on water transfer scheduling during the ice period of the Middle Route of the South-to-North Water Diversion project

Air temperature is an important factor affecting the changes in ice conditions in rivers and canals, and water diversion projects located in high latitudes must consider the safety and efficiency of water transfer in winter. They often adopt the method of reducing water flow to suppress the ice jam risk, but it also causes the temporal and spatial loss of water transfer benefits, aggravating the water shortage dilemma in winter. Taking the Middle Route of the South-to-North Water Diversion Project as an example, an ice prediction model based on the actual characteristics of the project is established by the numerical simulation method. This paper uses the model to display the ice condition evolutions in the project under different short-term air temperature changes and reveal the law of the freezing range of the canal system under the coupling of air temperatures, water temperatures, and water flows. Finally, a mode for improving the water transfer benefits in winter based on the short-term air temperature forecast is proposed. The study results indicate that the initial water temperature and 7-day air temperature probability are inversely proportional to the freezing range and ice cover thickness of the canal system, and the 7-day air temperature changes in the project can form an ice cover with a maximum thickness of 0.17 m, which is 8.5 times the thickness of the ice cover under actual air temperature conditions. The larger the water transfer flow in the canal system, the shorter the freezing range, but it may increase the risk of ice jam formation. The model can predict future ice development by inputting the current hydraulic data of the project and the future short-term air temperature forecast data, and the errors are acceptable. Combined with the mode for improving the water transfer benefits, the flexibility, safety, and comprehensive benefits of the project operation in winter can be effectively improved.