Abstract:

The implementation of the Yangtze-to-Hanjiang River Diversion Project will significantly alter the hydrology and water quality of the Three Gorges Reservoir(TGR). To predict its environmental impacts on the water source area of TGR, we develop a two-dimensional hydrodynamic and water quality model to analyze changes in hydrological and hydrodynamic conditions across wet, normal, dry, and extremely-dry years, and also reveal the spatiotemporal distribution characteristics of COD, NH₃-N, and TP concentration. Based on these results, we propose corresponding water environment protection measures. Results indicate a substantial improvement in the hydrodynamic conditions at the Longtanxi water intake following the project’s implementation, with monthly flow velocities increasing by 0 to 0.04 m/s. Due to the river diversion’s dragging effect, the water quality in the intake area approaches that of the main reservoir area. The annual average changes in COD, NH₃-N, and TP concentration at the water intake during different typical years range from -2.31% to 0.41%, 4.18% to 8.2%, and 0.77% to 1.82%, respectively. Additionally, there is a risk of eutrophication in the intake area during non-diversion periods. These findings provide theoretical and technical support for the protection and remediation of water environment in the water source area.

Key words: Water Diversion Project from the Yangtze River to the Hanjiang River, water source area of the Three Gorges Reservoir, water environmental impact prediction, numerical simulation, two-dimensional hydrodynamic and water quality model, protection and remediation of water environment