Abstract: After the impoundment of the Three Gorges Reservoir, the hydrodynamics of branch bay together with the distribution of water temperature in vertical direction has changed. To investigate into the distribution of water temperature in the presence of different types of density current, we monitored the water temperature in-situ in different sections of the Xiangxi Bay, and established a hydrodynamic model (CE-QUAL-W2). We conclude that the main hydrodynamic conditions and water temperature distribution in normal periods of reservoir operation vary correspondingly: in discharge period, backward density current at surface layer is the major hydrodynamic pattern with conventional water temperature distribution; in flood season at low water level, backward density current at middle layer is the major hydrodynamic pattern, with water temperature distributes in double mixing-thermocline type; while in storage period, backward density current at bottom layer is the dominant hydrodynamic pattern, with the water temperature distributes in a half-U shape. The research results offer theoretical and technical support for revealing the water temperature distribution and nutrients transport as well as forecasting water bloom in the Xiangxi Bay.

Key words: Three Gorges Reservoir (TGR), Xiangxi Bay, different density current, CE-QUAL-W2, thermal stratification