Abstract: The gravity wave driven by the daily operation of Three Gorges Reservoir (TGR) has a significant influence on the dynamic process of its tributaries. In particular, the high-frequency water fluctuation remarkably affects the vertical transport or diffusion of materials and energy, and further on the algal blooming process. The influence of high-frequency oscillation in tributary bay driven by TGR’s daily operation on water temperature structure was examined based on the monitoring data of hydrodynamics and vertical structure of water temperature in Xiangxi Bay of TGR at the end of 2021 impoundment period. Results demonstrated that the daily fluctuation of outflow of the TGR also gave rise to daily fluctuation and high frequency fluctuation of the water level of its tributaries. The amplitude of daily fluctuation of water level was about 0.3-0.5 m, and the high frequency fluctuation reached around 0.04 m. The high-frequency fluctuation in the bottom of the bay was more obvious than that in the mid-and-upper layer due to the water depth reduction from the estuary to the upper reaches. Power spectrum analysis of near-bottom water temperature fluctuation in tributaries showed that the turbulent dissipation rate of Xiangxi Bay (6.5×10^-7 W/kg) is significantly higher than that of other reservoirs, indicating that the high frequency fluctuation of water driven by reservoir operation leads to strong turbulent development and dissipation.

Key words: daily discharge regulation, tributary oscillation, water temperature fluctuation, power spectrum analysis, turbulent dissipation