Abstract: The Xiluodu reservoir is a typical deep run-of-river reservoir where hydro-peaking under stratification induces internal waves at its metalimnion. In this study, we take long-term measurement of water temperature in the reservoir using a thermistor chain, and develop a longitudinal-vertical two-dimensional numerical model to simulate these waves, focusing on the internal wave phenomenon and its formation and propagation features. Results show that the waves have a period of 24 hours and are induced by epilimnetic withdraw and hydro-peaking. They travel upstream along the metalimnion with decaying amplitudes and their travelling speeds agree well with the calculations using the Kelvin-Helmholtz wave theory. Also, they have no significant influence on the hypolimnion deepening. Currently, only a few exiting studies about internal waves in deep run-of-river reservoirs can be found. This study would shed light on our understanding of internal waves in reservoirs and help the analysis and design of related engineering applications.

Key words: reservoir, water temperature, internal wave, hydro-peaking, on-site observation, numerical simulation