Exploring water-level fluctuation amplitude in an approach channel under the regulation of a dual cascade hydro-plant in the dry season

Water-level fluctuation is a crucially important hydraulic factor to meet the safety of ship navigation. Due to the uncertainty and evolution of the maximum amplitude of water level variation in the approach channel, the river reach between two dams located along the Yangtze River in China is selected as a study area and the impact of various operating conditions of the cascade hydro-plant on the maximum amplitude of water level variation at typical sites is revealed combining the orthogonal test method and a hydrodynamic model. In addition, the critical threshold for the water level variation at the lower lock head of the ship lift is explored using maximum entropy method. Results demonstrate that flow variation and regulation time are the most prominent factors affecting water-level fluctuation at the lower lock head of the ship lift, and the existing standard (0.5 m within one hour and 0.3 m within 30 min) for controlling the maximum variation in water level at the lower head of the ship lift is reasonable and more safety-oriented. This study provides a novel perspective to understand the response of water level fluctuation to the stochasticity of operating conditions for the cascade hydropower stations.