Hydrodynamic-sediment transport response to waterway depth in the Three Gorges Reservoir, China

Abstract

Since the Three Gorges Dam began operation in 2003, hydrodynamic-sediment conditions changes have occurred not only downstream but also in the Three Gorges Reservoir, contributing to variations in the navigation conditions of the backwater area. Based on the measured channel data from 2003 to 2018, this study investigates changes in the waterway dimension and the factors that impact navigation conditions. The navigation-obstructing channels in the permanent backwater area (PBA) mainly resulted from the occurrence of fine grained sedimentation, which led to a decrease in the effective navigable width. Meanwhile, in the fluctuating backwater area (FBA), bed load behavior during the falling stage from April to June lowered navigation depths. Decreasing sediment supply can alleviate reservoir sedimentation and maintain navigation safety in the PBA, while it is necessary to focus on the waterway depth clearance that is sensitive to temporary deposition during the falling stage of high water-sediment discharge years in the FBA. Water level variation near gravel excavation pits indicates that sediment mining decreases waterway depth, negatively impacting the navigable dimension, especially during low water discharge. These findings provide useful information for assessing the sustainable development of the navigation in the Three Gorges Reservoir, and aid economic development in the Yangtze River.