Possibilities and challenges of expanding dimensions of waterway downstream of Three Gorges Dam

Abstract

The waterway in the middle and lower reaches of the Yangtze River has long been known as the Golden Waterway and has served as an important link in the construction of the Yangtze River Economic Belt. Therefore, expanding its dimensions is a significant goal, particularly given the long-range cumulative erosion occurring downstream of the Three Gorges Dam (TGD), which has been concentrated in the dry river channel. With the regulation of the volume from upstream reservoirs and the TGD, the minimum discharge and water level of the river downstream are increasing, and creating favorable conditions for the increase of the depth of the waterway. The discharge compensation effect during the dry season offsets the decline in the water level of the river channel caused by the down-cutting of part of the riverbed, but the minimum navigable water level of the segment near the dam still shows a declining trend. In recent years, several waterway remediation projects have been implemented in the downstream reaches of the TGD and although the waterway depth and width have been increased, the channel dimensions are still insufficient in the Yichang-Anqing reach (with a total length of 1026 km), as compared to the upstream reservoir area and the deep water channel in the downstream tidal reaches. A comprehensive analysis of the water depth and the number and length of shoals in the waterway indicates that its dimensions can be increased to 4.5 m × 200 m and 6.0 m × 200 m in the Yichang-Wuhan and Wuhan-Anqing reaches, respectively. This is also feasible given the remediation technologies currently available, but remediation projects need to be coordinated with those for flood prevention and ecological protection.