Climate change and human activities have profoundly changed the evolutionary processes and developmental trends of the hydrology and geomorphology of rivers and lakes. Such changes have affected the evolution of bars and channels at the intersections of rivers and lakes and the utilization of water depth resources in waterways, which, in turn, have affected the sustainable development of waterways, such as the “Golden Waterway” of the Yangtze River. Considering the confluence of Dongting Lake and the Yangtze River as the present study area, we analyzed the effect of the hydrology of Dongting Lake and the evolution of bars and channels in the Jingjiang reach of the Yangtze River on the depth of the waterways. Our results indicated that from before the operation of the Three Gorges Project (1960–2002) to after its operation (2003–2021), the flow and sediment volume of the three inlets of Dongting Lake demonstrated a continuous decreasing trend. Furthermore, the relative increase in the runoff of the Jingjiang reach increased channel erosion. Channel erosion at the river–lake confluence from 2003 to 2021 created favorable conditions for increasing the dimensions of the waterways. The total length of the river–lake confluence that did not meet the requirements for safe navigation [4.5 × 200 m (water depth × width)] was 12.6 km, accounting for 68.35% of the total length of the Jingjiang reach with obstructed navigation. We observed that a decrease in the low‐water level and “steep slope and rapid flow” were the major factors hindering the navigation of the reach (from Zhicheng to Dabujie) affected by the Songzikou diversion of Dongting Lake. This was mostly reflected by the width of the 4.5 m waterway being less than 200 m. A declining water level, shrinking sandbanks and tidal flats, and alternating branches that destabilize the low‐water route were the major factors hindering navigation in the reach (from Taipingkou) affected by the Taipingkou diversion of Dongting Lake. Consequently, alternative waterways were implemented during low‐water periods with the water depth decreasing below 4.5 m. The obvious collapse of sandbanks and tidal flats and their erosion and migration were the major factors hindering navigation of the Ouchikou diversion of Dongting Lake. In addition, the scattered submerged shoals in the navigation channel restricted the width of the 4.5 m channel to less than 200 m. The reach affected by the Dongting Lake confluence (from Xiongjiazhou–Chenglingji reach) was subject to the erosion and silting of bends and the jacking effect of lake outflow, causing shoals with a water depth of less than 4.5 m in the channel. However, the jacking effect slowed the current, thereby assisting in improving channel conditions.

In China’s Yangtze River Basin, systematic waterway improvement and dredging maintenance have increased the waterway water depth compared with that before the implementation of the Three Gorges Project. Although the water depth of the middle section increased from 2.9 m in 2002 to 4.2 m in 2021, it remains less than 6.0 m in the lower section and 4.5 m in the Three Gorges Reservoir area. This study explores the Chenglingji—Wuhan reaches in the middle section of the Yangtze River, using hydrological data from 1954 to 2021 and topographic data from 2002 to 2021 to analyze river channel scouring or deposition characteristics, verify the waterway scale with a multi-scale width of 4.5 m water depth, and propose waterway management countermeasures. After the implementation of the Three Gorges Project, the Chenglingji—Wuhan reaches were scouring using a low-flow channel (94.95%), thereby facilitating waterway depth improvement. A serious obstruction area was located in the branching channel, and an unstable relationship between the boundary of the continental bank and the branching channel was found to be the main factor hindering navigation, with a water depth below 4.5 m. The Chenglingji—Wuhan reaches waterway water depth has been raised from 2.9 m in 2003 to 4.2 m; it can be raised to 4.5 m through waterway scale improvement. This study explains the navigation obstruction characteristics of alluvial waterways, which has important reference value for waterway scale improvement and planning, and the efficient utilization of deep-water resources.

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