ABSTRACT Variations in water coverage are of great importance to ecological systems. After the water stored in Three Gorges Reservoir was filled in 2003, the water area in the mid‐lower Yangtze River was affected. To reveal the variation of water coverage in 2003–2022 in the middle and lower Yangtze River and its affecting factors, this study rebuilt continuous datasets based on Landsat and MODIS images, then extracted a long time‐series water coverage using the Adaptive Step Length–Quantum‐Behaved Particle Swarm Optimisation–Random Forest (ASL‐QPSO‐RF) approach with an accuracy of more than 90%. Based on the extracted water coverage, from 2003 to 2022, the water coverage decreased by 10%, 24%, and 7% for effective, seasonal, and permanent water bodies, respectively. For the lower river, during 2003–2022, the coverage declines of permanent water bodies in the lower river dominated that in the mid‐lower Yangtze River with a contribution of 70% and were significantly affected by the deepening of the channel in the lower river (increased by 27%) with a coverage reduction of 145 km 2 for a 1‐m deeper channel. During 2003–2012, that deepening was both related to the decline of sediment transport and the increase in sand mining, with contributions of 57% and 43%, respectively. In addition, the reduction of sand mining in the lower river weakened the coverage decline of the water body and the deepening of the channel during 2017–2022. For the middle river, the decline in the coverage of seasonal water bodies in the middle river dominated that in the mid‐lower Yangtze River, with a contribution of 108%. Considering that the guaranteed channel depth increased by 37% in the middle river, the coverage decline of the effective water body in the middle river was mainly related to the significant deepening of the channel in the middle river (1 m deeper, a reduction of 184 km 2 ) during 2003–2022. The deepening of the channel in the middle river was dominated by a significant decline in sediment transport during 2003–2012. These results provide a reference for better management of the mid‐lower Yangtze River.
Pan et al. (Thu,) studied this question.