186 / 2024-02-27 10:07:42

Prediction of the non-equilibrium response process in the Middle Yangtze River after the operation of Three Gorges Reservoir

Middle Yangtze River; non-equilibrium response process; adjustment potential; temporal scale; spatial scale

Since the operation of the Three Gorges Reservoir, the Middle Yangtze River has entered a strong erosion process, leading to the drastic adjustment of the channel geometry, which may threaten the flood control safety and ecological health of the river channel. Therefore, it is crucial to clarify the magnitude and spatiotemporal scale of the non-equilibrium evolution adjustments. This paper focus on the Middle Yangtze River, and simulates the spatiotemporal adjustment process following operation of the Three Gorges Reservoir by using the established spatiotemporal equilibrium response equation. The results indicate that: (i) In terms of adjustment potential, there are significant differences in each reach. Laterally, the channel width of YC-ZC Reach and Upper Jingjiang Reach remains unchanged, while the broadening potential in the Lower Jingjiang Reach and other lower reaches is slightly larger, showing a widening range of about 20~30 m. Vertically, the adjustment potential of cumulative riverbed degradation in most reaches is close to or more than 2.0m, except for the meandering Lower Jingjiang River. (ii) In terms of spatial and temporal scale, it is indicated that, the spatial and temporal scales of the adjustment of channel morphological variables in each reach are obviously different. Temporally, except for the YC-ZC Reach and Lower Jingjiang Reach which are close to the equilibrium state, the remaining reaches will still have obvious erosion until 2030. Spatially, the erosion intensity downstream of dams decreases nonlinearly along the channel until it eventually diminishes, showing obviously nonlinear attenuation characteristics. The full-line erosion of the Middle Yangtze River can be realized, and it may even affect the estuary. The above results can provide scientific basis for flood control planning and river regulation in the Middle Yangtze River.