438 / 2024-03-17 22:32:29

Investigation of water level fluctuations in the main stream of the middle reaches of the Yangtze River before and after the Three Gorges Reservoir impounded

reservoir regulation; water level fluctuation; flood control; the middle reaches of the Yangtze River

Subtheme 7: Sediment Regulation and Management > Topic 3: River Regulation and Sand Mining

The Three Gorges Reservoir (TGR) offers substantial benefits, including flood control, energy generation, and navigation along the Yangtze River, through flood peak reduction, staggered scheduling and replenishment during the flood season. However, reservoir regulation has also significantly changed the runoff conditions entering the river downstream of the dam. For example, the maximum daily average water level fluctuation of the main stream has significantly increased, which has adversely affected the stability of the river bank and navigation safety etc. Based on the long-time series of measured daily average water level data from Yichang, Shashi, Chenglingji, and other major hydrological stations on the main stream of the middle reaches of the Yangtze River, we analyzed the maximum 1-day, 2-day, and 3-day average water level fluctuations changes before and after the TGR impoundment. The results indicate that since the impoundment of the TGR, the maximum annual 1-day average water level has risen and fallen downstream of the dam at various stations have generally exhibited a continuous increasing trend. The influence of the TGR along the watershed on the amplitude of extreme water level fluctuations at each station has gradually diminished. After the impoundment, the timing of extreme water level fluctuations downstream of the dam shifted, resulting in new peak periods in their distribution patterns.