|Zhou Weixing,Sun Zhaohua,Zhou Kun,Li Zhiqing,Chen Li.Characteristics of discharge frequency and their effects on flood channel formation in the middle and lower reaches of the Yangtze River before/after the impoundment of the Three Gorges Reservoir. J. Lake Sci.2022,34(2):616-629. DOI:10.18307/2022.0221
|关键词: 流量频率 概率密度函数 造床流量 河道萎缩 长江中下游 三峡水库 蓄水前 蓄水后
|Characteristics of discharge frequency and their effects on flood channel formation in the middle and lower reaches of the Yangtze River before/after the impoundment of the Three Gorges Reservoir
Zhou Weixing, Sun Zhaohua, Zhou Kun, Li Zhiqing, Chen Li
State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, P. R. China
|The variations of flow characteristics and their effects on channel formation in the middle and lower reaches of the Yangtze River before and after the impoundment of the Three Gorges Reservoir (TGR) have drawn much concern. Based on the data of the average daily discharge at six hydrological stations including Zhicheng Station, the empirical flow frequency distributions were calculated, and the applicabilities of eight probability density functions were tested. Furthermore, the relationships between the flow frequency distribution characteristics and the channel-forming discharges before and after the impoundment of the TGR were discussed. The results show that the flow frequency distributions in the study reach are segmented, which cannot be described as a whole by common functions such as Pearson Ш or Lognormal distribution. However, the frequency distributions of the medium-high flow conform to the broken power-law (BPL). The turning point of the BPL obtained by fitting approximately reflects the channel-forming discharge. Moreover, affected by the regulation and storage of Lake Dongting, the characteristic parameters including the critical values quite differently in the upper and lower reaches of Luoshan Station. After the TGR is impounded, the subsection characteristics of the flow frequency distributions are enhanced by the flood reduction, and the applicability of BPL are still considerable. Due to the influence of the flow process change and frequency adjustment by the impoundment of the TGR, the channel-forming discharge at Zhicheng, Shashi, Jianli, Luoshan, Hankou and Datong stations will be 0.79, 0.73, 0.74, 0.89, 0.90 and 0.93 times of that before the impoundment, respectively. The method presented in this paper are of reference value for the analysis of runoff characteristics and the calculation of channel-forming discharge in the middle and lower reaches of the Yangtze River.
|Key words: Flow frequency probability density function channel-forming discharge river channel shrinkage middle and lower reaches of the Yangtze River Three Gorges Reservoir before the impoundment after the impoundment