长江口入海水沙通量变化及其影响分析

Variation of water and sediment flux and its influence on the Yangtze River Estuary

基于大通站1960−2020年长系列的径流量和输沙量资料,研究了长江口入海水、沙通量的季节变化、年际变化和趋势性,并讨论了其影响因素。研究结果显示:多年长江口入海平均径流量为8906亿m^(3),各年的平均径流量值围绕着多年平均值上下摆动,没有明显的变化趋势;入海径流量的季节性变化明显,每年的5−10月的径流量占全年的70.3%;多年平均年输沙量为3.35亿t,输沙量过程总体呈现减小的趋势;长江口入海水沙通量变化受中上游的水土保持和水库建设等因素影响明显,其中三峡水库蓄水后,大通站输沙量与之前相比减少了62.8%;受长江流域来沙锐减的影响,长江口河势也发生了明显变化,出现了河口含沙量明显减小、河口总体上由淤积环境向冲刷环境转化、长江口水下三角洲前缘大面积冲刷河口拦门沙及水下三角洲泥沙补给出现“源汇转化”的结构性变化等现象。

Based on the runoff and sediment discharge data of Datong Station from 1960 to 2020, the seasonal and interannual variations and trends of seawater and sediment flux into the Yangtze River estuary were studied,and the influencing factors and their effects were discussed. Results show that during the data coverage period: the annual average runoff was 890.6 billion m~3, and the annual average runoff fluctuated around the annual average with no obvious variation trend;seasonal variation of runoff into the sea was obvious, and the annual runoff from May to October accounted for 70.3% of the whole year;the annual average sediment transport was 335 million tons, and the sediment transport process showed generally a decreasing trend;the change of sediment flux into the Yangtze River estuary was obviously affected by the factors of water and soil conservation and reservoir construction. After the impoundment of the Three Gorges Reservoir, the sediment flux at Datong Station decreased by 62.8% compared with that before;the river regime of the Yangtze River estuary had also changed obviously due to the decrease of sediment flux in the Yangtze River basin. The sediment concentration in the estuary decreased significantly, the estuary changed from siltation environment to scour environment, the subaqueous delta front of the Yangtze River estuary occurred the large area of scour, and the estuary sandbar and the subaqueous delta sediment supply occurred the structural change of "sourcing-sink transformation".