长江口近期来水来沙量及输沙粒径的变化

摘要

长江来水来沙变化影响因素众多,除自然因素外,人类活动对河流水沙运动影响越来越显著.作为长江流域的终端,长江口地区既受自然因素影响,同时也显著地受到流域人类活动的影响.通过对比分析徐六泾站与大通站的水量和沙量,得出大通站能够作为代表流域进入长江口水沙情势的控制站.利用大通站的水文数据,统计分析1950—2011年的径流量、数量及输沙粒径的变化,得出长江口近期来水来沙量及输沙粒径的变化.研究结果表明:1) 长江流域年来水量没有发生趋势性变化;2003年后三峡水库发挥调蓄作用,来水量年内分配呈现洪季径流量减少,枯季径流量增加的特征.2) 1986年以来长江流域来沙量大幅减少,季节变化总体呈现洪季比例减小、枯季比例增大的特征.2003年三峡水库蓄水后,来沙量进一步减小,洪季输沙量明显减小.3) 2003年前后大通站悬沙中值粒径变化不显著,从粒度组分上看粒度略有粗化.%The factor of runoff and sediment changes of the Yangtze River is numerous,and influence from human activities to water and sediment movement is becoming more and more obvious besides natural factors.Runoff and sediment changes of the Yangtze estuary are influenced by natural and human activities.Comparing and analyzing the runoff and sediment discharge of Xuliujing station and Datong station,we know that Datong station can be used as the control station of the Yangtze estuary.Based on the hydrological data of Datong station,this paper analyzes the variation of runoff,sediment discharge and suspended sediment particle size in the the Yangtze estuary during 1950—2011,and obtains the runoff,sediment discharge and sediment diameter of the Yangtze estuary.The results show that there is no trend change of runoff in the Yangtze River basin.After 2003,the Three Gorges reservoir plays a regulating role,and the distribution of runoff during the year shows the decrease in the flood season and the increase in the dry season.Since 1986,the sediment discharge in the Yangtze River basin has been greatly reduced.The seasonal variation proportion generally shows that it's decreasing in the flood season and increasing in the dry season.After the impoundment of the Three Gorges reservoir in 2003,the sediment discharge has been further reduced and during flood season sediment discharge is decreasing obviously.The average suspended sediment particle size in Datong station is not obvious before and after 2003,and the grain size is slightly coarser from grain size component.