1955-2021年期间长江中游枝城至螺山河段与三口洪道水沙输移变化规律

Variation of water and sediment transport in the Zhicheng-Luoshan section of the middle reaches of the Yangtze River and three diversion floodways from 1955 to 2021

长江与洞庭湖之间存在复杂的江湖水沙交换关系,水沙变化引起江湖冲淤变化,从而对长江中游区域防洪、水资源利用、航运及水生态环境等产生较大影响。本文利用实测资料较为系统地分析了荆江与洞庭湖水沙输移变化规律,结果表明:1955-2021年期间枝城、沙市、螺山站年径流量变化趋势不明显,监利站年径流量增幅为17.4%,三口分流洪道与七里山站均以减少为主;1955-1989年期间枝城与沙市站年输沙量变化趋势不明显,监利站明显增加,三口分流洪道与七里山站明显减少,1990-2021年期间各站均显著减少,其中三峡工程运用后荆江河段(枝城站)、三口分流洪道、洞庭湖出湖及城螺河段年输沙量分别减少90.1%、90.2%、22.5%及76.6%;受水库下泄径流过程改变的影响,荆江河段、荆江三口分流洪道、洞庭湖出湖与城螺河段年内径流过程均呈不同程度的坦化,枯水期平均流量均显著增加,消落期平均流量稍有增加,汛期出现一定程度的减少,蓄水期稍有减少,下泄径流过程坦化以及2006、2011年特枯水年分别引起荆江三口年均分流量减少41.2亿和32.4亿m~3。随着三峡上游水库群陆续建成运用,荆江河段、三口分流洪道、洞庭湖出湖及城螺河段径流量将进一步坦化,由于干流河床泥沙补给逐渐减少,输沙量将进一步减少,预计长江与洞庭湖水沙输移变化规律将基本保持现有变化格局。

There is a complex exchange relationship between the Yangtze River and Lake Dongting,and changes in water and sediment transport cause changes in river and lake erosion and deposition,which have a significant impact on flood control,water resources utilization,shipping,and water ecological environment in the middle reaches of the Yangtze River.This article systematically analyzed the variation laws of water and sediment transport in Jingjiang and Lake Dongting using the latest measured data,and obtains the following main insights.During the period of 1955-2021,the annual runoff at Zhicheng,Shashi and Luoshan stations showed no obvious change trends,except for Jianli station with an increase of 17.4%.Meanwhile,the Sankou diversion floodway and Qilishan station mainly decreased.During the period of 1955-1989,the trend of annual sediment transport at Zhicheng and Shashi stations was not obvious,while the Jianli station increased significantly,and the Sankou diversion floodway and Qilishan station decreased significantly.During the period of 1990-2021 since the operation of Three Gorges Project,all stations decreased significantly,with the annual sediment transport at the Jingjiang River section(Zhicheng station),the three diversion floodways,the Lake Dongting outlet,and the Chengluo River section decreasing by 90.1%,90.2%,22.5%and 76.6%,respectively.Due to the changes in the discharge process of the Three Gorges Reservoir,the runoff processes of the Jingjiang River section,the Jingjiang River Sankou diversion floodway,the Lake Dongting outlet and the Chengluo River section showed certain of flattening during the year.The average flow during dry seasons increased significantly,the average flow during drawdown periods increased slightly,and the average flow during flood seasons decreased to a certain extent.The discharge process flattened and the average annual discharge of the Three Gorges Reservoir in 2006 and 2011 decreased by about 4.12 billion m 3 and 3.24 billion m 3,respectively.With the gradual completion and operation of the upstream reservoirs of the Three Gorges,the runoff of the Jingjiang River section,the three diversion floodways,the Lake Dongting outlet and the Chengluo River section will become further flatten.Due to the gradual reduction of sediment supply in the main stream riverbed,the sediment transport volume will also decrease further.It is expected that the change law of water and sediment transport in the Yangtze River and Lake Dongting will basically maintain the existing change patterns.