长江流域资源与环境 >> 2014, Vol. 23 >> Issue (09): 1251-.doi: 10.11870/cjlyzyyhj201409010

• 生态环境 • 上一篇    下一篇

长江口徐六泾水沙过程对流域的响应研究

谢卫明,田欣,郭磊城,何青   

  1. (华东师范大学河口海岸学国家重点实验室,上海 200062)
  • 出版日期:2014-09-20

H]HYDRODYNAMICS AND SEDIMENT DYNAMICS AT XULIUJING IN#br# THE YANGTZE ESTURARY IN RESPONDING TO #br# UPSTREAM HYDROLOGIC PROCESSES

XIE Weiming,TIAN Xin,GUO Leicheng,HE Qing   

  1. (State Key Laboratory of Estuarine and Coastal Research,East China Normal University,Shanghai 200062,China)
  • Online:2014-09-20

摘要:

以长江口徐六泾断面2009年实测水沙数据为基础,分析了其水沙特征,重点研究了三峡蓄水及长江流域旱情对徐六泾节点径流、潮位和泥沙过程的影响。结果表明:观测期间寸滩站以上流域来水减少、三峡蓄水和中下游干旱共同导致进入河口的径流量减少,各自造成的影响权重分别为38%、13%和49%。与蓄水前相比,蓄水期间徐六泾涨潮历时增加05 h,落潮历时减少05 h,潮差增大约04 m;涨潮平均流速增加35%~126%,落潮平均流速浅滩处基本不变,而深槽处减幅约为22%;蓄水期间涨落潮历时、流速流向等特征由不对称趋于较对称,说明徐六泾的水动力特征对径流减少的响应敏感。伴随径流减少,徐六泾含沙量由蓄水前的0129 kg/m3大幅下降至蓄水期间的0052 3 kg/m3,悬沙中值粒径则由3 μm增大到5 μm。综合得知进入河口徐六泾断面的水沙过程受到流域人类活动和自然条件改变的双重影响

Abstract:

The Yangtze Estuary (YE) is a complicated dynamic system influenced by both huge river inflow and medium tides Large amounts of sediments input have built large subaerial and subaqueous deltasis The annual averaged discharge in Datong hydrological station (DT) is 28300m3/s (1950-2009). The YE receives 389 million tons sediment annually (1951-2009),which is material filling the Holocene incised Yangtze valley and building the modern Yangtze Delta Previous studies usually consider the discharge of DT (tidal limit of the YE) as the discharge of the Yangtze River into the sea However,DT is still 540 km from the mouth of the river Xuliujing station (XLJ) is about 500 km downstream DT,and since 1960s,the channel in XLJ has been stable XLJ is also the starting point of threeorder bifurcations and four outlets of the YE So the runoff and sediment flux of XLJ are more representative for intosea flux than those of DT In addition,after the third construction phase (2004-2009),all construction of the Three Gorges Reservoir (TGR) has nearly been finished and most of its units have been into operation,and then the normal reservoir storage water level will reach 175 m The flood control reservoir storage capacity will be 2215 billion m3 The impoundment of the Three Gorges project and [JP2]the constant drought situation (2006-2009) [JP]in the Yangtze River basin jointly result in that downstream water flow becomes very low,which will bring certainly corresponding impacts on the runoff and sediment flux into the YE So it is urgent to understand what the respondse of the YE to these change is However,in view of the complexity of the flow and sediment movement in the YE,the impacts of the change of water and sediment environment in the Yangtze River basin on estuarine flow and sediment processes have not been clearly studied In this paper,we try to examine the hydrodynamics and sediment dynamics at XLJ in the YE in the circumstances of low waters in the Yangtze River basin and the TGR impoundment in 2009 based on field data The analysis shows that the runoff reduction during the impounding period is caused by both regional dry climate (87%:the proportion of the upper reach of the TGR (its lower boundry is Cuntan station) and that of the basin below the TGR are 38%,49%,respectively) and TGR impoundment (13%). The flood tidal duration increases by 05 hour and mean tidal range increases by 04 m due to reduced discharge The mean flood tidal velocities increase by 35%-126% and ebb tidal velocities in the channel decrease by 22%. These results indicate that the tidal asymmetry is lessened during lower discharge period The suspended sediment concentrations (SSCs) decrease from 0129 kg/m3 in preimpoundment to 0052 3 kg/m3 in postimpoundment period Correspondently,the median suspended sediment grain size (D50) increase from 3 μm to 5 μm Overall,it is concluded that the hydrodynamics and sediment processes at Xuliujing are noticeably influenced by the upstream hydrologic regime which undergoes changes in both climatic aspects and TGR regulation.

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