长江口水沙入海通量的观测与分析

在长江口用声学多普勒流速剖面仪（ADCP）进行走航式断面观测，结果表明，采集水样获取的悬沙浓度与ADCP记录的声学信号（后向散射强度）之间存在显著相关关系，因此可据ADCP声学数据获得沿观测断面的高时空分辨率的悬沙浓度剖面。分析结果表明．在徐六泾附近断面以往复流占优势．大潮期间单位时间最大水、悬沙通量值出现于涨潮期．落潮历时较长．落潮期水、悬沙通量分别大于涨潮期水、悬沙通量，净通量向海。长江口南槽拦门沙外侧主要为旋转流．涨潮期间内的水、悬沙通量均分别大于落潮期间的水、悬沙通量。2003年11月12日的观测结果表明．潮周期内通过徐六泾断面向海输运的水与悬沙通量分别为10^9m^3和10^8kg量级：径流量与悬沙输运率分别为10^4m^3／s和10^3kg／s量级。1998年以来徐六泾ADCP流量观测数据与同时间的大通径流量之间存在着显著的相关关系．故可由大通径流量估算徐六泾径流量。作为长江人海径流量．以作为历史资料整编的一种手段。结果表明，长江人海年径流总量略大于大通年径流总量：而在枯水期间人海径流量小于大通径流量。

Measurements and Analysis of Water Discharges and Suspended Sediment Fluxes in Changjiang Estuary

An RDI WH600 ADCP has been deployed on a moving vessel for the water and suspended sediment fluxes measurements in the Changjiang Estuary. The acoustic signals recorded have a significant relationship with the suspended sediment concentrations (SSCs) obtained by in-situ water sampling during the measurements. Then the acoustic SSC models established were used to convert ADCP acoustic signals into high-resolution SSCs along the cross-sections at Xuliujing and the bar shoal at South Trough in the Changjiang Estuary. The analysis of current velocity profiles shows that the study area is characterized by the rectilinear current at the Xuliujing area. The maximum water and suspended sediment fluxes present during the flood period. However, since the ebb period is much longer than the flood period and the river discharge is huge, the water and suspended sediment fluxes are larger during the ebb than those during the flood. Thus, the net water and suspended sediment transport towards the sea. For example, the net water and suspended sediment are 0.71×10⁹ m³ and 2.5×10⁸ kg during a tidal cycle on November 12, 2003, respectively. Nevertheless, the current is with a rotary pattern at the bar shoal at South Trough of the Changjiang Estuary. The surveyed data also shows that the water and suspended sediment fluxes are larger during the flood than those during the ebb. We also find that a significant relationship exists between the water discharge measured at Datong Station and that at Xuliujing cross-sections from 1998 to 2004. Hence, the derived equations could be used to estimate the daily water discharge through Xuliujing, which can represent the discharge into the sea from the Changjiang River. And the historic water discharge into the sea can be retrieved by using this method. In addition, the annual water discharge into the sea is slightly larger than the annual discharge at Datong Station. However, during the dry period (water discharge < 10⁴ m³/s at Datong Station), the discharge into the sea is smaller than that measured at Datong Station, which may be resulted from the human activities.