潮汐分汊河口盐水入侵类型探讨──以长江口为例

Study on Type of Saltwater Intrusion for Tidsl Braoching Estoarits──A Case Stody on the Changjiang Estuary

长江河口具有分汊、心滩、串沟和江心沙岛等地貌形态，系典型的潮汐分汊河口。咸潮入侵形式有外海直接入侵、倒灌、漫滩归槽和浅滩通道水体交换等四种类型，形成其特有的盐度时空变化规律，导致南支主槽存在一个氯离子含量比其上下游均要高的高氯度带，以及大潮期盐度低，小潮或寻常潮期间盐度反而高等特殊现象。

The geomorphic features of the Changjiang Estuary are characterized by the multi-order bifurcations, active submerged sandbars, mid-channel sandbars, creeks and riffle. Our study indicates the saltwater intrusion has the following four forms: l) direct intrusion from the outer sea; 2) saltwater intrusion by tidal flooding, 3) water exchange between creeks or shallow water channel, 4) salt water upstream from other waterways. These results complicate temporal and spatial changes in salinity. A high chioriulty concentration zone exists between the Liuhekou to the Sidongkou along the South Branch. The salinity value during neap tider or ordinary tide is higher than that of during spring tide.