1996 年3 月长江河口水文观测和分析

基于长江河口1996 年3 月现场水文观测资料分析，得出：北支涨潮流速明显大于落潮流速，余流指向上游，存在着严重的外海盐水入侵。在南支中上游，盐度的变化受外海盐水的入侵和北支盐水的倒灌的共同影响，盐度变化与一般河口的变化规律不同；在大潮和中潮前期，盐度主要受下游外海盐水入侵的影响，在中潮和小潮期间，盐度主要受大潮期间上游北支倒灌盐水下移的影响。在南支下游，落潮流大于涨潮流，落潮历时大于涨潮历时；盐度最大值发生在涨憩，最小值发生在落憩，盐度变化受外海盐水入侵的影响，水文状况遵循一般河口变化规律。

Observed and Analysis on Hydrology in the Chagnjiang Estuary in March of 1996

Based on the analysis of the observed hydrological data in March of 1996 in the Changjiang Estuary, the following results are concluded. In the North Branch, the velocity of the flood current is obviously larger than that of the ebb current, the residual current land-ward flows, and there exists serious saltwater intrusion. At the upper and middle reaches of the South Branch, the salinity variation is affected by the saltwater intrusion from outer sea and from the upstream, i.e., from the North Branch, and is different with the variation pattern in regular estuary. The salinity is mainly influenced by the saltwater intrusion from the outer sea during spring and early middle tide, and by the saltwater intrusion from upstream during neap and later middle tide. At the lower reaches of the South Branch, the velocity of the ebb current is larger than that of the flood current and the ebb tide duration is longer than that of the flood. The maximum salinity occurs at the flood slack, and the minimum salinity occurs at the ebb slack. The salinity variation is affected by the saltwater intrusion from the outer sea, the hydrology obeys normal variation pattern in regular estuary.