长江河口咸潮入侵规律及淡水资源利用

The Pattern of Saltwater Intruding into the Changjiang Estuary and the Utilization of Freshwater Resources

长江河口系多级分汊潮汐河口 ,其盐水入侵有外海入侵、倒灌、浅滩通道水体交换及漫滩归槽等 4种形式 ,时间上有周日、朔望、洪枯季、年际等变化特点 ,南支—南港河段纵向上存在 3条盐度梯度急剧变化分界线 ,形成其特有的盐度时空变化规律。研究成果对宝钢水源长江引水方案的形成起了重要作用 ,并为陈行水库的选址、库容设计提供了基础数据。在长江河口建库 ,研究工作的重点是推算最长连续取不到合格水的天数 ,它是确定库容的关键数据。

The geomorphic features of the Changjiang estuary are characterized by the multi order branching. The saltwater intrusion has the following four distinct forms:direct intrusion from the outer sea;saltwater exchange by shoal passages;saltwater downstream from other waterways;saltwater intrusion by tidal flooding. Temportal changes in the salinity of the Changjiang estuary have daily, semimonthly, seasonal and yearly variation. There exists the sharp three demarcation lines of salinity gradient along the South Branch-South Channel. Two main problems had to be solved before building reservoirs of avoide saltwater and store freshwater in the Changjiang estuary. One is to calculate the longest duration that the chlorinity exceeds 250×10 6 in the water resources area, which is the criterion value for determining the storage capacity of reservoirs. Mathematical methods including the cybernetics, the frequecncy spected analysis and mathematical modelling are adopted here to get more correct times when the chlorinity exceeds 250×10 6 . And the other is to determine reasonably site of the pumping station and the height of water intake of water pumps from the river bed. The above problems can be solved after understanding the pattern of temporal and spatial variation of the saltwater intrusion in the Changjiang estuary. The above conclusions have played an important role in forming the reservoir scheme of the Baoshan lron and Steel Plant, and supplied basic data for selection of the postion and storage capacity for the Chenhang reservoir.