应对长江口咸潮入侵的临界流量经验模型研究

1994年以来,长江口咸潮入侵严重威胁当地供水安全,随着长江上游水库群陆续建成,有关部门提出了通过上游水库群压咸调度保障长江口地区供水安全的方案。为明确压咸调度的目标流量(即临界流量),基于统计分析的方法,采用多元回归分析和主成分分析方法,选取实测站点数据建立了盐度-潮差-入海流量的相关关系统计模型,研究了咸潮发生的机理;通过模型分析多次咸潮入侵数据,确定临界流量为一个变化值,潮差290～335 cm下的临界流量在9 390～21 633 m³/s之间。研究表明,当长江口咸潮入侵时,单独依靠长江上游水库调度压咸所需的流量大,响应时间长,压咸效果不明显。因此,实际压咸调度应通过流域整体调度与本地蓄淡避咸水库共同作用应对咸潮入侵。

Empirical Model of Critical Flow Rate in Response to Salt Water Intrusion in the Yangtze River Estuary

Salt water intrusion severely threatens the water supply safety in the Yangtze River estuary. To determine the target (critical) flow rate for the scheduling of repelling salt water, we studied the mechanism of salt tide by establishing an empirical model of the relation among salinity, tidal range, and flow rate into the sea via statistical analysis. We conclude that the critical flow rate is a varying value ranging between 9 390 m³/s and 21 633 m³/s when tidal range is 290-335 cm. In response to salt water intrusion, scheduling of reservoirs in the upstream of Yangtze River alone has no significant effect as it requires large discharge and long time. In conclusion, in practice we should combine the comprehensive scheduling of the whole watershed with the storage of freshwater and repelling salt water in local reservoirs.