三峡水库运行以来入海径流与盐水入侵响应研究

Research on response of salt water intrusion to runoff emptying into the sea since Three Gorges Reservoir operation

为研究三峡水库运行以来盐水入侵对长江河口的影响,采用自行编译完成的Delft3D 4.01.01版本源代码,建立了大通到长江口外的二维水流盐度数学模型,综合分析入海径流量与盐水入侵的响应机制。研究表明Ddlft3D 4.01.01源代码能很好地模拟计算长江口水动力盐度分布,验证误差仅有10%~15%。从计算结果可以看出,盐水入侵情况与径流量关系明显,当大通站径流量为5 000 m^3/s时,长江口南支与北支均发生盐水入侵。随着径流量增大,淡水区域面积由南支右岸向下游进一步扩大。当径流量超过30 000 m^3/s时,南支基本不存在盐水入侵情况,可以保证水库正常取水安全。当存在风力作用时,盐水入侵明显,盐水浓度达到3.5 ppt以上,而无风情况下,盐水入侵趋势减弱,长江口南支河段区域的盐度一般满足灌溉水的标准(2.2‰)。

Salt water intrusion is a widespread problem in coastal tidal estuary,in this paper,the compiled source code of Delft 3 D 4. 01. 01 was used to establish a two-dimensional mathematical model of salinity in the estuary of the Yangtze River to study the response mechanism between runoff into the sea and salt water intrusion. The result shows that the Delft 3 D 4. 01. 01 source code is qualified to simulate the hydrodynamic salinity distribution in the Yangtze Estuary with only 10% ~ 15% verification errors. Otherwise,the case is evident that saltwater intrusion is related with the runoff. When the runoff at Datong station is5000 m^3/s,the saltwater intrusion occurred both in the South and the North Branch. As the runoff increases,the fresh water area expands toward downstream from the right bank of South Branch. When the flow rate exceeds 30000 m^3/s,salt water intrusion no longer occurs in the South Branch,so the security of water intake can be guaranteed. In windy day,there will be obvious salt water intrusion with salinity concentration more than 3. 5 ppt,in calm weather,the trend of saltwater intrusion become weak,and the salinity concentration in the South Branch generally meet irrigation water standard（ 2. 2 ‰）.