长江河口淡水资源利用与避咸蓄淡水库

THE UTILIZATION OF FRESHWATER RESOURCES AND THE RESERVOIRS OF AVOIDING SALTWATER AND STORING FRESHWATER IN THE CHANGJIANG ESTUARY

开发利用长江口的淡水资源 ,首先要研究河口水质的污染程度以及咸潮入侵的时空变化规律。长江河口水质除边滩存在局部污染外 ,主槽水质良好。长江口南支、南港、北港盐水来源主要有北支倒灌和外海盐水直接入侵两种形式 ,盐水入侵具有周日、半月、季节和年际变化规律 ,由于北支倒灌咸水团的影响 ,低盐度值往往出现在大潮期和涨憩附近。通过修建边滩水库 ,达到控制引水时间、避咸蓄淡的目的。最长连续超标天数的推算是确定水库库容的关键问题 ,采用数理统计、二维数值模拟、ARMAX模型 +Markov模型等方法推算 ,几种方法相互印证 ,计算结果基本上符合实际情况。“避咸潮取水 ,蓄淡水保质” ,这是宝钢干部、科技人员总结出来的长江河口引水经验。长江口取水工程由取水系统、调蓄水库和输水系统等三大部分组成。长江口避咸蓄淡水库的成功经验 ,对沿海潮汐河口的淡水资源开发利用具有示范作用。

To exploit and utilize the freshwater resources of the Changjiang Estuary,studies on the pollutants of estuarine waters and the spatial and temporal variation of saltwater intrusion are very important.The results show that the water quality is good from -5 m isobath to the main channel in the Changjiang Estuary except local pollutions in shoal waters by the south bank,and that there are two sources of saltwater intrusion in South Branch,South Channel,North Channel of the Changjiang Estuary,one directly from the outer sea and the other from North Branch.Temporal changes in the salinity of the Changjiang Estuary have daily,semimonthly,seasonal and yearly variations.There exists lower salinity during spring tide and at flood slack in South Branch.The Baogang and Chenhang Reservoirs have been built in accordance with the regulation of saltwater intrusion,in order to control the time of intake of water and to avoid saltwater.The longest duration when the chlorinity continuously exceeds 250 mg/L were estimatied with statistics,numerical simulation,ARMAX model+Markov model,which are the key values for determining the storage capacity of reservoirs.The water intake engineering of the Changjiang Estuary is composed of water intake system,regulative reservoir and the system of water supply.The successful experience of avoiding saltwater and storing freshwater sets us a good example for exploiting and utilizing freshwater resources in tidal estuary.