三峡水库运用后长江倒灌鄱阳湖特性研究

三峡水库建成后，长江与鄱阳湖的关系变化一直是社会各界关注的热点问题。江水倒灌是长江与鄱阳湖关系的主要特征，其变化特性和发生条件目前仍存在一定争议。本文利用长江干流九江、八里江和大通站及鄱阳湖星子、都昌、康山、湖口站的实测资料，从江湖水位、流量关系及径流的年际、年内变化等方面，分析了三峡水库2003年建成运行后长江干流与鄱阳湖关系的变化。基于能量平衡的基本原理，研究了江水倒灌鄱阳湖的内在机理，提出江水倒灌条件的理论公式。结果表明：1）鄱阳湖具有洪水湖相、枯水河相的特性。都昌站水位在15 m以上时，湖区由河相向湖相过渡；康山站水位在17 m以上时，湖区呈现湖泊特性。2）江水倒灌主要发生在汛期7-9月，7、8、9月分别占倒灌总天数的41.6 %、24.8 %、28.8 %。三峡水库175 m试验性蓄水后，水库汛期拦蓄洪峰，在一定程度上削弱了倒灌强度。3）长江水位高于鄱阳湖水位，长江出现大的洪水过程且鄱阳湖5河总入流消退或过程平稳是倒灌形成的必要条件，而倒灌流量的大小和持续天数主要取决于长江洪水的持续时间和洪峰量级。提出的研究方法和结论可为深入认识江湖关系及影响机理提供参考，也可为鄱阳湖综合治理提供科学依据。

Characteristics of Backflows from the Yangtze River to the Poyang Lake After Using of the Three Gorges Reservoir

The change of the relationship between rivers and lakes affected by the Three Gorges Reservoir has been a major focus in recent years.The backflows from the Yangtze River to the Poyang Lake is the main feature of the relationship,and its variation characteristics and occurrence conditions are still controversial.The hydrological data since 2003 of the Jiujiang,Balijiang and Datong hydrological station located in the Yangtze River and the Duchang,Kangshan and Hukou hydrological station located in the Poyang Lake were used.The relationship between the Yangtze River and the Poyang Lake after the operation of the Three Gorges Reservoir was analyzed from the aspects of water level,flow rate,inter-annual variation and annual distribution of runoff.The internal mechanism of the backflows from the Yangtze River to the Poyang Lake based on the basic law of energy balance was discussed and the theoretical formulas were deduced.The results showed that: 1) Poyang Lake had the characteristics of both river channel and lake.The characteristics transforms from river channel to Lake when the water level of Duchang station was above 15 m.The lake characteristics was presented when the water level of Kangshan station was above 17 m;2) The backflows from the Yangtze River to the Poyang Lake occued mainly in the flood season from July to September.In the total days of backflows,41.6 %,24.8 % and 28.8 % belonged to July,August and September respectively.The intensity of backflows was weakened to a certain extent by the flood control operation after the 175 m deep experimental impoundment of the Three Gorges Reservoir.3) The conditions of water level of Yangtze River were higher than that of Poyang Lake,large floods in the Yangtze River,and total inflow of the Poyang Lake receding or remaining stable were necessary for the formation of backflows.Furthermore,the magnitude and duration of the backflows mainly depended on the Yangtze River flood peak.The proposed methods and conclusions can provide a reference for further understanding the relationship between rivers and lakes and their interaction with each other,and provide scientific evidence for the comprehensive management of the Poyang Lake.