倒灌是发生在湖泊与周围水体交汇处的一个重要物理过程,对湖泊水文水动力与水环境带来严重影响或干扰,进而对湖泊水质产生重要的影响或控制作用.本文采用统计方法和二维水动力-粒子示踪耦合模型来分析倒灌物理成因、倒灌发生判别与指示以及倒灌对鄱阳湖水文水动力的影响.统计表明,流域＂五河＂入湖径流、长江干流径流情势以及两者叠加作用均是倒灌的影响因素,但长江干流径流情势是影响或者控制倒灌频次与倒灌强度的主要因素.＂五河＂来水与长江干流的流量比可用来判别与指示倒灌发生与否.当流量比低于约5%时,倒灌可能发生且最大发生概率可达25%;当流量比高于10%时,倒灌发生概率则低于2%.水动力模拟结果表明,倒灌对湖区水位与流速的影响向湖区中上游逐渐减弱,湖泊水位和流速受影响最为显著的区域主要分布在贯穿整个湖区的主河道,而浅水洪泛区的水位和流速则受倒灌影响相对较小.倒灌使得湖泊空间水位提高约0.2~1.5 m,湖泊主河道的流速增加幅度可达0.3 m/s.粒子示踪结果表明,倒灌导致湖区水流流向转变约90°~180°,倒灌导致的水流流向变化能够使湖区大部分粒子或物质向上游迁移约几千米至20 km,且粒子在下游主河道的迁移距离要明显大于中上游洪泛区.
Backflow is an important mechanism controlling flow and transport in many connected river-lake systems. This study used statistical methods and hydrodynamic-particle tracking models to examine primary causal factors of backflow,indication of backflow occurrence and influences of backflow on the hydrodynamics in a large floodplain lake（ Poyang Lake,China）. Statistical analysis indicates that although both catchment inflows and the Yangtze River discharge are all the influencing factors of backflow,the Yangtze River discharge is the main controlling factor of backflow during July and October,rather than catchment inflows to the lake. The ratio of Poyang Basin inflows to Yangtze River discharge can be used as an indication of the daily occurrence of backflow,which is most likely to occur during periods when this ratio is lower than 5%. If this ratio is higher than 10%,the probability of backflow occurrence is lower than 2%. Hydrodynamic modeling reveals that,in general,backflow causes an increasing in lake water levels ranging from 0.2 to 1.5 m,and tends to increase the magnitude of the water velocities（ by up to 0.3 m/s） in the lake＇s main flow channels. Backflow disturbs the normal northward water flow direction in range of 90°-180° across Poyang Lake,and transports mass varied from a few kilometers to approximately 20 km southward into the lake. Backflow tends to increase the magnitudes of the water velocities and water levels in the lake＇s main flow channels more than in the shallow floodplain areas. The influence of backflow on the hydrological regimes in Poyang Lake attenuates with distance from the Yangtze River,as expected,but nonetheless propagates to virtually its upstream extremity.
Journal of Lake Science
hydrodynamic-particle tracking model
hydrology and hydrodynamics