基于鄱阳湖物理模型的江湖关系水流交换特征研究

Poyang Lake is the largest freshwater lake in China, which plays an important role of flood regulation and storage water supply as well as the ecology and environment compensation in the middle and lower Yangtze River and the lake. Recently, extreme flood and drought frequently occur in Poyang Lake and middle and lower Yangtze River, and the people's life is under threatened.It is necessary to study relationship among the system of Yangtze River-Poyang Lake-"Five Rivers" thoroughly. As the foundation characteristic, water exhange is the most important process in this study. In this project, characteristics of water exchange among the system of Yangtze River-Poyang Lake-"Five Rivers" will be studied by the methods of mathmatic modeling and physical modeling. Based on the impact of geometry scale distortion and time scale on the flow characteristics, corrected methods of eliminating the effect of scale distortion will be proposed in this study. Eventually, the distorted physical modeling experiment with corrected methods will be used to simulate water process of water exchange between rivers and lake. This will be the first time of simulating water exchange process between rivers and lake by using distorted lake modeling. This research will not only attribute to expand research contents and theory system of distorted physical modeling, but also quantitively analyze the effect of the Three Gorges Project on the water exchange beteween rivers and Poyang Lake to a certain extent. Results of this research will provide scientific support for the follow-up study, such as sediment exchange and pollutant exchange beteween rivers and Poyang Lake.

鄱阳湖是我国最大的淡水湖，对长江中下游及鄱阳湖区洪水调蓄、水源供给和生态环境调节具有重要作用。近年来鄱阳湖及长江中下游地区极端洪旱事件频发，给人民生活造成了极大威胁。因此有必要对鄱阳湖江湖关系进行深入研究，其中水流交换关系作为江湖关系的基础，成为当前研究的重点。本项目旨在通过数学模型和物理模型相结合的方法研究长江-鄱阳湖-江西五河之间的水流交换关系，在分析物理模型几何变率和时间比尺效应对水流特征影响的基础上，提出降低实体模型变态对试验精度影响的补偿校正方法，在数学模型中进行交互验证，并最终利用校正后的模型系统模拟江湖水流交换过程。这是国内首次将变态实体模型用于模拟鄱阳湖江湖关系水流交换的研究，本项目不仅能够丰富实体模型的研究内容以及模型变态问题的理论体系，还能一定程度上定量描述三峡水利枢纽工程对鄱阳湖江湖水流交换的影响大小。研究成果可为后续的鄱阳湖水沙、污染物交换研究提供科学支撑。

通过考虑三峡工程正常蓄水运用后的调度方式，采用江湖河网水沙数学模型研究预测三峡水库在汛前增泄期、汛末减泄期、枯期等不同时期的调度运行对湖口水位流量的影响。在前期数值模拟研究的基础上开展物理模型试验研究典型特征年份三峡工程预泄期、蓄水期和枯水发电期运行对鄱阳湖水情的影响，预测三峡工程运用初期湖区水位、面积变化过程和趋势。建立了鄱阳湖区二维水动力数学模型，开展了长江干流和五河来流对鄱阳湖水动力变化影响的研究，进行了不同变化情景下的计算。.研究表明，1）按三峡枢纽初步设计阶段确定的调度原则，对典型年进行调度计算；鄱阳湖出口湖口站在枯水年和中水年的预泄期5～6月平均水位抬高约0.21～0.62m；蓄水期10月月均水位降低约1.57～2.17m；丰水年汛期7～8月平均水位比天然情况降低约0.14～0.19m；2）三峡预泄期，鄱阳湖区水位出现了不同程度的抬高，但是不会增大湖区防洪压力；蓄水期，鄱阳湖区水位明显降低，水位下降幅度从湖口至湖区逐渐减弱，水位下降幅度表现为枯水年>中水年>丰水年；枯水发电期，鄱阳湖入江水道水位升高，水位影响程度表现为枯水年>中水年>丰水年，星子站上游湖区各站不受影响；蓄水期将造成鄱阳湖湖区水面面积较大损失，增泄期调度增加湖区面积；枯水期基本无影响；3）湖口水位变化对鄱阳湖水位影响的程度和范围有限，水位变幅从湖口向湖区呈递减的状态；在枯水期鄱阳湖受湖口水位影响范围相较于汛期要小；湖口水位增加对水位的影响范围比湖口水位减小对水位的影响范围小；湖口水位和入湖流量同增或同减，会加强湖区的水位变化，减弱湖区的流速变化；其他情况结果则正好相反。.研究成果有助于三峡工程对鄱阳湖区水情影响的定量的认识和宏观把握，深入揭示鄱阳湖江湖关系及变化规律，为鄱阳湖综合治理方案制定和实施提供科学依据和技术支撑。