鄱阳湖与长江干流水量交换效应及驱动因素分析

The analysis of water exchange regime research on Poyang Lake and Yangtze River and driving factors

针对长江与鄱阳湖复杂的江湖关系,立足于"湖补江"、"湖分洪"等水量交换过程,基于概念解析、方法定义等手段,提出了顶托强度指数、倒灌强度指数及水量交换系数的概念和计算方法,定量表征了长江与鄱阳湖间顶托、倒灌、"湖补江"、"湖分洪"等水量交换相互作用及年内变化过程,并利用了TFPW-MK和MK趋势分析法研究了水量交换年际变化趋势,从流域来水差异、三峡水库调度及湖区水位容积变化角度,探讨了驱动江湖水量交换效应变化的机制及量化影响.研究成果表明:综合影响下鄱阳湖汛期7~9月多年平均顶托强度27.5%,时常发生倒灌现象,平均倒灌强度8.3%,水量交换以"湖分洪"状态为主;枯水期12~4月多年平均顶托强度8.8%,水量交换以"湖补江"状态为主.2003年三峡水库运行调度以来,增加了长江中下游干流12~3月流量,湖口顶托强度增加6.0%;汛期削峰作用降低湖口顶托强度4.8%,倒灌强度减弱2.3%.近20年来鄱阳湖湖区容积变化导致多年平均顶托强度降低0.14%.长江与鄱阳湖流域来水差异是直接驱动江湖关系变化的主因.本文加深了对通江湖泊水量交换机理的认识,研究成果可为鄱阳湖湖泊综合治理提供借鉴.

In Yangtze river basin, the interaction of mid-lower stream of river and lake is becoming increasingly complex nowadays because the dam construction and the reservoir operation upstream are changing the natural coming water condition. Based on the water exchange process analysis of Yangtze River and Poyang lake in which the Poyang lake diverts flood from Yangtze river in flood season and replenishes water in dry season, three indexes are defined to quantify the water exchange characterization and monthly variation of the Yangtze River and Poyang Lake, i.e., the index ofjacking strength （JSI）, the index of intruding strength （ISI） and the coefficient of water exchange （WEC）. The method of trend-free pre-whitening Mann-Kendall （TFPW-MK） is employed to analysis the trend of annual water exchange as well as the Mann-Kendall （MK） method. The regime of river-lake water interaction are revealed in perspectives of the difference of coming water, the operation of the Three Gorges reservoir and the stage-capacity variation of Poyang lake. Results show that the flood from Yangtze River diverting to Poyang Lake is the major state during flood season （July to September）, the annual mean JSI is 27.5% with a frequently intruding phenomenon （the average ISI is 8.3%）; the water from Poyang lake flowing into Yangtze River is the major state during non-flood season （December to April） with the annual mean JSI 8.8%. After the Three Gorges being put into operation since 2003, the flow of mid-lower Yangtze River increased during the period of December to March with a JSI enlarged by 6% at Hukou station; the peak clipping effect of the Three Gorges in the flood season weakened the jacking strength and intruding strength by 4.8% and 2.3%, respectively. Also the average annual JSI is further deceased 0.14% due to the capacity evolution of the Poyang Lake in the past 20years. The differences of coming water from Yangtze River and Poyang Lake is the dominant factor which drives the evolution of river-lake interaction. This research explored the water exchange regime of Yangtze River and Poyang Lake which could be used as a reference for the comprehensive management of Poyang Lake.