Study On Evolution,Protection And Management Of Poyang Lake’s Wetland

Poyang Lake is a throughput type,seasonal,large shallow lake.It is essential for the guarantee of the sustainable development of Poyang Lake area to understand the evolution pattern of Poyang Lake and its wetland ecosystem,especially to have further understanding of the interrelation between the wetland ecosystem and the lake hydrology and water environment and thus to put forward administrative countermeasures and suggestions to protect the “clear water” in the Lake and maintain a healthy situation of the ecosystem.This dissertation sets out to analyze the prerequisites for the formation of flooded lakes(Levee lakes).Through collecting and analyzing the historical records of floods and droughts occurred in the Poyang Lake Basin during the 435 years from the Eastern Han Dynasty to the period of the Republic of China as well as the 138 seismic records of the north and central part of Jiangxi Province,it provides background information for the research on the historical evolution and evolution of wetland ecosystems in Poyang Lake area.It also examines the historical process and influencing factors of the formation and evolution of Poyang Lake via the historical data and poems which have been handed down so far.The results show that the vast water surface in the south of Songmenshan came into being in the Early Northern Song Dynasty,then expanded quickly and didn’t take its full form until the Southern Song Dynasty.The natural force mainly contributed to such expansion in this period.In the Ming and Qing Dynasties,the evolution was further affected by both the climate change and human activities.After the founding of new China,activities such as a large-scale embankment reinforcement and land reclamation were carried out around the Lake,which prevented the trend of an natural expansion.Then it explores the hydrological and water environment evolution in the Lake from the aspects like the characteristics of hydrological situation in modern Poyang Lake Basin,the phenomena and causes of low water level,the condition of the inlet lake sandy sludge variation as well as the Silting/scouring process and the quality of the water environment.Taking the relationship between ecology and hydrology as the mainline,it studies the dynamic evolution process of the ecological system of the wetland around the Lake and its mechanism from the aspects such as the plankton in the Lake and its distribution in terms of time and space,the evolution of wetland vegetation,the distribution and variation of macrobenthic fauna and fish resources,the dynamic changes of overwintering migratory birds and their response to the water level of the Lake.Finally,it predicts the possible development trend of the wetland ecological system around Poyang Lake in the way of analogy according to the historical evolution clue,the hydrological and water environment status quo and the revealed inside connection and the dynamic evolution mechanism of the ecological system.Meanwhile it also demonstrates the administrative goals and principles for the ecological system of the wetland around Poyang Lake and proposes related measures for the maintenance of the health of the wetland accordingly.Innovations involved in this research include:(1)Grade the floods and droughts in the historical records scientifically and assign them corresponding humidity indicators;make improvement on the P-III frequency curve fitting method to serialize the statistics about the past dry and humid periods in Poyang Lake.(2)Demonstrate that the vast water surface in the south of Poyang Lake came into being in the Early Northern Song Dynasty,then expanded quickly and didn’t take its full form until the Southern Song Dynasty as well as the influencing factors.Before the Ming and Qing Dynasties,the major cause is the natural force,while after 1949,human activities dominated the evolution.(3)Reveal the feature of the distribution,transfer,scatter and attenuation of nitrogen and phosphorus pollutants by analyzing 7 times of grid-positioning and locating and flow field water quality synchronous monitor data since 2010,which will direct the control and prevention of pollution around Poyang Lake.(4)Command knowledge about ecology and hydrology to analyze the internal relation between the wetland ecological system and the hydrological condition and water environment of the Lake and the evolution mechanism.The research results possess a significant theoretical value in protecting “a clear water” of Poyang Lake and in maintaining the health of the wetland ecological system.The countermeasures and suggestion proposed in the dissertation bring about application value in managing the Lake.