Study On Hydrological Driving Mechanism Of The Yellow River Delta Wetland Evolution

Wetland is unique ecosystem and transitional landscape on the surface of the earth.It is not only an important resource of economic,social,cultural,life and scientific for human beings,but also the best place to test the theory of edge effect and moderate interference.Wetland is a significant part of the national and regional ecological security system.It is the basic condition of human survival and development.The Yellow River Delta wetland is the newly formed,most completely preserved and widely distributed estuary wetland ecosystem in warm temperate zone of China.It plays an important role in keeping regional water balance,water logging flood control,regulating climate,conserving biodiversity,maintaining river system integrity,etc.The Yellow River water resource is the most ecological factor that affects estuary wetland dynamic change.Hydrological process control and water supply are the necessary method for the Yellow River Delta wetland ecosystem conservation.Therefore,the study on the Yellow River Delta wetland evolution due to hydrological driving mechanism has theoretical significance and practical value for protection and restoration of wetland ecosystem in the Yellow River Delta wetland.In this paper,the Yellow River Delta wetland takes as the topical area to study the relationship between water sediment process and Delta wetland evolution.The research had carried out based on the data during from 1976 to 2014 of water and sediment and remote sensing image which got from the main hydrologic station located in the middle and lower Yellow River.The main research content includes:(1)The runoff and sediment discharge decreased of Xiaolangdi,Huayuankou and Lijin stations from 1976 to 2014.The runoff fluctuated in 1976-1977,however,during 1997-2014 it slowly increased of the three stations.The sediment discharge decreased from 1976 to 2002,and stabilized after 2002.However,after the water and sediment regulation,the runoff was slowly increased,and the sediment discharge was basically stable.(2)The Yellow River Delta wetland evolution characteristics of area,landscape pattern index and vegetation index were systematically analyzed in this paper,which was based on the data of remote sensing image interpretation in 1976,1984,1992,1996,2001,2004,2006,2010 and 2014,etc.also combined with field investigation.Due to water and sediment regulation,ecological water supplement,etc.The wetland area decreased from 1976 to 2014,and the wetland center of gravity was shifted from northwest to southeast as a whole.Plaque area,plaque number,plaque density decreased,however,the degree of fragmentation slowly increased.The coverage area of reed,tamarisk and suaeda heteopterakitag were decreased firstly and then increased.After the Xiaolangdi water and sediment control experiment in 2002,the Yellow River Delta wetland area,landscape pattern index and vegetation index were gradually recovered and stabilized.(3)The formation and evolution of the Yellow River Delta wetland is controlled by hydrological process,which is an important driving force for shaping the wetland ecosystem structure and function,the dynamic characteristics of wetland landscape pattern.Ecological evolution affected the flow and sediment process was analyzed.The results showed that water and sediment had significantly effect on the area of natural wetland,however,the area of constructed wetland was affected by human activities such as field culture,etc.in the Yellow River Delta.The plaque area,patch number and patch density of the Yellow River Delta wetland were increasing,but water and sediment which from Lijin station also strongly affected them.The protection and restoration strategies for the Yellow River Delta wetland were proposed on the basis above all.