Hydrodynamic Model And Water Level Dynamic Analysis Of Poyang Lake Based On MIKE 21 And Landsat TM Images

In view of the complex water level of Poyang Lake,the hydrodynamic module of MIKE software is used to establish the hydrodynamic model of Poyang Lake.The unstructured triangular grid with side length of 300-500m is selected for the calculation grid of the model,and the local encryption of 100-200m is carried out for the place with large terrain change.Then the terrain elevation data of Panyang Lake extracted from Google elevation map is imported into the grid and interpolated.Finally,the Poyang Lake calculation grid with terrain elevation data is obtained.The grid area is 3815km2,including125195 nodes and 81490 units.The model is improved on the basis of previous studies.The five River tributaries are added to the model as an open boundary,and a hydrodynamic model connecting the tributaries of the five rivers with the main lake area of Poyang Lake is established.Taking the water level and discharge data of Poyang lake hydrological stations provided by Jiangxi Provincial Hydrological Bureau as the boundary conditions of the model,the hydrodynamic characteristics of Poyang Lake from 2008 to2012 were simulated,and the hydrodynamic laws of Poyang Lake were analyzed from three aspects of water level,water area interannual variation,intra annual variation and seasonal characteristics.In addition,the influence of water level change in the main lake area of Poyang Lake on the six butterfly lakes,namely Benghu lake,Dahu lake,dacha lake,faba lake,Ni lake and Linchong lake,is also analyzed.Finally,the Landsat TM images of Poyang Lake from 2008 to 2012 were downloaded.After radiometric correction and atmospheric correction,MNDWI method was used to extract the water area of the image,which was compared with the simulated water area.The main conclusions of this paper are as follows:(1)In this model,the section of characteristic hydrological stations at the end of the five rivers is taken as the open boundary,and the MIKE 21 hydrodynamic model connecting the tail end of the five rivers and Poyang Lake is established by encrypting the section of the characteristic hydrological stations at the end of the five rivers.On the other hand,compared with the water level model of Poyang River,it is easy to improve the accuracy of the model.The absolute error percentages of simulated water level in Xingzi,Duchang,Tangyin and Kangshan are 1.07%,1.90%,2.55%and 2.73%respectively.The R2 of simulated water level and measured water level are more than 90%.The simulated water area is slightly larger,and the average error is 6.47%.The average error of simulated water area is 2.81%in wet season,4.01%in dry season and 10.31%in normal season.(2)From April to may,the water level of Poyang Lake changes from the normal period to the wet period,and from October to November,it changes from the normal period to the dry period.In 2008-2012,the interannual difference of water level in May is the largest,and the minimum in January.The variation range of water area is the largest from February to March and from September to October,and the largest is in April,and the smallest is in July.The correlation between water level and water area is the highest in the normal water period.The water level increases by 1 m,and the water area increases by 300 km^2.(3)The inundation frequency is opposite in wet year and dry year.The area with small inundation frequency is smaller in wet year,and the area with high inundation frequency is larger,while the area with 90%-100%submergence frequency is basically the same in different years.From the distribution of inundation frequency,the area with 90%-100%inundation frequency accounts for the largest proportion,the area with 80%-90%inundation frequency accounts for the smallest proportion,and the inundation frequency is higher in the eastern and southern regions.(4)The water level of Dishu lake is affected by the water level in the lake area,which can be divided into three types:low water uncorrelated,middle water changing and high water consistent.The dike elevation and water level outside the dike are the main factors leading to these three relationships.When the Xingzi water level is lower than 10m,the dishevel lake water level is not related to the lake area water level.When the Xingzi water level is between 10m and 16m,the dishevel lake water level and the lake area water level are the same change relationship.When the Xingzi water level is higher than 16m,the dishevel lake water level and the lake area water level are consistent.In January,February,October,November and December,there was no correlation between the water level of saucer lake and the low water level in the lake area.In March and April,the relationship between the water level and the variation was the most,and the consistency relationship between the high water level and the high water level from May to September was the most.