Long Time Series Analysis Of Poyang Lake Water Area Changes Based On Remote Sensing Data

As the largest freshwater lake in China,Poyang Lake covers most areas of Jiangxi province.As a typical seasonal lake,its hydrological changes have been a research hotspot in recent years.Lakes have the functions of conserving water resources in the basin,maintaining the balance of ecological functions in the basin,maintaining water and soil,and maintaining biodiversity.Since the beginning of the 21 st century,with the economic development in the basin,the construction of water conservancy facilities has increased,the reclamation of lakes,the increase of sand mining ships,and the expansion of construction land.These human factors have caused a certain degree of impact on the ecological environment in the basin,making the lake water regime change not only affected by natural factors,but also more driven by human factors,making the water regime change more complicated.The development of remote sensing technology has enriched the monitoring methods of lake water regime changes.It has the characteristics of all-weather,multi-directional and multi-time.Compared with traditional hydrological monitoring methods,it improves the monitoring ability and monitoring methods.In order to analyze and explore the changes of Poyang Lake in recent decades,this paper uses long-term remote sensing image data(AVHRR and MODIS)to extract and analyze the water body of Poyang Lake area.And explore the driving factors of water area change.In order to extract the water area of Poyang Lake area,this paper establishes a water extraction model for MODIS and AVHRR images,and finally extracts 1340 remote sensing images of Poyang Lake area,calculates the number of water pixels in remote sensing images,and obtains the water area to analyze the multi-year changes and trends of Poyang Lake water area.The results show that the seasonal variation of water area in Poyang Lake area is obvious,and the ratio of the highest water area to the lowest water area is as high as 4 times.In recent years,the water area of Poyang Lake has a trend of prolonged dry season and shortened wet season,and the water area has shown a downward trend as a whole.The water area change of Poyang Lake has periodicity.The main period is 18 m(m represents month),and the sub-periods are 30 m,68 m and 96 m.The periodic change signal of water area is strong.The results of M-K mutation test showed that there were mutation points in the water area in 2003,2010 and 2016.2010-2012 was a year of sudden drought and flood,and the extreme water level increased in recent years.In order to explore the meteorological factors affecting the change of water area in Poyang Lake area,wavelet analysis and M-K mutation test were carried out on the meteorological data of six stations in Poyang Lake area.The results of wavelet analysis show that there is a main period of 18 m in all meteorological factors,and the secondary periods of rainfall are 68 m and 80 m,which are more similar to the period of water area.The periodic changes of water vapor pressure and meteorology are highly consistent,and the periodic changes of relative humidity fluctuate more strongly,but the periodic changes of four meteorological factors and the periodic changes of water area are global and stable.The results of M-K mutation test showed that the change trend of precipitation was similar to that of water area.There were mutation points in 2003 and 2010,and other meteorological factors also had mutation points in 2003.The results of correlation test showed that all meteorological factors were significantly correlated with the change of water area,and the correlation between rainfall and water area change was the highest.In order to explore the hydrological factors affecting the change of water area in Poyang Lake,the trend analysis was carried out in combination with the changes of runoff and sediment transport in Poyang Lake Basin.The results showed that the annual sediment transport of each station showed a significant decreasing trend.The decrease of sediment transport in Ganjiang-Waizhou station was the largest,and the decrease of sediment transport in Yangtze River-Hukou was not significant.There is a significant correlation between runoff and water area,and the correlation between them is weakened with the increase of water area and runoff,indicating that in addition to the influence of runoff,the increase of water area is also affected by other driving factors.In order to explore the influencing factors of land use change in Poyang Lake water area change,the land use type change in Jiangxi Province was analyzed.The results showed that the dynamic degree of land use change of construction land was the largest,and its area increased by 2871.2 km2 during the study period,expanding by 2 times.The type of land use in the water area has increased,which is related to the water conservancy facilities such as reservoirs and dams built in the basin.The storage and release of water conservancy facilities have an impact on the area of lake waters.In recent years,the dry and wet seasonal variation characteristics of Poyang Lake have changed,the dry season has been prolonged,and the time to enter the wet season has gradually become later.The land area of soil and water conservation such as woodland and swamp has decreased,and the ability of soil and water conservation has decreased,which also makes extreme hydrological phenomena occur.In this paper,the long-term multi-source remote sensing image data is used to quantitatively and qualitatively analyze the water area change of Poyang Lake in the past 35 years,and the time series is more detailed to show the long-term change law of Poyang Lake water area.Using the meteorological data,land use change data,sediment discharge and runoff hydrological data corresponding to the time of remote sensing image data,the changes of Poyang Lake water area and its influencing factors were explored in many aspects.