Remote Sensing Monitoring And Evolution Analysis Of The Waters In The Xingyun Lake Basin

Satellite remote sensing image characterized by rapid and efficient extracting information of terrestrial object has been a significant method for extracting water information in the investigation and detection of water resources.Water resource on high mountains,as an crucial and special components of water resource,is likely to influenced by many factors because of complex topography.Hence,it is very important and practical to seek a suitable water extraction method applied to the plateau section.Remote sensing technique is only one method for extracting information of the water in plateau area.Since water resource in these areas,especially the plateau lakes,are easy to be negatively influenced,water resources protection in plateau area is badly needed.Therefore,it is necessary to dig out the problems existed in the evolution of plateau lakes by analyzing the existing water information and discovering the spatial-temporal evolution and driving mechanism of these lakes,and then find a possible program to protect and manage them.After a further understanding of different water extraction methods,this paper selects Xingyun Lake as its researching objects.The data of Landsat 8 OLI image,combined with Single-band threshold method,method of multi-band spectral relationship and water body extraction index will be used in this paper to extract water information and evaluate its extraction accuracy.In order to get a complex water information,DEM also will be used to extract information in linear rivers where Landsat 8 OLI image cannot due to the low image resolution and the realities of the rivers.According to the water information that has been obtained,the Xingyun Lake will be analyzed in aspect of spatial-temporal evolution and driving mechanism.The analysis of spatial-temporal evolution is based on the regulation of the area change and shape shift,and the driving mechanism can be analyzed not only in the driving factors but also the direction and speed of the evolution to achieve an all-around research.Several achievements can be drawn from this study,as follows.1)In the process of extracting water information of the Xingyun Lake,three methods are used but get different results.The Single-band threshold method cannot eliminate the shadow.The method of multi-band spectral relationship can eliminate the shadow less effectively,but when improved with B5/b3<0.9,it can eliminate a part of shadow.Using the water body extraction index to extract water brings about many scrawled map spots,when improved with b3>8150,it rises the extraction accuracy of the water and eliminate shadow well.2)Without high image resolution,DEM can be used when extracting water information from the tight river which is broken seasonally in the Xingyun Lake basin.But it does not perform well,because using DEM to extract is closely related to the accuracy of the DEM as well as the river's depth and width.3)The spatial-temporal evolution of the Xingyun Lake presents a trend of year-by-year decreasing in the area change.After 2001,the area of Xingyun Lake reduced faster and faster,and it reduced the most fast during the period of the 2009 and 2014.The shape increasingly narrowed down from the lake shore to the center of the lake.The change of partial shape shows different in different time.The riparian zone around the main river entrance changes most in the shape.4)There are many driving factors of the spatial-temporal evolution of the Xingyun Lake,in which they can be divided into two aspects,the climates and human activities.Climates are mainly influenced by the annual precipitation and the annual average temperature.Human activities mainly include sediment deposition,hydraulic engineering construction,the lake pollution and the beach development.The driving factors of the spatial-temporal evolution of the Xingyun Lake are interact and interplay with each other,hence it is difficult to analyze it only in one aspect.After fully understanding the terrain characteristics,regional environment and basic parameters of the image,the spectral information based on remote sensing image can extract the water information of the plateau region quickly and efficiently,but because of the limitation of image resolution and the complexity of water information situation,some small water information can not be effectively extracted.With the rapid development of remote sensing technology today,the resolution of the image is also constantly improved,the texture information,size information and shape information become richer,if only using spectral information for water extraction,it will cause data information waste,so finding a suitable method for the plateau area of small waters of the extraction is urgently needed to solve the problem.