3.1 Extraction Method of Water Area
Using the multi-band pixel value comparison method to extract water information and calculate water area. Using spectral characteristics of water images to set thresholds, and extract lake water information, calculate the mean area of the annual flood and dry season(Vahtmäe and Kutser 2013). Landsat7 satellite broke down, repaired it, and the result was consistent with the pixel values of adjacent pixels. After manual visual verification, the extraction of water information is accurate.