Abstract:

NDVI and RVI are applied to extract water body information of Dongting Lake from MODIS images,and the accuracies are assessed with CCD images chosen as reference. The NDVI model is selected and different thresholds are set for the different months, which can effectively avoid extracting other features as water body by mistake in dry season and can also resolve the problem of the missing of water body in wet season. With the statistics of the water area of Dongting Lake and the corresponding observed daily average water levels, it is available to establish the relation of the water area of Dongting Lake to the water levels. In consideration that deriving the lake area from the water level information of a single station is not fully reasonable because of the uneven distribution of water levels among different hydrological stations, the formulas between the lake area and the water levels of multiple stations for the  period of 2003~2006 are established by stepwise multiple regression method with SPSS. After validated by 〖WTBX〗F〖WTBZ〗test and ttest, the regression equations and the regression coefficients are both extremely significant and can be used for forecast. Conclusions from the study are made as follows.There is no significant variation in the lake areawater level relationship at high or low water levels for the period of 2003~2006, but for a certain water level between 24 m and 29 m, the area of Donting Lake has a trend of decrease