Monitoring Area Changes Of Important Lakes Across The Yangtze Basin Downstream Of Three Gorges Dam By MODIS Data

In this study, the time series of area changes of four typical lakes including Poyang Lake, Dongting Lake, Tai Lake and Chao Lake are examinedusing Terra/MODIS 16-Day L3 global vegetation index product(MOD13Q1) with a spatial resolution of 250 m between 2000 and 2014. The driven factors of lake area variations are analyzed with station-based meteorological and hydrological data. The results show:(1) To discriminate the spectrum value of water body from vegetation, land and others, suitable thresholds are selected using a decision tree model developed in this study.Lake area derived from Landsat ETM+ and MODIS data indicate a good correlation( r=0.91) and overall high accuracy(89.59%);(2) Four lake show seasonal variability,especially Poyang Lake and Dongting Lake. The annulaverage of four lakes showed a decrease during 2000-2014. Poyang Lake's area ranges from763.12 to 3260.12km2 and Dongting Lake in 462-3046km2. However, Tai Lake and Chao Lake show a smaller area changes, 436.83, 183.75km2, respectively;(3)The annual inundation index and Monthly inundation index show Spatialdistribution of four lakes,The extracted area of four lakes whichannual inundation index is greater than 70%, 80% and 90% are decreasing from 2000 to 2014.(4)The decreased precipitation plays a dominant factor for lake area decrease, although the construction of Three Gorges Dam could contribute to lake shrink indry season.