Normalized Difference Water Index (NDWI) among the years of 2000-2014 was calculated with 500 m-resolution surface reflective data, which was synthetized by Terra/MODIS data in 8 days.With spectral characteristics analyzed for extracting water, the dynamic changes of water area in Dongting Lake among nearly 15 years were monitored.Result shows that the water area of Dongting Lake presents regular changes with the seasons in one year: drought period generally lasts from November to April;and water area is relative larger from May to October.From 2000 to 2014, drought disaster occurred frequently in Dongting Lake during the 15 years.Water area shrank remarkably, and the function of regulating the balance between drought and fllod was weakened greatly.%利用2000-2014 Terra/MODIS卫星8 d合成的500 m地表反射率数据,计算归一化水体指数NDWI,结合地物光谱特征提取水体信息,对洞庭湖近15 a来的水体面积进行动态监测.结果表明:洞庭湖水体面积年内呈明显季节性变化,一般11月至来年4月水体面积较小,为枯水期,5月至10月面积较大,为丰水期;2000-2014 近15 a洞庭湖旱灾发生频繁,面积明显萎缩,调洪蓄水功能减弱.
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