近10年来洞庭湖区水面面积变化遥感监测分析

The remote sensing monitoring analysis of Chinese Dongting Lake water area variations in last 10 years using Terra/MODIS data time series

以Terra/MODIS 8d合成的250m地表反射率数据产品MOD09Q1(MODIS Terra Surface Reflectance 8-Day L3 Global 250m)为主要数据源,采用多源信息水面提取的方法对2000年3月—2008年12月间洞庭湖区水面面积的变化特征和趋势进行了监测分析。分析结果显示:(1)洞庭湖区水面变化的季节性特征显著,其中枯水期11月—次年4月份间的湖区水面相对较小,基本在500km2左右,而洪水期5—10月份的水面则相对较大,尤其每年的7—9月份最大,维持在2000km2左右,两者几乎相差了4倍;(2)受气候变化与三峡工程初期运行等因素的共同影响,洞庭湖区水域面积总体上呈现出一定程度的下降趋势;(3)通过流域年降水量变化分析和三峡水库蓄水运行前后松滋、太平和藕池三口年径流量变化对比,发现流域内降水带来的入湖水量偏少是近年来洞庭湖区水面面积减小的主要驱动因子;(4)近年来9、10月份洞庭湖流域降水减少与三峡水库汛末蓄水同期,将共同造就最终入湖水量锐减,加重湖区夏秋连旱程度,进而诱发系列生态安全问题。

Based on the time series of MODIS Terra Surface Reflectance 8-Day L3 Global 250 m（MOD09Q1）dataset and with a multi-source information extraction method,the variation of water surface over Dongting Lake area between March 2000 and December 2008 was monitored.According to this water extent monitoring,firstly the typical seasonal（monsoon）lake＇s behavior was well observed.The minimum of surface,about 500 km 2,was in the dry season from November to the following April,while with an increasing in May,the maximum of water extent,around 2 000 km 2,was detected between July and September for each year.The water body＇s area of Dongting Lake presented an important fluctuation of 1 500 km 2 from dry season to wet（monsoon）season.On the whole,the Dongting Lake was in a vast expanse of water in the flood period,but in the dry season it only remained a few ribbon waters.There was an obvious impact from seasonality of precipitation and flood of Yangtze River.Secondly,due to the effect of regionalc limate change and initial operation of Three Gorges Project,one other major result was the decreasing of water surfaces in the Dongting Lake area during the monitoring period.Thirdly,through the analysis of annual precipitation change in Dongting Lake basin and contrast the annual runoff amount in the three bayous of Jingjiang River flowing into Dongting Lake between before and after the operation of Three Gorges Project,it was found that less runoff caused by the basin precipitation decreasing in the last ten years wast he main factor affecting the water area change of Dongting Lake from 1999 to 2008.Fourthly,becauset hat the monthly precipitation decreasing in September and October over Dongting Lake basin with the water filling of Three Gorges Reservoir starting at the end of flood season was over the same period,it would lead to the sharply falling of runoff amount which finally dropped into the lake,aggravate the drought degree of Dongting Lake area in summer and autumn,and thus induce series of ecological safety problems.