卫星遥感洞庭湖主汛期水体时空变化特征及影响因子分析

基于1989~2011年的长时间序列卫星遥感数据,利用综合水体信息提取方法提取了洞庭湖区6~9月主汛期的水体信息,通过较高分辨率卫星遥感数据验证,水体面积提取精度达到90%以上。洞庭湖年平均径流入湖量、NCEP再分析资料计算的湖体上空和流域累计月平均降水量分别与水体面积变化的关系进行分析,结果表明: 1989~2011年间洞庭湖水体面积最大值主要分布在7和8月,这两个月也是洞庭湖区域发生洪涝灾情的高风险期;洞庭湖水体面积与年平均径流入湖水量的相关系数为0.67(置信度为95%);2003年以前,洞庭湖主汛期间水体面积波动比较大,2003年三峡水库运行后,洞庭湖的面积波动有所减少;洞庭湖上空累计月平均降水量对于水体面积存在正相关性,相关系数为0.68(置信度为99%);2003年以前,洞庭湖流域累计月平均降水量和水体面积相关系数为0.50(置信度为90%),2003年三峡水库运行后,两者相关性有所减弱。

ANALYSIS OF SPATIAL-TEMPORAL VARIATIONS IN THE MAIN FLOOD SEASON AND THEIR INFLUENCING FACTORS OF THE DONGTING LAKE BASED ON METEOROLOGICAL SATELLITE DATA

The study on the spatial-temporal distribution characteristics of the water in this lake and their influence factors is useful to research the climate events and the balance of sediment transport in this region. In this paper, based on the long-time meteorological satellite remote sensing data from 1989 to 2011, Dongting lake water areas were extracted using the comprehensive methods during the main flood season from June to September. The water area results were compared to the water information extracted by the remote sensing data with high spatial resolution, which showed that the accuracy reached more than 90%. The frequency map of Dongting Lake during the flood season from 1989 to 2011 year was made. This map could reflect the spatial and temporal characteristics of water distribution and could be used to assess the flood risk in the Dongting Lake region. Based on the long-time water area information, the relationship of average annual runoff amount into the lake and the Dongting lake water area was researched. The results showed that, from 1989 to2011, the largest and mean maximum of water area occurred in July and August of every year. The correlation coefficient of the lake's water area and average annual runoff amount into the lake was 0.67 from 2003 to 2011. In 2003, the Three Gorges Reservoir started to operate. Dongting Lake water area's fluctuation was large before the impoundment of the Three Gorges Reservoir. But, since after 2003 years, the Dongting Lake area fluctuation reduced significantly. Furthermore, utilizing the NCEP data, the average monthly total precipitations over the lake and over the basin were calculated, respectively. The relationships of the average monthly total precipitation over the lake, monthly total precipitation of basin and the water area were studied. The average monthly total precipitation over the lake showed significant positive correlation relationship with the lake water area. The correlation coefficient was 0.68. Before the impoundment of the Three Gorges Reservoir, the correlation coefficient of the average monthly total precipitation of the basin and lake water area was 0.50 in the main flood season. But, the correlation was weakened after 2003, which may be affected by artificial regulation. We also selected the two typical years of 1996 and 1998 to analyze their difference based the average monthly total precipitation over the lake and over the basin, which showed that the difference of precipitation over the lake and over the basin may result in the big difference of water spatial distribution. These research results were valuable to the drought and flood disaster analysis.