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 20 11,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 20 11 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 to 20 11,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 20 11.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.