Monitoring seasonal changes in the water surface areas of Poyang Lake using Cosmo-Skymed time series data in PR China

Abstract

Poyang Lake, the largest freshwater lake in China, is well known for its ecological importance as a wetland system.. Understanding dynamics change in wetlands may benefit from a joint variation analysis in changes of size, shape, position and extent of water bodies. In this study, we used Cosmo-Skymed ScanSAR mode (HH) data for one-year monitoring of seasonal changes in the water surface areas of Poyang Lake from January 2014 to December 2014. To delinate water surface area, a histogram analysis with a global threshold classification was performed, and the results were validated using Landsat8 OLI data. The results showed: Poyang Lake water body area showed a significant seasonal variation, minimum value was about 690 km2 and maximum value reached 3500 km2. A unique spatial pattern occurred during those months that a dramatic flooding or recession happened. The Cosmo-Skymed time series could capture temporal changes in the water body spatial distribution. Comparison of the resultant classification of Cosmo-Skymed and Landsat8 OLI yielded 95% of mapping accuracy and 87% of puduct accuracy. This demonstrates the X-band Synthetic Aperture Radar is applicable to detect the wetland inundation area and there is a great potential of Cosmo-Skymed constellation for water bodies monitoring, regarding relative great revisit frequency and high resolution.