The use of HJ-1A/B satellite data to detect changes in the size of wetlands in response in to a sudden turn from drought to flood in the middle and lower reaches of the Yangtze River system in China

This study analysed the response in the size of wetlands to a sudden turn from drought to flood along the Yangtze River system in China. The wetlands and their spatial distributions in the provinces of Hubei, Hunan, Jiangxi, Anhui and Jiangsu for three periods (April and May 2010, April and May 2011 and June and July 2011) were identified by the artificial visual interpretation of charge-coupled device images obtained in 2010 and 2011 by the HJ-1A and HJ-1B satellites. The sizes of the wetland areas of all five provinces in the three periods were 30,087.10, 23,427.68 and 31,346.49 km2, respectively, with the largest changes occurring in Jiangxi. Changes in the mean standardized precipitation index (SPI) and its patterns of spatial distribution had similar trends to the changes in the size of the wetlands of each province in the three periods. SPI was positively correlated (R2 = 0.360, p < 0.05) with changes in the proportions of the wetlands during the drought. The mean SPI of the final period after the flood was positively correlated (R2 = 0.406, p < 0.01) with changes in the proportions of wetlands. Poyang Lake and Dongting Lake were impacted most by the flood, and Hongze Lake and Caohu Lake were the least affected.