2.1 Study area
Study area in the Poyang Lake basin, which belongs to the south bank of the middle Yangtze proper and connects with the Yangtze River, with latitude 28°22 ’– 29°45’ north and longitude 115°47 ’– 116°45’ East. The basin covers an area of 162225km2. The Poyang lake basin has five streamflows, including the Ganjiang, Fuhe, Xinjiang, Raohe, and Xiushui. Those ‘five rivers’ runoff flow into Poyang Lake and retarded. After inflow storage, the lake water flows into the Yangtze River through the estuary of the lake. Meanwhile, because of the connection with the Yangtze River, the Yangtze River runoff also will flow into the lake through the lake estuary (Shankman, Keim, and Song 2006).
Poyang Lake basin belongs to the subtropical monsoon climate, with intense solar radiation. Due to the apparent difference in precipitation in the basin, the seasonal variation of runoff into the lake of the ”Five Rivers” is very significant; from April to September, the runoff into the lake accounts for 75% of the whole year. Therefore, the flood season in Poyang Lake is from June to September yearly, and the dry season is from November to February the following year. In winter, the area of the lake shrink, and the lake bed is bare(X. Li and Zhang 2015).