Quantitative Attribution of the Surface Area Reduction of Poyang Lake over the Last Two Decades

The surface area of Poyang Lake, the largest freshwater lake in China, has decreased substantially in recent decades due to multiple potential factors, including the change in inflow into the lake, flow rate regulation of the Three Gorges Reservoir (TGR), shifts in the Yangtze River stage-discharge relationship, and sand mining in the lake. Here, the daily surface area of Poyang Lake is estimated using Landsat image data and water-level measurements. Multiple regression models are then used to establish the relationship between the surface area and the predictor variables of inflow into the lake, Yangtze River water level, and cumulative sand mining. The contributions of each driving factor to the reduction of Poyang Lake’s surface area are quantified by scenario comparison method. The results reveal that the mean annual surface area of Poyang Lake decreased by 388 km2 (approximately 15% of the total surface area), from 2,585 km2 in 1980–2002 to 2,197 km2 in 2003–2016. In terms of overall contribution, sand mining is identified as the most important factor in the surface area reduction, followed by the shift in the Yangtze River stage-discharge relationship and the TGR flow rate regulation. In terms of monthly scale impacts, sand mining reduced the surface area by more than 260 km2 each month. The shift in the Yangtze River stage-discharge relationship reduced the surface area by 16–156 km2 during the dry season (November–May) of the Yangtze River and increased the surface area by 33–84 km2 during the flood season (June–October). The TGR flow rate regulation has the opposite effects: it reduced the surface area by 109–172 km2 during the impoundment period from September to October and increased it by 19–68 km2 during the release period from December to June.