Runoff and sediment load transport and cause analysis in Poyang Lake basin over the period 1956—2008

This paper characterizes the temporal and spatial patterns evident in annual runoff and sediment load data from selected hydrological stations in the Poyang Lake region over the period 1956—2008. The Mann-Kendall test was used to analyze for trend, interannual variability was characterized, and change point years were identified. The main causes of the observed patterns in runoff and sediment load were investigated among the variables catchment rainfall and runoff, reservoir sediment trapping, soil erosion and soil conservation works. The results indicate that overall lake inflows and outflows display a slightly increasing trend. Inflowing sediment load to the lake displayed a significant decreasing trend, with a change point occurring in 1998—1999. Outflowing sediment load from the lake for the 10 years beginning in 2002 displayed a decreasing trend. Reduced rainfall within the catchment of Poyang Lake had a significant influence on the observed pattern of decreasing lake inflow and outflow, while trapping of sediment within catchment reservoirs was the primary reason for reducing the sediment load to the lake. The reduced sediment outflow from the lake was mainly influenced by the reduced sediment inflow and sand mining within the lake.