The study looked at how runoff and sediment flow into Dongting Lake from three channels changed over time. They found that the amount of water and sediment coming from Zhicheng and Three Channels has been decreasing since the late 1970s. This decrease was mainly due to changes in the Jingjiang River and the Three Gorges Reservoir. The researchers used data from 1956 to 2008 to analyze these trends and pinpoint when the changes occurred.