Human activities have impacted the flow and sediment in the Lower and Middle Yangtze River. The researchers studied changes in runoff and sediment from 1950 to 2011 in different parts of the river and lakes. They found that annual runoff remained stable in some areas but decreased in others. Sediment load decreased significantly in most areas, except for the Poyang Lake. Human activities like reservoir sediment trapping and sand mining play a role in these changes, with the Three Gorges Reservoir having a significant impact on water and sediment variations in the river.