Quantitative Study of Climatic and Anthropogenic Contributions to Streamflow and Sediment Load in the Yangtze River, China

Under intensifying human activities and climate change, runoff and sediment load have changed significantly in the Yangtze River Basin, China. Daily discharge data at six hydrological stations and daily precipitation at 175 weather stations from 1961-2020 were collected to analyze the changes in hydrological regimes. Two periods, namely the natural period (1961-1980) and the impacted period (1981-2020), were proposed to estimate the impacts of climate change and human activities by using regression analysis to reconstruct the natural runoff and the natural sediment load. The results show that there was a 0-3% difference in runoff reduction in the affected period, compared with the natural period at the five hydrological stations, except for the Datong station, while the sediment load in the whole river basin shows a downward trend varying from 17% to 40%. Human activities are the main reason for the reduced annual runoff at the other five stations during the impacted period, while climate change is the dominant factor for the increased runoff at Datong stations. This is because the precipitation-increased runoff in the basin of Lake Poyang exceeded the human-decreased runoff in the upper reaches. Human activities are the reason for the reduced sediment load in the mainstream during the impacted period, and their effects enhance over time, while climate change brings the opposite.