Streamflow and sediment load changes from China's large rivers: Quantitative contributions of climate and human activity factors

Riverine water and sediment discharge drive global material circulation and energy transfer, and they are crucial to the biogeochemical cycle. We investigated the changes in water-sediment fluxes in six major rivers from north to south in China from the mid-1950s to 2020 under the influence of climate change and human activities, and quantified the contributions of these specific influencing factors to water-sediment flux changes. Results showed that streamflow of the Songhua, Liao and Yellow rivers decreased significantly (p < 0.05). The sediment load of all rivers reduced significantly (p < 0.01) except the Songhua River. Streamflow or sediment fluxes to the oceans have increased or stabilized since around 2000, and the terrestrial sediment yielding center in China has shifted southward from the Yellow River to the Yangtze and Pearl rivers. The contribution of precipitation to the streamflow and sediment load changes decreased from north to south across the six rivers. From the mid-1950s to 2020, the underlying land surface change was the dominant contributor (>70 %) to reducing streamflow in the Songhua and Yellow rivers, while climate change (>50 %) was responsible for decreased streamflow in the Liao and Huai rivers. The sediment load reduction of the six rivers was attributed mainly to human activities. Among them, dam construction, human water consumption and catchment land surface change have reduced the total sediment load into the sea by 49 %, 25 % and 19 %, respectively. These results highlight that north-south variability in water and sediment flux are driven by both natural and anthropogenic forcing agents.