Assessing natural and anthropogenic influences on water discharge and sediment load in the Yangtze River, China

- A significant decrease in sediment load in the mainstream and seven tributaries of Yangtze River
- Quantitative assessments of climate and human activity on water discharge and sediment load have been analyzed.
- Dam construction and soil and water conservation played an important role in sediment reduction.
- The change of sediment affected the mid-lower reach river channel and delta of Yangtze River.

The water discharge and sediment load of rivers are changing substantially under the impacts of climate change and human activities, becoming a hot issue in hydro-environmental research. In this study, the water discharge and sediment load in the mainstream and seven tributaries of the Yangtze River were investigated by using long-term hydro-meteorological data from 1953 to 2013. The non-parametric Mann-Kendall test and double mass curve (DMC) were used to detect trends and abrupt change-points in water discharge and sediment load and to quantify the effects of climate change and human activities on water discharge and sediment load. The results are as follows: (1) the water discharge showed a non-significant decreasing trend at most stations except Hukou station. Among these, water discharge at Dongting Lake and the Min River basin shows a significant decreasing trend with average rates of − 13.93 × 108 m3/year and − 1.8 × 108 m3/year (P < 0.05), respectively. However, the sediment load exhibited a significant decreasing trend in all tributaries of the Yangtze River. (2) No significant abrupt change-points were detected in the time series of water discharge for all hydrological stations. In contrast, significant abrupt change-points were detected in sediment load, most of these changes appeared in the late 1980s. (3) The water discharge was mainly influenced by precipitation in the Yangtze River basin, whereas sediment load was mainly affected by climate change and human activities; the relative contribution ratios of human activities were above 70% for the Yangtze River. (4) The decrease of sediment load has directly impacted the lower Yangtze River and the delta region. These results will provide a reference for better resource management in the Yangtze River Basin.

The double mass curve (DMC) were used to detect trends and abrupt changes-points in water discharge and sediment load and to quantify the effects of climate change and human activities on water discharge and sediment load in the Yangtze River. The detail description for quantifying the contributions of climate change and anthropogenic activities on water discharge and sediment load see Supplement data Fig. S1.231