Quantitative analysis of the impacts of natural factors and human activities on runoff and sediment change in Tingjiang 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. Quantitative analysis of the impacts of natural facts and human activities on water and sediment changes has important practical significance for the rational development and utilization of water resources and the control of soil and water conservation in the region. In this study, the water discharge and sediment load of GuanYin Bridge and ShangHang Stations in the Tingjiang River were investigated by using long-term hydro-meteorological data from 1982-2013. And then the Cumulative Anomaly method and Multivariate Linear Ridge Regression were used to detect trends and abrupt change-points in water dischange and sediment load based on long-term observation data and GIMMS NDVI and other data and to quantify the effects of climate change and human activities on water discharge and sediment load. The results are as follows: (1) the runoff and sediment series of changring section from 1982 to 2013 mutate in 1991 and 2000, and the runoff and sediment had a similar time change trend in different stages; (2) the change trend of GuanYin Bridge and ShangHang stations was slightly different in 1982-1991, with the GuanYin Bridge showed a decreasing trend and the shanghang station showed a non-significant increasing trend. During 1991-2000, the two sites increased significantly, while the trends in 2000-2013 were significant decreasing; (3) the contributions of natural and human activities to changes in runoff and sediment are different at different time periods. However, the contributions of natural factors are generally greater than those of human activities during 1982-2013.Rainfall factor has its maximum effect of all the influence factors in changting section of Tingjiang river, with the contribution rate of more than 50% while the temperature has its minimum effect with the contribution rate of less than 10%,the proportion of NDVI and government funds is about 10%-15%; (4) in 1982-1991 and 1991-2000, the contribution of natural factors to runoff and sediment dominated by about 80%, with a weak impact on human activities of about 20%. As 2000-2013, with the continuous large amount of government funding investment, soil and water conservation projects have achieved more significant results, human activities greatly contribute to changes in runoff and sediment, accounting for about 45%.This shows that the impact of human activities on runoff and sediment has a good response to the intensity of soil erosion control in Changting County.