Effects of Climate Variability and Human Activities on Suspended Sediment Load in the Ganjiang River Basin, China: Fid-Bau Portal

Effects of Climate Variability and Human Activities on Suspended Sediment Load in the Ganjiang River Basin, China

Wen, Tianfu / Xiong, Lihua / Jiang, Cong / Hu, Jianmin / Liu, Zhangjun

Climate variability and human activities have substantially affected the delivery process of suspended sediment load (SSL) in rivers, which is a major driving force of river configuration and process in a basin. Thus, it is important to quantitatively identify how the SSL responds to environment changes. In this study, the Ganjiang River Basin (GRB), the main sediment source of Poyang Lake, China, is chosen to investigate how SSL changes under both climate variability and human activities. First, two nonparametric statistical methods, Mann-Kendall and Pettitt tests, are employed to detect the long-term trend and change point, respectively, of the SSL from 1958 to 2014. Then, the subbasins of GRB are divided according to the terrain slope gradient considering that the erosion rate of suspended sediments is probably influenced by terrain gradient. Effective annual areal rainfall above 12 different intensity threshold levels for different subbasins over the identified prechange period are investigated to identify the most effective rainfall vector affecting SSL in the multiple linear regression analysis. Finally, taking the prechange years as the baseline period, the impacts of environment changes on SSL during the postchange period are quantified using two methods (i.e., multiple linear regression and climate elasticity method). Benchmarked against the baseline period of 1958–1989, the mean annual SSL of GRB has decreased by 48% in 1990–2002, followed by 75% in 2003–2014. The consistent results of the two methods indicate that the impacts of human activities are the governing factor for the reduction of SSL, whereas climate variability enlarges the SSL due to the increase of areal rainfall. Furthermore, among the human-induced reductions of the SSL, about 47% (1990–2002) and 24% (2003–2014) are attributed to the sedimentation caused by the Wan’an Reservoir, the largest reservoir in the GRB, until 2014.