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Spatiotemporal variation of erosive rainfall and its influence on sediment discharge in the Ganjiang River Basin

Li-Ping Guo, Xiu-Long Chen, Kai-Tao Liao, Yi He, Tai-hui Zheng, Xiao-Fei Nie, Bing-Shi Xu, Li-Chao Zhang, Zhi-Jun Luo*

*Corresponding author:

ABSTRACT: Expected increases in extreme rainfall events due to global warming could lead to increased soil erosion in mountainous areas. In order to study this impact on specific areas, the present study identified the spatiotemporal variation of erosive rainfall, and the influence of its variation on streamflow and sediment discharge within the Ganjiang River Basin. Daily average rainfall at 23 national meteorological observation stations, and streamflow and sediment concentration data collected from 1964 to 2013 at six control stations were obtained. The nonparametric Mann-Kendall method and the Pettitt test were used for trend analysis and change-point detection, and the modified double mass curve method was used to quantify the effects of both erosive rainfall variation and human activities on hydrological regime shifts. Results showed that erosive rainfall had significant monthly variation, rainstorms significantly increased over the entire watershed, particularly in the downstream and in the northeast corner of the upstream subzone. While moderate rain showed an insignificant decrease in both subzones and the entire watershed, heavy rain showed no significant variation over the entire watershed, but did show a significant increase at both midstream and downstream subzones. The changes of accumulative erosive rainfall had only small effects on the sediment discharge reduction after the change-point year. In contrast, human activities contributed to more than 50% of the changes in sediment discharge in the entire basin. These findings provide a research basis for the study of extreme climate, flood disaster prevention, and soil erosion prediction over the entire watershed.