Variation of Extreme Precipitation and Its Influence on Sediment Transport in Xiangjiang River Basin

［Objective］ To explore the variation of extreme precipitation in Xiangjiang River basin and its influencing factors on sediment transport. ［Methods］ Daily precipitation data from 13 meteorological stations in Xiangjiang River basin and its surrounding areas during 1965—2018 were collected, and seven extreme precipitation indices were selected and calculated using the RClimDex model. The spatial distribution characteristics were analyzed by linear fitting method and five-year moving average method, and the Cv value of each index, Spearman correlation coefficients and Kendall correlation coefficients were calculated. The temporal characteristics were observed from the linear exponential change and the five-year moving average process line. M-K mutation test, Lee-Heghinian test and ordered clustering method were used to test the mutation of the average annual sediment transport in Xiangjiang River basin. The contribution rate of extreme precipitation index to the variation of sediment transport during this period was quantitatively analyzed by double accumulation curve. ［Results］ 1) The interannual variation trend of extreme precipitation indices in the basin during 54 years showed an increasing trend except for CWD (consecutive wet days). The duration of extreme precipitation events was prolonged, and the precipitation and precipitation intensity increased significantly. 2) The spatial distribution of each precipitation index was basically consistent with the topographic characteristics, and the trend was gradually increasing from the southwest to the northeast of the basin, and the maximum values of the seven indices were found at Nanyue Station. 3) Abrupt changes occurred in 1984 and 1997. During 1985—1997, the extreme precipitation index R99P (extremely wet days) had the greatest impact on the reduction of sediment transport in the basin, with a contribution rate of 10.5%. During 1998—2018, the same extreme precipitation index R95P (very wet days) had a change in the reduction of sediment transport. The contribution rate was 18.1%, but the influence of extreme precipitation index on sediment transport reduction was less than 20%. ［Conclusion］ Extreme precipitation has a certain effect on the reduction of sediment transport in the basin, but human activities are still the main factor leading to the reduction of sediment transport.