Rainfall erosivity is a key driver of soil erosion and sediment delivery in the Lancang River Basin, but its spatiotemporal variations and relationship with sediment delivery changes remain unquantified. Based on the daily precipitation data from meteorological stations and the annual sediment delivery data from the Yunjinghong hydrologic station, the spatial and temporal variations in rainfall erosivity and how rainfall erosivity changes contribute to the sediment delivery changes were examined in this study. The results showed that the annual average rainfall erosivity varied from 202.6 to 15,946.6 MJ mm ha−1 h−1 a−1 among stations. The rainfall erosivity increased from the upstream to the downstream as elevation decreased. Basin-wide average rainfall erosivity declined by about ten percent from 1958 to 2019, with a decreasing rate of −6.3 MJ mm ha−1 h−1 a−1 per year. Summer rainfall erosivity accounted for the largest portion of the rainfall erosivity throughout the whole year. The sediment delivery increased from 1963 to 2000 but has sharply decreased since 2001. Double mass curve analysis revealed that rainfall erosivity reduction accounted for 32% of the sediment delivery decrease after 2001, with human activities (vegetation restoration and dam operations) contributing the remaining 68%.
Ximeng Xu (Fri,) studied this question.