Temporal and spatial variation of rainfall erosivity in the Loess Plateau of China and its impact on sediment load

Rainfall erosivity is one of the key dynamic factors leading to water erosion, which causes widespread soil erosion worldwide. This study calculated the rainfall erosivity from 1965 to 2019, based on daily precipitation data, for 17 watersheds on the Loess Plateau. The data were also used to analyze the temporal and spatial variation of rainfall erosivity, and assess the impact of rainfall erosivity changes on sediment load in these typical watersheds. The possible causes of rainfall erosivity and sediment load changes are also discussed. The results of the study revealed that on different time scales, the spatial distribution of rainfall erosivity showed a pattern of decreasing from southeast to northwest in the Loess Plateau. Moreover, the rainfall erosivity measured by some weather stations increased significantly in May, June, and September (p < 0.05). Additionally, the changes brought on by ENSO and sunspots had a specific influence on the changes of rainfall erosivity in the Loess Plateau. Furthermore, the sediment load in the typical watersheds of the Loess Plateau showed a significant decreasing trend in yearly and monthly time scales (p < 0.05). Before 1980, the change in rainfall erosivity was an important reason for the change of sediment load and the construction of backbone check dams also intercepted a large amount of sediment. However, from 1980 to 1998, the interception effect of backbone check dams and the increase in vegetation together caused sediment load changes. After 1999, the restoration of vegetation was the main factor instigating a further reduction in sediment load. Studying the changes in the rainfall erosivity will provide a useful reference for future ecological construction and soil erosion control in the Loess Plateau.