Dynamic Changes of Rainfall Erosivity and Its Correlation with ENSO in Huaihe River Basin, China

Rainfall erosivity constitutes a crucial driving factor in soil erosion. Based on daily rainfall data collected from 38 meteorological stations in the Huaihe River Basin (HRB) of China during 1960–2019, using Sen’s slope estimation and the Mann-Kendall trend test methods, we employed a daily rainfall erosivity model to analyze the dynamic variations of rainfall erosivity and its correlation with the El Niño-Southern Oscillation (ENSO), to investigate the spatial and temporal evolution of rainfall erosivity in the HRB and its relationship with ENSO, which plays a key role in the monitoring, evaluation, prediction, and prevention of regional soil and water loss. The results indicate that the annual mean rainfall erosivity in the HRB between 1960 and 2019 is 5522.14 MJ·mm/(hm²·h) and exhibits a decline rate of 46.32 MJ·mm/(hm²·h·10yr). Spatially, the annual mean rainfall, erosive rainfall, and rainfall erosivity display a decreasing trend from the south to the north, as well as from the southeast to the northwest of the basin. The variation trend of rainfall erosivity differs markedly across regions. Specifically, the central plain area of the basin exhibits an increasing trend, while both the western and eastern areas present an opposite trend. Furthermore, the rainfall erosivity varies significantly across various sub-watersheds with the order: upper-HRB > lower-HRB > Yishusi River watershed > middle-HRB. In addition, ENSO is regarded as one of the main factors that lead to regional rainfall erosivity changes. During the El Niño period, a relatively lower rainfall erosivity compared to that of the La Niña period is observed, while its correlation with ENSO indices is more significant than that in La Niña periods and passes the 0.05 significance level test.