Spatial-temporal changes of rainfall erosivity in the loess plateau, China: Changing patterns, causes and implications

摘要

Rainfall erosivity is one of the key factors influencing soil erosion by water. Improved knowledge of rainfall erosivity is critical for prediction of soil erosion and the implementation of soil and water conservation plan as well as sediment management projects under climate change. In this study, the Jing River Basin (JRB), a typical eco-environmentally vulnerable region of the Loess Plateau in China was selected as a case study. Spatial temporal changing patterns of rainfall erosivity in the JRB were first examined, followed by detailed investigations of the underlying causes through exploring the relations among annual rainfall, large-scale atmospheric circulation patterns and rainfall erosivity using the cross wavelet technique. Furthermore, implications of changing rainfall erosivity for sediment load and vegetation cover were analyzed. Results indicated that: (1) the year 1985 was a turning point in the time series of annual rainfall erosivity, demonstrating the non-stationary feature. Seasonal rainfall erosivity showed a spatial gradient with decrease from the upper to the lower stream. Rainfall erosivity was the largest in summer, and has increased significantly in the eastern basin; (2) annual rainfall erosivity showed a strong positive correlation with annual rainfall amount, implying that decrease of rainfall may have led to the reduction of rainfall erosivity in recent decades; (3) El Nino-Southern Oscillation and Pacific Decadal Oscillation were correlated with rainfall erosivity during 1982-1991, suggesting that large-scale atmospheric circulation patterns have strong influences on the changing patterns of rainfall erosivity; (4) changing rainfall erosivity had negligible impacts on the variation of vegetation cover (as indexed by the Normalized Differential Vegetation Index), but has detectable influence on sediment discharge which was further modulated by local soil and water conservation practice since the 1970s. These findings are helpful for prediction of soil erosion and adaptation strategies through local soil erosion control measures and sediment control projects.