Variability of extreme precipitation and rainfall erosivity and their attenuated effects on sediment delivery from 1957 to 2018 on the Chinese Loess Plateau

Abstract

The Chinese Loess Plateau, characterized by severe soil erosion and a vulnerable environment, is highly sensitive to extreme weather events. Understanding the changing patterns of extreme precipitation events and the associated rainfall erosivity, as well as their effects on the soil erosion and sediment delivery, is essential to the application of planning and ecological restoration on the Loess Plateau. In total, 100 meteorological stations with high-quality daily data spanning from 1957 to 2018 were used to extract eight indices to evaluate the variations in extreme precipitation and the associated rainfall erosivity, and to identify the contribution of extreme precipitation to rainfall erosivity and thus to sediment delivery. The annual extreme precipitation from six of eight indices all exhibited insignificant decreases in the study area. The average annual rainfall erosivity was 1159 MJ mm ha−1 h−1 year−1, with a slight decreasing rate of\u2009−\u20093.16 MJ mm ha−1 h−1 year−1 over a 10-year period. The rainfall erosivity presented a staged descending change ranging from the 1960s to the late 1990s, but a promptly ascending change since 2000. These variations in extreme precipitation and the associated rainfall erosivity in the region were very likely to be affected by the changing pattern of the East Asian summer monsoon. The annual precipitation from three kinds of extreme events, namely, maximum 5-day precipitation (RX5d), heavy precipitation (R20), and very wet day precipitation (R95p), contributed 60–90% of the annual rainfall erosivity, respectively. Compared with the reference period (1957–1979), the rainfall erosivity resulting from extreme precipitation events contributed less to the dramatic reduction in sediment delivery on the Loess Plateau in the periods of 1980 to 1999 and 2000 to 2018. The results imply a reduced impact of rainfall erosivity and increased human intervention on sediment delivery on the Loess Plateau in the last 60 years. These findings are useful in understanding the processes of ecohydrology and soil erosion delivery in the region.