Relationship between the periodicity of soil and water loss and erosion-sensitive periods based on temporal distributions of rainfall erosivity in the Three Gorges Reservoir Region, China

Abstract

More variable or extreme rainfall caused by global climate change is likely to cause much uncertainty in soil erosion. Exploring the effects of changes in the timing and magnitude of rainfall erosivity on soil erosion allows to better understand the sensitivity of soil erosion to rainfall. The aim of this study was to investigate the relationships between the periodicity of soil and water loss and erosion-sensitive periods based on the temporal distributions of rainfall erosivity in the Three Gorges Reservoir Region, China. A daily rainfall erosivity model and field runoff plot monitoring were used to achieve these goals. We found that extreme rainfall has a great effect on the distributions of rainfall erosivity. The average annual erosive rainfall frequency accounts for only 21.2% of the average annual total rainfall frequency, but the average annual erosive rainfall amount accounts for 70.4% of the average annual total rainfall amount. The monthly runoff yields and sediment yields show synchronization with variations in rainfall erosivity to some extent, but the former are closer to the changes in monthly rainfall erosivity. The annual runoff yields and soil loss rates do not show synchronization, but the changes in annual soil loss rates are closer to the interannual variations of rainfall erosivity. The annual soil erosion in the study area can be divided into three periods, namely, highly sensitive periods, moderately sensitive periods and slightly sensitive periods, which indicate the erosion risks from high to low, respectively. Additionally, low vegetation coverage in highly sensitive periods and human activities in moderately sensitive periods can aggravate soil erosion.