Temporal and Spatial Variation Trend of Rainfall Erosion in Songtao Reservoir Basin of Hainan Island

Based on the daily rainfall data from 25 rainfall sites (1960-2015) in Songtao Reservoir Basin and surrounding area, the rainfall erosion of each station was calculated, and the statistic and inverse distance weights methods were used to analyze the spatial and temporal variability trend of rainfall erosion. The results showed that the average rainfall erosion force range from 1.27×10⁴ MJ·mm·(hm²·h)^-1 to 2.19×10⁴ MJ·mm·(hm²·h)^-1, and the average value is 1.62×10⁴ MJ·mm·(hm²·h)^-1, which is significantly correlated with the annual average rainfall in the watershed (correlation coefficient 0.693, P＜0.01), the spatial distribution law is consistent with the average rainfall for many years, generally, from north to south, it is increased firstly, and then decreased; with the increasing of latitude, the rainfall erosion force increased, with the increasing of longitude, the rainfall erosion force decreased; in spring, autumn, and non flood season, the change trend of rainfall erosion is not significant, there are no significant changes, however, in the year, summer, winter and flood season, the change of rainfall erosion is significant; in the rainy season, the rainfall erosion decreased, while the remaining periods increased; the rainfall erosion in the most sites in the basin are increased, the rainfall erosion in Laocun, Yafu, and Fulei are increased during most period of time significantly; which means the greater risk of soil and water loss. In 1970, the significant mutation was taken place. The variation period of rainfall erosion force in watershed was 3.5a, and the oscillation period was 5-16a.