Study on rainfall erosivity in typically small basin of Three Gorges Reservoir Area

Rainfall erosivity (R) is a classical index for the potential capacity that a rainfall erodes soil. With rainfall data from 2002 to 2009 of WangZhou Ecology Station, the paper applied Mann-Kendall test and Gini-coefficient to systematically research the characteristic on annual and midyear rainfall erosivity. The results indicate that: 1) the annual mean of rainfall erosivity for 8 years is 2611.84 MJh·mm/(hm2h·h·a) at WuQiao River basin, the maximum of annual rainfall erosivity is 5186.62 MJh·mm/(hm2h·hh·a), and the minimum is 1427.82 MJh·mm/(hm2h·hh·a). The coefficient of variation (Cv) is 0.52, so the annual erosivity has a medium variability. 2) The annual rainfall erosivity R-value manifests trend of changes in the local serial of annual rainfall erosivities, but the trend isn´t marked in the whole. In 2004, annual rainfall erosivity jumped from high value to low value, so the 2004 is a year of mutation. 3) In the basin, the distribution of rainfall erosivity is quite uneven, and the mean of Gini-coefficient is 0.675, rainfall erosivity highly collects in 5 months (from May to September), the proportion is at least 80% in a year and most of years is more than 90%. In addition, annual Gini-coefficients show periodicity to a certain extent, which is about 4 years.