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

Abstract

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.