Rainfall Erosivity Assessment Base on Daily Rainfall Values in the Menglun Area of Xishuangbanna

Using the daily rainfall values to calculate the rainfall erosivity will benefit to the local soil and water conservation activities,improve the sustainable development of tropical agriculture ecosystem.Based on the annual mean rainfall value(1 492.9 mm)from 1959 to 1998 at Menglun climatic station in Xishuangbanna,the erosive rainfall standard referring the values higher than 12.7 mm per 24 h,the daily rainfall values during 1992 to 2006 at the station were analyzed,with the help of formula M=α∑k j=1(Pj)β,which derived from the RUSLE generated from USA for rainfall erosivity calculation,the rainfall erosivity under the unit of half-month was calculated,then the seasonal variation pattern of the rainfall erosivity was generated.The results showed that in terms of annual rainfall amount,45% years were the normal rainfall amount level,the numbers of abundance rainfall years more than deficit rainfall years,total annual rainfall amount increased slightly in the focusing duration comparison with the historical annual mean rainfall records;the annual erosive rainfall amount accounted for over 75% of the total yearly rainfall amounts,the erosive rainfall amounted basically appear in the monsoon season;the annual rainfall erosivity varied from 160.742 to 350.393 MJ·mm·hm-2·a-1,the largest value appeared in 2001;monthly rainfall erosivity changed dramatically from 1.107(in Jan.)to 57.189(in Jul.)MJ·mm·hm-2·h-1,the differences reach over 50 times in different months;the general changing pattern was similar with the rainfall amount variation,and typical seasonal patterns.