Temporal distribution characteristics of rainfall erosivity in Fuling District, Chongqing

Rainfall erosivity reflects potential ability of soil erosion and is the initial drive of potential water erosion. Characteristics of annual variation and interannual variation of rainfall erosivity were researched meteorological data of 49 years in Fuling District. The results indicate that: (1)The mean annual rainfall erosivity is 3571.07 MJ?mm?hm-2?h-1?a-1 in Fuling District, maximum annual rainfall erosivity is 4039.07 MJ?mm?hm-2?h-1?a-1 and minimum is 1193.76 MJ?mm?hm-2?h-1?a-1, variation of interannual rainfall erosivity is significant difference, the variation range of the annual R is greater than the variation of the annual rainfall and its erosive rainfall. (2)The seasonal distribution of R value is a single peak, concentrating from April to October and taking 94.06% of total annual R value, which can be divided into four periods, including high value period、medium value period、low value period and no erosive period. The maximum of R value is June with 670.94 MJ?mm?hm-2?h-1?a-1, next is July with 664.26 MJ?mm?hm-2?h-1?a-1, the minimum value is 0. The main variety tendency of R value is coincident with rainfall amount and its erosive rainfall but has the biggest amplitude. (3)Temporal change of rainfall erosivity and the slope surface condition can have significant effects to the occurrence of soil erosion. The crisis periods of soil erosion in Fuling District includes these conditions, May, June and July, in which rainfall varying from 147.4 mm to 176.0 mm; April, August, September and October, in which rainfall varying from 101.9 mm to115.7 mm; the special year, in which rainfall beyond 1090.6 mm.（4）The coverage situation of cultivated slope land should be put great importance for comprehensive management of a small watershed during May, June and July every year in Fuling District. All kinds of development and construction projects should avoid these three months, rational implementation for soil and water conservation should be developed on the exposed slope and the ground subsidence before the rainy season, at the same time. These sound measures are especially useful for reducing soil erosion caused by artificial activities.