Rainfall erosivity represents the potential of rainfall causing soil erosion. The EI30 index is a method to determine rainfall erosivity and is calculated by the product of the total kinetic energy of rainfall and the maximum intensity in 30 min. The objective of this study was to calculate rainfall erosivity in Uruguaiana, RS, Brazil, for practical applications in soil conservation, based on daily rainfall charts. For each rainfall chart, segments with the same intensity were separated, registered in worksheets, digitalized and analyzed with the software Chuveros. This program estimated the precipitation and erosivity for each rainfall, its monthly and annual totals and means, as well the rainfall patterns. 978 erosive rainfalls in Uruguaiana in the period 1963-1991 were analyzed. Mean values of annual precipitation of 1.399 mm and annual mean rainfall erosivity of 8.875 MJ mm ha-1 h-1 were found. The period from October to April accounted for 67 and 77.5 % of the annual precipitation and rainfall erosive potential, respectively. February is the month with the highest erosive potential, with 1.403 MJ mm ha-1 h-1. Of the total rainfall in Uruguaiana, 49.2 % was classified in the advanced, 24.5 % in the intermediary and 26.3 % in the delayed rainfall pattern. The mean annual erosivity in Uruguaiana may be equaled or exceeded at least once every two years. The mean monthly EI30 of Uruguaiana and surroundings can be estimated based on the relation with the rainfall coefficient, allowing to use rainfall data from pluviometers. The mathematical model with the best correlation between the mean monthly EI30 and rainfall coefficient Rc was the square model (r = 0.9948).
erosive potential; precipitation; rainfall patterns; return period; rainfall coefficient
