Modelling the spatial dependence of the rainfall erosivity index in the Brazilian semiarid region

Abstract

The objective of this work was to model the spatial dependence and to map the rainfall erosivity index (EI₃₀) in the semiarid region of Brazil. Registers of monthly erosivity from 210 rainfall stations were used, with daily time series equal to or greater than 15 years. Based on the values of the EI₃₀, a spatial dependence model was made by adjusting the semivariogram. From the semivariogram models, erosivity isoline maps were generated with a kriging interpolator. According to the historical data series, the maximum monthly average value of the EI₃₀ was observed in March, and the annual value ranged from 1,439 to 5,864 MJ mm ha^-1 per year, classified as low and moderate, respectively. The highest EI₃₀ values were obtained in the northern and southern extremes of the semiarid region. Average spatial dependence was observed for rainfall erosivity, in most months, especially with the spherical semivariogram model. The range of erosivity varied from 62 to 1,508 km for the monthly EI₃₀ and was of approximately 1,046 km for the annual one. The applied model, with the validation of the semivariograms using the jackknife test, allows the spatialization of the EI₃₀ for the semiarid region of Brazil.