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

André Quintão de Almeida,Diego Campana Loureiro,Jodnes Sobreira Vieira,Rodolfo Marcondes Silva Souza,Marcus Aurélio Soares Cruz,Donizete dos Reis Pereira

doi:10.1590/s0100-204x2017000600001

Abstract

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.

Highlights

Brazil, due to its size, is affected by different climate types
The study was carried out using data from the semiarid region of Brazil (Figure 1 A), which has an area of 969,589 km2, including parts of nine Brazilian states (Brasil, 2005): Alagoas, Bahia, Ceará, Minas Gerais, Paraíba, Pernambuco, Piauí, Rio Grande do Norte, and Sergipe
The greatest standard deviation in the data was obtained in December and the smallest one in September, which showed the greatest rate of generalized drought throughout the semiarid region; it should be noted that this month had a low average erosivity index (57 MJ mm ha-1), this value might be enough to cause soil loss, depending on other factors

Summary

Introduction

Due to its size, is affected by different climate types. According to official data from Ministério da Integração Nacional, the Brazilian semiarid is located in most of the Northeastern region of the country and covers an area of 969,589 km (Brasil, 2005). The semiarid climate has very peculiar characteristics: low annual rainfall values, ranging from 445 to 1,218 mm, Pesq. The characterization of rainfall in a certain region is an important tool for soil management and conservation (Silva et al, 2010). This is because, in the erosive process, the factor erosivity reflects the capacity of rainfall to erode the soil in an area with no cover, which is directly related to the duration, intensity, and frequency of precipitation events (Montebeller et al, 2007; Peñalva Bazzano et al, 2010; Mello et al, 2012)

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Conclusion