Erosividade das chuvas no Estado do Mato Grosso

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Considering the importance of agriculture on conservation planning and management of water resources combined with the agricultural character of the Mato Grosso State, it is fundamental important the development of research that can help farmers and technicians in planning the soil conservation use and management. In this way, the objective of this study was to determine the rainfall erosivity for the meteorological stations of the Mato Grosso State, and make its spatialization to localities of the State without stations. The work was divided into 4 stages: the first in the calculation of rainfall erosivity (EI30), using the methodology for estimating the kinetic energy proposed by Foster et al., 1981, the rainfall coefficient (Rc), using the methodology proposed by Lombardi Neto (1977), and relations between EI30 and Rc for 10 stations pluviographic of the Mato Grosso state. The second is consisted of equations adjusting in order to estimate the monthly EI30 from Rc monthly values. The third corresponded to estimate the EI30 monthly of the 105 stations without pluviographic data. The choice of equations was based on the rainfall similarity of the rainfall between the pluviographic and pluviometric stations which was obtained from correlation study of the precipitation average daily of the stations. Finally, the fourth step was to generate maps of isoerosivity which has been achieved by adjustments of semivariograms andr later interpolation using the krigage technique. The adjusted equations with the data set of plviographic stations, except the Poxoréu station, were significant (p = 0.01) and determination coefficients (R) high, ranging from 0,67 to 0,99. After applying these equations to Rc data of 105 pluviometric stations of the state, it was observed that, in general, the more erosive rains were concentrated in the period of October to march for all stations analyzed, concentrating this period of 77% to 94% of average annual erosivity. In the station Passagem da BR309 was detected the largest index of rainfall erosivity (13.122 MJ.mm.(ha.h.year)-1) while the lowest was observed in the General Carneiro station (3.895,2 MJ.mm.(ha.h.year)-1). From the maps of monthly average isoerosivity is possible to see that the highest values of EI30 occurred in the months of December, January, February and March in which, in general, ranged from 700 to 2.200 MJ.mm.(ha.h)-1, concentrating the largest values in the north of state. In the months that showed lower index EI30, the highest values were in the south of state. The values of average annual rainfall erosivity (R) for the State of Mato Grosso ranged from 4.000 to 13.000 MJ.mm.(ha.h.year)-1. Regarding the spatial distribution of R for the State, it was found that the highest values of R were recorded in the north and the south central region, with R values large than 10.000 MJ.mm.(ha.h.year)-1. These results led to draw the following conclusions: the rainfall erosivity of the sites studied are quite different due to the physiographic features and stations location, so it is not recommended to use R values from a place to another, with the exception of Poxoréu station, the potential model was significant to represent the relationship of the EI30 and Rc; the most rainfall erosive potential concentrated in the period October to March, this is, period, for most stations of the Mato Grosso state, with higher possibilities of water erosion; ; and form of the spatial distribution map of average annual erosivity was possible to divide the Mato Grosso State in three zones with annual rainfall erosivity similar: a high average, high and very high.

ASSUNTO(S)

erosão ciencias agrarias coeficiente da chuva (rc) e dados pluviográficos erosion the rainfall coefficient (rc) and rain charts data

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