Variabilidade espacial dos coeficientes da equação Intensidade-Duração-Frequência (IDF) de chuvas no estado do Rio Grande do Sul

Abstract

For the management and conservation of natural resources, quantifying and understanding the spatio-temporal behavior of rainfall is of great importance and for this, the Intensity-Duration-Frequency (IDF) equation has been one of the most used tools in water resources engineering. However, the IDF equations are adjusted based on observed data. The absence of these data causes decision makers to end up using IDF equations that were not adjusted for the place of interest and end do not represent the region's rainfall intensity. Thus, having this information in abundance is of great relevance for many purposes involving this variable. Therefore, this study aimed to model the spatial variability of the coefficients of the IDF equation and provide their spatial interpolation for the state of Rio Grande do Sul using Ordinary Kriging and Ordinary Cokriging. For this purpose, IDF equations were adjusted for 258 localities using data from Annual Maximum Daily Rainfall (AMDR) of the period between 1912 and 2018. The methodology consisted of adjusting the IDF equations, performing an exploratory analysis in the series of the IDF equation coefficients, as well as in secondary variables as Average AMDR and maximum AMDR, model the spatial variability structure of the primary and secondary variables, and proceed to geostatistical interpolation using Ordinary Kriging and Ordinary Cokriging in the SGeMS software. The estimate of coefficients a and b were assessed qualitatively and quantitatively based on the results provided by the cross-validation. Among the interpolators used, Ordinary Cokriging was the method with the best performance in spatial interpolation of both coefficients, resulting in maps of the coefficients a and b of the IDF equation for the state of Rio Grande do Sul, with a spatial resolution of 5 km. It is highlighted that the results of this study will be made available on an iterative WebPage, with a friendly and easy-to-use interface so that the society can make use of this information in the management and conservation of natural resources.