Analysis of Daily Rainfall and Spatiotemporal Trends of Extreme Rainfall at Paraná Slope of the Itararé Watershed, Brazil

Paulo Miguel De Bodas Terassi,Givanildo De Gois,Bruno Serafini Sobral,José Francisco De Oliveira Júnior,Vitor Hugo Rosa Biffi,Emerson Galvani

doi:10.1590/0102-7786352025

Abstract

Abstract The knowledge of intensity and frequency of rainfall allows establishing predictive measures to minimize impacts caused by high volume of rainfall totals in a region. Therefore, the objective is to evaluate daily rainfall for Paraná slope of the Itararé watershed (PSIW) and to verify the spatiotemporal trend of intense and extreme daily rainfall. Rainfall data from 14 stations collected from 1976 to 2012 were used with less than 4% of data faults. Multivariate analysis based on cluster analysis technique (CA) was used applying the Euclidean distance for the identification of homogeneous groups, and the quantiles technique to classify daily rainfall. The Mann-Kendall (MK) test was used to identify trends for annual rainfall totals, annual number of rainy days (ANRD) and for the occurrence of intense (R95p) and extreme (R99p) rainfall. The CA technique identified three rainfall groups (HG I, II and III). Given the latitudinal position of the area, rainfall at the southern sector is characterized by its greater similarities with the subtropical climate, whereas in the North sector there is a consistent reduction of rainfall totals in autumn and, especially, during winter months, which are characteristic of the tropical climate. The MK test identified the downward trend of ANRD, with greater significance for the south-centered sectors of the basin. The observed trends for the intense (R95p) and extreme (R99p) daily rainfall show the predominance of reduction for the Southwest and central sector, followed by a significant increase in the Southeast and North sectors of the PSIW.

Highlights

Rainfall studies are of great importance for supporting planning and territorial management and influence several sectors of the economy and society, with direct impacts in tourism, agriculture, commerce, urban drainage, maintenance of forests and industries (Sant'anna Neto, 2008; Tostes et al, 2017)
The predominance of rainfall isolines between 1400 and 1600 mm for a large part of the Paraná slope of the Itararé watershed (PSIW) and the increase of the annual rainfall mean for the southeast sector (SE), with values ranging 1600 and 1800 mm, was verified in a similar way to the results obtained by Cavaglione et al (2000)
PSIW presents a higher average of annual number of rainy days (ANRD) for the W and S sectors, approximately 110 days, followed by a significant reduction towards the northeast (NE) sector, which averaged less than 80 days (Fig. 2b)

Summary

Introduction

Rainfall studies are of great importance for supporting planning and territorial management and influence several sectors of the economy and society, with direct impacts in tourism, agriculture, commerce, urban drainage, maintenance of forests and industries (Sant'anna Neto, 2008; Tostes et al, 2017). Hydrological studies are significant elements commonly applied for the management of water use in river basins (Araújo et al, 2008; Wang et al, 2013; Oliveira Júnior et al, 2014; Lyra et al, 2014; Terassi et al, 2016; Silva et al, 2018). In the tropical rainy regions extreme rainfall events usually cause a number of disturbances to society and cause socioeconomic and environmental damages (Amorim and Monteiro, 2010, Koga-Vicente and Nunes, 2011, Andrade et al, 2015)

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