Variabilidade das precipitações pluviais e ocorrência de secas na Bacia do Rio Uruguai - Brasil

Abstract

In the current context of climate change, extreme events are intensifying and causing greater damage and losses on a global scale; therefore, studies in Geographical Climatology are becoming increasingly necessary. The focus of this research is on drought patterns and minimum rainfall extremes in the Uruguay River Hydrographic Region (RHU), taking into account recent records of more intense droughts during the summers of 2020 to 2025 in different areas of the Basin. This is related to the impacts of drought on rural areas and urban water supply, with a view to ensuring Water Security for the 16 Basin Committees of this Hydrographic Region. It is important to note that each of these has its own socio-spatial particularities, such as: (i) rainfall regime, (ii) vegetation type, (iii) territorial extent, (iv) number of municipalities, (v) population density, among others. These are some of the elements that highlight the multiscalar nature and complexity of the subject. The overall objective of this research is to analyze rainfall variability in the Uruguay River Hydrographic Region (RHU), focusing on the characterization of rainfall patterns and the occurrence of droughts. The methodological procedures were carried out through the collection and organization of daily rainfall data from 17 meteorological stations distributed across the RHU territory, covering the period from 1991 to 2020. The analyses and quality control were performed using six climate indices on the Climpact platform: (i) PRCPTOT (annual total precipitation); (ii) CWD (consecutive wet days); (iii) R95p (very wet days, extreme precipitation); (iv) R99p (maximum extreme precipitation); (v) CDD (consecutive dry days); and (vi) SPI/12 (12-month Standardized Precipitation Index). The second stage of the analysis involved mapping the spatial variations of the indices for each station. Next, a detailed assessment was carried out to identify the number of stations and the years with above-average values, as well as the maximum values recorded at each station during those years. The analysis of rainfall variability in the RHU revealed important patterns of consecutive dry and wet periods between 1991 and 2020. The results indicate a trend toward an increase in dry days in some areas, particularly in the middle section of the basin, and point to an intensification of drought events. The lowest precipitation records were concentrated in the northern region of Santa Catarina and in the locality of Palmeira das Missões, in Rio Grande do Sul. The study enabled the identification of trends in drought patterns that should be considered in the planning of public policies aimed at climate risk adaptation and mitigation. Finally, it highlights the need to strengthen water management among the 16 Basin Committees and the 347 municipalities of the RHU, with a focus on the region’s water security.