Extremos de precipitação e vazão associados às características naturais e antrópicas das regiões hidrográficas do São Francisco e do Paraná

Abstract

The occurrence of natural disasters due to extreme extremes of reasoning and flow is an increasingly common reality in the world. In most cases, the lack of prevention and mitigation plans associated with lack of management by public agencies maximizes damages and losses. In Brazil, hydrographic regions determine water management throughout the territory. However, it is worth emphasizing that the methodologies and solutions created to face such stresses are not necessarily the same for any region, given that each of them presents different characteristics in the economy, social, demographic and water management. In this context, the research aims to estimate the recurrence of rainfall, as well as to search the existing relationship with the physical, socioeconomic and demographic characteristics in the hydrographic regions of São Francisco and Paraná. For that, three data sets were used: meteorological, hydrological and demographic data with time series between 1988 and 2017. Rainfall data were obtained from the National Institute of Meteorology and National Water Agency. The streamflow data came from the National Water Agency. In addition, information on demography was obtained from the Brazilian Institute of Geography and Statistics. In the methodology, the descriptive statistics of the precipitation and flow data were used, together with the cluster analysis capable of identifying homogeneous sub regions of rainfall and stream flow in each hydrographic region. The generation of these homogeneous sub-regions was tested using the Silhouette Index. Subsequently, the subregions were inserted in the Extreme Values Theory to generate the estimation of the return periods of rainfall. The analysis of information about the physical, socioeconomic and demographic characteristics allowed the analysis of the use and occupation of the soil of areas susceptible to occurrence the occurrence of phenomena of this size. The results indicated the formation of four homogeneous sub-regions of rainfall in the two hydrographic regions studied. The scenarios for the recurrence of events of rainfall and streamflow show the high degree of severity by which certain subregions can be submitted, and the use and occupation of the soil of these hydrographic regions has been changed abruptly in recent years. The urban growth of most cities and the change of natural areas for the practice of extensive agricultural and livestock farming can aggravate the numerous damages due to the scenarios for homogeneous sub-regions inserted in the two hydrographic regions.