Estudo dos eventos extremos, probabilidade e período de retorno na Bacia hidrográfica do rio São Francisco

Abstract

The frequency of extreme precipitation events has been growing in recent years, with greater intensity and duration, and thus favoring natural disasters such as floods and severe droughts. It is necessary to know the causes or what triggered the disaster, in order to define the preventive measures that will be adopted. In this way, the detection of the causes of rainfall cycles and extremes, especially in socioeconomically vulnerable regions, becomes a low-cost way to help the management of water resources and local socioeconomic sectors, in addition to preventing the loss of human lives. . Yet, in several regions, changes in temperature extremes have been observed over the past 50 years. Such changes in extreme events have impacts on human activities such as agriculture, health, urban development and planning, and water resource management. Within the theme of extreme events, it is of paramount importance, especially within a watershed, to know the return period of the main extreme events, both for water security and for construction works and safety of the local population. Associated with the knowledge of the return period, it is important to know and calculate the probability of the occurrence of extreme events in urban areas, agricultural areas or areas susceptible to the extreme event, because in this way, economic activities, new works and constructions and even populations can be displaced, in an attempt to mitigate possible economic losses and even human lives. Therefore, the objective of this work is to study extreme weather events, probability and return period in the São Francisco River Basin. For this, daily rainfall data were used, which were obtained through the National Water Agency (ANA), with a data period from 1949-2019 for 26 rainfall stations arranged along the entire São Francisco River. Through the Standardized Precipitation Index (SPI) it was possible to quantify and qualify the extreme events that occurred and, with the use of other techniques, such as wavelet analysis, it was possible to verify and associate the possible causes of these events. In addition, in general, through probability maps, it was found that for the São Francisco River there is a greater probability of occurrence of rainy events than drought events.