EXTREME PRECIPITATION DEFICITS IN THE SÃO FRANCISCO RIVER WATER BASIN OF BRAZIL

Abstract

The phenomenon of droughts is inherent to climate dynamics, though intensified by human activities. They can occur under any climate regime and can be characterized by conditions of deficits or absence of rainfall in a specific location. This work aims to analyze the occurrence of Extreme Precipitation Deficits (EPD) in the São Francisco River basin, Brazil, in the period between 1985 and 2018, using the Standardized Rainfall Drought Index (SRDI), using monthly precipitation data from 190 stations pluviometrical data from the National Water Agency (ANA). This method consists of calculating standardized accumulations of negative deviations of monthly precipitation in relation to the historical median for each month. The results showed that EPD represents 2.9% of total monthly occurrences, being more frequent in stations close to headwaters (1,309) of the São Francisco River in comparison to the mouth (31). The longest drought event lasted 27 consecutive months, and the most recurring months were December and January. For the period considered, EPD in the years 2017 and 2018 represented 75% of the total.