Hydrological Response to Drought Occurrences in a Brazilian Savanna Basin

Abstract

The Brazilian savanna is one of the world’s 25 biodiversity hotspots. However, droughts can decrease water availability in this biome. This study aimed to analyze meteorological and hydrological droughts and their influence on the hydrological behavior in a Brazilian savanna basin. For that, hydrological indicators were calculated to analyze the hydrological behavior in the Pandeiros river basin (PRB). The Standardized Precipitation Index (SPI) and Standardized Streamflow Index (SSI) were calculated for the hydrological year and rainy season from 1977 to 2018. The propagation of the meteorological to hydrological drought was studied by means of the Pearson coefficient of correlation between the SSI and SPI with 0, 3, 6, 9, and 12-month lags. A longer meteorological drought was observed from 2014/15 to 2017/18 which caused a reduction in the groundwater recharge, besides potentially reducing the ecological functions of the Brazilian savanna. This drought was intensified by an increase in the average annual temperature, resulting in the increasing of evapotranspiration. Regarding drought propagation, there is no significant difference among the coefficients of correlation from 0 to 6-month lags. For the lags of 9 and 12 months, the correlation decreases, indicating a greater influence of the current rainy season than the past ones.