Drought occurrences and impacts on the upper Grande river basin, Brazil

Abstract

Natural hazards, such as droughts and floods, are the main challenge for research related to water resource management worldwide. Understanding how the climate affects the occurrence and propagation of droughts can assist in water management. This study aimed to investigate the occurrence and characteristics of meteorological and hydrological droughts in the upper Grande river basin (UGRB). For this purpose, the Standardized Precipitation Index (SPI) and the Streamflow Drought Index (SDI) were calculated on an annual time scale, considering the regional water year, i.e., a period beginning in October of a year and ending in September of the following year. Besides, it was aimed to verify the impact of macroscale climatic phenomena on seasonal precipitation anomalies using composite analysis. The SPI was calculated from the monthly precipitation series from October 1976 to September 2017. To calculate the SDI, daily naturalized streamflows were obtained from October 1990 to September 2017. The most severe droughts were observed in 2000/01, 2013/14, and 2014/15 water years. Although there was an agreement between the meteorological and hydrological droughts, the SDI indicated that the impacts on the streamflow were longer. The propagation from meteorological to hydrological drought was greatest with up to a 6-month lag in SPI, after that the influence of SPI on SDI was less. Composite analysis revealed an antiphase relationship between Pacific and Atlantic climatic indices and seasonal precipitation anomalies, indicating interannual-to-multidecadal variability.