Drought severity indexes for the Tocantins River Basin, Brazil

Abstract

Water resource management is one of the great challenges for achieving public welfare and food security, mainly in developing countries. Droughts are natural phenomena that occur due to prolonged moisture deficit and affect large areas. This study aimed (i) to analyze the spatial and temporal distribution of the drought occurrences and intensity; (ii) to verify the interaction of meteorological and hydrological droughts using both the Standardized Precipitation Index (SPI) and Standardized Streamflow Index (SSFI) for annual and quarterly scale in the Tocantins River Basin (TRB); (iii) to examine the influence of macroscale climatic phenomena in this basin; and (iv) to analyze the impact of potential evapotranspiration on the meteorological droughts, using the self-calibrating Palmer Drought Severity Index (scPDSI). Data from 113 rain gauge stations and 9 streamflow stations in TRB were analyzed. To assess the macroscale climatic phenomena influence, the KNMI Climate Explorer (CE) platform was used to correlate anomalies in the sea surface temperature (SST) with monthly historical series of precipitation in the TRB. Monthly scPDSI maps were acquired from the Climatic Research Unit database for the three driest years. The most severe droughts were observed in 1997/98, 2015/16, and 2016/17. Also, a strong influence of the climate on the hydrological drought was verified. The SST’s influence on the occurrence of drought and wet events in the basin, mainly in the North region, was also observed. Overall, there is an agreement between the SPI and scPDSI, which showed a strong weight of the precipitation on the drought occurrences.