Linking drought propagation with episodes of climate-Induced water insecurity in Pernambuco state - Northeast Brazil

The semiarid region of Northeast Brazil is characterized by recurrent drought episodes. The magnitude of drought events may be assessed using standardized climate indices (SCIs) based on hydrometeorological variables, including precipitation, evapotranspiration, soil moisture, and streamflow. Drought monitoring may be improved using the concept of drought propagation, which considers the existing link between different types of droughts. Thus, correlations between the SCIs can be used to identify propagation patterns and, subsequently, predict the magnitude of a drought occurring after the first identification of a meteorological drought. In this study, five river basins located in the Pernambuco state in Northeast Brazil were selected for SCI application. The results showed that drought duration plays an important role in the final value of the SCI. Further, events between 2012 and 2017 had more severe SSMI (Standardized Soil Moisture Index) and SSI (Standardized Streamflow Index) values than SPI (Standardized Precipitation Index) and SPEI (Standardized Precipitation Evapotranspiration Index). Thus, the SPI alone may not be able to properly detect the magnitude of some droughts. The results of this study show the potential of the SCIs for monitoring systems and how information of soil moisture and streamflow, besides precipitation, can be useful for drought preparedness.