Investigating drought in Apulia region, Italy using SPI and RDI

The Apulia region is highly vulnerable to meteorological and hydrological droughts, due to its low rainfall and higher agricultural water demand. In this study, we investigated the spatial and temporal drought characteristics in the Apulia region based on the Standardized Precipitation Index (SPI) and Reconnaissance Drought Index (RDI) for the period 1960–2013. SPI was derived based on precipitation, whereas RDI was derived based on both precipitation and potential evapotranspiration. The overall objective is to identify whether these two selected drought indices are able to characterize drought equally or they differ in space and time. Results indicated that the number of drought events decreases and the average drought duration increases by increasing the time scale of the SPI and RDI. The RDI metrics was able to represent a more severe drought event compared to SPI. There is an increasing drought severity trend in the western part of Apulia and a decreasing drought severity trend in the eastern region. The study also shows that temperature (and so potential evapotranspiration) plays an important role in distinguishing drought characteristics between RDI and SPI.