Analyses of Drought Events in Calabria (Southern Italy) Using Standardized Precipitation Index

A deficit in precipitation has different impacts on soil moisture, snowpack, streamflow, groundwater and reservoir storage. In this study, drought, expressed using the SPI, has been analysed in a region of southern Italy (Calabria) using a homogenised and gap-filled database for 129 monthly rainfall series in the 1916-2006 period. Both the short-term (3 and 6 months) and the long-term (12 and 24 months) SPI were estimated and, in order to identify the worst events, the percentages of the regional area falling within severe or extreme dry conditions have been evaluated. With the aim to spatially characterize the most severe drought event, the SPI data were estimated at ungauged locations and mapped using a geostatistical approach. Finally, a time series analysis of long-term SPI was performed to detect possible trends. Results showed that several heavy drought episodes have widely affected the Calabria region and, among these events, the worst one occurred between December 2001 and April 2002. The trend analysis showed a reduction in the SPI values that is a tendency towards drier conditions, although the running trend approach, carried out only for the long-term SPI, revealed that this tendency is not persistent throughout the series length, but it depends on the period examined.