Assessment of the Drought Hazard in the Tiber River Basin in Central Italy and a Comparison of New and Commonly Used Meteorological Indicators

Abstract

Drought is one of the most common natural hazards with adverse effects on agriculture and the water resources. This study aims to spatially analyze the drought hazard in the Upper Tiber River basin and find a representative indicator on the basis of meteorological data that are widely available. To this end, the significance of using solely precipitation versus including evapotranspiration (ET) in drought characterization is thoroughly investigated. Three relevant indicators are considered: (1) a new index Standardized Effective Precipitation EvapoTranspiration Index (SPETI) incorporating, besides ET, the losses due to runoff; (2) the commonly used Standardized Precipitation Index (SPI); and (3) the Reconnaissance Drought Index (RDI). A comparison is undertaken at various timescales (9, 12, and 24 months) using precipitation and temperature data from two stations for the period 1953–2011, for which complete rainfall and temperature time series are available. This analysis demonstrates (1) the very similar evolution and behavior of the three indexes and (2) the reliability of the SPI for drought monitoring and characterization in the case of the Upper Tiber River basin, also using observed hydrological effects. Based on these findings, a longer data set of available precipitation data (45 stations, 96-year-long time series from 1916 to 2011) is used to calculate the