Maccioni, Pamela; Kossida, Maggie; Brocca, Luca, 2015, Assessment of the Drought Hazard in the Tiber River Basin in Central Italy and a Comparison of New and Commonly Used Meteorological Indicators (vol 20, 05014029, 2015), Journal of hydrologic engineering 20 (2015). doi_10.1061/(ASCE)HE.1943-5584.0001155,
URL: http://www.cnr.it/prodotto/i/358474

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 SPI12 and to derive four new subindicators reflecting the intensity, magnitude, duration, and frequency of drought events. These subindicators, once classified, are blended into a Drought Hazard Index (DHI), thus providing a more holistic characterization of the drought hazard on a scale of 1 to 4. A spatial analysis is finally performed across the resulting DHI values in order to investigate the spatial variability of a drought hazard and identify drought-prone areas. It is found that the most vulnerable areas are located in the southern and eastern part of the Upper Tiber River basin, and the north-central part is less affected by drought conditions.

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