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Title: COMPARISON OF DROUGHT INDICES IN GREECE

Author: A. Mitropoulou, G. Papaioannou, H. Michalopoulou and P. Kerkides

Year: 2009

Publisher: European Water Resources Association (EWRA)

Description:

Drought is one of the major natural hazards, most often caused by a departure of the precipitation from the normal amount. Many drought indices have been developed to identify the beginning, end, spatial extent and severity of a drought, using various meteorological and hydrological parameters. One of the prospects of the farming community is to handle agricultural drought on an increased temporal and spatial resolution. The drought indices AWn and ETDIn were developed using a daily single layer water balance model that calculates daily evapotranspiration from daily measured meteorological variables, expressing soil moisture deficit. The drought indices EDI365 and EDI28, based only on daily precipitation, are also calculated to express the amount of precipitation needed for the recovery from the accumulated deficit since the beginning of drought. All these indices have a high temporal resolution (daily). On the other hand, one of the most widely used drought indices, the Standardized Precipitation Index (SPI), based only on rainfall data and accepted as a good measure of short- and longterm drought, has a coarse temporal resolution (monthly). In this study, SPI is calculated on 1-, 2-, 3-, 6-, 9-, 12- months time scale (SPI1, SPI2, SPI3, SPI6, SPI9, SPI12 respectively) in 28 stations in Greece, for the period 1974-2001. These SPIs are compared with the monthly values of the four other indices, the available water index (AWn), the evapotranspiration deficit index (ETDIn) and the effective precipitation indices (EDI365 and EDI28) that estimate droughts in a finer temporal (and spatial) resolution. SPI index is in great agreement with the finer water balance index AWn, (representing the effects of both precipitation and potential evapotranspiration in droughts) mainly for the short-length time scales of about three months, while for the long-length time scales between six and twelve months, SPI is in better coincidence with the effective rainfall index EDI365.