Drought analysis in aegean region with the standardized precipitation evapotranspiration index

This study analyzed and monitored the temporal and spatial change in agricultural drought with Standartized Precipitation Evapotranspiration Index (SPEI) between 1975-2014. Acoording to SPEI values, 2007 and 2008 were recorded as severe drought (SPEI≤-2) at 1, 3, 6 and 12 timescales and at 24 timescales respectively on the basis of stations. The most severe drought period was idenified as the decade between 2005-2014. In different time scales, the lowest (dry) values were found in Afyon, Çeşme, Nazilli, Bergama and İzmir stations respectively and 2007 had the most severe drought values in both short and long time scales. According to Modified Mann-Kendall trend test results of SPEI values, in all time scales, there was a statistically significant downward trend (dry) in Nazilli, Sultanhisar, Denizli, Dikili, Gediz, Kütahya, Simav, Tavşanlı stations, whereas in Güney, Emirdağ and Salihli stations, there was a statistically significant downward trend in some time scales. Sen's Slope Estimator maps of SPEI values were created by IDW deterministic method for spatial analysis. Drought trends were examined, and it was estimated a negative slope values in the inner parts of the region including Denizli, Kütahya and Aydın, and along with the coastal area between İzmir and Dikili on The Sen's Slope Estimator maps about SPEI values.