Spatial characteristics and temporal trends of meteorological and hydrological droughts in northwestern Iran

摘要: In recent years, droughts have become more intense and frequent in arid semi-arid regions like Iran on the one hand, water demand has been rising other hand and, as a result, their impacts are being aggravated. Therefore, meteorological hydrological receiving much attention. This paper focused drought characteristics for overlapping periods of 3, 6, 9, 12 months northwestern over period 1981–1982 to 2010–2011. The results showed that majority events reference were last 15 years from 1995–1996 Furthermore, driest year based index was 2007–2008, while it detected be 2010–2011 index. Spearman’s rho Kendall’s tau tests used temporal trends analysis droughts. decreasing time series evident streamflow than standardized precipitation series. general, study area suffered Moreover, revealed drier during three decades. Finally, Spearman correlation applied explore relationships between which indicated strong May–Jul-SPI Jun–Aug-SDI with value 0.65.