Evaluation and Monitoring of drought using of drought Indexes; Case study the Dez watershed

Drought is a hydrologic and climatic phenomenon¡ this phenomenon can occur in different watersheds and climatic conditions. Water resources management¡ design of water transmission and distribution systems and determination of agriculture water demands depend to applied methods for management and controlling of drought considerably. In this study for distinguishing of occurred droughts in upstream of the Dez Dam¡ annual precipitation data of Tangpanj and Telezang stations have been applied in a 17 years period (1994-2010) . Occurred droughts have been determined using of these data and drought indexes as Percent of Normal (PN)¡ Deciles Index (DI)¡ Standard of Precipitation Index (SPI)¡ Chinese Z Index (CZI)¡ Modified Chinese Z Index (MCZI) and Z-Score index (ZSI). Results illustrated that most of severe droughts were observed in Telezang station. PNI¡ MCZI¡ ZSI indexes showed them (these indexes showed one drought in 2007-2008¡ 1995-1996 and 2007-2008 respectively). Also DI and SPI indexes illustrated an occurred severe drought in Telezang (2007-2008) and Tangpanj stations (1999-2000) respectively. But CZI index did not show occurrence any drought in these stations. RAI index distinguished that three (1999¡ 2008 & 2011) and four (1994¡ 1999¡ 2008 & 2011) severe droughts occurred in the Tangpanj and Telezang stations respectively. These indexes showed that most of droughts have occurred from 2007 till 2009.