The Recognition of Drought with Dri and Siap Method and its Effects on Rice Yield and Water Surface in Shaft,Gilan,south Western of Caspian Sea

Drought in Iran is a recognized phenomena, Trend and velocity of drought in recent years, especially in 1998 and 1999 in Gilan, South western of Caspian Sea, is very noticeable. The aim of this paper is recognition of drought years with DRI(Dependable rainfall Index) and SIAP Index (Standard Index of Annual Precipitation) in Shaft township, Gilan,South Western of Caspian Sea and comparison its effects has been on Rice yield and water surface. The result of this paper has shown that in years of 1998 to 2003 has observed of drought in Shaft township with around area, in Shaft,Rasht and Ghalehrudkhan with 6 years and Pasikhan and Chobar with 3 years has been seen. Its effects have direct relationship on water surface and rice production that submitted by comparison figures in full paper. The return period of drought in two models has been in 10 years (1976, 1986) and before of drought years has been normally years in two years ago. Drought years are harmonious with deficit of low discharge in water surfaces and yield production of rice in same years. The toward of SIAP and DRI models in area shows that its toward to drought .This phenomena is high important for environmental planning and executive managers