Spatial Irrigation Scheduling for Winter Wheat in Fars Province Using Stochastical Analysis of Rainfall Data

Wheat is one of the most important product in Fars province and accurate irrigationscheduling causes to increase irrigation efficiency and optimal use of water resources. Because، most of rain events occurs during wheat growing period in Fars province، irrigation of winter wheat is important. Therefore، in this study، a simple daily rainfall generator model with two components was used. Stochastic output of this model coupled to a water balance model that used average deterministic ETp values. Irrigation dates and amountsat 32 climatologically stations in Fars province were determined. The model was based on daily water balance approach and used crop and soil data as input. In the next step، a predictive irrigation schedule at selected probability level for irrigation dates developed with Arc GIS. Finally، spatial maps of simulated values under same probability level was drawn. Because wheat is most sensitive to water stress during critical stages of booting and two weeks before pollination، predictive scheduling does not lead to water stress. The results showed that number of irrigation in southern، west southern and east southern stations in Fars province is higher. Under 75 probability also the highest irrigation requirement was predicted in southern and east southern station. Analyzing the result of model according to certain risk level، is helpful in determining irrigation requirement ofwinter wheat and water resources strategies in Fars province.