Studying the effect of rainfall on cropping pattern and total gross margin in the right side irrigation network of Nekuabad diversion reservoir

Available water is one of the limited factors of agricultural development and has a strong correlation with rainfall. Rainfall is one of the most important factors of uncertainty in determining optimal cropping pattern, which have been neglected. In the current study, the influence of rainfall on optimal cropping pattern and total gross margin was investigated in the right side irrigation network of Nekuabad diversion reservoir, Isfahan Province. Optimization Model with degree of conservative controller parameters was used as model. Data were obtained from the agriculture department and Mirab-e-Zayandehrood Corporation in 2009. Results showed that rainfall has positive effects on cropping pattern and total gross margin. The total gross margin was increased from 197 to 233 billion Rails and agriculture areas from 7241 to 10726 in the constraint violation probability level of one (p=0.1). Therefore, it is recommended to pay more attention to rainfall at the policy making level by considering the influence of this factor on farmers’ decision making in determining of mixed crops.