objective functions

In this study, to determine the optimum crop pattern of Kermanshah plain, Iran, a dynamic model was developed in Vensim PRO x32 software to simulate the actual situation in the region. Stochastic simulation of time series method was used to predict the values of climate parameters in the future. After ensuring the performance of the dynamic model as well as time series model, optimization process of crop pattern was performed using the existing optimization tool in Vensim PRO x32 software in addition to multi objective mathematical programming approach by Powell method in three different scenarios. The objective functions included maximizing the economic benefit for farmers and minimizing the extracted water from aquifer. The results showed that ratio of the gained benefit to the amount of water extracted from the wells in optimized conditions was always higher than the current conditions. The value of this ratio for the three scenarios was 1.23, 0.89, and 0.94, respectively, which in all three scenarios are higher than the current value (0.68). The results showed that according to a case in which variations in the crop coefficients of all crops are possible, in order to optimize the crop pattern,  the area allocated to wheat, barley, grain and forage maize, tomato, clover, and onion must be decreased in the current crop pattern. Furthermore, the results of optimization indicated an increase in the area under the cultivation of saffron, rose, greenhouse, medicinal plants, and olive, compared to the current conditions.