Applying System Dynamics Approach for Simulation and Optimization of the Cropping Pattern in Esfahan Right Side Abshar Irrigation and Drainage Network

Integrated operation of water resources in Esfahan Right Side Abshar Irrigation and Drainage Network was studied, applying system dynamics methodology. The network is a critical one of Zayande Rood Basin the ratio of income to expense of which was investigated, considering the two cases of no change in cropping pattern vs change in cropping pattern during 1385-86 base years to obtain the optimal cropping pattern in the region. For an optimization of the cultivation pattern, maximization of the ratio of income to cost was defined as an objective function. The objective function was defined for two different cases of keeping the sum of cultivated areas using different methods of irrigation water management and requiring percent limits of change in cultivated area and in proportion to the base year, applied to each crop within the model. Following statistical analysis and calculation of the Root- Mean-Square Error, standard error, and correlation coefficient, the adjustment between the performances of the assessed vs simulated network products was determined. The values of these product indexes, according to the conditions prevailing on the network, were estimated as 209.98 kg/ha, 0.007, and 0.99, respectively. The results indicated a fair reasonable accuracy. Furthermore, the ratio of income to expense in the network amounted to 3.025 and 3.144 for the two cases of: no change in the cropping pattern vs change in the cropping pattern within the base year. The optimal cropping patterns were obtained through an application of 50% limit of the cultivated area for each crop within the base year. Results finally indicated that the existing cultivated area is very different from the desired one, and the combination of the dominant crops adopted is far from beneficial.