Optimizing cropping patterns using Goal programming in the case of using different water sources case study: Varamin Plain

Background and Objective: The growth of population, industry and agricultural activities has led to an increase in water consumption in the domestic, industrial and agricultural sectors, which has created a new challenge for planning and exploiting water resources. Therefore, water projects need efficient design, implementation and management. The imbalance of water resources in the Varamin Plain has raised the need to use effective water management policies, one of the appropriate solutions to achieve sustainable harvesting of water resources is to provide a suitable model of cultivation. In this regard, the present study investigates the optimization of agricultural crop cultivation pattern in Varamin Plain. Two main goals have been considered in this study, the first goal is to provide a suitable model of cultivation to simultaneously achieve maximum profit and minimum water consumption with existing water resources, and the second goal is to achieve simultaneous increase in cultivation area and maximization of profit with new water resources.
Materials and Methods: The ideal planning approach is a method based on the principles of mathematical optimization, which appears in the form of linear inequalities in order to analyze the final and desirable decisions of managers and officials. This model has more flexibility in the actual decisions of the managers of economic units due to considering the simultaneous achievement of several goals based on the priority of the issues of the studied area. Therefore, in order to achieve the objectives of the study, linear and ideal mathematical programming models were used in four scenarios. In the first scenario, the goal is to maximize gross profit, the second scenario is to minimize water consumption while maintaining profit, the third scenario is to simultaneously achieve the goals of maximizing profit and minimizing water consumption, and the fourth scenario is to simultaneously achieve land use and profit maximization with new water sources.
Results: The results of scenario one with the aim of profit maximization showed that the physical and economic productivity of water and profit increased by 4.33, 19.26 and 14.22 percent, respectively, and water consumption decreased by 4.23 percent. The results of scenario 2, with the aim of minimizing water consumption while maintaining profit, show that the economic productivity of water increased by 17.4% and water consumption decreased by 14.81%. The first main objective of the research was examined in scenario 3 and products with the highest economic productivity in the cultivation pattern were proposed, which would increase profit by 14.22 percent and reduce water consumption by 6.96 percent. According to the second main goal of the research in scenario 4, it was determined that with an increase of 24.13 percent of agricultural water, the cultivation area will increase by 80 thousand hectares and profit will increase by 34.16 percent compared to the current situation.
Conclusion: According to the results, it was found that the cultivation pattern in all four scenarios is better than the current situation. Also, it was found that melons, in addition to high water consumption, also have low water economic productivity and were excluded from the model in all four scenarios. Therefore, it is recommended not to cultivate this product in the Varamin plain, which faces the phenomenon of land subsidence. Also, considering the positive effect of increasing surface water supply on the cultivated area, production level, improving the level of underground aquifers, it was suggested that the government provide the conditions for improving the agricultural economy of Varamin plain by accelerating the phase 2 project of transferring Tehran's wastewater treatment.