University of Tehran Press Iranian Journal of Soil and Water Research 2008-479X 57 3 2026 05 22 Application of Game Theory in the Reallocation of Agricultural Water to Improve Water Use Efficiency Application of Game Theory in the Reallocation of Agricultural Water to Improve Water Use Efficiency 589 610 107247 10.22059/ijswr.2026.403271.670016 FA Mohammadhashem Sarafha M.Sc. in Water Resource Management, Imam Khomeini International University, Qazvin, Iran. 0009-0007-1356-8286 Sheyda Kakavand M.Sc. in Water Resource Management, Imam Khomeini International University, Qazvin, Iran. 0009-0008-1864-4679 Hashemi Masoumeh Department of Plants, Soils, and Climate, Utah State University, Logan, UT, USA. 0000-0001-8649-5208 Hamed Mazandarani Zadeh associate professor, water eng. group, Imam Khomeini International University، Qazvin 0000-0003-2727-9577 Journal Article 2025 10 01 In recent years the water allocated for the Qazvin irrigation network has reached a staggering level of reduction at half the agreed upon total. Rather than the original allocation of 250 million cubic meters per year, it has dropped below 120 million cubic meters per year. An assessment of the situation shows that in addition to the nearly 50% reduction of water flowing in, the actual distribution pattern of water to the farmers remains unchanged. The objective of this study is to reallocate water among farmers in the Qazvin irrigation network in order to resolve existing disparities among them. To this end, the income of each farmer was first calculated under the current non-cooperative condition. Then, assuming the establishment of full cooperation, a genetic algorithm was employed to optimize the allocation of 122 million cubic meters of water within the network. Subsequently, to encourage participation, the additional benefits generated through cooperation were redistributed among farmers using the Shapley value theory. The results demonstrate that if farmers cooperate in water extraction, not only will all of them earn higher profits compared to the current situation, but the total profit will also increase significantly by about 104% (from 8.902 to 18.233 million USD). The combined application of the genetic algorithm and Shapley value theory can serve as an effective approach in managing conflicts, enhancing equity in resource allocation, and improving the economic efficiency of irrigation networks. In recent years the water allocated for the Qazvin irrigation network has reached a staggering level of reduction at half the agreed upon total. Rather than the original allocation of 250 million cubic meters per year, it has dropped below 120 million cubic meters per year. An assessment of the situation shows that in addition to the nearly 50% reduction of water flowing in, the actual distribution pattern of water to the farmers remains unchanged. The objective of this study is to reallocate water among farmers in the Qazvin irrigation network in order to resolve existing disparities among them. To this end, the income of each farmer was first calculated under the current non-cooperative condition. Then, assuming the establishment of full cooperation, a genetic algorithm was employed to optimize the allocation of 122 million cubic meters of water within the network. Subsequently, to encourage participation, the additional benefits generated through cooperation were redistributed among farmers using the Shapley value theory. The results demonstrate that if farmers cooperate in water extraction, not only will all of them earn higher profits compared to the current situation, but the total profit will also increase significantly by about 104% (from 8.902 to 18.233 million USD). The combined application of the genetic algorithm and Shapley value theory can serve as an effective approach in managing conflicts, enhancing equity in resource allocation, and improving the economic efficiency of irrigation networks. https://ijswr.ut.ac.ir/article_107247_1476c43a0157db2addd340d344577ffe.pdf