Determining the optimal exploitation of groundwater resources by using Game Theory (Case study: Gorgan County)

Background and purpose: One of the main limiting factors of the development of Iran's agricultural sector is the shortage of water resources. The annual recharge of groundwater aquifers due to atmospheric precipitation has not been able to compensate for this amount of reduction in groundwater level. Also, farmers do not have enough economic incentives to minimize negative environmental effects, such as reducing groundwater aquifers level. Therefore, most decision-making issues in natural resources such as water resources management face the problem of the existence of conflicting objectives, such as maximizing economic benefits and minimizing negative environmental impacts. According to this, in the present study, the game theory method was used to manage the groundwater resources. The statistical population of this study is the total water wells of Gorgan. In current study The 88 questionnaires was completed by using stratified random sampling. The information required includes the production costs and agricultural water wells informations in the 2014-2015. Accordingly, five scenarios for the exploitation of groundwater were considered. In order to estimate the economic benefits and environmental impacts, farmers' net income and groundwater resources exploitation were used respectively. The optimal application of groundwater resources was then determined by Non- symmetric Nash equilibrium method.
Achievements: Based on the results of this study, the optimal crop area and the net income of farmers were decreased by declining groundwater exploitation for irrigation. Furthermore, the results of this study showed that when economic profit is considered as the only target, groundwater exploitation is at its highest level of 579 million cubic meters, and when environmental goals are considered as the only target, the optimal groundwater scenario is in the minimum volume of groundwater exploitation as 66 million cubic meters. When the same weight is considered to environmental and economic goals, the best scenario for exploitation of groundwater resources is 246 million cubic meters and farmers' income is 2340000 million Iranian Rials per year. According to the results of sampling, farmers' exploitation from the groundwater resources of the region is wasteful. Although this operation in the short run has led to an increase in net profits, but it will lead to irreversible damage to the hydropower potential of the region and the environment in the long run. Also, the results of this study show that the optimum exploitation from groundwater by game theory model should be less than the current exploitation. The results of optimal cropping pattern show that the optimum cropping area is reduced by decreasing the used water.