Achieving Optimal Path of Extracting Groundwater Resources Considering the Side Effects in Hamadan-Bahar Plain

Stable modeling in water resources management requires recognizing the relations between the different uses of water and their long-term results on one hand and taking into account the current and future access to water resources and demands for them, on the other hand. In recent years, Hamedan-Bahar plain has been identified as one of the restricted groundwater areas in Hamedan province. In this plain, the groundwater level has decreased remarkably due to lack of the proper water management. The aim of this study is to provide a model to maximize the net benefit of farmers considering the stability of the groundwater. Since the effect of discharge groundwater is accumulated over time, time is taken as an essential variable in solving water optimization problems. Accordingly, applying dynamic models such as the optimal control method is appropriate for this purpose. The optimal path for water extraction from groundwater resources can be determined using the optimal control model. In this model, the additional cost of water extraction due to the further exploitation has been considered as a constraint in the modeling process. The effect of the added costs on optimal path and the price of water has also been investigated. Considering the optimal use of water and maximum welfare of the farmers, the results show that it will take about 45 years for the water level to increase from 1716 meters to the optimal level of 1732 meters. During this period, the price of water will decrease from 3200 to 2200 Riyals per cubic meter and the annual harvest from the groundwater resources will reduce to the level of 1.7 million cubic meters. Therefore, fulfilling the specified limit not only results in stable groundwater resources, but also leads to a sustainable agricultural development and enhancement of farmers’ income.