Assessment of the effects of developmental and climatic scenarios on the future of water resources and consumptions in Behesht Abad Basin using System Dynamics Approach

Due to complexity in water resources management problems and its direct relation with other sciences, it is impossible for only one decision-maker to consider all of the necessary aspects in integrated managing and planning of water resources. Various sub-systems of social, economic, and natural diversity communicate and affect each other in river basins. Understanding the interactions among subsystems, feedbacks and their side effects and also knowing the developmental and climatic scenarios of the future are important for making decisions by politicians, more efficiently. With a partial view to the water resources management, traditional approaches do not consider the complexity of water management. But, a growing understanding in this regard that the water crisis is originally a management crisis has emerged, recently. It is necessary to consider proper methods for coordinating policy-making, planning and implementing in a consolidated and cross-sectional way. In this study, considering the development conditions and needs of the future of Behesht-Abad basin, as well as the prediction of climatic parameters (such as precipitation), we estimated the future vision of water resources and water uses in this basin. Therefore, a wide range of information in various specialized areas related to water resources was needed to design a comprehensive model. First, through interview with relevant experts, the required information was collected and integrated with Delphi method. Then, a comprehensive model of water resources for the basin was designed, using system dynamic techniques. The model simulations, for different developmental and climatic scenarios, were implemented in order to investigate various alternatives of policy-making and their effects. The boundaries of the model was determined through interview with experts of related fields, using Delphi method to incorporate the comments about the effective parameters on water resources and uses in Behesht-Abad basin and their relations with each other . Interviews were performed in several meetings to reach a consensus among the experts. Then, the water resources and uses model of Behesht-Abad basin was designed, based on the obtained results. The model's simulations for various scenarios were performed by considering the development conditions and needs in the future of the basin, as well as the prediction of climatic parameters, in order to investigate various alternatives of policy-making and their effects. The results showed that the current development trend will lead to a sharp drop in groundwater resources levels and a critical condition in plains after the year 2015. Also, water tension index showed a severe water tension in the basin after the year 2033 and the output runoff of Behesht-Abad basin do not provide the minimum need of downstream river in some years. However, by comparing the results of model simulation in scenarios 1 and 2, it was observed that the modification of growth rate of water needs- only in the industry sector- has a significant effect on groundwater resources and aquifer sustainability index. Therefore, the volume of groundwater resources in the final year of the simulation in Scenario 2 is about three times more than its value in Scenario 1. Also, the comparison of the value of water tension index in scenarios 1 and 2 showed that reducing the rate of growth of water demand in the industrial sector prevents the basin from severe water tension in the final onward years of the simulation. So, it seems that by applying the procedures of water saving in the industry sector such as using high-tech industries that require less water and also reusing wastewater in industry sector can prevent severe water tension in the basin and plains, in the critical condition. In addition, according to the simulation results for climate change scenarios and due to a significant decrease in precipitation and increase in evaporation rate in the basin, the volume of water in the basin will drop significantly. Also, the amount of water tension index, especially in the final years of the simulation period, indicated that the water tension is more severe, comparing with the scenario of continuing developmental and climatic trend. Finally as a suggestion, the developmental policies in the industry and agriculture sectors of the basin should be adopted by examining of all aspects and considering the consequences expressed in this research for the water resources and environmental needs, to improve the aquifers sustainability in Behesht-Abad basin