Water demand increases every day by the non-stop population growth and the rapid agricultural and industrial developments. The limited manageable water and the constant increase in its demand, justifies the need for an appropriate planning and management in the field of water resources for the better exploitation of these rare and limited resources. If the existing resources are used in a better manner, present and even near future demands could be improved. In a region, simultaneous optimal operation management of surface and groundwater resources is the most effective way for the protection of water sources in order to prevent the probable challenges related to water shortage. So simultaneous study of the surface and groundwater of a region aids the proper exploitation of the water resources of the region, by applyin g the best management scenario, compliance the balance in operation of both resources at current and future and it helps to sustainability of the water sources in a region. The prediction of probable changes in the condition of water resources because of different policies for water operation and use can be a great help for the achievement of the important goal which is optimal operation management of water resources. Dam reservoirs are one of the most important water supplies in Iran and as well as all around the world. The method of system dynamics, derived from systematic thinking, is a useful tool in management and planning and is a feedback and object oriented approach, that not only can simulate the complicated system of water resources but also can evaluate the present and future behavior and the mechanism of system. In the current research, by investigating Taleghan dam using the system dynamics approach, the effects of dam construction on sustainability and groundwater resources control as well as their operation management approach is studied. this dam has been constructed in order to utilize the potencial of surface water resources of river Taleghan to supply the agricultural demand of ghazvin plain better and also to supply drinking water of some area in Tehran. Thus, the model includes Taleghan river basin and dam reservoir, river Ziaran, irrigation network of the mentioned area, the other concerned main rivers in the plain and underground water resources. Validation of the model was done by using the comparison between behavior of the model and observational data in addition to statistical criteria . Then by running the model with dam and without dam, the effects of the construction of the dam on supplying the agricultural demand and the groundwater resources were studied . Also, by the presentation of various scenarios, indices like agricultural supply reliability by dam, dam vulnerability and sustainability were calculate d. It was found that the construction of the dam has had a positive effect on groundwater resources and agricultural demand supply , but supplying more amount of water of Tehran drinking by the dam reduce the reliability of agricultural demand supply , and it causes a decrease in the region’s groundwater level, to reduce this effect the increase in irrigation efficiency is recommended.