Due to Iran's weather conditions and lack of water resources, dam construction projects are particularly important for the country's development and progress. Water resources management based on system dynamics is capable of simulating complex water resources systems. This model for the simulation of water resources has various capabilities, such as increasing the speed of model development, the possibility of group development of the model, effective communication of the results, and increasing confidence in the model through user participation. In this research, the model of the dynamic system of the multipurpose dam of Qamshek in Hormozgan province has been simulated using the probabilistic simulation method. The purpose of this modelling is to realize different needs of the dam (domestic, environmental, industrial and agricultural) before its construction and to check the quality conditions of the reservoir. The study of the results of the quantitative modelling was done after calculating the annual and monthly percentage of volumetric and temporal supply of different needs and their source of supply. The results show that the volumetric supply percentage of domestic, environmental, industrial and agricultural needs of the dam is 95.53, 95.02, 94.18 and 93.14% respectively, and the temporal supply percentage of domestic, environmental, industrial and agricultural needs is 95.19, 94.94, 93.67 and 92.91% respectively, which are all within the acceptable range of the Ministry of Energy. Qualitative modelling of the dam was carried out for the most pessimistic case with a discharge electrical conductivity of 3000 and a base discharge of 10000 micromos/cm, on the basis of which the maximum electrical conductivity of the reservoir was calculated to be 11900 micromos/cm. Based on this research, it was found that by modelling based on model evaluation indicators, including percentage of volume supply and percentage of time supply of different needs, it is easy to quantify the effect of exploitation and management policies on the way of determination and allocation. Observed the quality of water resources and made the most optimal decision.
