Water resources simulation is efficient tools to evaluate different options and decision in development conditions. Supply of water demand with high reliability need to exact and perfect planning. So, dam behavior recognition and it operation is from essentials of water resources systems management and future planning. In this study, the software VENSIM the method based on the dynamics of the system has been used. What makes using system dynamics different from other approaches used for studying complex systems (such as optimization) is the use of feedback loops.The model for evaluating the performance of existing systems, predict trends and evaluate the use of reservoirs already studied input is required. Model based on the data of the current status Shahid Yaghoobi dam has been comparison and verification. After validation of the simulation model constructed in terms of its logical structure for a period of 14 years (1378-1391) is conducted. In order validation results, performance calculation and observation were compared volume and values of root mean square error (RMSE), standard error (SE) and the correlation coefficient (R 2 ), respectively, 3.1, 2.467 and 0.89. The result of field research and simulation is showing that inflow because of soil dam in reservoir upstream and Dewatering in upstream by motor pumps from Kalsallar river had been very low and a significant amount is evaporated from dam back water, too (over 4.7 mcm in year). Based on these findings , it was determined that the actual conditions with the original goals before dam construction ( adjustable volume 39 million cubic meters annually ) with input data status quo ( adjustable annually, 5 million cubic meters of water ) does not match and negative consequences on downstream plains ( plain Roshtkhar and plain Jangal), including the reduction of surface currents have been feeding and the result of Water Delivery Performance index evaluating equal to 0.128 that it is showing project failure in access to plan of targets. And finally was operated scenarios is including irrigation efficiency increase (10% to 30%).