Background and Objectives: Regarding the recent droughts, water resources management and prioritization of water allocation to different demands are important and essential issues. The amount of water allocation in storage dams at different months is determined based on reservoir storage. Therefore, the objective of this study is to determine the suitable operation policy regarding the sum squares of water deficit.Materials and Methods: In this study the Standard Operation Policy (SOP) and Yield models were developed for planning and water resources management. In these models amount of water release from reservoir is determined by storage volume at beginning of the period. For assessment of models efficiency in development of rule curve, Shahid Rajaei dam was studied.In mentioned models, river discharge in dam site and middle basin between Shahid Rajaei dam and Tajan diversion dam were used. By means of these models, five operation scenarios consisted of supplying 100 percent of drinking, industrial and environmental demands; with 40 to 80 percent of agricultural demand from the reservoir were simultaneously investigated.Results: In the first, second and third operation scenarios, deficit sum squares in Yield model compared to SOP model was less, equal to 83.72, 63.32 and 34.70 percent; respectively. In the fourth and fifth operation scenarios this parameter in the Yield model was greater than SOP model. Average annual water deficit in the SOP and Yield models was 23.6 and 15.16 MCM; respectively. Average and minimum reliability in Yield model were 3.81 and 52.29 percent more than SOP model; respectively; whereas, maximum vulnerability in Yield model was 80 percent less than SOP model.Conclusion: First, second and third operation scenarios with the aim of supplying 100 percent drinking, industrial and environmental demands and 60, 70 and 80 percent agricultural demand were acceptable with sum squares of water deficit of 3.97, 2.23 and 0.99; respectively. Fourth and fifth operation scenarios with the aim of supplying 100 percent drinking, industrial and environmental demands, and 40 and 50 percent agricultural demand were not acceptable with sum square of water deficit of 8.93 and 6.20; respectively.