Constraints on water resources and increasing the number and variety of water users has led to appeal of the importance of optimal water allocation. The Khanmirza watershed in Chaharmahal Va Bakhtiari Province, has experienced unsustainable development by relying on groundwater resources.  As a result of this imbalance, a dramatic drop occurred in the aquifer of the Khanmiza plain. The Khanmirza watershed allocation model in WEAP environment were developed to investigate the allocation and spatial changes, considering the base year (2015), the horizon year of the plan (2025), and the one-month timeline. The four scenarios examined in the WEAP model included the reference scenario, pessimistic scenario, optimistic scenario and realistic scenario over the next ten years. The results showed that 51 million cubic meters of demand, in a pessimistic scenario, 79 million cubic meters, in an optimistic scenario, 30 million cubic meters, and in a realistic scenario 41 million cubic meters cannot be provided. Therefore, given the high volume of water requirements in the agricultural sector, the need for special management and planning in this area to prevent groundwater loss is quite tangible. It is also clear that the use of water for agricultural in the studied area acts as a competitor to the environment and without land use management, water management will face tension.