Considering water resources limitations, increasing water demands and occurrence of frequent droughts in our country, reducing water consumption and using available water with optimal management are to be dealt with. The main objective of this study is to compare the optimization and equitable water reduction approaches in agriculture water demand management during drought in such way that minimizes the consequent damages. To explore these methodologies, the 1999 drought of the Zayandeh Rud irrigation system has been evaluated. Furthermore, the required models have been developed. In the case of the Optimization method, the crops growth stages and their sensitivity to water stress were embedded in the calculations. The results show that the Optimization method associates 36% more income for the agriculture sector applying the same amount of water. This difference emphasizes the importance of water allocation with respect to growth stages rather than cutting the same amount of water to combat water scarcity. However managing the system by the Optimization method is more complex and needs more infrastructures to make it applicable.