Abstract: The optimal water allocation under limited water supply is studied with a multi-source and multi-crop irrigation area as a background.Both optimal reservoir operation and optimal allocation of water to lands are considered in this paper.The whole irrigation area is divided into units according to the distribution status of water resources and land resources.On every unit is planted several crops.If the field where each crop in each unit is planted is looked upon as a soil reservoir,the optimization methods employed in the operation of multi-reservoir system can be used to study the optimal water allocation in irrigation area.The optimal control algorithm is employed in this paper.To show the validity of the integrated model,the three different models are simulated in this paper.In model Ⅰ,neither reservoir nor canal irrigation systems is operated optimally.In model Ⅱ,only optimal operation of reservir is considered.In model Ⅲ,only optimal operation of canal irrigation systems is considered.The case study shows that the integrated model can generate more benefit than the other three models,especially in drought years,and the optimal control algorithm performs well.