Abstract:The constant downstream depth method of operation will be used by the middle route of the South-to North water diversion project, but the canal system operated by this method has a bad response and recovery property when combined with the downstream operation concept which is a demand-oriented operation. Combining discharge active compensation according to the real time downstream water demand and feedback control of the real time target water level, a new canal system operation method of constant downstream depth is designed. Based on canal hydraulics characteristics, a mathematical model of canal system operated by this method is constituted. As an example, the simulation of automatic operation of the emergency sector of the South to North water diversion project is carried out and the results show that the operation of this new method has a good response and recovery property,thus overcome the incompatible problem between the traditional constant downstream depth method and demand oriented operation concept.