Optimal water distribution of canal system is an important water-saving management measure to reduce the leakage loss and improve the water use efficiency of the canal system. However, the current calculation method of leakage loss of the optimized water distribution model is difficult to reflect the dynamic change characteristics of the soil permeability of the canal bed over time, resulting in more or less artificial water distribution. In view of this, this paper introduces the concept of pre-effect water content of canal-bed soil to describe the dynamic change of soil moisture in canal bed in the process of water transmission, and then puts forward a new dynamic calculation method for water leakage loss of canal bed. On this basis, an optimal water distribution model with no aftereffect is established. The case study on the optimal water distribution for summer irrigation in 2012 of general main canal system of Hetao Irrigation District shows that: compared with the traditional optimal water distribution mode based on Kostiakov formula, the new model accelerates the water distribution process in the initial stage of water distribution, makes the soil in the canal bed reach the moist state as soon as possible, shortens the duration of soil free seepage, and delays the water distribution process at the end of water distribution. Without increasing the total amount of water diverted from the general main canal, 15.6 million m3 of water loss is reduced and the water use efficiency of the canal is increased by 1%. The discovery of this law has important guiding value for scientific and rational water distribution and centralized and unified operation of irrigation canal system. © 2021, China Water Power Press. All right reserved.
