The iteration method is utilized to compute the multi-curve regression for the nonlinear multiple functional values in the relationship between water level and flow rate in the heavy-silt-carrying channels. The testing method is also proposed for the rationality of the regression curves. Thus, the computer management system for water diversion of irrigation area is developed, which includes the system research, the operating environment, the menu design and the sub module function design. The project computations show that the management system is universal and multiple-functional, and it can meet the demand of the computation and allocation of water diversion. The system can be also applied to the calculating of charge for water resources. It can be applied in a wide extension.