Schuurmans et al. (1995a) presented a model for the design of water level controllers for irrigation and drainage canals that describes the essential characteristics of the processes relevant for canal control (such as water movements and control structures). This paper evaluates the accuracy of this model in two ways: (1) by comparing its frequency response with a model based on a finite difference approximation of the linearized St. Venant equations, and (2) by comparing simulation results with data from field experiments. Using these results, we characterize the accuracy of the model and discuss how these results can be taken into account in controller design.