INFORMED USE AND POTENTIAL PITFALLS OF CANAL MODELS

Numerical models of unsteady flow in canals are used in the design, analysis, and operation of irrigation-canal systems. Their informed use requires knowledge of the potential pitfalls and sources of error. There are three model parameters that influence errors in the model output: the distance step DELTAx, the time step DELTAt, and a weighting factor theta. The influence of the Courant number on the accuracy of the results is studied. Calibration of topographical and hydraulic parameters and verification of the model are important steps in the successful implementation of canal models, Two tests are presented that can be used to check the accuracy and stability of the programs. The first is a mass-conservation test, and the second is a ramp-discharge test. The results of these tests on several commercially available programs are presented. The intricacies of model calibration, model interpretation, and performance parameters are also discussed.