DESCRIPTION AND EVALUATION OF PROGRAM MODIS

MODIS is an implicit hydrodynamic modeling package that computes the unsteady water flow in open canals. MODIS has been developed to investigate the hydraulic performance of dynamic controlled irrigation systems. The MODIS model can run in various computational modes varying from steady-state mode to a full dynamic mode in which the complete Saint Venant equations are solved. The applied numerical solution technique is always based on finite differences using the Preissmann implicit numerical scheme. In the MODIS model. priority has been given to robustness rather than accuracy, although warning messages are produced when accuracy considerations are violated. The model's innovative features are its accurate computation of structure flow and the real-time structure-operation possibilities. The model can also compute the structure parameters needed to realize a specified water level or discharge. This option is useful to generate operational instructions for manually controlled systems. Furthermore, the model has performance indicators that allow for a fast and diagnostic interpretation of the model results. The models weak points are that the user interface is not vet fully menu driven and that the program is not public domain. The program has been applied in many countries for wide variety of water-management problems.