TWO-DIMENSIONAL LEVEL-BASIN IRRIGATION MODELLING WITH A FIRST ORDER UPWIND SCHEME: VALIDATION WITH EXPERIMENTAL DATA

摘要

Numerical models of overland flow have been applied to a number of practical problems of interest in Engineering. Basin irrigation is a surface irrigation system characterized by its potential to use water very efficiently. It consists on flooding from a point source, a squarish, relatively large field, leveled to zero average slope and fully surrounded by a dike to prevent runoff. The idea behind basin irrigation is very simple, although its real world applications have been limited by the difficulty to level the basin with the accuracy required to flood the field quickly and uniformly. A 2D first order upwind scheme is used to build a basin irrigation simulation model considering differences in bottom level. The implementation of upwind methods is not straightforward when source terms are relevant so that an upwind approach is adopted for the discretization of bed slope terms. Due to the small initial values (zero at initial conditions) for the variables and the high value of the Manning coefficient required to take into account the effects of the vegetation in the field, the friction terms become dominant and the numerical solution is affected. The infiltration parameters included in the source terms do not need any special treatment. The model is applied to reproduce two field experiments illustrating the relevance of land leveling on basin irrigation performance. Simulation results show a clear improvement over previous simulation efforts and are in a close agreement with experimental data.