MODELING MICROTOPOGRAPHY IN BASIN IRRIGATION

Microtopography has long been regarded as a key variable affecting bas in irrigation performance. This paper reports on the extension of a fl at bed two-dimensional basin irrigation model to the simulation of irr igation events in basins with microtopography. The model incorporates the local surface slopes in the x and y directions to the governing se t of partial differential equations. Three field experiments were used to validate the extended model. Elevation was measured over irregular grids, and geostatistical techniques were applied to estimate the nod al elevation of the computational grids. Results indicate that inclusi on of microtopography improves the estimation of the advance and reces sion processes and produces lower, more realistic estimates of irrigat ion performance. To further explore this phenomenon, two numerical exp eriments were devised consisting of a series of simulations on a level basin with gradually growing microtopography. The times of advance an d recession and the irrigation performance indexes are significantly a ffected by field microtopography, even if laser leveling is used.