2-DIMENSIONAL SIMULATION OF BASIN IRRIGATION .1. THEORY

Overland flow of water over a porous bed in two spatial dimensions is governed by three partial differential equations accounting for continuity of momentum in the x- and y-directions and continuity of mass. A leapfrog explicit finite-difference numerical scheme was applied to solve this system of equations for the initial and boundary conditions that characterize level-basin irrigation. The numerical procedure is stable and robust for different applications, and can accommodate three different inflow configurations: line, corner, and fan. These configurations simulate inflow from an overflowing canal on a field boundary and at point sources from a corner or in the middle of a straight boundary, respectively. A numerical test was performed to assess the effect of grid fineness on the results of the simulation and on central-processing-unit time requirement. Data from two field tests were used to validate the model in quasi-one-dimensional and two-dimensional conditions.