Simulation of trickle irrigation, an extension to the US Geological Survey's computer program VS2D

A method is presented for simulating water movement through unsaturated porous media in response to a constant rate of application from a surface source. Because the rate at which water can be absorbed by soil is limited, the water will pond; therefore the actual surface area over which the water is applied may change with time and in general will not be known beforehand. An iterative method is used to determine the size of this ponded area at any time. This method will be most useful for simulating trickling irrigation, but also may be of value for simulating movement of water is soils as the result of an accidental spill. The method is an extension to the finite difference computer program VS2D developed by the U.S. Geological Survey, which simulates water movement through variably saturated porous media. The simulated region can be a vertical, 2-dimensional cross section for treatment of a surface line source or an axially symmetric, 3-dimensional cylinder for a point source. Five test problems, obtained from the literature , are used to demonstrate the ability of the method to accurately match analytical and experimental results. (Author 's abstract)