THERORITICAL BACKGROUND AND APPLICATIONS OF THE HYDRUS COMPUTER SOFTWARE PACKAGES

Hydrus-2D/3D is a numerical software to simulate water and solute movement in porous media. Currently, three different versions of the Hydrus software packages are available: Hydrus-1D, Hydrus-2D, and Hydrus (2D/3D). Similar basic processes are involved on the three models and they only differ by the dimensionality of the problems they are treating. Linear finite elements are used on Hydrus 2D to numerically solve the Richard equation for saturated-unsaturated water flow and Fickian-based advection-dispersion equations for both heat and solute transport. It is also included on the flow equation a sink term to account for root water uptake as a function of both water and salinity stress. The unsaturated soil hydraulic properties can be described using van Genuchten, Brooks and Corey, modified van Genuchten, Kosugi, and Durner analytical functions. The heat transport equation considers conduction as well as advection with flowing water. The solute transport equations assume advective-dispersive transport in the liquid phase and diffusion in the gaseous phase. The uniform variably saturated water flow in all of these models is described using the Richards. Objective of this paper is to present the theoretical background of hydrus 2D and to reviews the different application of the model on agricultural sciences, such as evaluating different irrigation schemes, plant water uptake and transport of particle-like substances in the subsurface.