Enhanced Subsurface Irrigation Hydrology Model

This paper provides a theoretical basis for new features added to the SWMS_3D model of Simunek et al., including spatially varied land use, dynamic root distributions and water uptake, and various fluxes at the soil-atmosphere interface due to different irrigation practices. Spatially varied land use is incorporated into the model by separating ETp into Ep and Tp. Distribution of roots is made a function of time by introducing a root growth function and root length density distribution with crop specific parameters. Various fluxes at the soil-atmosphere interface are accommodated in node-specific boundary conditions for each ground surface node by switching between specified head and specified flux boundary conditions. Ponding on the surface is allowed to account for different irrigation practices. After incorporating new features, the model is tested with analytical solutions or experimental data available in the literature. Comparison of analytical/experimental and model generated values shows that the model can produce satisfactory results.