Abstract
•This is the 2nd part of a surface and subsurface drip simulation two-part study.•Studied the effect of geometries, shapes, discharges & textures on simulations.•The mass balance errors of subsurface simulations are less than 0.9%, unlike surface ones.•We found that the 2D domains mostly underestimate the 3D slices.•To simulate subsurface drip use 2D or 3D. For surface simulations, use only 3D.
This is the second part of the companion papers assessing HYDRUS simulations of drip irrigation. While the first part focused on surface drip simulations, this part focused on the subsurface simulations and how they differ from the surface simulations. We evaluated the effect of different domain geometries, emission element shapes, coordinate systems, emitter discharges, and soil textures on the accuracy and stability of the simulation. The results showed that all the 2D and 3D simulations were done with a mass balance error of less than 0.9%, in contrast to the surface 2D cases that have large error values. The flux-conductivity ratio for subsurface simulations does not have the same influence on the mass balance error as in the surface simulations. We found extreme differences in the simulation speeds that were attributed to the emitter’s location (the subsurface is faster), the domain axes (axisymmetric is faster than Cartesian), soil texture (the lighter is faster), the elapsed time or stage (the redistribution is hugely faster than redistribution). For the 2D-3D comparisons, we found that the 2D domains mostly underestimate the 3D slices. Finally, we found that the flux profiles of the 2D domains perfectly match the flux profiles of the 3D domains, in contrast to the surface comparisons. Hence, we can use 2D simulations reliably for subsurface drip, but not for the surface drip.