A grid refinement approach for a three‐dimensional soil‐root water transfer model

Three dimensional soil‐root water transfer models require a fine soil and root discretization in order to obtain accurate results. This goes along with a considerable computational effort. One way of reducing the computational effort is the usage of grid refinement techniques. With such techniques irregular grids are obtained that combine the accuracy of a fine grid resolution with a considerable reduction in computational costs. As a consequence of plant transpiration roots take up water and large soil water potential gradients around roots are created. Especially in these regions a fine soil discretization is needed. The root spatial distribution can therefore be used for refinement of the soil grid, a priori. Simulations show that the accuracy is indeed maintained for a priori refined grids but with reduced computational costs as compared to regular fine grids. Comparison with a well recognized a posteriori error estimate strengthen these results.