Modeling soil-crack–water–atmospheric interactions: a novel root water uptake approach to simulate the evaporation through cracked soil and experimental validation

Few studies numerically investigated evaporation through cracked soil using macro pore size distribution approach (conventional approach). In previous studies, the experimental results used for the simulation were usually obtained by evaporation from a very small mould. Moreover, those results are prone to size and boundary effects and can influence simulated soil moisture distribution around crack. In addition, difference between volumetric water contents (VWCs) computed using conventional approach and measured VWCs is relatively high. The main objective of the present study is to propose a new approach for simulating evaporation through cracked soil. The new approach draws analogy from root water uptake model, which includes a sink term. For validation, a large-scale experimental setup was designed and developed to obtain the experimental results by minimizing boundary effects. The experimental setup was instrumented to measure suction and VWC. Commercial finite element package “HYDRUS” was used to numerically solve (simulate) the Richards equation coupled with sink term. This study revealed that, root water uptake approach is appropriate for simulation of large reduction in VWCs under evaporation. Maximum difference between computed VWCs using conventional method and measured VWCs was observed to be 21%. Whereas, maximum difference between VWCs computed using novel root water uptake approach and measured VWCs was observed to be 16%. The proposed approach was able to predict soil moisture distributions more reasonably as it allows loss of water through cracks on soil surface.