Modeling the impact of tillage and consolidation on the vadose zone hydrological behavior for data-limited conditions

Traditional hydrological models often assume static soil hydraulic properties, neglecting the dynamic changes induced by agricultural practices and climatic stressors such as tillage and natural consolidation. However, it remains unclear if these changes produce long-term hydrological disturbances that undermine the static system modeling assumption. To address this gap, in this study, the HYDRUS-1D model is modified to simulate dynamic changes in soil bulk density and hydraulic properties induced by tillage and natural consolidation. The model is first verified against observations characterizing the joint temporal change of soil bulk density and hydraulic properties after tillage in a bare field soil in the USA. Next, Bayesian inference is combined with temporally sparse volumetric water content measurements collected from two agricultural hillslopes in Czechia, to statistically compare the dynamic model with its static counterpart. The analysis reveals that the increased complexity of the dynamic model does not lead to major fitting improvements, but instead increases the predictive uncertainty, thus suggesting that the hydrological impact of tillage-consolidation is not sufficient to outweigh the measurement errors, and it does not cause major changes in the long term hydrological balance of the system. In these conditions, the Richards-based solver with static soil hydraulic properties is sufficient to describe the hydrological behavior of the hillslopes, which the model reveals as being characterized by higher surface runoff and, thus, higher erosivity in the central part.