Thermodynamic Controls on Dynamic Soil Configuration and Non-uniform Infiltration Processes

Non-uniform infiltration is a very common observation and one manifestation of non-diffusive physics in soil-water processes. It is posing a fundamental challenge to conventional Darcy-scale approaches in soil-water processes, revealing limitations in our current understanding of complex soil-water interactions. While infiltration is fundamental to many ecohydrologic and hydropedologic aspects, its manifestation through structured soil and dynamically connected flow paths demands a more sophisticated system description.

Through a series of plot-scale irrigation experiments, we characterized infiltration flow fields based on observed soil moisture, tracers and time-lapse GPR data. Based on these data we conceptualised a thermodynamic representation for characterizing soil-water dynamics and their interactions. We observe celerity distributions in flow fields shifting to higher values with higher antecedent soil moisture. We also see shifting soil reconfigurations in precipitation events. 

In the view of soil water dynamics as dissipative processes, we propose that these dynamic soil configurations systematically adapt to meet the system's dissipation demands. The thermodynamic perspective offers new insights into the physical constraints governing soil-water dynamics and provides a theoretical foundation for improved and scaleable prediction of non-uniform flow processes. Our results contribute to an advanced understanding of soil-water constitutive laws under non-equilibrium conditions and may help bridge the gap between observed soil-water dynamics and their representation in models.