The principle of ‘maximum energy dissipation’: a novel thermodynamic perspective on rapid water flow in connected soil structures

Preferential flow in biological soil structures is of key importance for infiltration and soil water flow at a range of scales. In the present study, we treat soil water flow as a dissipative process in an open non-equilibrium thermodynamic system, to better understand this key process. We define the chemical potential and Helmholtz free energy based on soil physical quantities, parametrize a physically based hydrological model based on field data and simulate the evolution of Helmholtz free energy in a cohesive soil with different populations of worm burrows for a range of rainfall scenarios. The simulations suggest that flow in connected worm burrows allows a more efficient redistribution of water within the soil, which implies a more efficient dissipation of free energy/higher production of entropy. There is additional evidence that the spatial pattern of worm burrow density at the hillslope scale is a major control of energy dissipation. The pattern typically found in the study is more efficient in dissipating energy/producing entropy than other patterns. This is because upslope run-off accumulates and infiltrates via the worm burrows into the dry soil in the lower part of the hillslope, which results in an overall more efficient dissipation of free energy.

Download Full-text

Agricultural hillslope soil heterogeneity challenges: first experimental results from SUPREHILL critical zone observatory

10.5194/ismc2021-44 ◽

2021 ◽

Author(s):

Vedran Krevh ◽

Jasmina Defterdarović ◽

Lana Filipović ◽

Zoran Kovač ◽

Steffen Beck-Broichsitter ◽

...

Keyword(s):

Numerical Modeling ◽

Soil Moisture ◽

Solute Transport ◽

Soil Water ◽

Water Flow ◽

Preferential Flow ◽

Soil Heterogeneity ◽

Local Scale ◽

Soil Water Flow ◽

Critical Zone Observatory

<p>SUPREHILL is a new (2020) and first Croatian critical zone observatory (CZO), focused on local scale agricultural e.g., vineyard hillslope processes. The experimental setup includes an extensive sensor-based network accompanied by weighing lysimeters and instruments for surface and subsurface hydrology measurement. The field measurements are supported by novel laboratory and numerical quantification methods for the determination of water flow and solute transport. This combined approach will allow the research team to accurately determine soil water balance components (soil water flow, preferential flow/transport pathways, surface runoff, evapotranspiration), the temporal origin of water in hillslope hydrology (isotopes), transport of agrochemicals, and to calibrate and validate numerical modeling procedures for describing and predicting soil water flow and solute transport. First results from sensors indicate increased soil moisture on the hilltop, which is supported by precipitation data from rain gauges and weighing lysimeters. The presence of a compacted soil horizon and compacted inter-row parts (due to trafficking) of the vineyard seems to be highly relevant in regulating water dynamics. Wick lysimeters confirm the sensor soil moisture data, while showing a significant difference in its repetitions which suggests a possibility of a preferential flow imposed by local scale soil heterogeneity. Measured values of surface and subsurface runoff suggest a crucial role of these processes in the hillslope hydrology, while slope and structure dynamics additionally influence soil hydraulic properties. We are confident that the CZO will give us new insights in the landscape heterogeneity and substantially increase our understanding regarding preferential flow and nonlinear solute transport, with results directly applicable in agricultural (sloped agricultural soil management) and environmental (soil and water) systems. Challenges remain in characterizing local scale soil heterogeneity, dynamic properties quantification and scaling issues for which we will rely on combining CZO focused measurements and numerical modeling after substantial data is collected.</p>

Download Full-text

Interaction Between Plant Roots and Soil Water Flow in Response to Preferential Flow Paths in Northern China

Land Degradation and Development ◽

10.1002/ldr.2592 ◽

2016 ◽

Vol 28 (2) ◽

pp. 648-663 ◽

Cited By ~ 13

Author(s):

Yinghu Zhang ◽

Jianzhi Niu ◽

Mingxiang Zhang ◽

Zixing Xiao ◽

Weili Zhu

Keyword(s):

Soil Water ◽

Water Flow ◽

Preferential Flow ◽

Northern China ◽

Plant Roots ◽

Flow Paths ◽

Preferential Flow Paths ◽

Soil Water Flow

Download Full-text

A new modelling approach to simulate preferential flow and transport in water repellent porous media: Parameter sensitivity, and effects on crop growth and solute leaching

Soil Research ◽

10.1071/sr04098 ◽

2005 ◽

Vol 43 (3) ◽

pp. 371 ◽

Cited By ~ 19

Author(s):

G. Kramers ◽

J. C. van Dam ◽

C. J. Ritsema ◽

F. Stagnitti ◽

K. Oostindie ◽

...

Keyword(s):

Soil Water ◽

Water Flow ◽

Crop Production ◽

Preferential Flow ◽

Crop Growth ◽

Parameter Sensitivity ◽

Uniform Flow ◽

Parameter Analysis ◽

Water Repellent ◽

Soil Water Flow

A modified version of the popular agrohydrological model SWAP has been used to evaluate modelling of soil water flow and crop growth at field situations in which water repellency causes preferential flow. The parameter sensitivity in such situations has been studied. Three options to model soil water flow within SWAP are described and compared: uniform flow, the classical mobile-immobile concept, and a recent concept accounting for the dynamics of finger development resulting from unstable infiltration. Data collected from a severely water-repellent affected soil located in Australia were used to compare and evaluate the usefulness of the modelling options for the agricultural management of such soils. The study shows that an assumption of uniform flow in a water-repellent soil profile leads to an underestimation of groundwater recharge and an overestimation of plant transpiration and crop production. The new concept of modelling taking finger dynamics into account provides greater flexibility and can more accurately model the observed effects of preferential flow compared with the classical mobile–immobile concept. The parameter analysis indicates that the most important factor defining the presence and extremity of preferential flow is the critical soil water content. Comparison of the modelling results with the Australian field data showed that without the use of a preferential flow module, the effects of the clay amendments to the soil were insufficiently reproduced in the dry matter production results. This means that the physical characteristics of the soil alone are not sufficient to explain the measured increase in production on clay amended soils. However, modelling with the module accounting for finger dynamics indicated that the preferential flow in water repellent soils that had not been treated with clay caused water stress for the crops, which would explain the decrease in production.

Download Full-text

Simulating preferential soil water flow and tracer transport using the Lagrangian Soil Water and Solute Transport Model

10.5194/hess-2019-132 ◽

2019 ◽

Author(s):

Alexander Sternagel ◽

Ralf Loritz ◽

Wolfgang Wilcke ◽

Erwin Zehe

Keyword(s):

Solute Transport ◽

Soil Water ◽

Water Flow ◽

Field Experiments ◽

Preferential Flow ◽

Sensitivity Analyses ◽

Tracer Transport ◽

Soil Matrix ◽

Soil Water Flow ◽

Water And Solute Transport

Abstract. We propose an alternative model to overcome these weaknesses of the Darcy-Richards approach and to simulate preferential soil water flow and tracer transport in macroporous soils. Our LAST-Model (Lagrangian Soil Water and Solute Transport) relies on a Lagrangian perspective on the movement of water particles carrying a solute mass through the soil matrix and macropores. We advance the model of Zehe and Jackisch (2016) by two main extensions: a) a new routine for solute transport within the soil matrix and b) the implementation of an additional 1-D preferential flow domain which simulates flow and transport in a population of macropores. Infiltration into the matrix and the macropores depends on their moisture state and subsequently macropores are gradually filled. Macropores and matrix interact through diffusive mixing of water and solutes between the two domains which depends on their water content and matric potential at the considered depths. The LAST-Model is then evaluated with sensitivity analyses and tested against tracer field experiments at three different sites. The results show the internal and physical validity of the model and the robustness of our solute transport and the linear mixing approach. Further, the model is able to simulate preferential flow through macropores and to depict well the observed 1-D solute mass profile of a tracer experiment with a high computational efficiency and short simulation times.

Download Full-text