Performance of preferential flow models in predicting infiltration through a remolded soil with artificial macropores

Abstract

Preferential flow in soils contributes to water and contaminant leaching to groundwater and subsurface drains. At practical scales, preferential flow is often neglected due to the lack of consensus or guidance on how to simulate this process. Dual-permeability (DP) approaches are a standard, but their applicability in practice is limited by the large number of parameters involved. The sourceresponsive (SR) model simulates preferential flow as flow films along the walls of macropores that interact with the soil matrix. The objective of this study was to evaluate the ability of the SR model and a DP model with calibration limited to macropore parameters to simulate hydrologic variables of interest for practical applications. Infiltration experiments were conducted in a 150-cm-long by 50-cm-wide by 40-cm-deep soil column with vertical artificial macropores, with preferential flow being the most prevalent flow process. Two macropore configurations and various rainfall rates were tested. The DP model provided relatively accurate predictions of the bottom drainage rates, but inaccurate soil parameter estimates resulted in poor predictions of matrix flow. Critical limitations in the SR model formulation were highlighted, and the model was revised. The refined SR model provided accurate predictions of bottom drainage rates and water contents under steady-state rainfall. The DP model with a reduced calibration appeared valid to estimate subsurface fluxes with negligible matrix flow. The SR model applicability is limited to steady-state scenarios with negligible matrix flow. Critical developments are needed for the SR model to be applicable in practice. 1 INTRODUCTION Preferential flow through soil macropores promotes the fast downward movement of water, solutes, and small par-Abbreviations: DP, dual-permeability; REV, representative element volume; SR, source-responsive This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Tracing lateral subsurface flow in layered soils by undisturbed monolith sampling, targeted laboratory experiments, and model‐based analysis

“…Percolation experiments using soil columns with artificial macropores have also been conducted by Köhne and Mohanty (2005) and Castiglione et al (2003) to quantify macropore and matrix flow, as well as the interdomain water transfer. Macropore induced flow along texture contrasting layers (Lin et al, 2006) was observed in the field (Noguchi et al, 1999) and has also been observed in laboratory experiments after drilling artificial macropores down to the horizon boundary (Guertault & Fox, 2020). Sakaki et al (2011) developed an experimental scheme to simultaneously determine the two-dimensional (2D) distribution of soil water content (SWC) and soil water potential in a soil monolith to assess water retention during wetting and drainage cycles.…”

“…In a second experiment, two holes (diameter = 0.8 cm) were drilled into the monolith from above representing earthworm burrows reaching down to the horizon boundary (Figure 3) similar to Guertault and Fox (2020). By only filling the holes with water, an artificial local saturation was created, possibly leading to LSF.…”

Quantifying the Importance of Preferential Flow in a Riparian Buffer

“…Such observations, when combined with the magnitude of preferential flow demonstrated in this study, support the need for hydrologic and solute transport preferential flow routines within riparian buffer models. Orozco-López et al (2018) and Guertault and Fox (2020) reviewed and evaluated several of those approaches for future incorporation into models such as VFSMOD. Such advances will require a trade-off between improving model physical description and increasing parameterization efforts, especially regarding the preferential flow models being considered.…”

“…Source-responsive models have been recently proposed as alternatives to dual-permeability and dual-porosity models (Orozco-López et al, 2018). Advances are currently underway in the mechanistic modeling of riparian buffer systems that are considering the most effective and efficient approach to handle preferential flow (Orozco-López et al, 2018;Fox, 2019;Guertault and Fox, 2020;Orozco-López, 2020; with the goal of improving riparian buffer and vegetative filter strip design tools. Being able to partition between matrix and preferential infiltration will allow us to elucidate the contributions of matrix and preferential flow in riparian buffers.…”

Coupled Effects of Pore Water Velocity and Soil Heterogeneity on Bacterial Transport: Intact vs. Repacked Soils

“…The bacterial spread could become further significant in soils with macropores, which are favorable to rapid formation of preferential flow. Preferential flow can greatly increase the contamination of water by pathogenic bacteria ( Allaire et al, 2009 ; Li et al, 2017 ; Guertault and Fox, 2020 ). Therefore, it is important to understand how soil structure (e.g., macroporosity of intact soil) influence the dependence of bacterial transport on rainfall intensity.…”