Modeling water infiltration into soil under fractional wettability conditions

TL;DR

This paper introduces a new analytical model for water infiltration into soil with fractional wettability, accounting for heterogeneous surface properties and improving fit to experimental and synthetic data.

Contribution

The paper presents a novel infiltration model that captures the effects of fractional wettability and heterogeneous soil surfaces, filling gaps in existing models.

Findings

Model accurately fits experimental infiltration data

Successfully simulates mixed infiltration curve shapes

Enhances understanding of water flow in heterogeneous soils

Abstract

The heterogeneous distribution of water-repellent materials at the soil surface causes a phenomenon known as fractional wettability. This condition frequently triggers destabilization of the wetting front during water infiltration, resulting in the formation of fingered bypass flow. However, few analytical tools exist to understand and model this behavior. Moreover, existing infiltration models fail to fit certain infiltration curves that exist in experimental data. For these reasons, we introduce a novel infiltration model to simulate water infiltration under fractional wettable conditions. We conceptualize the soil surface as a composite of two distinct portions: a water-repellent fraction, where hydrophobic effects impede water infiltration, and a wettable fraction, where capillarity and gravity are the dominant forces controlling the process. The new model was validated using a dataset comprising infiltration data from 60 field measurements. Additionally, validation was performed using 660 analytically generated infiltration curves from six synthetic soils with varying textures. This innovative approach enabled us to account for the combined influence of these two fractions and to enhance the interpretation of infiltration curves with mixed shapes, which other common methods are unable to reproduce.