Modeling Macroporous Soils with a Two-Phase Dual-Permeability Model

L Stadler,R Hinkelmann,R Helmig

doi:10.1007/s11242-012-0064-3

L Stadler, R Hinkelmann + Show 1 more

Open Access

https://doi.org/10.1007/s11242-012-0064-3

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Abstract

Fast water infiltration during heavy rainfall events is an important issue for hillslope hydrology and slope stability. Most hillslopes are strongly heterogeneous and contain macropores and soil pipes, so that infiltrating water can bypass the soil matrix and reach rapidly deeper regions. Water infiltration into macroporous soils is usually simulated with dual-permeability models based on Richards equation (RDPM) which only describes water flow. In this article, we present a two-phase dual-permeability model (TPDPM) for simulating water and air flow in macroporous soils. Water and air flow are simulated in both domains and mass transfer for water and air between the domains is included with first-order transfer terms. The main objectives of this article are to discuss the differences between TPDPM and RDPM and to test the application of the TPDPM on the slope scale. First, the differences between RDPM and TPDPM were studied using a one-dimensional layered soil. For the chosen high infiltration rate, we observed significant differences in the macropore domain and small differences in the matrix depending on the transfer parameter. Second, we applied the model to simulate fast water infiltration and flow through an alpine hillslope, where the water flow mainly occurs in the macropore domain and the matrix domain is bypassed because it is low permeability. A good agreement of simulated and measured travel times of Wienhofer et al. (Hydrol Earth Syst Sci 13(7):1145–1161, 2009) was obtained. Finally, we recommend using TPDPM for high infiltration in layered macroporous soils.

Highlights

IntroductionMost field soils are structured and contain large continuous pores and voids, so called macropores which are generated by soil mechanical processes like swelling and shrinking, soil flora (e.g., decayed plant roots), soil fauna (e.g., earthworm burrows) and further soil processes (Beven and Germann 1982)
Most field soils are structured and contain large continuous pores and voids, so called macropores which are generated by soil mechanical processes like swelling and shrinking, soil flora, soil fauna and further soil processes (Beven and Germann 1982)
With the two-phase dual-permeability model (TPDPM), the high saturation of the matrix domain in the upper part limits the escape of soil air; whereas the water front infiltrates deeper for the RDPM, only limited by low conductivity of the silty clay loam

Summary

Introduction

Most field soils are structured and contain large continuous pores and voids, so called macropores which are generated by soil mechanical processes like swelling and shrinking, soil flora (e.g., decayed plant roots), soil fauna (e.g., earthworm burrows) and further soil processes (Beven and Germann 1982) Because of their different origin, macropore texture in terms of surface properties, orientation, ramification, and connectivity may be manifold. The mass transfer between matrix and macropores is controlled by the properties of the macropore surface and can be strongly inhibited, especially when the macropores are affected by lining and coating (Thoma et al 1992; Gerke and Köhne 2002) All these complex processes should be covered by numerical models to simulate water flow in macroporous soils (macropore flow)

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