Estimation of the Dual‐Permeability Model Parameters using Tension Disk Infiltrometer and Guelph Permeameter

Abstract

A determination of the parameters describing the soil hydraulic properties of matrix and macropore domains and mass exchange between these domains is crucial when preferential water flow in structured soils is simulated using the dual‐permeability model. This study focused on estimating the parameters of the radially symmetric dual‐permeability model from cumulative infiltration measured in the surface horizon of a Haplic Luvisol. While parameters obtained from the numerical inversion of the tension disk infiltration, using the single‐porosity flow model in HYDRUS 2D/3D, were used to describe the matrix domain, the parameters characterizing the macropore domain and mass exchange between domains were estimated using the Guelph permeameter infiltration and the dual‐permeability flow model in HYDRUS 2D/3D. The mass transfer coefficient between the two pore domains affected the simulated water regime considerably, and subsequently, the calibrated value of the saturated hydraulic conductivity in the macropore domain, K sf A less significant impact of the aggregate shape factor was observed due to a low range of possible values compared with the other two parameters, which either varied within orders of magnitude (the effective saturated hydraulic conductivity of the interface between the two pore domains, K sa ) or were squared (the characteristic length of an aggregate, a ). The K sf values increased when mass exchange decreased (when a increased and K sa decreased). Since both parameters are mutually correlated and therefore have a similar impact on simulated data, we suggest that a be determined independently, and K sa and K sf should be simultaneously optimized when the parameters of the dual‐permeability model are evaluated using the presented experimental procedure.