TY - JOUR

T1 - Using an inverse method to estimate the hydraulic properties of crusted soils from tension-disc infiltrometer data

AU - Šimůnek, Jiří

AU - Angulo-Jaramillo, Rafael

AU - Schaap, Marcel G.

AU - Vandervaere, Jean Pierre

AU - Van Genuchten, Martinus Th

PY - 1998/10

Y1 - 1998/10

N2 - An inverse procedure was used to estimate the soil hydraulic characteristics of a two-layered soil system - soil surface crust and subsoil - from data obtained during a tension-disc infiltration experiment. The inverse procedure combined the Levenberg-Marquardt nonlinear parameter optimization method with a numerical solution of the axisymmetric variably-saturated flow equation. The objective function was defined in terms of the cumulative infiltration curve and the final water content measured directly below the tension-disc infiltrometer at the end of the experiment; this final water content was assumed to correspond to the final supply pressure head. We analyzed two infiltration experiments carried out with a 25-cm diameter tension-disc infiltrometer. One experiment was carried out on a two-layered system, and a second after removal of the surface crust covering the sandy subsoil. Both experiments were performed with six consecutive supply tensions. We first analyzed the infiltration experiment for the subsoil only, thus yielding its hydraulic characteristics. Subsequent analysis of the infiltration experiment for the two-layered system with known hydraulic properties of the subsoil provided estimates of the hydraulic properties of the surface crust. We further compared the estimated hydraulic parameters of the subsoil with those obtained using Wooding's analytical method [Wooding, R.A., 1968. Steady infiltration from a shallow circular pond. Water Resour. Res. 4, 1259-1273] and predictions based on a neural network model requiring textural input information. All three methods generated roughly the same results. The numerical inversion technique proved to be a convenient tool for estimating the soil hydraulic properties of both the surface crust and the subsoil.

AB - An inverse procedure was used to estimate the soil hydraulic characteristics of a two-layered soil system - soil surface crust and subsoil - from data obtained during a tension-disc infiltration experiment. The inverse procedure combined the Levenberg-Marquardt nonlinear parameter optimization method with a numerical solution of the axisymmetric variably-saturated flow equation. The objective function was defined in terms of the cumulative infiltration curve and the final water content measured directly below the tension-disc infiltrometer at the end of the experiment; this final water content was assumed to correspond to the final supply pressure head. We analyzed two infiltration experiments carried out with a 25-cm diameter tension-disc infiltrometer. One experiment was carried out on a two-layered system, and a second after removal of the surface crust covering the sandy subsoil. Both experiments were performed with six consecutive supply tensions. We first analyzed the infiltration experiment for the subsoil only, thus yielding its hydraulic characteristics. Subsequent analysis of the infiltration experiment for the two-layered system with known hydraulic properties of the subsoil provided estimates of the hydraulic properties of the surface crust. We further compared the estimated hydraulic parameters of the subsoil with those obtained using Wooding's analytical method [Wooding, R.A., 1968. Steady infiltration from a shallow circular pond. Water Resour. Res. 4, 1259-1273] and predictions based on a neural network model requiring textural input information. All three methods generated roughly the same results. The numerical inversion technique proved to be a convenient tool for estimating the soil hydraulic properties of both the surface crust and the subsoil.

KW - Neural networks

KW - Parameter estimation

KW - Soil hydraulic properties

KW - Tension-disc infiltrometer

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U2 - 10.1016/S0016-7061(98)00035-4

DO - 10.1016/S0016-7061(98)00035-4

M3 - Article

AN - SCOPUS:0344404203

VL - 86

SP - 61

EP - 81

JO - Geoderma

JF - Geoderma

SN - 0016-7061

IS - 1-2

ER -