Numerical inverse procedure to estimate soil hydraulic properties using Excel
2004
Noborio, K. (Iwate Univ., Morioka (Japan). Faculty of Agriculture)
Abstract There Is a b?g demand to predict water movement and solute transport ?n soil not only in agricultural but also in environmental fields. To predict water distribution in soil, soil hydraulic properties, i.e. a water characteristic curve and hydraulic conductivity, should be known in priori. Measurement of soil hydraulic properties, however, is usually time consuming and laborious work. Recent improvements of computing power on PC enabled us to inversely estimate hydraulic properties using a numerical simulation model along with experimental data. Spreadsheet-type software, which has a macro language and a solver, is also popular. In this study Excel was used to numerically simulate soil water movement using the finite difference method written in Visual BASIC as a macro function. The solver function of Excel successfully worked with the numerical model to estimate best-fitted values for soil hydraulic properties by comparing simulated results with temporal changes in soil water content measured. The temporal changes in water content were measured with time domain reflectometry (TDR) at 20 cm below the soil surface during water infiltration into loamy sand. A water characteristic curve with parameters inversely estimated reasonably agreed with that with parameters experimentally determined. Saturated hydraulic conductivity inversely estimated also agreed well with that determined by an experiment. Excel would be alternative software to estimate soil hydraulic properties with an inverse procedure.
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