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DETERMINATION OF VAN GENUCHTEN PARAMETERS
Abstract
The effectiveness of hydrological models application depends immensely on exact knowledge of parameters included in these models. Their experimental determination is often difficult and costly task. The alternative to experimental measurement of these parameters is inverse modeling when sought-in parameters are determined as a result of comparison of modeled and observed values of some physical quantities . It is assumed that the experimental determination of these quantities is not difficult. In this article, within the framework of this approach, the problem of identifying parameters included in formulas for hydrophysical characteristics, namely van Genuchten parameters, is considered. In this regard, a model of water transfer in unsaturated soil is used. The simulated movement of soil moisture is described by the Richards equation. The simulated and observed values of soil moisture are compared in some area. The proximity of the selected parameter values to their true values is estimated by mean-square deviation of the observed soil moisture values from its modeled values, corresponding to the selected parameter values. It is necessary to choose such parameters values so that this deviation is minimal. This optimization problem is proposed to be solved using a procedure that uses derivatives of the objective function. These derivatives are calculated using technique of fast automatic differentiation.
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References13
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