Estimation De La Teneur En Eau Immobile Et Du Coefficient D’Échange Selon Deux Méthodes
2001
Majdoub, R. | Gallichand, J. | Caron, J.
Use of the mobile-immobile transport equation requires the knowledge of two key parameters: the immobile water content, θim, and the exchange coefficient between mobile and immobile phases of groundwater, αm. In this paper, these two parameters were 1) estimated by a tension infiltrometer, and 2) optimized by a numerical model. For the parameter estimation, a tension infiltrometer was used to apply four tracers to three fixed pan lysimeters that served to monitor variations of water content, bromide transport and drainage volume during a growing season. Estimated values of θim varied from 0.144 to 0.232 cm3 cm−3 (average of 0.191), which corresponds to a θim/θ ratio between 0.52 and 0.81 (average of 0.67). Values of αm ranged from 4.08 10−7 to 1.49 10−5 min−1 (average of 4.57 10−6). Values of θim/θ estimated in the present study were greater than published values, while αm values were less. Optimized parameters θim and αm were obtained by minimizing the difference of the sum of squares between weekly simulated and observed values of bromide concentration and mass drained. Optimized values of θim were less than those estimated with the infiltrometer, with an average difference of 38% for the three pan lysimeters. However, optimized values of αm were slightly different from those estimated with the infiltrometer, with a difference of 4.00 10−6 min−1 for the three pan lysimeters.
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