Estimating unsaturated hydraulic conductivity of undisturbed Japanese soils by multi-step outflow experiment
2001
Mori, Y. (Shimane Univ., Matsue (Japan). Faculty of Life and Environmental Science) | Kihara, Y. | Inoue, M. | Fukushima, A.
Multi-step outflow experiments were performed to investigate unsaturated hydraulic properties of undisturbed Japanese soils under different management; paddy field, upland field, and forest. Cumulative outflow volume and soil water pressure head were measured to estimate the unsaturated hydraulic properties by inverse technique. Mualem-van Genuchten's model was employed to solve the Richard's equation. Relative error objective function showed best results, since care should be paid at high water content because of the deviation from log-normal properties. Repacked soils showed good correlation between direct method and multi-step outflow method. On the other hand for undisturbed soils, effect of macropore caused abrupt changes in hydraulic conductivity near saturation. Because measured K sub(s) showed maropore K sub(s) whereas K sub(s) in the models showed matrix K sub(s), it is appropriate to apply K sub(s), as variable for undisturbed soils. Multi-step outflow experiment was acceptable as an unsaturated hydraulic conductivity experiment for Japanese soils except near saturation.
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