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| Titel |
Numerical results on perched waters in 1D and sloping 2D gradually layered soils |
| VerfasserIn |
Marco Peli, Stefano Barontini, Mark Bakker, Thom A. Bogaard, Roberto Ranzi |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250054494
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| Zusammenfassung |
| The hydraulic conductivity at saturation Ks usually decreases across the upper soil layers.
This pattern strongly characterises the soil water circulation and affects a number of
physical phenomena, including perched water formation and landslide triggering
mechanisms.
Aiming at better understanding the involved hydrological processes, the case of
infiltration at constant rate in an undeformable soil layer of finite depth, with exponentially
decreasing Ks, was numerically investigated. Both one–dimensional and sloping
two–dimensional cases were simulated by means of Hydrus1D and Hydrus2D/3D. At
the bottom of the domain saturation conditions were assumed, thus representing
both the presence of a water table or of a soil layer which is not able to act any
retention.
The 1D simulations confirmed previous theoretical analyses of the steady case,
providing the threshold of the infiltration rate above which a saturated layer onsets, its
thickness, the maximum pressure head and its position within the saturated layer.
They moreover enlightened soil water dynamics before the steady state is reached.
Accordingly with an analytical solution of the Richards equation for a gradually layered
soil, a peak of water content onsets at the soil surface. It is then enveloped as the
maximum water content moves downward. Then two different behaviours can be
expected. Either the soil saturation is reached at one point, thus leading to a perched
water table which rapidly reaches steady conditions, or the peak vanishes and the
solution recovers its monotonicity with a flux in the direction of the increasing water
content.
The 2D simulations, instead, reveal how a greater infiltration rate is required for the
perched water to onset, with respect to the 1D case, due to the lateral flux which strongly
increases as a saturated layer is formed. If slopes one order of magnitude longer than the soil
depth are considered, an almost uniform flux can be observed in a long branch of their central
part, thus allowing to perform stability analyses in the framework of the infinite slope
approach. |
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