Water Movement in Horizontally Layered Soils

Samani, Zohrab; Cheraghi, Ali; Willardson, L. S.

doi:10.1061/(asce)0733-9437(1989)115:3(449)

Cited by 24 publications

(13 citation statements)

References 11 publications

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“…For a reverse sequence of a coarse texture over a fine texture, Hill and Parlange (1972) found the front to move uniformly through the coarse top layer and to remain stable in the fine bottom layer. In related experiments by Samani et al (1989), the authors established the critical hydraulic conductivity ratio between layers to be 20. Though the effect of initial moisture content on this critical ratio has not been studied, we expect the latter to increase with the former due to its stabilizing influence, as will soon become evident.…”

Section: Laboratory Infiltration Into Layered Mediamentioning

confidence: 99%

An overview of instability and fingering during immiscible fluid flow in porous and fractured media

Chen¹,

Neuman²,

Taniguchi³

1995

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Section: Laboratory Infiltration Into Layered Mediamentioning

confidence: 99%

An overview of instability and fingering during immiscible fluid flow in porous and fractured media

Chen¹,

Neuman²,

Taniguchi³

1995

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“…The soil stratification affects the uniform distribution of irrigation and drainage water and the shape of soil water layer. The distribution and movement of soil water in layered soils characterised by 'downward movement' of water have gained more attention due to their effects on water infiltration, root growth, transportation of chemicals and pollutants, hydrological process, and ecological quality and stability (Samani et al 1989;Antonopoulos 1993). Soil water movement and distribution studies involving layered media are important for investigating how restricting layers affect rates of water and solute migration in the soil profile and, more generally, for examining the influence of soil heterogeneity on water and solute transport.…”

Section: Introductionmentioning

confidence: 99%

“…The obtained data of infiltration could be well explained by the proposed new concept of saturated and unsaturated refraction flow. The ratio of hydraulic conductivities at which the wetting front loses its one-dimensionality and breaks into "fingers" by laboratory experiments was determined by Samani et al (1989). Finally, the impact of layered soil is important in more general studies of the effect of soil heterogeneity and anisotropy on water movement.…”

Section: Introductionmentioning

confidence: 99%

“…However, few studies focused on the soil water in dam farmland where the heterogeneous layered soil existed on the Loess Plateau of China as far as we know. Moreover, the studies focusing on water distribution and movement in layered soils were mainly conducted in laboratory (Stauffer and Dracos 1986;Miyazaki 1988;Samani et al 1989;Antonopoulos 1993;Sakellariou-Makrantonaki 1997) and very few studies have conducted in field for complex field condition under tougher operations (Heilig et al 2003;Gish et al 2003).…”

Section: Introductionmentioning

confidence: 99%

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Soil Water Distribution and Movement in Layered Soils of a Dam Farmland

Zhao

Shao

Melegy

2010

Water Resour Manage

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In soil profiles, special emphasis has been placed on the migration of agricultural chemicals spread intentionally or accidentally into deep soils or groundwater body. To prevent soil water pollution and estimate the magnitude of the hazard caused by these chemicals, it is necessary to know the processes controlling their movement from the soil surface, through the root zone and eventually to the water table. This paper deals with two-dimensional soil water distribution and movement in sloping layered soils of a dam farmland on the Loess Plateau of China. In the dam farmland, soil water content showed horizontal distribution corresponding to spatial patterns of the particle sizes. The soil water content of deeper soil was relatively stable compared with topsoil. Generally, rainfall infiltration was limited to 0.8 m in the study period. Funnel flows were found in the layered soils of the dam farmland after rainfall proving the existence of this phenomenon which was observed in simulation experiments and field observation by previous researches. In the study area, the wetting front was unstable due to the layered soils. The spatial correlation analysis of the soil water content showed water movement along the layers in the wetting process with 7 m day −1 only on the first day after rainfall. On the vertical direction, the velocity of water movement was 0.3 m day −1 on the first day after P. Zhao State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, P. Zhao et al.rainfall. The results indicated that the quantity of funnel flow increases with distance along the inclined interfaces in the dam farmland which can cause contamination of groundwater. Consequently, future studies should consider the funnel flow and the management of agriculture chemicals in dam farmlands.

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“…Preferential flow caused by wetting front instability leading to fingered flow is termed here as "unstable flow". There are many situations occurring in nature which have been found to favour the initiation and development of an unstable wetting front in unsaturated porous media (Hill & Parlange, 1972;White et al, 1976White et al, , 1977Diment & Watson, 1985;Samani et al, 1989;Glass et al, 1988Glass et al, , 1989aGlass et al, , 1989bBaker & Hillel, 1990;Starr et al, 1978Starr et al, , 1986Glass et al, 1988;van Ommen et al, 1989a,b;Tamai et al, 1987;Babel et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

Simulation of stable and unstable flows in unsaturated homogeneous coarse sand

Babel

Gupta

Loof

1997

Hydrological Sciences Journal

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A numerical model developed to simulate stable and unstable flows in unsaturated porous media is described. Results of numerical studies carried out to simulate laboratory experiments with the assumption of stable flow demonstrate the occurrence of unstable flow for the initial conditions of both air dry and field capacity for unsaturated infiltration in sands. This indicates that the Richards flow equation based on moisture content and potential variables averaged over total crosssectional area may not be applicable for flow under instability-prone boundary conditions. The unstable flow due to wetting front instability is modelled using the steady-state theory proposed by Hillel & Baker (1988). Simulation results for fingered flux calculated with the theory represent the experimental data reasonably well. The pore water velocity remains constant irrespective of the incident flux as long as the flux is smaller than the hydraulic conductivity value at the water entry suction of the porous media. The effect of antecedent wetness on the unstable flow behaviour is to reduce the pore water velocity drastically from air dry to field capacity conditions. Simulation d'écoulements stables et instables dans un sable grossier homogène et non saturéRésumé Nous avons développé un modèle numérique afin de simuler des écoule-ments stables ou non dans des milieux poreux non-saturés. Les résultats des études numériques entreprises pour simuler les expériences de laboratoire dans l'hypothèse d'un écoulement stable montrent que, pour l'infiltration dans des sables non saturés, un écoulement instable apparaît que le milieu soit initialement sec ou à la capacité au champ. Cela indique que l'équation de Richards qui concerne des variables de charge et d'humidité moyermées selon des sections n'est peut être pas applicable à des écoulements dont les conditions initiales favorisent l'instabilité. L'écoulement instable causé par l'instabilité du front d'humectation a été modélisé en utilisant la théorie en régime permanent proposée par Hillel & Baker en 1988. Les résultats des simulations de flux digités s'appuyant sur cette théorie reproduisent les résultats expérimentaux de façon satisfaisante. La vitesse de pore de l'eau demeure constante quel que soit le flux incident tant que ce flux reste inférieur à la conductivité hydraulique correspondant à la succion d'entrée du milieu poreux. L'effet de l'humidification antérieure sur le comportement instable de l'écoulement est une très importante réduction de la vitesse de pore entre l'état sec et la capacité au champ.

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Water Movement in Horizontally Layered Soils

Cited by 24 publications

References 11 publications

An overview of instability and fingering during immiscible fluid flow in porous and fractured media

An overview of instability and fingering during immiscible fluid flow in porous and fractured media

Soil Water Distribution and Movement in Layered Soils of a Dam Farmland

Simulation of stable and unstable flows in unsaturated homogeneous coarse sand

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