The effects of truncating the capillary fringe on water‐table dynamics during periodic forcing

The term "capillary fringe" is ambiguous due to differing definitions. Above a water table there exists a zone wherein total potentials of the soil water are equal. Laboratory experiments conducted in columns of sandy soil showed that, whilst this equipotential zone developed most rapidly over a lowered water table, less rapidly over a water table raised into moist soil, and least rapidly over a water table raised into dry soil, the final height of the zone was approximately equal in all cases. When a soil overlying an impermeable layer with no outlet was wetted from above, an equipotential zone developed prior to the development of a water table.Permeability was the factor dominating the development of the equipotential zone. Once developed, the zone exhibited high permeability, and experiments showed that water movement could occur rapidly even with extremely small total potential gradients, especially where the zone developed by desorption above a lowered water table.The height of the equipotential zone equals numerically the value of matric potential (in centimeters of water) which prevails at field capacity.The term "equipotential zone" is superior and preferable to "capillary fringe" since it describes accurately the prevailing situation and cannot be misinterpreted.

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Effects of capillary fringe and truncation factor on pore-water pressure and water table variation in dewatering and watering sand column experiments

Advances in Water Resources ◽

10.1016/j.advwatres.2018.09.012 ◽

2018 ◽

Vol 121 ◽

pp. 361-368

Author(s):

Jincheng Hang ◽

Haijiang Liu

Keyword(s):

Pore Water ◽

Water Table ◽

Pore Water Pressure ◽

Water Pressure ◽

Column Experiments ◽

Capillary Fringe ◽

Sand Column

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Identifying a soil hydraulic parameterisation from on-ground GPR time lapse measurements of a pumping experiment

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-9-9095-2012 ◽

2012 ◽

Vol 9 (8) ◽

pp. 9095-9117 ◽

Cited By ~ 1

Author(s):

A. Dagenbach ◽

J. Buchner ◽

P. Klenk ◽

K. Roth

Keyword(s):

Quantitative Analysis ◽

Numerical Simulations ◽

Water Content ◽

Water Table ◽

Ground Penetrating Radar ◽

Time Lapse ◽

Radar Signal ◽

Capillary Fringe ◽

Ground Penetrating ◽

Over Time

Abstract. We show the potential of on-ground Ground-Penetrating Radar (GPR) to identify the hydraulic parameterisation with a semi-quantitative analysis based on numerical simulations of the radar signal. A pumping experiment has been conducted at the ASSESS-GPR site to establish a fluctuating water table, while an on-ground GPR antenna recorded traces over time at a fixed location. These measurements allow to identify and track the capillary fringe in the soil. The typical dynamics of soil water content with a transient water table can be deduced from the recorded radargrams. The characteristic reflections from the capillary fringes in model soils that are described by commonly used hydraulic parameterisations are investigated by numerical simulations. The parameterisations used are: (i) full van Genuchten, (ii) simplified van Genuchten with m = 1 − 1/n and (iii) Brooks-Corey. All three yield characteristically different reflections, which allows the identification of an appropriate parameterisation by comparing to the measured signals. We show that these are not consistent with the commonly used simplified van Genuchten parameterisation with m = 1 − 1/n.

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Distinguishing Capillary Fringe Reflection in a GPR Profile for Precise Water Table Depth Estimation in a Boreal Podzolic Soil Field

Water ◽

10.3390/w12061670 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1670

Author(s):

Chameera Illawathure ◽

Mumtaz Cheema ◽

Vanessa Kavanagh ◽

Lakshman Galagedara

Keyword(s):

Water Table ◽

Shallow Groundwater ◽

Depth Estimation ◽

Water Table Depth ◽

Soil Conditions ◽

Capillary Fringe ◽

Growing Seasons ◽

Sampling Volume ◽

Highly Correlated ◽

Using Data

Relative permittivity and soil moisture are highly correlated; therefore, the top boundary of saturated soil gives strong reflections in ground-penetrating radar (GPR) profiles. Conventionally in shallow groundwater systems, the first dominant reflection comes from the capillary fringe, followed by the actual water table. The objective of this study was to calibrate and validate a site-specific relationship between GPR-estimated depth to the capillary fringe (DCF) and measured water table depth (WTDm). Common midpoint (CMP) GPR surveys were carried out in order to estimate the average radar velocity, and common offset (CO) surveys were carried out to map the water table variability in the 2017 and 2018 growing seasons. Also, GPR sampling volume geometry with radar velocities in different soil layers was considered to support the CMP estimations. The regression model (R2 = 0.9778) between DCF and WTDm, developed for the site in 2017, was validated using data from 2018. A regression analysis between DCF and WTDm for the two growing seasons suggested an average capillary height of 0.741 m (R2 = 0.911, n = 16), which is compatible with the existing literature under similar soil conditions. The described method should be further developed over several growing seasons to encompass wider water table variability.

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Shallow Water Table Contribution to Soil-Water Retention in the Capillary Fringe of a Very Gravelly Loam Soil of South Florida

10.13031/2013.26999 ◽

2009 ◽

Author(s):

Luis P Barquin ◽

Kati W Migliaccio ◽

Rafael Muñoz-Carpena ◽

Bruce Schaffer ◽

Jonathan Crane ◽

...

Keyword(s):

Shallow Water ◽

Soil Water ◽

Water Table ◽

Water Retention ◽

South Florida ◽

Soil Water Retention ◽

Capillary Fringe ◽

Shallow Water Table ◽

Loam Soil

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The Soil System

Soil Water Dynamics ◽

10.1093/oso/9780195126051.003.0006 ◽

2003 ◽

Author(s):

Arthur W. Warrick

Keyword(s):

Water Table ◽

Vadose Zone ◽

Soil Profile ◽

Atmospheric Pressure ◽

Root Zone ◽

Pore Space ◽

Critical Role ◽

Chemical Properties ◽

Parent Material ◽

Capillary Fringe

Soil exists at the boundary between the atmosphere and the Earth’s subsurface. It plays a critical role in the hydrologic cycle, in addition to serving as the location of most human activity. An examination below the Earth’s surface generally reveals a profile similar to that shown in figure 1-1 A. The first zone encountered is the soil zone. This soil has developed from parent material through biological and other factors of weathering. If time is sufficient, then horizons will have formed with differing physical and chemical properties. At greater depths the soil merges with additional unconsolidated material. Eventually, at still greater depths, bedrock is encountered. The dimensions of these various zones are highly variable. For example, the soil profile may exist on bedrock that is partially exposed at the soil surface. Conversely, the unconsolidated layer can be hundreds of meters thick, as is the case in many alluvial basins. The subsurface can also be described in terms of water regimes that exist.The hydrologic profile consists of the vadose zone and the phreatic zone. The vadose zone is from the ground surface to the permanent water table, and includes the root zone, the soil profile, and the capillary fringe, which is a tension-saturated zone bordering the water table. The water at the water table is at atmospheric pressure; above the water table the pressure is less than atmospheric pressure and below the water table it is greater. The system is unsaturated above the capillary fringe, meaning that not only is the water under tension, but that some of the pore space is filled with air. The extent of the capillary fringe is dependent on the porous material. Generally, itextends a few centimeters for coarse material, or perhaps a meter for fine materials. A more complete depiction would include further saturated regions in the vadose zone, such as those due to surface infiltration or due to impeding layers that result in a perched water. Historically, the term groundwater was used to denote water beneath the permanent water table, but it is now commonly used to describe all subsurface water.

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The relationship of water-table changes to the capillary fringe, evapotranspiration, and precipitation in intermittent wetlands

Wetlands ◽

10.1007/bf03160590 ◽

1992 ◽

Vol 12 (2) ◽

pp. 91-98 ◽

Cited By ~ 66

Author(s):

Philip J. Gerla

Keyword(s):

Water Table ◽

Capillary Fringe ◽

Intermittent Wetlands ◽

Relationship Of ◽

The Relationship

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Spatial distribution of lepidocrocite in a soil hydrosequence

Clay Minerals ◽

10.1180/0009855023740070 ◽

2002 ◽

Vol 37 (4) ◽

pp. 687-697 ◽

Cited By ~ 4

Author(s):

N. E. Smeck ◽

J . M. Bigham ◽

W. F. Guertal ◽

G. F. Hall

Keyword(s):

Spatial Distribution ◽

Water Table ◽

Base Saturation ◽

Capillary Fringe ◽

Perched Water ◽

Soil Temperatures ◽

Regional Water ◽

Observation Period

AbstractThree terrace soils comprising a hydrosequence were examined to determine how the spatial distribution of lepidocrocite was related to depth and duration of saturation. Vertical relief was 1.0 m with well drained, moderately well drained, and somewhat poorly drained pedons spaced ∼60 m apart. All soils contained brittle, slowly-permeable subsoil horizons and were acidic with <35% base saturation throughout the upper sola. The well drained soil (Fragic Hapludult) had no morphological indicators of wetness within a depth of 180 cm, and water was perched above a brittle horizon at 82 cm for a total of only 41 days during the 3.4 year observation period. Nevertheless, trace amounts of lepidocrocite were detected in the subsoil. The moderately well drained soil (Typic Fragiudult) was saturated at a depth of 180 cm for 6% of the time, and water was perched on top of a fragipan at 74 cm for 13% of the time. Lepidocrocite was most abundant in this pedon and reached maximum concentrations below the fragipan in the capillary fringe of the regional water table (150–183 cm). The somewhat poorly drained member of the hydrosequence (Aeric Fragiaquult) was saturated at a depth of 180 cm for 96% of the observation period and also contained perched water above a fragipan for >90% of the time. Lepidocrocite occurred throughout this pedon but was most concentrated in fragipan horizons (86–135 cm) between the perched and regional zones of saturation. These horizons were saturated from 22 to 48% of the observation period. The results of this study suggest that lepidocrocite formation was favoured in horizons that were saturated for 5–50% of the time when soil temperatures exceeded 5°C.

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