Studies of Water Velocity in the Capillary Fringe: The Point Velocity Probe

Berg, Steven J.; Gillham, Robert W.

doi:10.1111/j.1745-6584.2009.00606.x

Cited by 18 publications

(12 citation statements)

References 12 publications

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“…The results presented here are consistent with the findings of Berg and Gillham (2010), who measured the horizontal water velocity using a point velocity probe in a laboratory experiment. They showed that the water velocity profile was continuous from below the water table up to 0.44 m above the water table, corresponding to the air‐entry pressure of the sand used.…”

Section: Resultssupporting

confidence: 92%

Observing Solute Transport in the Capillary Fringe Using Image Analysis and Electrical Resistivity Tomography in Laboratory Experiments

Persson

Dahlin

Günther

2015

Vadose Zone Journal

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Five laboratory experiments were conducted to study solute transport in the capillary fringe in a sand‐filled glass tank containing an artificial groundwater zone, an unsaturated zone, and a capillary fringe in between. Dye‐stained water, applied at the soil surface, moved downward through the unsaturated zone and then horizontally in the capillary fringe. The horizontal velocity of the dye plume front was calculated using optical image analysis and electrical resistivity tomography (ERT) measurements. Both methods gave similar velocities if an appropriate value of the threshold ratio describing the dye front was used. The hydraulic model HYDRUS‐2D was used to simulate dye movement in the glass tank. After calibrating the dispersivity value in the hydraulic model, the horizontal velocity was found to be in the range −10 to 17% compared with the values measured using image analysis and −12 to 24% compared with the values measured by ERT; the differences could probably be attributed to uncertainties in the hydraulic parameters and soil heterogeneities. Both experimental and numerical results showed that the horizontal velocity of the capillary fringe is more or less identical to the one in the saturated zone. Thus, from a water transport perspective, the results suggest that the capillary fringe should be treated as a part of the saturated zone in hydrologic modeling.

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Section: Resultssupporting

confidence: 92%

Observing Solute Transport in the Capillary Fringe Using Image Analysis and Electrical Resistivity Tomography in Laboratory Experiments

Persson

Dahlin

Günther

2015

Vadose Zone Journal

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“…Several PVP designs, varying in size and construction materials, have been described in the literature for both laboratory and field studies. These have included probes with stainless steel bodies and accessory parts (Labaky et al ; Berg and Gillham ), polyvinyl chloride bodies with plastic accessory parts and a gas diffuser stone injection port (Devlin et al ; Devlin et al ). In each case, the cost of probe construction tended to be dominated by personnel time rather than material costs (Devlin et al ).…”

Section: Introductionmentioning

confidence: 99%

Application of 3D Printing to the Manufacturing of Groundwater Velocity Probes

Walter¹,

Devlin²

2017

Groundwater Monitoring Rem

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For the purposes of risk mitigation and remediation design, Darcy's Law calculations, that are typically used to estimate flow direction and magnitude, can be usefully supplemented with more direct measurements. The point velocity probe (PVP), which measures groundwater velocity by conducting a mini‐tracer test across a cylindrical probe surface, was developed to address this need. Laboratory and field experiments have shown that these probes can provide accurate velocity magnitude and direction measurements at the centimeter scale. In an effort to streamline the production of PVPs, three‐dimensional (3D) printing was investigated. The 3D printer produces a plastic probe body with designated detector and injection port locations. The subsequent installation of injection lines and detector wires requires, for a single‐port probe, no longer than 1–2 h of assembly time, compared to approximately 10 h to assemble previous designs (mainly determined by injection port installation). Probes can be printed in batches with the number of units made depending on the printer and probe size. Laboratory tests of the original PVP models yielded velocity magnitudes and directions with average errors (from expected values) of ±9% to ±15% and ±8°, respectively. A printed PVP was tested in a nested storage tank system (NeST) packed with sand that mimics flow conditions through a sandy aquifer. The probe was tested at multiple pumping rates with the injector port at angles of (α =) 30°, 45°, and 75° from the expected linear flow direction. The printed PVPs provided an average magnitude percent error of ±13.5% and an average direction error of ±4°. This shows that in laboratory tests, printed PVPs performed as well as the original probes previously reported, making them viable units for field applications as well as being quicker to assemble than the earlier designs.

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“…Recently, point velocity probes (PVPs) have been used to characterize groundwater velocities in aquifers composed of sand or sand and gravel (Labaky et al , ; Berg and Gillham ; Schillig et al ; Devlin et al 2012). The PVP operates by injecting a small volume of tracer—usually saline—on the surface of a cylindrical probe.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Density‐Induced Tracer Movement in Groundwater Velocity Measurements with Point Velocity Probes (PVPs)

Schillig¹,

Devlin²,

McElwee³

et al. 2014

Groundwater Monitoring Rem

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The concept of equivalent freshwater head was adapted to predict the conditions under which density‐driven flow would adversely impact measured groundwater velocities using point velocity probes (PVPs). Theoretically, vertical flow will result from any density contrast between the PVP tracer and the groundwater. However, laboratory testing of tracers with salinities ranging from 0 to 2000 mg NaCl/L showed that horizontal velocities could be determined with good accuracy with up to 60% of the total flow being vertical due to density effects in a gravel medium. The available data suggest that density effects are less likely to be pronounced in sandy sediments. The relative amount of vertical flow due to tracer density can be estimated from vertical and horizontal velocities measured with PVPs, or from the ratio of vertical to horizontal hydraulic gradients. The equivalent freshwater gradient produced from a given tracer salinity at 10 °C (a typical groundwater temperature at moderate latitudes) can be estimated from 7.80 × 10−7 × (MNaCl), where MNaCl is the mass of NaCl added, in mg, to 1 L of site groundwater in the mixing of the tracer. Equations for other temperatures were also determined.

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Studies of Water Velocity in the Capillary Fringe: The Point Velocity Probe

Cited by 18 publications

References 12 publications

Observing Solute Transport in the Capillary Fringe Using Image Analysis and Electrical Resistivity Tomography in Laboratory Experiments

Observing Solute Transport in the Capillary Fringe Using Image Analysis and Electrical Resistivity Tomography in Laboratory Experiments

Application of 3D Printing to the Manufacturing of Groundwater Velocity Probes

Assessment of Density‐Induced Tracer Movement in Groundwater Velocity Measurements with Point Velocity Probes (PVPs)

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