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

Schillig, P. C.; Devlin, J.F.; McElwee, Carl D.; Walter, Katja; Gibson, Brian C.

doi:10.1111/gwmr.12075

Cited by 12 publications

(7 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The disagreement could stem from several causes including: (1) the number of PVP measurements averaged was insufficient; (2) the PVPs were placed strategically to sample the aquifer and the high velocity zone, resulting in a positive bias to the average of the measured velocities; (3) two multilevel PVPs were limited to measuring horizontal velocities. In some tests, PVPs 1 and 2 returned anomalous signals that were hypothesized to be caused by a dominant vertical component to flow and this unmeasured component could have contributed to inaccuracies (Schillig et al ); and (4) the values of K , and to a lesser extent i , used in the Darcy calculations were biased or otherwise unrepresentative of the true site character.…”

Section: Resultsmentioning

confidence: 99%

Upscaling Point Velocity Measurements to Characterize a Glacial Outwash Aquifer

Schillig

Devlin²,

Rudolph

2015

Groundwater

Self Cite

View full text Add to dashboard Cite

Small-scale point velocity probe (PVP)-derived velocities were compared to conventional large-scale velocity estimates from Darcy calculations and tracer tests, and the possibility of upscaling PVP data to match the other velocity estimates was evaluated. Hydraulic conductivity was estimated from grain-size data derived from cores, and single-well response testing or slug tests of onsite wells. Horizontal hydraulic gradients were calculated using 3-point estimators from all of the wells within an extensive monitoring network, as well as by representing the water table as a single best fit plane through the entire network. Velocities determined from PVP testing were generally consistent in magnitude with those from depth specific data collected from multilevel monitoring locations in the tracer test, and similar in horizontal flow direction to the average hydraulic gradient. However, scaling up velocity estimates based on PVP measurements for comparison with site-wide Darcy-based velocities revealed issues that challenge the use of Darcy calculations as a generally applicable standard for comparison. The Darcy calculations were shown to underestimate the groundwater velocities determined both by the PVPs and large-scale tracer testing, in a depth-specific sense and as a site-wide average. Some of this discrepancy is attributable to the selective placement of the PVPs in the aquifer. Nevertheless, this result has important implications for the design of in situ treatment systems. It is concluded that Darcy estimations of velocity should be supplemented with independent assessments for these kinds of applications.

show abstract

Section: Resultsmentioning

confidence: 99%

Upscaling Point Velocity Measurements to Characterize a Glacial Outwash Aquifer

Schillig

Devlin²,

Rudolph

2015

Groundwater

Self Cite

View full text Add to dashboard Cite

show abstract

“…Other singlewell techniques to estimate velocity include point dilution (Drost et al 1968), passive flux meter (Annable et al 2005), colloidal borescope (Kearl et al 1992), and the laser Doppler velocimeter (Momii et al 1993). Groundwater velocity can also be estimated without the use of wells through probing techniques such as the in situ permeable flow sensor (ISPFS) (Ballard 1996) and the point velocity probe (PVP) (Devlin et al 2009(Devlin et al , 2012Schillig et al 2014). The ISPFS allows thermal measurements to be made from direct contact with the soil, and the PVP makes cm-scale velocity measurements based on electrical conductivity of a tracer transported by groundwater.…”

Section: Introductionmentioning

confidence: 99%

Estimation of Interstitial Velocity Using a Direct Drive High‐Resolution Passive Profiler

Schneider

Jackson²,

Rainwater

et al. 2019

Groundwater

View full text Add to dashboard Cite

The fate and transport of groundwater contaminants depends partially on groundwater velocity, which can vary appreciably in highly stratified aquifers. A high‐resolution passive profiler (HRPP) was developed to evaluate groundwater velocity, contaminant concentrations, and microbial community structure at ∼20 cm vertical depth resolution in shallow heterogeneous aquifers. The objective of this study was to use mass transfer of bromide (Br−), a conservative tracer released from cells in the HRPP, to estimate interstitial velocity. Laboratory experiments were conducted to empirically relate velocity and the mass transfer coefficient of Br− based on the relative loss of Br− from HRPP cells. Laboratory‐scale HRPPs were deployed in flow boxes containing saturated soils with differing porosities, and the mass transfer coefficient of Br− was measured at multiple interstitial velocities (0 to 100 cm/day). A two‐dimensional (2D) quasi‐steady‐state model was used to relate velocity to mass transfer of Br− for a range of soil porosities (0.2–0.5). The laboratory data indicate that the mass transfer coefficient of Br−, which was directly—but non‐linearly—related to velocity, can be determined with a single 3‐week deployment of the HRPP. The mass transfer coefficient was relatively unaffected by sampler orientation, length of deployment time, or porosity. The model closely simulated the experimental results. The data suggest that the HRPP will be applicable for estimating groundwater velocity ranging from 1 to 100 cm/day in the field at a minimum depth resolution of 10 cm, depending on sampler design.

show abstract

“…In each of the six measurement locations, the SBPVP was installed 5 to 10 cm below the streambed with a hyporheic shield in place to prevent any influence from horizontal flow on the upward velocity measurements (Cremeans and Devlin ; Cremeans et al ). Tests were conducted with tracer injection volumes ranging from 0.1 mL to 0.4 mL and with tracer concentrations ranging from 1 to 2 g/L NaCl, which have been shown to exert no discernable density effects on flow in PVP tests in sandy media (Schillig et al ). The tests required between ~30 and ~180 min to complete.…”

Section: Methodsmentioning

confidence: 99%

A Comparison of Tools and Methods for Estimating Groundwater‐Surface Water Exchange

Cremeans¹,

Devlin²,

Osorno³

et al. 2020

Groundwater Monitoring Rem

Self Cite

View full text Add to dashboard Cite

A comparison of tools for measuring discharge rates in a sandy streambed was conducted along a transect near the north bank of the Grindsted Å (stream), Denmark. Four tools were evaluated at six locations spaced 3 m apart in the stream: mini‐piezometers, streambed point velocity probes (SBPVPs), temperature profilers, and seepage meters. Comparison of the methods showed that all identified a similar trend of low to high groundwater discharges moving westward along the transect. Furthermore, it was found that the differences between discharges estimated from Darcy calculations (using the mini‐pizometers), and SBPVPs were not statistically different from zero, at the 90% confidence level. Seepage meter estimates were consistently lower than those of the other two methods, but compared more reasonably with the application of a correction factor of 1.7, taken from the literature. In contrast, discharges estimated from temperature profiling (to a depth of 40 cm) were found to be about an order of magnitude less than those determined with the other methods, possibly due to interferences from horizontal hyporheic flow. Where the various methods produced statistically different discharge estimations at the same location, it is hypothesized that the differences arose from method‐specific sources of bias, including installation depths. On the basis of this work, practitioners interested in measuring flow across the groundwater‐surface water interface achieve the least variability with seepage meters and the SBPVP. However the accuracy of the seepage meter depended on a calibrated correction factor while that of the SBPVP did not.

show abstract

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

Cited by 12 publications

References 19 publications

Upscaling Point Velocity Measurements to Characterize a Glacial Outwash Aquifer

Upscaling Point Velocity Measurements to Characterize a Glacial Outwash Aquifer

Estimation of Interstitial Velocity Using a Direct Drive High‐Resolution Passive Profiler

A Comparison of Tools and Methods for Estimating Groundwater‐Surface Water Exchange

Contact Info

Product

Resources

About