Probe for Measuring Groundwater Velocity at the Centimeter Scale

Abstract

A novel method of measuring small-scale groundwater velocities in unconsolidated noncohesive media uses the travel time of a tracer pulse between an injection port and two detectors located on the surface of a cylindrical probe, called a point-velocity probe (PVP), as the basis for velocity estimation. The direction and magnitude of the water velocity vector were determined to within +/- 9% of magnitude and +/- 8 in direction, on average, in ten laboratory tank tests conducted with the PVP, when the velocities were between 5 and 98 cm/ day. Numerical simulations supported the accuracy of the underlying theory for interpretation of the PVP data and indicated that the technology is capable of measuring velocity at a very fine scale (0.5 cm around the circumference). The benchtop and modeling investigations indicated that the probe is moderately sensitive to the condition of the porous medium immediately next to the cylinder surface, suggesting that challenges exist for the deployment of the instrument in the field.

Velocity measurement of water flow within gravel layer with electrolyte tracer method under virtual boundary condition

“…Due to the lack of effective and widely-acceptable methods for the precise determination of shallow water flow, the errors in measured velocities cannot be directly estimated (Labaky et al, 2007;Lei et al, 2010). An analysis of the relations between estimated velocities and measurement distances, slope gradients and flow rate was required to provide proof of relevance to a physical system (Fig.…”

Estimation of water velocities in boreholes using a new passive flowmeter

“…Recently, Devlin et al (2009) undertook the development of a specific apparatus using polyvinyl chloride (PVC) capable of deriving the seepage groundwater velocity for a wide range of measurements and at centimetre depth intervals. This interesting point-velocity method, which is based on water-specific conductance measurements, was derived from a previous prototype of stainless steel proposed by Labaky et al (2007). Note that this probe cannot be used in a well, i.e.…”

Field GPR monitoring of biostimulation in saturated porous media

“…Since the growth of a biomass may reduce the hydraulic conductivity and effective porosity in a geologic material, biomass growth can be inferred by direct measurements of groundwater velocity over time. Centimeter-scale groundwater velocity measurements can be obtained with PVPs (Labaky et al, 2007(Labaky et al, , 2009. In this investigation, we utilized PVPs in a multilevel 2D array (or fence) to monitor groundwater velocity changes over the duration of the experiment.…”