Probe for measuring groundwater velocity at the centimeter scale

Area of Science:

• Hydrogeology
• Environmental Science
• Geotechnical Engineering

Background:

• Accurate measurement of small-scale groundwater velocities is crucial for understanding contaminant transport and subsurface flow dynamics.
• Existing methods often lack the precision or resolution required for detailed analysis in unconsolidated porous media.

Purpose of the Study:

• To introduce and validate a novel point-velocity probe (PVP) for measuring groundwater velocities at a small scale.
• To assess the accuracy and limitations of the PVP in unconsolidated noncohesive media.

Main Methods:

• Utilized a point-velocity probe (PVP) employing tracer pulse travel time between an injection port and two surface detectors.
• Conducted ten laboratory tank tests with the PVP in unconsolidated noncohesive media.
• Performed numerical simulations to support data interpretation and assess fine-scale velocity measurement capabilities.

Main Results:

• The PVP determined groundwater velocity direction and magnitude with an average accuracy of +/- 8 degrees and +/- 9%, respectively.
• Effective velocity measurements were achieved for flow rates between 5 and 98 cm/day.
• Numerical simulations confirmed the probe's accuracy and its capability for fine-scale (0.5 cm) velocity mapping.

Conclusions:

• The point-velocity probe (PVP) offers a reliable method for measuring small-scale groundwater velocities in laboratory settings.
• The technology demonstrates potential for high-resolution subsurface flow characterization.
• Further research is needed to address the probe's sensitivity to near-surface porous medium conditions for successful field deployment.