Applications and implications of direct groundwater velocity measurement at the centimetre scale

• Published in: Journal of contaminant hydrology 2012, Vol.127 (1), p.3-14
• Main Authors: Devlin, J.F., Schillig, P.C., Bowen, I., Critchley, C.E., Rudolph, D.L., Thomson, N.R., Tsoflias, G.P., Roberts, J.A.
• Format: Article
• Language: English
• Subjects: Aquifers; Biodegradation, Environmental; Bioremediation; Denitrification; Dipole well; Earth sciences; Earth, ocean, space; Exact sciences and technology; Groundwater; Groundwater - microbiology; Groundwater velocity measurement; Heterogeneity; Homogeneity; Hydrogeology; Hydrology; Hydrology. Hydrogeology; Models, Theoretical; Ontario; Point velocity probe; PVP; Tracers; Transient heterogeneity; Velocity measurement; Water Movements; Water Purification - methods
• ISSN: 0169-7722; 1873-6009
• DOI: 10.1016/j.jconhyd.2011.06.007

Three projects involving point velocity probes (PVPs) illustrate the advantages of direct groundwater velocity measurements. In the first, a glacial till and outwash aquifer was characterized using conventional methods and multilevel PVPs for designing a bioremediation program. The PVPs revealed a highly conductive zone that dominated the transport of injected substances. These findings were later confirmed with a natural gradient tracer test. In the second, PVPs were used to map a groundwater velocity field around a dipole recirculation well. The PVPs showed higher than expected velocities near the well, assuming homogeneity in the aquifer, leading to improved representations of the aquifer heterogeneity in a 3D flow model, and an improved match between the modelled and experimental tracer breakthrough curves. In the third study, PVPs detected subtle changes in aquifer permeability downgradient of a biostimulation experiment. The changes were apparently reversible once the oxygen source was depleted, but in locations where the oxygen source lingered, velocities remained low. PVPs can be a useful addition to the hydrogeologist's toolbox, because they can be constructed inexpensively, they provide data in support of models, and they can provide information on flow in unprecedented detail. ► There is a need for methods of collecting groundwater velocity data through direct measurements. ► Three PVP studies show that horizontal and vertical velocities can be measured with PVPs, subtle changes in detected. ► PVP velocities were validated by comparisons with independent field data and modelled results.