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

摘要

A recently developed probe for measuring groundwater velocity at the centimetre scale in porous media, the Point Velocity Probe (PVP), was deployed in separate projects to measure transient heterogeneity in a sandy aquifer undergoing aerobic bioremediation, as an aquifer characterization tool for the design of an in situ denitrification program, and as a tool for mapping flow in unprecedented detail around a dipole well. In the first project, local flow magnitudes varied in time by up to a factor of 3, and directions varied by over 40° in association with biological activity, which was independently confirmed. In the second project, detailed velocity measurements were made in a glacial outwash aquifer with average groundwater velocities estimated to be about 2-4 m/day. A thin zone of high water flux, with velocities in excess of 10 m/day was detected. This zone was later confirmed by a tracer test and by hydraulic conductivity determinations of core material from the site. In the third project, detailed measurements of flow, in three dimensions, immediately next to a dipole well, agreed well with model predictions in most locations. If PVPs continue to prove reliable in future research, much may be learned about small scale flow phenomena, including flow in reactive treatment zones.