HR: 0800h
AN: H41F-0478    [Abstracts]
TI: Characterizing High-Resolution Aquifer Heterogeneities Using Borehole Radar and Multi-Level Point Velocity Probes
AU: * McGlashan, M A
EM: mam10@ku.edu
AF: The University of Kansas, Lindley Hall, rm 120 1475 Jayhawk Blvd., Lawrence, KS 66945 United States
AU: Tsoflias, G P
EM: tsoflias@ku.edu
AF: The University of Kansas, Lindley Hall, rm 120 1475 Jayhawk Blvd., Lawrence, KS 66945 United States
AU: Devlin, J F
EM: jfdevlin@ku.edu
AF: The University of Kansas, Lindley Hall, rm 120 1475 Jayhawk Blvd., Lawrence, KS 66945 United States
AU: Schillig, P C
EM: schillig@ku.edu
AF: The University of Kansas, Lindley Hall, rm 120 1475 Jayhawk Blvd., Lawrence, KS 66945 United States
AB: Small-scale heterogeneities overlooked in relatively homogeneous aquifers may introduce significant changes in groundwater flow. The work presented here employs two independent methods for high-resolution characterization of the hydrostratigraphy of the Borden aquifer in Ontario, Canada: a) borehole radar, and b) multi-level Point Velocity Probes (PVPs). High-resolution borehole radar data were collected across a 2x4 m area of potential bacterial growth, with six wells forming a dense array of 12 tomographic well-pairs to obtain a 3-D image of aquifer heterogeneity down to 5 m depth. Dielectric constants, from radar velocities, determine aquifer volumetric water content ranging from 38% to 42%. Overall, radar velocities are higher over half of the 2x4 area surveyed, they display an increasing trend with depth, and a lower velocity zone is consistently present at approximately 3.5 m depth. The scale of the radar velocity changes is relatively small (10-3 m/ns) and therefore an independent method that can validate and complement the radar observations of aquifer heterogeneity is desirable. We employ a novel method of measuring in-situ groundwater velocity using multi-level Point Velocity Probes. Five probes were installed in the aquifer to measure flow velocity at four different depths down to 5 m and across a 4 m long transect of the aquifer. PVPs show spatial variability of groundwater velocities ranging from 6 cm/day to 14 cm/day. Regional groundwater flow velocity is 10 cm/day. PVP determined velocities follow similar trends to the radar velocities. High PVP velocities are observed spatially in areas of high EM velocities, whereas an overall low flow velocity occurs at 3.1 - 3.9 m depths. The two independent methods tested at the relatively homogeneous Borden Aquifer correlate well in identifying areas of fine scale aquifer heterogeneity. This gives us confidence in our applied methodology to distinguish high resolution hydrostratigraphy in a relatively homogeneous aquifer.
DE: 0699 General or miscellaneous
DE: 1829 Groundwater hydrology
DE: 1835 Hydrogeophysics
SC: Hydrology [H]
MN: Fall Meeting 2005