USGS Groundwater Information: Branch of Geophysics
L. Slater1 (firstname.lastname@example.org), F.D. Day-Lewis2 (email@example.com), D. Ntarlagiannis1 (firstname.lastname@example.org), K. Mwakanyamale1 (email@example.com), R. Versteeg3 (firstname.lastname@example.org), A. Ward4 (email@example.com), C. Strickland4 (firstname.lastname@example.org), C.D. Johnson2 (email@example.com), J.W. Lane, Jr.2 (firstname.lastname@example.org), and A. Binley5 (email@example.com)
1 Rutgers-Newark, Newark, NJ, United States
2 USGS, Office of Groundwater, Branch of Geophysics, Storrs, CT, United States
3 Idaho National Laboratory, Idaho Falls, ID
4 Pacific Northwest National Laboratory, Richland, WA, United States
5 Lancaster University, Lancaster, United Kingdom
A critical challenge in advancing prediction of solute transport between contaminated aquifers and rivers is improving understanding of how fluctuations in river stage, combined with subsurface heterogeneity, impart spatiotemporal complexity in solute exchange along river corridors. Here, we investigated the use of waterborne geoelectrical imaging, in conjunction with fiber-optic distributed temperature sensor (DTS) monitoring, to improve the conceptual model for uranium transport within the Columbia River hyporheic corridor at the Hanford 300 Area. We first inverted waterborne geoelectrical (resistivity and induced polarization) datasets to estimate distributions of electrical resistivity and polarizability, from which the spatial complexity of the primary hydrogeologic units was reconstructed. Variations in depth to the interface between the overlying coarse-grained, high permeability Hanford Formation and the underlying finer-grained, less permeable Ringold Formation, an important contact that limits vertical migration of contaminants, were resolved along ~3 km of the river corridor centered on the 300 Area. Polarizability images were translated into lithologic images using established relationships between polarizability and surface area normalized to pore volume (Spor). The spatial variability captured in the geoelectrical datasets suggests that previous studies based on borehole projections and point probing overestimate the contributing area for uranium exchange within the Columbia River at the Hanford 300 Area. The DTS data, recorded on 1.5 km of cable with 1-m spatial resolution and 5-min sampling interval, revealed locations showing (1) high temperature anomalies and (2) strong correlation between temperature and river stage, both indicative of groundwater influxes during winter months. The DTS datasets confirm the hydrologic significance of the variability identified in the geoelectrical imaging and reveal a pattern of focused hyporheic exchange concentrated where the Hanford Formation is thickest, coinciding with a paleochannel identified in ground penetrating radar surveys at one location. No evidence for focused hyporheic exchange is observed in the DTS data where the Ringold Formation is in contact with the riverbed. Our findings illustrate how the combination of waterborne geoelectrical imaging and DTS technologies can be used to characterize hyporheic exchange in a complex, coupled river-aquifer system.
Final copy as submitted to American Geophysical Union (AGU) for publication as: Slater, L., Day-Lewis, F.D., Ntarlagiannis, D., Mwakanyamale, K., Versteeg, R., Ward, A., Strickland, C., Johnson, C.D., and Lane, J.W., Jr., 2009, Hydraulic characterization of the hyporheic corridor at the Hanford 300 Area using geoelectrical imaging and distributed temperature sensing (DTS) methods [abs.]: EOS Transactions, American Geophysical Union, v. 90, no. 52, Fall Meeting Supplement, abstract H53J-05 (invited).