f COMPARISON OF TIME-LAPSE RESISTIVITY AND WELL DATA IN THE HYPORHEIC ZONE BENEATH STREAMS

Characterization of the hyporheic zone beneath streams, where surface water and groundwater mix, is critical for understanding stream ecology and contaminant fate and transport. Tracer tests can identify storage zones, but cannot distinguish between tracer lingering in pools and subsurface storage. Wells monitor the subsurface, but prohibitively many may be required to avoid spatially undersampling the plume, and with mixed porosity sediment wells preferentially sample the more hydraulically conductive sediments. Additional information can be obtained by monitoring saline tracer using time-lapse resistivity – continuous spatial coverage and sensitivity to the tracer distribution irrespective of the hydraulic conductivity – at the expense of a more ambiguous interpretation.