Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/hess-2016-559
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
01 Nov 2016
Review status
A revision of this discussion paper is under review for the journal Hydrology and Earth System Sciences (HESS).
Electrical Resistivity Dynamics beneath a Fractured Sedimentary Bedrock Riverbed in Response to Temperature and Groundwater/Surface Water Exchange
Colby Steelman1, Celia S. Kennedy2, Donovan Capes2, and Beth L. Parker1,2 1School of Engineering, University of Guelph
2School of Environmental Sciences, University of Guelph
Abstract. Bedrock rivers occur where surface water flows along an exposed rock surface. Fractured sedimentary bedrock can exhibit variable groundwater residence times, anisotropic flow paths, heterogeneity, along with diffusive exchange between fractures and rock matrix. These properties of the rock will affect thermal transients in the riverbed and groundwater–surface water exchange. In this study, surface electrical methods were used as a non-invasive technique to assess the scale and temporal variability of riverbed temperature and groundwater–surface water exchange beneath a sedimentary bedrock riverbed. Conditions were monitored on a semi-daily to semi-weekly interval over a full annual period that included a seasonal freeze-thaw cycle. Surface electromagnetic induction and electrical resistivity imaging methods captured conditions beneath the riverbed along a pool-riffle sequence within the Eramosa River, Guelph, Ontario, Canada. Geophysical datasets were accompanied by continuous measurements of aqueous specific conductance, temperature and river stage. Vertical temperature profiling conducted in an inclined borehole underlying the river revealed active groundwater flow zones through fracture networks within the upper 10 m of rock. Resistivity measurements during cooler high-flow and warmer low-flow conditions identified a spatiotemporal riverbed response that was largely dependent upon riverbed morphology and groundwater temperature. Time-lapse resistivity profiles collected across the pool and riffle identified seasonal transients within the upper 2 m and 3 m of rock, respectively, with spatial variations controlled by riverbed morphology (pool verses riffle) and dominant surficial rock properties (competent verses weathered rock rubble surface). While the pool and riffle both exhibited a dynamic resistivity through seasonal cooling and warming cycles, conditions beneath the pool were more dynamic, largely due to the formation of river ice. Although seasonal resistivity trends beneath the riverbed suggest groundwater discharge may be influencing the spatiotemporal extent of a groundwater-surface water mixing zone, intraseasonal resistivity transience suggest potential groundwater–surface water exchange across the upper few meters of rock.

Citation: Steelman, C., Kennedy, C. S., Capes, D., and Parker, B. L.: Electrical Resistivity Dynamics beneath a Fractured Sedimentary Bedrock Riverbed in Response to Temperature and Groundwater/Surface Water Exchange, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-559, in review, 2016.
Colby Steelman et al.
Colby Steelman et al.
Colby Steelman et al.

Viewed

Total article views: 215 (including HTML, PDF, and XML)

HTML PDF XML Total BibTeX EndNote
176 35 4 215 1 6

Views and downloads (calculated since 01 Nov 2016)

Cumulative views and downloads (calculated since 01 Nov 2016)

Viewed (geographical distribution)

Total article views: 215 (including HTML, PDF, and XML)

Thereof 213 with geography defined and 2 with unknown origin.

Country # Views %
  • 1

Saved

Discussed

Latest update: 25 Apr 2017
Publications Copernicus
Download
Short summary
The Eramosa River flows along a fractured sedimentary bedrock aquifer with large subsurface channel features. This study examines the potential for groundwater–surface water exchange beneath the fractured bedrock riverbed and the impacts of seasonal and intraseasonal flow system transience on the geoelectrical properties of the rock. Our results will have implications to the conceptual understanding of groundwater–surface water interaction within fractured bedrock river environments.
The Eramosa River flows along a fractured sedimentary bedrock aquifer with large subsurface...
Share