Event Title

Towards Using Time-Lapse Electrical Resistivity Imaging for Improved Subsurface Snowmelt Characterization

Presenter Information

Robert Heinse

Location

ECC 303/305

Event Website

https://water.usu.edu/

Start Date

3-31-2008 11:45 AM

End Date

3-31-2008 12:00 PM

Description

In the intermountain west, snowmelt accounts for the majority of the annually available water. Understanding the fate of snow packs in the melting phase and particularly the infiltration of snowmelt is therefore central for maximizing the harvestable water and for maintaining the quality of snowmelt. Some of the open questions at the field-scale regard the localized infiltration of water and the nature and patterns of subsurface flow in the soil overlying bedrock. Electrical resistivity imaging (ERI) is known to be able to noninvasively image processes if state variables (i.e. water content) associated with the processes give rise to contrasts in the electrical conductivity. In the Vadose zone, the interpretation of such images is hampered by the equivalency of different model solutions. However, in time-lapse measurements, changes in electrical resistivity can be more directly related to changes in water content. In this way, flow processes in the subsurface can be characterized with high spatial and temporal resolution. The presented study was conducted within the well characterized and instrumented TWDEF experimental watershed in the Cache National Forest close to Logan, UT. To monitor the spatio-temporal evolution of snow melt, we installed 72 Electrodes with 5 m spacings on a sloping profile in the previous autumn. Automated measurements at this remote site were collected daily at 5 p.m. over several weeks using a Wenner/Schlumberger acquisition array. Measured data were inverted to produce apparent resistivity images of the subsurface. Subsequent temperature correction and differential comparison of temporal changes in subsurface resistivity were accompanied by soil surveys and depthto-bedrock soundings that guided in the interpretation and calibration of the measurements. Results suggest localized infiltration of snowmelt and subsurface flow bounded by non-conductive layers. Such behavior is consistent with visual observations of localized snowpack decreases and surface runoff patterns.

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Mar 31st, 11:45 AM Mar 31st, 12:00 PM

Towards Using Time-Lapse Electrical Resistivity Imaging for Improved Subsurface Snowmelt Characterization

ECC 303/305

In the intermountain west, snowmelt accounts for the majority of the annually available water. Understanding the fate of snow packs in the melting phase and particularly the infiltration of snowmelt is therefore central for maximizing the harvestable water and for maintaining the quality of snowmelt. Some of the open questions at the field-scale regard the localized infiltration of water and the nature and patterns of subsurface flow in the soil overlying bedrock. Electrical resistivity imaging (ERI) is known to be able to noninvasively image processes if state variables (i.e. water content) associated with the processes give rise to contrasts in the electrical conductivity. In the Vadose zone, the interpretation of such images is hampered by the equivalency of different model solutions. However, in time-lapse measurements, changes in electrical resistivity can be more directly related to changes in water content. In this way, flow processes in the subsurface can be characterized with high spatial and temporal resolution. The presented study was conducted within the well characterized and instrumented TWDEF experimental watershed in the Cache National Forest close to Logan, UT. To monitor the spatio-temporal evolution of snow melt, we installed 72 Electrodes with 5 m spacings on a sloping profile in the previous autumn. Automated measurements at this remote site were collected daily at 5 p.m. over several weeks using a Wenner/Schlumberger acquisition array. Measured data were inverted to produce apparent resistivity images of the subsurface. Subsequent temperature correction and differential comparison of temporal changes in subsurface resistivity were accompanied by soil surveys and depthto-bedrock soundings that guided in the interpretation and calibration of the measurements. Results suggest localized infiltration of snowmelt and subsurface flow bounded by non-conductive layers. Such behavior is consistent with visual observations of localized snowpack decreases and surface runoff patterns.

https://digitalcommons.usu.edu/runoff/2008/AllAbstracts/10