Date of Award

8-2019

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Engineering and Earth Sciences

Committee Member

Brian Powell, Committee Chair

Committee Member

Stephen Moysey

Committee Member

Christophe Darnault

Abstract

Preferential flow is a common occurrence during infiltration yet is often not accounted for in predictive flow models. This has implications for contaminant transport in that the extent of constituent plumes are often underestimated, thereby reducing the effectiveness of any remediation efforts. Electrical resistivity monitoring could be a useful tool to determine if infiltration is bypassing parts of the subsurface through preferential flow pathways and to better inform predictive models. The viability of this method was evaluated through simple electrical simulations and with multiple column experiments across scales using advanced observation techniques like 4D computed tomography. Electrical resistivity was used to monitor the progression of uniform wetting fronts as well as preferential flow and infiltration through macropore networks. Results indicate that certain characteristics in the response of apparent resistivity to preferential flow are distinct from uniform flow. Vertical bulk resistivity reduces rapidly as wetting in a macropore network increases the connectivity between electrodes. Strong positive spikes in electrical anisotropy are observed during preferential flow events and the arrival of a wetting front observed through resistivity monitoring occurs much earlier than predicted using bulk soil properties. These characteristics indicate that electrical resistivity monitoring is a viable method for the application of detecting preferential flow during infiltration in a heterogeneous system.

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