HighlightsSingle macropores can be detected using temporal electrical resistivity imaging under controlled conditions.Macropore flow can be detected based on preferentially wetted fingers of increased conductance.Macropore activation does not appear to require saturated surface conditions to induce preferential flow.Abstract. Riparian soils are uniquely susceptible to the formation of macropores, which are hypothesized to promote fast transport of water and contaminants through upper soil layers. Electrical Resistivity Imaging (ERI) can locate spatial heterogeneities in soil wetting patterns and evaluate differences due to vegetation, thus optimizing the design of riparian buffers. Temporal ERI (TERI) imaging was conducted in a fine and coarse field setting with artificial macropores to evaluate flow under unsaturated simulated rainfall conditions and saturated infiltrometer conditions. While single macropores are detectable using TERI datasets, the results in an average field setting would detect the wetted area surrounding a macropore, not the macropore itself. The results were similar for both the primary fine grain soil site in Oklahoma as well as the coarse grain site in North Carolina. TERI data indicated that without artificial conditions with low noise conditions, a single macropore would not be detected, a wetted zone would be the best detection. In ordinary field evaluation of natural macropores, the TERI technique would detect the wetted zone around a macropore similar to a high hydraulic conductivity zone in a heterogeneous soil matrix. Finally, the results confirmed that macropore activation does not require saturated conditions to generate preferential flow. Keywords: Hydrogeophysics, Preferential flowpaths, Riparian buffers, Temporal electrical resistivity imaging.

Riparian soils are susceptible to the formation of macropores, which provide opportunities for preferential flow in comparison to the surrounding soil matrix. Temporal electrical resistivity imaging (TERI) can locate spatial heterogeneities in soil wetting patterns caused by preferential flow through macropores. Quantifying macropore flow properties is important to optimize the design of riparian buffers. In a field evaluation of a riparian area with naturally occurring macropores, the TERI technique is able to detect the wetted zone around a macropore similar to a high hydraulic conductivity zone in a heterogeneous soil matrix. An experiment was established in a coarse soil in North Carolina to evaluate if TERI datasets could quantify the hydraulic properties of both the soil matrix and the preferential macropore pathways. Results show TERI is a viable method for calculating the vertical fluid velocity along orthogonal profiles in this coarse-grained field site. The datasets allowed the distribution and hydraulic properties of the preferential flow pathways to be quantified over a two-dimensional plane that is comparable with traditional soil datasets.

Riparian soils are susceptible to the formation of macropores, which provide opportunities for preferential flow in comparison to the surrounding soil matrix. Temporal Electrical Resistivity Imaging (TERI) can locate spatial heterogeneities in soil wetting patterns caused by preferential flow through macropores. Quantifying macropore flow properties is important to optimize the design of riparian buffers. In a field evaluation of a riparian area with naturally occurring macropores, the TERI technique is able to detect the wetted zone around a macropore similar to a high hydraulic conductivity zone in a heterogeneous soil matrix. An experiment was established in a coarse soil in North Carolina to evaluate if TERI datasets could quantify the hydraulic properties of both the soil matrix and the preferential macropore pathways. Results show TERI is a viable method for calculating the vertical fluid velocity along orthogonal profiles in this coarse-grained field site. The datasets allowed the distribution and hydraulic properties of the preferential flow pathways to be quantified over a two-dimensional plane that is comparable with traditional soil datasets.

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