Data from Voytek et al. (2016), Identifying hydrologic flowpaths on arctic hillslopes using electrical resistivity and self potential

Shallow subsurface flow is a dominant process controlling hillslope runoff generation, soil development, and solute reaction and transport. Despite their importance, the location and geometry of these flowpaths are difficult to determine. In arctic environments, shallow subsurface flowpaths are limited to a thin zone of seasonal thaw above permafrost, which is traditionally assumed to mimic surface topography. Here we use a combined approach of electrical resistivity tomography (ERT) and self-potential measurements (SP) to map shallow subsurface flowpaths in and around water tracks, drainage features common to arctic hillslopes. ERT measurements delineate thawed zones in the subsurface that control flowpaths, while SP is sensitive to groundwater flow. We find that areas of low electrical resistivity in the water tracks are deeper than manual thaw depth estimates and vary from surface topography. This finding suggests that traditional techniques may underestimate active layer thaw and the extent of the flowpath network on arctic hillslopes. SP measurements identify complex 3-D flowpaths in the thawed zone. Our results lay the groundwork for investigations into the seasonal dynamics, hydrologic connectivity, and climate sensitivity of spatially distributed flowpath networks on arctic hillslopes.