Investigating Subsurface Flow Delivery to a Small High Arctic River

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Gillman, Matthew
Subsurface Flow , Permafrost , Hydrology , Preferential Flow Pathways
Preferential flow pathways and hydraulic gradients along the hillslope-floodplain-channel continuum are dominant controls on the delivery of baseflow, stormflow and solutes to channels in temperate systems. Arctic systems are increasingly being shown to possess similar delivery mechanisms, however the topic is understudied, acutely so in the High Arctic. This work assesses the nature of delivery mechanisms in the High Arctic over the thaw season and in response to rainfall at the Cape Bounty Arctic Watershed Observatory (CBAWO). Two locations of persistent preferential subsurface inputs were observed over a 200 m section the study reach, one at the outlet of a previously active channel through the floodplain, and another at the outlet of a channelized sub-catchment. During baseflow, these inputs provided solute-rich, relatively cold water to streamflow. During stormflow, subsurface inputs remain active and in the case of the sub-catchment, there was evidence for increased flux of pre-event soil water. Over the 320 m study reach, heterogeneity in the nature of hydraulic gradients, in how gradients developed over the season, and in how gradients responded to rainfall was observed. Two monitored hydraulic gradients exhibited reversal of inferred flow direction; one due to rainfall and the other as the thaw season progressed. Economic feasibility of hydrological investigations concerning total dissolved solids and electrical conductivity (EC) becomes an issue when spatial and temporal scales increase, especially when the objective is to capture the variability inherent within aquatic systems. Chapin et al. (2014) presented a modified version of the Onset HOBO Pendant waterproof temperature and light logger with the ability to assess relative EC, however it was not dimensional EC (i.e. µS/cm). This work demonstrates these economical loggers can be calibrated and applied to quantify EC in the field with accuracies comparable to commercial loggers.
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