Characterizing groundwater flow within a discontinuous permafrost environmentOnline pre-recorded
Baseline hydrologic monitoring within Canada’s northern landscape is of value to the energy sector in advance of oil and gas development and can also elucidate gradual environmental change as a result of climate warming. However, baseline monitoring studies in these regions are complex and expensive to undertake due mainly to limited access, lack of infrastructure and presence of variable permafrost conditions. This is particularly true for the subsurface/groundwater component of the hydrologic cycle. Recent research completed within the Central Mackenzie Valley combined remote sensing techniques with portable field monitoring methods and geochemical/isotope tracing to map regions of groundwater discharge and improve the understanding of groundwater flow characteristics within discontinuous permafrost terrain. Two summer and one winter season field monitoring campaigns were completed within the Bogg Creek Watershed, a small subcatchment southwest of Norman Wells, NWT. Orbit-based optical imagery provided evidence of recurring icings within the study area suggesting locations of groundwater discharge. Low elevation IR camera surveys conducted during late summer, identified temperature anomalies indicative of cold groundwater discharge. The combined suite of potential groundwater discharge points was selected for helicopter-based terrestrial investigation to measure vertical groundwater flow gradients and to collect water samples for geochemical and isotopic analysis utilizing portable, manual equipment. Physical hydrogeologic data confirmed groundwater discharging conditions with evidence of upward groundwater flow in the shallow subsurface. A range of geochemical and isotopic signatures suggested the existence of several different groundwater sources including water from the shallow active zone and from deeper bedrock aquifers. Surface water and groundwater collected along the length of Bogg Creek illustrated variability in groundwater–surface water interaction and provided evidence of suprapermafrost and subpermafrost groundwater exchange. Establishing clear end-member geochemical/isotopic characteristics is challenging leading to a degree of uncertainty in confirming specific groundwater sources. Although uncertainty remains of exact groundwater origins, the results provide insight into the nature of groundwater flow within a discontinuous permafrost environment. Combining information from remote sensing systems and focused terrestrial monitoring utilizing portable sampling techniques provides a methodology for characterizing aspects of groundwater flow and for establishing priority, long-term monitoring locations without the need for conventional drilling and monitoring well installations. The overall approach would be applicable throughout discontinuous permafrost regions in Canada and elsewhere.