HUNTING FOR GROUNDWATER DISCHARGE IN THE FAR NORTH (Invited Presentation)

The investigation of groundwater flow systems in northern landscapes is particularly challenging due to the remote and inaccessible nature of the terrain, severe climatic conditions and the unique characteristics of the subsurface. The occurrence and continuity of permafrost significant influences groundwater circulation and the interaction of groundwater with the surface water system. Warming climatic conditions in the north is leading to an accelerated degradation of permafrost resulting in the creation or enlargement of groundwater flow pathways, enhancing the hydraulic connection between deep and shallow groundwater flow systems and the terrestrial surface. Documented implications of this are changes in stream flows, lakes levels and surface water quality, which may have direct influence on aquatic and terrestrial ecology for example. Identifying and monitoring groundwater discharge locations within this remote landscape can provide insight into the changing hydrologic conditions. However, conventional investigative techniques such as drilling and monitoring well installation is generally not feasible. In this presentation, a series of remote sensing techniques combined with surface geophysical surveys are proposed and applied as a method to map locations of groundwater discharge and delineate permafrost occurrence in the shallow subsurface. At a field site near Norman Wells, Northwest Territories, within the Central Mackenzie Valley, optical orbit-base surveys were employed to map the locations of seasonal icings at a watershed scale, which represent points of groundwater discharge or springs. Low elevation Infrared (IR) helicopter survey data were used to identify smaller scale groundwater discharge locations. The combined data helped direct ground surface monitoring activities focused on characterizing discharging groundwater. Airborne electromagnetic surveys merged with terrestrial electrical resistivity tomography surveys (ERT), were used to map the geometry of permafrost where groundwater discharge conditions were detected. The combined data provide insight into the nature of groundwater discharge within this remote northern landscape and serve as baseline information to track future changes under warming climatic conditions.