MONITORING GROUNDWATER FLOW DYNAMICS IN A GLACIAL AQUIFER SYSTEM CONTAINING DEGRADING AND DISCONTINUOUS PERMAFROST (UMIUJAQ, NUNAVIK, CANADA)

Field investigations have recently been conducted near the Inuit community of Umiujaq (Nunavik, Quebec, Canada), on the eastern shore of Hudson Bay, in order to assess the present and future potential of groundwater as a sustainable source of drinking water in northern communities. The field work combined detailed hydrologic, hydrogeologic, geophysical and thermal investigation methods in a small 2 km² watershed located in a large valley east of Umiujaq, which drains into the northern end of Lac Guillaume-Delisle. This site lies within the discontinuous permafrost zone where significant permafrost degradation has been observed over the last two decades. The watershed is characterized by the presence of a thick coarse-grained glaciofluvial deposit forming a good aquifer below a thick silty marine unit containing discontinuous ice-rich permafrost. A shallow surficial aquifer lies above the silty unit.

An extensive monitoring network has recently been installed in the watershed, including 3 weather stations, 24 groundwater monitoring wells, 9 drive points, 100 soil moisture and temperature probes in the unsaturated zone, 40 surface temperature probes, 3 snowpack thickness measurement stations, 4 heat flux plates and a H-flume at the outlet of the watershed. Twelve thermistance arrays have also been installed in permafrost and non-permafrost areas. Sampling of groundwater in the wells, and surface water in small lakes and at the catchment outlet, was carried out for geochemical analysis (inorganic parameters, stable isotopes of oxygen and hydrogen and radioactive isotopes of carbon, tritium and helium) and for assessment of water quality and origin.

In this presentation, the monitoring network will be introduced and a conceptual hydrogeological model of the watershed will be outlined based on a preliminary interpretation of the newly acquired data.