Hydraulic variations in permafrost due to open-pit mining and climate change: a case study in the Canadian Arctic

Abstract

The paper deals with numerical computations of hydraulic variations and groundwater flow changes in continuous permafrost due to climate change and open-pit mining in the cold regions of Northern Canada. The work is a case study in connection with the proposed Kiggavik project in Nunavut, Canada. A major challenge in simulating fluid flow through partially frozen porous media is how to define the transient hydraulic conductivity as a function of temperature. An indirect approach based on the similarity between soil freezing and soil–water characteristic curves for unsaturated soils is implemented to define the relation between unfrozen water content and cryogenic suction which is linked to temperature by the Clausius–Clapeyron equation. Richard’s equation is then used to model fluid flow in partially frozen ground conditions. Finite element numerical modelling results of a worst-case climate change scenario indicate that although the permafrost could disappear completely in about 750 years with an increase in $$7\,^{\circ }$$C in the mean annual ground surface temperature during the next 100 years, the groundwater level around tailings facility would be approximately 35 m below ground surface. Hence, tailings pore water would not likely to migrate upwards to reach the ground surface even after the permafrost is completely disappeared. These conclusions are certainly within uncertainties and limitations of the analysis.