Assessing Sensitivity of Subsurface Mine-Dewatering Activities to Climate Change

Abstract

Underground mining activities require constant removal of groundwater from their void spaces to maintain dry and safely accessible excavations for ore extraction in a process known as dewatering. The nature and degree of dewatering activities is heavily dependent on the amount of groundwater that can reach the mined areas and, conversely, dewatering of mines has a significant effect on the regional groundwater flow in their vicinity. Furthermore, groundwater supply to mining areas may be linked to climatic conditions, connected surface water bodies and the geologic structures that link the surface and subsurface. Typically, fully saturated groundwater models are used in industry to simulate site conditions and to plan mine dewatering infrastructure. These models often take historical climate averages into account when determining recharge to groundwater from the surface, and they do not typically account for feedback between groundwater and surface water systems. While this has been sufficiently accurate in the past, it is expected that the progression of climate change will yield future estimates of groundwater recharge that differ significantly from historical averages. These changes may be captured more accurately with fully coupled methods of simulating groundwater and surface water simultaneously in areas with large surface water bodies overlying aquifers, or in locations where geologic structures provide significant preferential pathways between the surface and subsurface. Here, we explored the changes in predicted dewatering rates for a real mining property in Central Quebec when considering a typical, industry standard fully saturated groundwater model with historically averaged recharge and a fully integrated groundwater/surface water iii model that incorporates results from future climate scenarios. The two models were constructed, parameterized, and calibrated for a site in Central Quebec. Simulations of underground mine dewatering were run with both models, and the predicted dewatering rates from each model were compared. Simulation results demonstrated that the fully integrated groundwater/surface water model with future climate yielded an estimated rate of dewatering that was approximately 2% higher than that predicted by the fully saturated groundwater model with historical climate averages.