Impact of climate change on extreme rainfall events and surface water management at mine waste storage facilities

Climate change will cause a significant increase in the intensity and frequency of extreme precipitation events in Quebec (Canada), and especially in the Abitibi region, an important mining region. Projections indicate an average increase of the intensity of the summer Probable Maximum Precipitation (PMP) between 18 and 30% by 2100. Greater PMP could affect the performance and integrity of mining infrastructure (berms, dams, spillways), and increase the risk of dike overtopping (a common mechanism for dike failure in the mining industry). In this paper, an approach using projected PMPs from regional climate models to design surface water management infrastructure is proposed and applied on a real mine site in Abitibi. Clavet-Gaumont and Hershfield PMP calculation methods are presented and compared. Rainfall and runoff were measured at Canadian Malartic Mine to characterize the rainfall-runoff characteristics of waste rock piles and tailings storage facilities. Field measurements were used to calibrate a numerical model and quantify the projected impact of climate change on runoff following extreme rainfall events. The effect of temporal rainfall distribution, waste rock/tailings initial conditions and catchment geometry on runoff were also studied. Results show that the peak discharge of summer/fall PMP could increase significantly, up to 49% considering Representative concentration pathway 8.5 (RCP8.5) scenario. The choice of the approach used to estimate PMP could cause major differences in the design of surface water infrastructure. The RCP scenario was also identified as a major cause for uncertainty in the projection of peak discharges.