In the Yukon, where 97% of the population depends on groundwater, water quality impacts from legacy mining activities are a significant concern for several communities. Uranium and manganese concentrations regularly exceed Canadian guidelines for drinking-water quality in the greater Whitehorse area, including in groundwaters and seepages interacting with mine wastes at the Whitehorse Copper mine. Delineating mobilization of these metals from mine waste weathering against other sources requires a detailed understanding of the local groundwater flow system and contaminant transport processes. Groundwater and surface water samples were collected from monitoring wells (n=29) and surface water bodies (n=18) at the mine site and downgradient locations from 2022–2025 and analyzed for isotopes of hydrogen and oxygen in water (δ2H, δ18O and 3H). Isotopic data will be used to characterize the age and source of groundwater in the area and determine groundwater recharge conditions in the underlying fractured rock aquifers. Preliminary results will be presented and will be used in conjunction with water level and bedrock lithological and structural data to develop a conceptual site model of groundwater flow and transport. With renewed interest in critical mineral resources in the region, the findings will help assess the vulnerability of local aquifers to mining activities and help protect drinking water users. The results will improve understanding of mining impacts on mobilization of geogenic contaminants, and the impacts of legacy mining projects on present-day groundwater across Canada.