Coppermine River sampling took place between two locations depending on seasonal site access either by boat, ATV, or from shore. The main sampling site was up river: 67.7633°N, -115.2538°E, and the secondary site was closer to the river mouth: 67.8173°N, -115.0765°E. When travel on the river was dangerous (ice break-up, freeze-up) samples were collected from a shoreline intake for the water plant adjacent to the secondary sampling site (67.8203°N, -115.0848°E).The sample collected on August 22, 2015 appears to have higher dissolved salt concentrations than usual for this river (in particular for Cl and Na). Strong winds required that this sampling event be carried out by ATV, so the sample was collected from shore near the primary site. Although this sample has been included in the presented analyses, it should be treated as potentially contaminated.