The Kettle River Basin in South central British Columbia (Canada) is under increasing anthropogenic pressures affecting both water quantity and quality of surface waters and aquifers. We investigated water quality and sources and processes influencing NO₃^– and SO₄^2– in the Kettle River Basin using a combination of chemical and isotopic techniques. The dominant water type in the Kettle River Basin is Ca–HCO₃ with surface waters having total dissolved solids (TDS) concentrations of<115mg/L and groundwaters having TDS values of up to 572mg/L. Based on   and   values and concentration data, NO₃^– in surface waters originates primarily from natural soil nitrification processes, with additional influences from anthropogenic activities, such as waste water effluents at sampling locations downstream from population centres. The source of NO₃^– in groundwater was predominantly nitrification of soil organic matter, although nitrate in a few groundwater samples originated from anthropogenic sources, including manure or septic systems. The dominant source of SO₄^2– in surface water and groundwater samples was the natural oxidation of sulfide minerals. With increasing distance downstream, surface water   values increase beyond the range of oxidation of sulfide minerals and into the range of soil and atmospheric-derived SO₄^2– that is in part derived from anthropogenic emissions. Hence, we conclude that recent anthropogenic impacts have affected water quality only marginally at only few sites in the Kettle River Basin. The presented data will serve as an excellent baseline against which future impacts can be assessed.