Abstract Nose Creek, a tributary of the Bow River, has a TDS load that is significantly higher than the Bow River or its other tributaries. Chemical and stable isotope analyses were used to elucidate the sources of TDS in Nose Creek. Oxygen and H isotopes indicate that water is added to Nose Creek by leaky municipal pipes, via groundwater infiltration, as the creek flows through the cities of Airdrie and Calgary. Upstream of Airdrie, the high δ 34S of dissolved S0 4 (+ 17‰), is consistent with derivation from the local sour gas industry. The S0 4 concentration of Nose Creek doubles as the creek flows through agricultural land between Airdrie and Calgary, while the δ 34S composition remains a consistent 5‰. This is indicative of S derived from local soils. Within Calgary, S0 4 is derived from oxidation of reduced forms of S in the till, related to the influx of municipal groundwater.