Controls on the chemistry of the Bow River, southern Alberta, Canada

Integrated chemical and stable isotope analyses were used to define the controls on the dissolved inorganic load in the Bow River, and thereby elucidate the chemical and hydrologic dynamics of the river.; The dominant sources of ions in the river are atmospheric deposition and rock weathering. The input by weathering is largely controlled by dissolution of carbonate and evaporite minerals. Calgary is the most significant point source input along the river. Effluent from the sewage treatment plants loads Na, K, and Cl to the river. Cation activity ratios are strongly controlled by exchange on smectite. Smectite is absent in the river, suggesting that activity ratios are an inherited signature of ground water.; Stable isotope data indicate that discharge in the fall and winter is fed by groundwater. The high discharge event in the spring is a mixture of snowmelt and displaced groundwater. Summer discharge is fed by rainfall. Despite seasonal variations in the TDS load, element ratios are constant, suggesting that the chemistry of snowmelt and rainfall are altered by the same processes controlling groundwater chemistry. This suggests snowmelt and rain fall must pass through the ground before becoming discharge. {dollar}rmdeltasp{lcub}18{rcub}Osb{lcub}(SO4){rcub}{dollar} data indicates dissolved sulfate undergoes a complex redox history before reaching the river, implying that the water transporting the sulfate passes through the anoxic zone before becoming discharge. Therefore, the Bow River is largely fed by ground water.; The chemical denudation rate for the Bow River at Banff is 678 kg/ha/y. The denudation rate for the basin as a whole is 340 kg/ha/y. Loading from Calgary accounts for 8 to 9% of the mass flux out of the basin in the spring and fall and 25% of the mass flux in the summer.