Factors Affecting Alkalinity Concentrations of Streamwater during Snowmelt in Central Ontario

Abstract

Relative contributions of changes in base cations and acid anions to alkalinity decreases during spring snowmelt in 1984–86 were analyzed for 15 headwater streams and lake outflows in three central Ontario catchments. During episodes, concentration changes in ions which contributed to alkalinity decreases were partially offset by smaller changes in other ions which contributed to alkalinity increases. The major contributor to alkalinity depressions was base cation dilution by snowmelt water. Akalinity depressions were more likely to be dominated by SO₄²⁻ increases in streams that were more acidic. Neither nitrate nor organic acid anions were significant contributors to alkalinity depressions. Discharge was highly correlated with alkalinity in a circumneutral stream but not in an acidic stream and is consistent with dilution being less important as a cause of alkalinity depressions as streams become more acidic.