, Volume 61, Issue 3, pp 337-355

Climate effects on sulphate flux from forested catchments in south-central Ontario

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access

Abstract

Net export of sulphate from watersheds may delay the response of surfacewaters to changes in acid deposition. Long-term (18-yr) sulphatebudgets were calculated for 8 headwater streams located in the acid-sensitiveregion of Muskoka-Haliburton, south central Ontario. Sulphate deposition inthisregion has decreased by almost 40% over the last 2 decades, and sulphate exportfrom catchments has also generally declined over time, but most catchments arestill a net source of sulphate to drainage streams. Net export of sulphateoccurred in the majority of catchments in most years of record, but wasparticularly large following dry, warmer than average summers, when stream flowceased for up to several weeks at a time. In years with warm dry summers, suchas occurred in 1983/84 and between 1987/88 and 1990/91, inclusive, streamexportfrom most catchments was between 1.5 and 2 times greater than was input viabulkdeposition. Annual average sulphate concentrations in streams were stronglycorrelated with stream dryness, and were greater in years in which streams weredry for longer periods of time. Temporal patterns of annual sulphateconcentrations and export were highly coherent among the 8 streams, and netsulphate export occurred in both wetland-draining and predominantly uplandstreams. Climate variables, specifically temperature and precipitation act on aregional scale and are likely responsible for similar temporal patterns ofsulphate retention among these 8 physiographically different catchments. Netsulphate export from catchments may delay the recovery of acid impacted surfacewaters, despite reductions in industrial SO2 emissions.