Influence of Snowcover Development and Ground Freezing on Cation Loss from a Wetland Watershed during Spring Runoff

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Abstract
Cation and water export were monitored from a small wetland watershed in south-central Ontario during spring runoff for two years with very different sequences of snowpack development. In 1977, a persistent snow cover developed in the watershed by 1 December, and snow accumulation was near normal for this region. In 1980, persistent snow cover did not develop until mid-January, and the final snowpack was well below average. Between years, major differences in the timing of ion export were found for calcium, magnesium, and sodium, ions which appear to be associated with the watershed's soils. Conversely, potassium, a cation not as strongly associated with soil ion sources, showed temporal patterns of export which were similar in timing during the two years. We hypothesize that concrete soil frost, which developed in 1980 as a consequence of the late-developing snow cover, strongly influenced the timing of ion export by isolating early spring runoff from the watershed's soils. Streamwater hydrogen ion concentrations decreased rapidly during the first week of spring runoff in 1980, indicating that hydrogen ion export was increased by a similar mechanism. We suggest that in poorly buffered systems, the formation of concrete soil frost may lead to significant increases in hydrogen ion export during spring snowmelt.