Processes of Flow and Transport in a Seasonal Snowpack
and the Underlying Seasonally Frozen Soil
R.P. Daanen1 and J.L. Nieber1
The problem of contaminant movement in snowpacks and underlying seasonally frozen soils has
become a relevant research topic within the last two decades. While some field studies have led to a
better understanding of the complexity of flow processes in snow, for example preferential or fin-
gered flow (Marsh 1991 and Bales 1997), the scarcity of field data limits further scientific develop-
ments related to flow and transport processes in snowpacks and frozen soils. To add to the store of
available data, we performed two dye tracing experiments in the winter of 1998, one experiment on
a small plot and the other on a small watershed.
On the small plot, three distinct dyes were used to trace the movement of the meltwater. The exper-
iment was performed during the last snowmelt event of the winter, occurring in February. It was
found that the transport time of dyes from the top of the snowpack to the bottom of the slope was
found to range between 16 minutes for an average travel distance of 1.5 meters (the dye on the lowest
portion of the plot) to 55 minutes for an average travel distance of 7.5 meters (the dye on the upper-
most part of the plot). The water balance showed that the meltwater partially infiltrated the frozen
soil. There is no direct relation between the recovered dye mass from the plot and the amount of
water that infiltrated with the observed concentration. Possible explanations for this result are 1) the
dye was adsorbed on the soil surface; 2) the dye infiltrated the soil at a higher concentration than that
observed at the outlet; and 3) some of the dye never left the top of the snowpack during the snowmelt
event. A simple reservoir model of the transport processes was developed and model parameters
optimized to produce a good comparison between model predictions and experimental observations.
For the small watershed study, Uranine dye was applied over a 10-m2 area at a location 200 meters
upgradient of the flow measurement weir. During the final snowmelt of the winter the first evidence
of the dye was found at the weir in the surface runoff at 9 days following the application of the dye.
Only a fraction of the dye applied was recovered in the surface runoff. The water balance at the small
watershed indicates that, like the small plot study, much of the meltwater infiltrated the underlying
partially frozen soil. We are continuing to collect spring flow data at the watershed and expect that at
some time the dye that infiltrated the water will eventually reach the weir.
1 Department of Biosystems and Agricultural Engineering, University of Minnesota, 1390 Eckles Avenue, St.
Paul, Minnesota 55108, USA
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