PERCOLATION: Water pathways within the snowpack
Students observe percolation channels in the snowpack by isolating a wall of snow and applying dyed water to the surface of the snowpack. Through observation and discussion, they consider how differences in snow grain and pore sizes and the interconnectedness of pore spaces can influence water flow within snowpacks. They may also observe changes to the snow surface where water was applied and discuss implications of rain-on-snow and melt-freeze events for wildlife.
Included in kits unless otherwise noted
● 32 oz. spray bottle
● food coloring
● extendable utility shovels (2) – from snow pit study
● straw whisk broom (1) – from snow pit study
1. Create a snow wall
Use the shovels to dig a vertical face in the snow, approximately 1 meter across, exposing the snowpack in cross section from the surface to the ground
Remove snow from both sides of the exposed snow profile, creating a vertical “wall” approximately 5-10 cm thick; thin enough to allow light through it to enhance the appearance of the different layers but thick enough to remain stable.
2. Apply cold water to the snow surface
Fill the spray bottle with cold water and add a few drops of food coloring so that the water will be visible as it percolates down through the snowpack layers.
Spray the dyed water on the top of the snow wall, being careful not to spray it directly onto the vertical snow faces.
Observe the pathways by which the dyed water percolates down into the snowpack, noticing places where it pools and runs horizontally (upon encountering an icy, non-porous layer) until it encounters another vertical channel. Note how slowly or quickly it travels downward through different parts of the snowpack.
If temperatures are below freezing overnight following the demonstration, return to site the next day and brush the looser snow away revealing the linear, icy percolation column structures.
3. Discussion topics
Snow is not uniform throughout the depth of the snowpack or even within layers. Some areas in the snow are more porous and permeable than others, depending on how interconnected the pore spaces between the grains are.
Sturm, Matthew. 2021. A Field Guide to Snow. University of Alaska Press.