Welcome to our ‘Watershed in Winter’ lab, it’s a lot of fun! One of the most beloved labs in our department, in this lab students explore the winter landscape, looking at how snow falls on landscape, and conducting some simple calculations to estimate water inputs to the watershed.
Heading out on a beautiful sunny day, our class trekked into the local woods once again to explore ‘the watershed in winter’.
I had been getting worried in the weeks leading up to this class, as we’d had a very dry winter thus far (our previous outdoor lab, while cold, had been snow free). But fortunately nature provided and we got multiple rounds of light fluffy snow just in time for our lab. We had made contingency plans to perhaps visit the local outdoor recreation ski park where there is at least always the guarantee of man-made snow! But, in the 25 years this class has been taught, there has never failed to be at least one some snow on the ground to allow the snow lab, and fortunately, this year ended up no different!
The snow lab is great, not only because it allows for student shenanigans and snow angels:
but also because it’s a fun way to think about water inputs to the landscape and how solar energy affects snow melt.
We have the students first look at the landscape and think about the path snow takes as it falls from the sky, and the various ways in which it might be intercepted along the way (by tree canopies for instance).We discuss how trees catch a lot of snow as it falls on their branches, and how this prevents a lot of water from reaching the ground, as it evaporates and sublimates directly back into the atmosphere. This is why in some areas that suffer from droughts or low flows, natural resource managers will actually thin forests, by cutting down some of the trees, to open up the canopy and allow more snow to reach the ground. With spring, more water ends up in streams.
Hillslope, Aspect, and Snow
Students then collect some physical measurements of fallen snow at different locations on the hillslope, from the summit, on the shoulder, the side slope, along the foot slope, and finally along the edge of the stream in the toe slope. They also look at differences between north and south facing slopes.
These factors affects how much solar energy reaches the snow and thus how much and how quickly the snow thaws/evaporates. North facing slopes often have much more snow on them than do south facing slopes, just as lower hillslope positions have more snow than higher positions.
Snow Density and Water on the Landscape
Lastly we have students collect snow in containers of known volume (no packing the snow!) so that they can measure snow density. Back in the lab, after the snow melts, they can compare densities from different hillslope positions and between north and south facing slopes. They can also, using maps of the watershed, estimate how much water could be expected to melt from all of that snow, thus allowing them to estimate stream flows (making the rough, and false, assumption that all the snow melt makes it directly to the stream). Many students are surprised by how much water there really is in all that snow!
The ‘Watershed in Winter’ lab is always a lot of fun. Students are provided the opportunity to think about stream flows in a season when few are thinking about running water and droughts. As with our previous outdoor lab, there is nothing like getting to go outside and learn about landscape concepts first hand, while walking the landscape in person. Plus, the snow always adds a festive and mischievous air to the day. With some pretty steep hills, it makes for great sliding opportunities! And of course, there’s always snow angels!
We go outside every week from here on out, so stay tuned for more posts on teaching outdoors!