Mad River U- Day 5

Riding a Phase Change: Snow and Western Rivers It’s hard to imagine that the same powdery white stuff that makes up the groomers at Jackson Hole Mountain Resort fuels the hits at Lunch Counter and Big Kahuna. While we all know that snow melts and water freezes, the thought of rafting on snow or snowmobiling on water seems bizarre and outside the realm of possibility. Yet, if we ignore the phase – solid, liquid, gas – of the playing surface and focus on the molecule both share – H20 – it’s all the same thing. When snow falls throughout the United States, it is measured by meteorologists, hydrologists and avalanche forecasters in a variety of different ways. If one lives in the Northern half of the United States, he or she is accustomed to hearing snow as measured in depth of inches and sometimes feet. The amount of snowfall measured in inches of actual depth allows us to project whether or not school will be canceled, what heroics the days commute will entail and if worth heading up the mountains to ski over the weekend. For hydrologists, avalanche forecasters and river runners, the depth of the snow only tells part of the story. In addition to measuring the depth of the snow, the snow-water equivalent (SWE) is often an equally important measurement. Snow water equivalence is measured by figuring how much water any given amount of snow contains: If ten inches of snow melt down to 1 inch of water, we can snow water density is 10%. This percentage is important as it helps define the snow on the ground during the winter, but also because it helps predict how much moisture the existing snowpack will contribute to the water table in the summer. In other words, a big snow year both in total accumulated snowdepth and in high SWE will lead to a big year in local rivers. In Jackson Hole, starting in late April following the closing of area ski resorts, this connection between our mountain slopes and rivers becomes increasingly visible. As temperatures rise, the area snowpack begins to melt, and early season runoff from the Greater Yellowstone Ecosystem begins a journey of over 1,040 miles to Columbia River with its final destination, the Pacific Ocean. Along the way, snowmelt passes through Snake River Canyon offering up the opportunity to ride on the tail waves of a phase change.