RENEWING FRESH WATER
            Snow falls silently covering everything in site – a visual portrait of a watershed. What does not evaporate and return to the clouds as water vapor will eventually run off over or under the ground renewing our fresh water supply – just as rain, sleet, and hail do.
            Lately we have experienced the fact that snow can fall even at incredibly cold temperatures. Snow can occur if there is moisture in the atmosphere and some way to lift or cool the air. Since air can hold more water vapor at warmer temperatures, heavier snowfalls usually occur at 15 degrees F or warmer. Besides needing moisture for snow to form, the temperature of the atmosphere must be at or below freezing. The snow reaches the ground only if the temperature at ground level is at or below freezing.
            Snow has qualities that make it more interesting than some other forms of precipitation. When snow accumulates, air temperature at its surface (the top 12 to 18 inches) controls snow temperature. When snow is deep, the snow closest to the ground is warmer because it takes its temperature from the ground. The ground retains some of its summer warmth because snow is a good insulator. Fresh snow is composed of 90-95 percent air trapped among the lattice structure of the snow crystals. The trapped air can barely move so heat is not readily transferred away from the ground.
            Sound travels differently because of the snow. When there is a thick layer of light fluffy snow, sound waves are absorbed by the snow and sounds are more muffled. Strong winds can make the surface of the snow smooth and hard or crusty. When this happens sound waves are reflected and become more clear and travel further.
            Sometimes snow makes a crunching sound. “A layer of snow is simply composed of ice grains with air in between the ice grains. Because the snow layer is mostly empty air space, when you step on a layer of snow you compress that layer – a little or a lot, depending on how old the snow is. As the snow compresses, the ice grains rub against each other. This creates friction or resistance; the colder the temperature, the greater the friction between the grains of ice. The sudden squashing of the snow at lower temperatures produces the familiar creaking or crunching sound. At warmer temperatures, closer to melting, this friction is reduced to the point where the sliding of the grains against each other produces little or no noise.” National Snow and Ice Data Center.
            The snow cover serves as a reminder that we have a responsibility to manage the precipitation that renews freshwater in such a way that our water supply is not harmed.
            This information and more can be found at http://nsidc.org/snow//faq.html.

Della Moen, Earth Team Volunteer, NRCS/Stephenson Soil and Water
Conservation District, an equal opportunity provider and employer, 12/1708/ (for publication on 12/29/08 in the Journal-Standard, Freeport, Illinois).
Della can be reached at info@stephensonswcd.org