Several terms are used when talking about how much moisture is contained in a certain amount of snow. In our area, the most frequently used is liquid equivalent. This is the depth of water that would result from melting of a sample of snow. Thus a liquid equivalent of new snow is the same as the amount of precipitation that snowfall represents. This is where the infamous “10-to-one” ratio has its roots. This is actually only an estimate, and is based on snow that is formed in the 34 to 28 degree ranges. If the temperatures are colder, say in the 10 to 15-degree range, the estimate is in the 30-to-1 range. In the mountains, however, you might be more interested in the snow water equivalent. This is the amount of water stored in the entire snowpack not just the most recent snowfall. It is determined by the snow density or the specific gravity of the snow sample. Freshly fallen snow usually has a snow density of 7 to 15 percent while values as low as 0.4 percent inch have been measured.
Mary Knapp, Weather Data Library