As winter storms continue to drop snow on various parts of the country and people contend with shoveling and scrapping away the products of those storms, think about this - if the snowfall amounts were translated into equivalent volumes of water - then how much water would that be? Using a rule of thumb that each 10 inches of snow, if melted, would produce one inch of water, then each inch of snow produces about 2,715 gallons of water per acre. Of course, the actual amount can vary considerably depending on whether the snow is heavy and wet or powdery and dry, so this is based on the "average" water content of snow. Heavy, wet snow has a very high water content and 4 or 5 inches of heavy, wet snow can contain about one inch of water, while it may take 20 inches of dry, powdery snow to equal one inch of water. The 10=1 equation also assumes a "perfect" snowmelt without evaporation or other losses. So how many gallons of water would that be for, say, Chicago? An inch of snow that falls evenly over the 1,358,599 acres of the "urbanized area" (acreage based on 2000 Census Bureau list of urbanized areas) of Chicago, Ill., is equivalent to about 3,689 million gallons of water (or 3.69 billion gallons). Curious about other cities? The table below lists several major cities and the approximate amount of water each would receive in an evenly distributed inch of average snow:
| City | Area (acres) "urbanized area" list from 2000 Census (Census Bureau) converted from square meters | Amount of water in one inch of average snow (millions of gallons) |
|---|---|---|
| Atlanta, GA | 1,256,051 | 3,410 |
| Boston, MA | 1,111,152 | 3,107 |
| Chicago, IL | 1,358,599 | 3,689 |
| Denver, CO | 319,237 | 867 |
| Detroit, MI | 807,328 | 2,192 |
| Minneapolis/St.Paul, MN | 572,300 | 1,554 |
| New York, NY | 2,145,666 | 5,825 |
| Philadelphia, PA | 1,151,688 | 3,127 |
| St. Louis, MO | 530,529 | 1,440 |
| Seattle. WA | 610,321 | 1,657 |
| Washington, DC | 740,330 | 2,010 |
The snowpack that accumulates each year in the mountains across the country are a vital part of the hydrologic cycle, according to USGS hydrologists. The snows that melt off each spring provide essential runoff to streams and reservoirs and provide recharge to the nation´s ground-water reservoirs as the ground thaws and the snows melt and filter downward into the aquifers (water-bearing rock formations). What happens to that inch of snow as it melts and how much water actually flows to streams and surface reservoirs or recharges ground water reservoirs is affected by many conditions, such as temperatures, topography, soil condition, the density of the area´s vegetation, rate of snowmelt and runoff, and the extent of urbanization. Want to keep an eye on what’s happening with the nation´s water resources on a daily basis? Go to: http://water.usgs.gov/waterwatch