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A healthy snowfall offers variety of environmental benefits

Jan. 19, 2011--Delaware got another taste of winter last week, with a storm system that delivered several inches of the white stuff to the northern part of the state.

Had enough of Old Man Winter? Fearful we're in for a repeat of the Snowmaggedeon of a winter we had last year? Can't believe spring is still nine long weeks away?

Cheer up and look on the bright side. There are a slew of environmental benefits to be had from a good snowfall, according to David Hansen, a University of Delaware Cooperative Extension soil and environmental quality scientist.

The phrase “blanket of snow” is more than a visual description -- it's also accurate in terms of warmth, says Hansen. Freshly fallen, un-compacted snow is typically 90 to 95 percent trapped air. Because the air can barely move, heat transfer is greatly reduced, thus slowing the flow of heat from the warm ground to the cold air above.

This blanket effect makes snow an excellent insulator for gardens and landscapes, protecting these natural areas and their animal inhabitants against frigid temperatures and damaging winds.

Snow also lessens -- to some extent -- the extremes of temperature fluctuation to which the soil is subjected, says Hansen. This can be critical for some plants, including evergreens. Even in mid-winter, if air temperature within the canopy of these plants rises during the day, the plants will try to take moisture from the soil. If the soil is frozen, the plants can actually die of thirst.

The extent to which snow insulates depends on its depth. Generally, temperatures underneath a layer of snow increase about 2 degrees Fahrenheit for each inch of accumulation. Because the soil also gives off some heat, the temperature at the soil surface can be much warmer than the air temperature. Hansen says that a study done at minus 14 degrees Fahrenheit found that the soil below a 9-inch deep snow registered a surface temperature of 28 degrees.

Melting snow provides needed moisture to many plants. Even dormant plants continue to lose moisture as water evaporates through their branches. Evergreens, which keep their foliage throughout the winter, are at even greater risk of injury from lack of moisture.

Snow also replenishes the water supply. You may have heard that 10 inches of snow equals 1 inch of rain, but it's actually much more complex than that, according to Hansen. This ratio only works well when temperatures hover around freezing.

At higher temperatures, say a few degrees above freezing, snow is often heavy and laden with water. Then, the ratio may be more like 5 to 1 -- 5 inches of snow will melt into 1 inch of water, says Hansen. At lower temperatures, the snow tends to be light and fluffy and the ratio can be as high as 15 to 1.

How well the snow replenishes the water supply all depends on how it melts, notes Hansen. A fast melt can cause flooding, especially in urban areas. Rapid melting combined with clogged drain systems can send polluted runoff directly into streams and rivers. But a slow snow melt means water trickles slowly into the earth, percolating through the soil and refilling our aquifers, providing water for our drinking supply.

If Mother Nature continues to bestow us with snowstorms in the weeks ahead, try to remember that those flakes are protecting your plants, your water supply and Delaware's wildlife.

Article by Margo McDonough