Forests Blanketed in Snow – A Good Sign for Groundwater Aquifers

Posted: December 17, 2014

Consider how winter snow fits into our annual water cycle. Snow is really important to groundwater recharge. Don't grumble about the white stuff falling any more!

Grumble. Grumble. It is going to snow. Grumble. Grumble. Why does it have to snow? Grumble. Grumble. It is so dark, cold, and snowy. You know how it is. Many folks have trouble accepting winter, cold, and snow. It seems, often, that everyone wants every day to be bright and sunny. They can tolerate the cold (maybe), as long as it doesn’t snow or rain. (It is not clear which most folks find preferable; a snowy blanket on the landscape, or rainy skies and wet feet.) Sometimes it seems that the only folks who appreciate snow are kids – no school. Maybe it is time for an attitude adjustment?

Let’s consider how winter snow fits into our annual water cycle. Across Pennsylvania, the amount of water we receive every month is relatively even. In the spring, summer, and fall, we have rain and in the winter our water often comes as snow. Snow as part of the water cycle is really important. Why champion snow?

Officially, on December 21, we move into the winter season, and many recreationists including hunters, skiers, and snowmobile enthusiasts excitedly look forward to snow-covered forests. But, forests blanketed in snow should also be appreciated by those who enjoy streams in the summer and rely on groundwater wells and springs for drinking water supplies. That’s because forests and the snowpack together are important for recharging underground aquifers that hold trillions of gallons of freshwater stored in pore spaces and rock cracks beneath the soil surface. These aquifers maintain streamflow throughout the year and provide water that supports industries, businesses, agriculture, and ensures drinking water for millions of Pennsylvania residents.

The forest creates a perfect environment to capture and to allow water from melting snow to slowly enter the ground. Soil under forest canopies acts like a sponge to soak up and pass water from the surface into groundwater aquifers. Where forests are removed, soils may become compacted or even paved, reducing the amount of water that infiltrates into the ground to support aquifers. Water infiltration into the ground occurs most efficiently during times when the forest is dormant. That’s where a thick snowpack becomes beneficial.

The snowpack that accumulates during the winter insulates the soil underneath it, keeping the soil largely unfrozen and able to absorb water from melting snow. Since trees and other plants are dormant during early spring, most of the snowmelt water entering the soil can infiltrate and recharge groundwater aquifers. The snowpack also represents a large volume of stored water that can be released slowly during the spring melt. A ten-inch snowpack covering just one acre may hold 30,000 gallons of water or more. Once the snow is gone and trees leaf-out in late spring, most infiltrating water from summer rainstorms is taken up by the roots of the growing trees. The water contributed to our aquifers during snow melt creates a cycle where we have high groundwater levels during March and April that typically fall throughout the summer and early fall.

Ground water aquifers recharged in the spring by melting snow provide water supply wells and streams with a steady source of cool ground water during the long, hot summer. Fish and other stream life have adapted to the increased stream flows in spring and the relatively cool ground water supplied to the stream throughout the summer. Without this spring recharge, stream levels may drop and stream temperatures may increase to dangerous levels during the summer. So the next time you cast a fly over a rising trout or take a drink of water from your well or spring, remember that the combination of undisturbed forests and winter snowpacks provide much of the groundwater that we rely on every day.

Hopefully, you now have a reason to appreciate the snow that falls from our winter sky and blankets us with a winter cover. Snow, just like rain, is important to ensure the high quality water we enjoy in Pennsylvania and for keeping our forests healthy and growing. Let it snow!

The Pennsylvania Forest Stewardship Program provides publications on a variety of topics related to woodland management. For a list of free publications, call 800 235 9473 (toll free), send an email to, or write to Forest Stewardship Program, Natural Resources Extension, The Pennsylvania State University, 416 Forest Resources Building, University Park, PA 16802. The Pennsylvania DCNR Bureau of Forestry and USDA Forest Service, in Partnership with Penn State’s Department of Ecosystem Science and Management, sponsor the Forest Stewardship Program in Pennsylvania.

Contact Information

Bryan Swistock
  • Extension Associate
Phone: 814-863-0194