Where do all the snowflakes go?
It's cold, it's slippery, it's a whole lot of fun. It makes winter a wonderland. But there's much more to snow than sledding. The very water you drink depends on it. Here's why.
Every winter I go skiing on our city's water supply. As I swoosh down the slopes, I marvel at the fact that much of the water we use in the summer - for drinking, bathing, watering the lawn, or washing the car - was put into storage during the winter.Skip to next paragraph
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How? Nature does the work.
In the winter, the Rocky Mountains and the Sierra Nevadas become giant refrigerators, jokes Robert Hartman of the California-Nevada River Forecast Center in Sacramento, Calif. These mighty peaks store frozen water in the form of ice and snow, to be used by people in the valleys below all the next summer.
Mr. Hartman is a hydrologist - a person who studies water cycles and predicts the amount of water that will be available in specific regions.
"It's great, all the ways we benefit from snow," he says. "We can play in it, ski on it, enjoy its beauty, and then put it to use when it melts in the spring."
If you're in an area where winters are cold, you might be able to ski or skate on your water supply, too.
In warmer areas, you could be walking over the stored H2O while it remains hidden underground in an aquifer (right) - a layer of porous rock or sand that contains water.
Areas that get cold in the winter have aquifers, too. Some parts of the United States rely on water that is stored in these underground layers during the winter.
Rain and melting snow sink into the ground and often collect in these aquifers. The soil or rock is loosely packed in these places, so water can seep in between the particles.
Out on the great plains, which lack snow-covered mountains, pumps are used to bring this water up to the surface. Other groundwater slowly sinks farther into the ground, until it seeps out into a river or lake.
In the Eastern and Southern states, winter also supplies water that is collected in lakes and ponds. But less storage is needed because rain falls more often during the summer.
Mountain snow is an important source of summer water in the Western part of the United States. Unlike the Eastern regions, where rain falls more frequently during the spring and summer growing seasons, much of the rain and snowfall in the West happen during the winter.
For example, while Tennessee averages more than 48 inches of rain each year, with several inches falling each month, Nevada averages fewer than 8 inches a year.
Most of the precipitation out West falls between October and April. To water crops and provide drinking water in the summer, Western states rely on the snow that gathers on the mountains each winter.
As this snow melts and becomes runoff in the spring and summer, it flows into valleys. As much as 70 percent of the water that flows into the valleys during the year comes from melting snow.
As the population has grown, however, more water has been needed. People realized that a lot of water was running down into lakes or to the ocean that would be helpful to people in other parts of the valleys. So they began building dams along the rivers to help store the water for later use.
The dams hold the water that collects from spring runoff, and it is gradually sent down the river to the people below throughout the summer. Dam construction also provides a few other benefits, such as a new lake above the dam where people can fish and swim.