The snowpack in the Rocky Mountains is getting smaller, according to a new study from scientists at the U.S. Geological Survey. 

It found the snowpack in the American Rockies has shrunk by roughly 20 per cent since 1980, largely because of warmer springs.

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Shawn Marshall, a climatologist and glaciologist at the University of Calgary, says effects of the shrinking snowpack have already been seen. (CBC)

Scientists say it will have serious repercussions for the water supply on both sides of the border.

"The trends we do see in Canada are consistent with this study and it is disconcerting," said Shawn Marshall, a climatologist and glaciologist at the University of Calgary.

"It's going to mean a real change in our water supply and our water systems here — things we're already seeing — but this is just more evidence that this is likely to continue and accelerate going forward."

The U.S. Geological Survey says runoff from the Rocky Mountain snowpack accounts for up to 80 per cent of the annual water supply for more 70 million people living in the western U.S.

  • For more on the story from CBC reporter Dave Gilson, watch the video above by clicking on the image.