What Happens When Rocky Mountain Snow Melts Too Fast In The Spring?

DENVER (CBS4) - As our planet warms, there is an expectation the deep snowpack that develops each winter in the mountainous regions of the country will melt increasingly earlier in the spring. That's a problem for several reasons.

First: snow reflects a lot of sunlight back into space. When there is no snow, the sunlight is absorbed by the ground and the ground heats up the air. That leads to even more heating and more snow melt.

The second problem is once the snow disappears, there is no more melt water to feed lakes, streams, and rivers which causes water levels to drop fast through the summer months.

Once the land dries out, wildfire season can start sooner and be more destructive than it was in the past.

"When snowpack persists late into the spring and toward the summer, it becomes a natural drip irrigation that is irrigating the mountains and is ultimately finding its way into streams and rivers," said Dr Keith Musselman, a snow hydrologist at the University of Colorado in Boulder.

"With warming, with earlier melting, earlier snow disappearance, you're going to be turning off that drip irrigation earlier and you can imagine what that would do," Musselman said.

Winter snowpack is critical for everyone in the western United States where 50% of the water supply comes from snow. Approximately 55 million people across the western half of North America rely directly on water from snow. And the demand for that water peaks in the summer long after the snow has stopped falling and increasingly long after it has melted.

Over the last 40 years, peak snowpack has trended three weeks earlier in many areas including in the southern Rocky Mountains of Colorado, the central mountains of Utah, and in the lake Tahoe area in the Sierra Nevada mountains.

The mismatch between when snow accumulates and when it is needed as water combined with the shift toward earlier peak snowpack means water management must change.

Becky Bolinger, Assistant State Climatologist for Colorado says, "Our entire state of relies on water that starts at the highest elevations. It's good we are all keenly aware what is happening with mountain snowpack since we know where our water comes from. Every snowflake that falls is incredibly important."

Most climate scientists agree most western states will have to adapt to less snow being available to melt later in the season. The question is how much will spring snow melt accelerate in the coming years and decades.