Monday May 9, 2022

NASA Earth Observatory

When it comes to mountain snow, the Sierra Nevada is notorious for booms and busts: One year is bad, while another can be exceedingly good. In 2021-22, there were booms and busts all within the same snow season. The result has been another year of inadequate snowfall and concerns about the impact on water supplies.

“The Sierras tend to get big storms, with a lot of snow in bursts, or we get years of very little snow,” said Noah Molotch, a mountain hydrologist at the Institute of Arctic and Alpine Research (INSTAAR) and NASA’s Jet Propulsion Laboratory. “It is rare that we have a snow year that is actually average.”

Snow that falls on the Sierra Nevada each winter becomes a natural reservoir that slowly melts and flows down into the river valleys in spring and summer. In a typical year, this snowpack accounts for about 30 percent of California’s water supply. Resource managers count on this snowmelt to fill reservoirs with sufficient water for the typically dry months of summer and autumn.

“This past winter was one of extremes within an overall downward trend,” Molotch noted. “These are natural events that could normally happen, but global warming has amplified everything. The trajectory of climate change has put us on a path where the normal wild swings of winter are now warp-drive wild.”

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