experienced very low snowpack levels in 2014 and historically low snowpack
levels in 2015; now a new study suggests that these occurrences may not be
anomalous in the future and could become much more common if average
temperatures warm just two degrees Celsius.
low snowpack levels were linked to warmer temperatures and not a lack of
precipitation, the researchers say. Based on simulations of previous and
predicted snowpack, the study suggests that by mid-century, years like 2015 may
happen about once a decade, while snowpack levels similar to 2014 will take
place every 4-5 years.
of the study http://www.the-cryosphere.net/11/331/2017/, which was supported
by the National Aeronautics and Space Administration and the National Science
Foundation, have just been published the journal The Cryosphere.
is a cautionary tale,” said lead author Eric Sproles, who conducted much of the
research as a doctoral student at Oregon State University and has been working
as a hydrologist in Chile. “California received a lot of attention for its
drought, but the economic and environmental impacts from those two low-snowpack
years were profound in the Pacific Northwest.”
set out to learn whether they were just off years, or if they would be likely
to happen more often with increased warming. Unfortunately, the data show these
will become more commonplace.”
key, Sproles said, is what happened in the Cascade Mountains at an elevation of
around 4,000 feet – a level that frequently is the boundary between rain and
snow. In 2014, winter precipitation in the mountain region was 96 percent of
normal and overall temperatures were 0.7 degrees (C) warmer than normal. But
temperatures in that snow zone were 2.7 degrees (C) warmer than average.
winter of 2014 led to drier springtime conditions and moderate to severe
drought throughout western Oregon. That pattern was even stronger in 2015. A
fair amount of precipitation still fell – 78 percent of normal – but
temperatures in the snow zone were 3.3 degrees (C), or 5.9 degrees (F) warmer
March 1 of 2015, 47 percent of the snow monitoring sites in the Willamette
River basin registered zero “snow water equivalent” – the amount of water
stored in snowpack.
result was a significantly reduced stream flow in the summer, water quality
concerns in the Willamette Valley, an increase in wildfires, high fish
mortality and a dreadful season for ski resorts,” said Sproles, who worked with
Anne Nolin and Travis Roth in the College of Earth, Ocean, and Atmospheric
Sciences on the project. “Hoodoo Ski Area was open for only a few weekends in
2013-14, and in 2015, they suspended operations in mid-January – the shortest
season in their 77-year history.”
Reservoir in the adjacent Santiam basin had reservoir levels that were as much
as 21 meters (or 68 feet) below capacity, and was plagued by high levels of
harmful blue-green algae concentrations.
study focused on the McKenzie River basin, which has a major influence on the
Willamette River – all the way to Portland. In fact, during summer months
nearly 25 percent of the water in the Willamette at its confluence with the
Columbia River originates from the McKenzie. As much as 60 to 80 percent of the
volume of the Willamette River in the summer originates from precipitation that
fell above 4,000 feet.
study shows how incredibly sensitive the region’s snowpack is to increasing
temperatures,” Sproles said. “The low snow years took place even though
precipitation wasn’t that bad. But when it falls as rain instead of snow, it
loses that ability to function as a natural reservoir in the mountains.”
typically consistent flow of the McKenzie River in the summer of 2015 was only
at 63 percent of its median flow.
don’t really know yet the impact of the 2015 low snowpack because some of the
water takes as long as seven years to percolate through the ground and end up
in the Willamette River,” Sproles said.
comparatively cold and wet winter has made many Oregonians forget about the
low-snowpack years of 2014 and 2015, Sproles said, but the region has been in a
La Niña cycle – which is typically colder and wetter – and is expected to move
toward neutral conditions by the end of February.
seems like much of the state has been socked with snow and ice this winter,”
Sproles said, “but despite that, snowpack for the Sandy and Hood River basins
is only 110 percent of normal and the Willamette basin snowpack is 124 percent
of normal. That is certainly positive, but it seems like those numbers would be
a lot higher considering what kind of winter we’ve had in the valley.”