Low snowpacks of 2014, 2015 may become increasingly common with warmer conditions.
Oregon 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).
The 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.
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 than average.
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.
"The study shows how incredibly sensitive the region’s snowpack is to increasing temperatures," Sproles said.
The typically consistent flow of the McKenzie River in the summer of 2015 was only at 63 percent of its median flow.
"We 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.
"It 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.