Snowfall is seriously lagging rainfall in Oregon and Washington, creating a precarious situation for irrigators as winter approaches.
Experts say that snowpacks must increase substantially in early 2015 to ensure adequate water supplies for next year’s irrigation season.
“We are behind the eightball,” said Scott Pattee, water supply specialist in Washington for the USDA’s Natural Resources Conservation Service.
Snowpacks are roughly 60 percent below average in Washington and 70 percent below average in Oregon while precipitation has been above average in both states, according to NRCS data.
At this point, however, the numbers signal a late start to the snow season rather than a dire outlook for irrigators, since there’s still the potential for significant snowfall in the early months of 2015, Pattee said.
“Right now, it’s not that worrisome,” he said.
Above average rainfall is good news because the soil is now saturated, which means the ground won’t have to absorb a lot of melting snow in springtime — contributing to healthier streamflows, Pattee said.
The downside is that rains have melted some snow at the mid-elevation level, he said. “The mid-elevation is probably the most critical because it has the most land mass.”
The current situation is nonetheless a marked improvement from last year, when inadequate rainfall caused a deficit in soil moisture, aggravating the effect of poor snowpacks, said Julie Koeberle, hydrologist for NRCS in Oregon.
However, rain cannot compensate for snow, which effectively provides water storage and allows irrigators to better plan for their season, she said.
“We were hoping for a better start,” Koeberle said.
Snowpacks reach their peak in early April, but in some areas they top out in mid-March, she said. “The writing is on the wall by then.”
Right now, there’s no reason to panic, but irrigators really need snowpack levels to improve by early February, Koeberle said.
If snowpacks remain low at that point, “we would be a lot more concerned,” she said.
Irrigators have less reason to be nervous in Idaho, where rainfall has been about average and snowpacks are only 20 percent below normal.
Above average snowpacks in western Wyoming are an important plus for irrigators in Idaho, as this region strongly contributes to water levels in the Snake River, said Ron Abramovich, water supply specialist for NRCS in Idaho.
“It all starts in the headwaters of the Snake, which is Wyoming,” he said.
The Boise basin, which feeds the Snake River in the western part of Idaho, has an average snowpack, which bodes well for irrigators in that part of the state, Abramovich said.
It’s too early to celebrate, though, as snow must continue accumulating through winter, he said.
The National Oceanic and Atmospheric Association has cast doubt on the prospect of heavy Northwest snow storms in the coming months.
The agency said there is a 65 percent chance of an El Niño ocean atmospheric pattern developing in the Pacific Ocean, which is usually associated with milder Northwest winters. Its long range weather forecast also predicts warmer conditions across the West this winter.