PORTLAND — It may have taken a bit longer than usual, but snow is finally starting to fly in the mountains across Oregon and Washington.
That is good news for farmers and ranchers who depend on ample snowpack to replenish streams and fill reservoirs heading into the summer irrigation season.
In just two weeks, Oregon’s snow water equivalent — the amount of water contained within snowpack — has jumped from 45% of normal to 79% of normal statewide, thanks to recent winter storms dumping several feet of new snow in places like Mount Hood and Santiam Junction in the Cascade Range, and Emigrant Springs in the Blue Mountains of northeast Oregon.
The biggest improvement has come in the Hood, Sandy and Lower Deschutes basins, which were at 26% of normal snowpack on Dec. 30 and are now at 90% of normal as of Jan. 14. The Willamette Basin also increased from 26% to 83%, and the Umatilla, Walla Walla and Willow basins rose from 43% to 89%.
Hydrologists with the USDA Natural Resources Conservation Service calculate “percent of normal” by measuring the current snowpack against a 30-year average from 1981-2010.
The NRCS released its first Oregon Water Supply Outlook Report for 2020 on Jan. 9. At the time it was published, the state was grappling with an especially dry start to the water year — November, typically one of the wettest months of the year, set records for lowest precipitation at 34 out of 90 snowpack telemetry sites monitored by the agency.
“The next three months will be critical in determining water supplies for the summer,” the NRCS reported.
So far, so good as Old Man Winter has returned with a vengeance in January.
Last year saw something similar unfold in Oregon. With snowpack lagging into February, a series of storms pummeled the mountains and boosted snow water equivalent by 20-30%. Coupled with heavy rains in April, conditions offered a much-needed reprieve from drought.
Snowpack is a crucial source of water for farms, especially in Eastern Oregon where it rains far less than it does west of the Cascades. As snow melts, it trickles down into creeks and rivers, sustaining healthy stream flows while providing irrigation supplies for crops and livestock.
While the latest snowstorms are an encouraging sign, there is still a long ways left to go.
Scott Oviatt, snow survey supervisor for the NRCS in Portland, said conditions are a vast improvement over the end of December, when stream flows were just 53% of normal. But he said it remains to be seen what the next three months will bring.
“Those are the questions that are still out there,” Oviatt said.
The National Oceanic and Atmospheric Administration’s Climate Prediction Center continues to forecast a higher probability of above-normal temperatures over the next three months across most of Oregon and Washington, along with an equal chance of high or low precipitation.
Washington’s snowpack was similarly bleak at the start of the new year, at just 47% of normal statewide. It too has rebounded dramatically, up to 88% as of Jan. 14.
The South Puget Sound, Lower Yakima, Lower Snake, Spokane and Upper Columbia basins are all at or near average for snow water equivalent, after they were no higher than 65% of normal a few weeks ago. Like Oregon, SNOTEL sites in Washington have experienced several feet of new snow in the Cascades.