Mother Nature has some catching up to do if Oregon expects to have adequate water supplies heading into summer.
Snowpack is lagging significantly across the state heading into 2018, at just 42 percent of normal levels. That is a stark contrast to last year, when January snowpacks surged to 124 percent of normal levels statewide.
Despite another La Niña winter — which usually predicts colder and wetter weather in the Pacific Northwest — temperatures are actually hovering above normal, especially in Southern Oregon. The highest levels of snowpack are in northeast Oregon, where the Umatilla, Walla Walla and Willow basins are just 55 percent of normal, and the Grande Ronde, Powder, Burnt and Imnaha basins are 53 percent of normal.
Scott Oviatt, snow survey supervisor for the Natural Resources Conservation Service, said it is still too early to tell what the water year will look like, but he would like to see more snow accumulating in the mountains.
“The closer to normal conditions, the more assurances you have adequate water supplies closer to irrigation season,” Oviatt said. “Obviously as time passes, we’ll have a better feel of what the trends and storm impacts look like.”
Not only is snowpack below normal, but overall precipitation is also down statewide at 89 percent of normal, compared to 105 percent of normal three weeks ago. The difference between this year and last year’s “snowpocalypse” has left Oviatt and weather forecasters scratching their heads.
“We’re really seeing this extreme variability in the last five to 10 years, where these trends don’t represent what we’ve seen historically,” Oviatt said.
Marilyn Lohmann, hydrologist with the National Weather Service in Pendleton, Ore., said each La Niña has its own spin, and the odds of having two winters like 2017 back to back are usually pretty slim.
Over the next three months, Lohmann said, the weather should shift back to normal temperatures and precipitation. “Sometimes we do get the bulk of our snow in that February and March time frame in the mountains,” Lohmann said. “It does look like hopefully we will be able to regain some of what we’ve lost.”
While statewide stream flows were less than 65 percent of normal at the end of December, the Oregon Water Resources Department says reservoir levels are above normal for this time of year, which may mitigate some impacts of a drier-than-usual winter.
According to OWRD, central Oregon reservoirs are between 44 and 88 percent of capacity, and eastern Oregon reservoirs continue to hover between 36 and 65 percent of capacity. Willamette and Rogue basin reservoirs also remain on track to fill.