After an erratic winter, Oregon snowpack rebounds
四月 10, 2020
An erratic winter for Oregon's mountain snowpack appears to be ending on a high note.
Recent snowstorms have lifted the state's overall average snowpack to 109% of normal as of April 8, compared to 91% of normal at the beginning of March, according to the USDA Natural Resources Conservation Service.
The highest totals are in Eastern Oregon, with the Umatilla, Walla Walla and Willow basins measuring 143% of normal; the Grande Ronde, Burnt, Powder and Imnaha basins at 126% of normal; the John Day Basin at 127% of normal; and the Owyhee Basin at 113% of normal.
The Willamette Valley — home of 60% of Oregon's population and nearly half its gross farm sales — is also above average for snow, at 110% of normal.
Agriculture relies on snowpack to act as a natural reservoir heading into the spring and summer irrigation seasons, gradually replenishing streams and filling reservoirs for farms and ranches to water their crops and livestock.
Snowpack in Oregon got off to a slow start in November and December before rebounding significantly in January, rising as much as 64% in the Hood, Sandy and Lower Deschutes basins. February and early March brought another round of warmer and drier weather, which turned to snow again by month's end.
Scott Oviatt, snow survey supervisor for NRCS Oregon, said snowpack typically peaks in April and May across the state. "The key," he said, "is going to be how quickly or rapidly that snowmelt runs off."
"We don't want it to come out in a sudden flush, with warm temperatures or rain on snow," Oviatt said.
That sudden flush was felt especially hard earlier this year, when warmer weather and rain-on-snow contributed to massive flooding on the Umatilla and Walla Walla rivers in northeast Oregon and southeast Washington, damaging farms and homes.
With so much snow at higher elevations in the region, Oviatt said local water managers are undoubtedly keeping a close eye on the situation. Conversely, if the snowmelt happens more slowly and gradually, it could be a boon for irrigators.
"It represents a lot of potential water for runoff," Oviatt said.
Despite relatively strong snowpack, the optimism is tempered by lower-than-normal total precipitation, Oviatt said, which remains at 80% statewide.
The driest areas are in southwest Oregon, where the Rogue and Umpqua basins are at 69% of average precipitation and the Klamath Basin is at 68%. Gov. Kate Brown has already declared a drought emergency in Klamath County.
Stream flows are expected to range between 42% to 90% in the region, and average to above-average in basins farther north.
Reservoir storage, meanwhile, is a mixed bag around the state. As of April 1, Clear Lake in the Hood, Sandy and Lower Deschutes basins was storing less than half the normal amount of water for this time of year. Reservoirs in the Rogue and Umpqua were also filling well behind schedule at 71% of average.
Elsewhere, reservoirs range between 80% and 116% of normal, and up to 121% at Lake Owyhee in southeast Oregon.
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