Snowpack above normal in Washington, light elsewhere
By JOHN O'CONNELL
Mountain snowpack throughout Idaho, Oregon and Northern California is lighter than normal following nearly 2 1/2 months of relatively dry weather.
Though Washington's statewide snowpack is still well above normal, water managers say they'd like to see more precipitation in the eastern part of the state.
For Western agriculture, having an adequate snowpack that releases gradually in spring is vital for replenishing soil moisture, bolstering stream flows and filling irrigation storage reservoirs.
Throughout the Pacific Northwest, a dry January followed an extremely wet December. Dry weather has persisted through February and into March.
Through March 11, Idaho's mountain snowpack was 84 percent of average, with precipitation for the water year beginning Oct. 1, 2012, at 97 percent of average, according to the Natural Resources Conservation Service.
Oregon's snowpack was 94 percent of average, with water year precipitation at 99 percent of normal.
Northern California's snowpack dipped to 76 percent of normal, with precipitation at 85 percent of normal for the water year.
Though Washington's snowpack was 114 percent of normal, with 104 percent of normal water-year precipitation, snowpack in eastern Washington ranges from 90 percent of average to normal.
Idaho NRCS water supply specialist Ron Abramovich said February precipitation was below average throughout Idaho, aside from the Salmon Falls and Bruneau areas. The dry February reduced southern Idaho snowpack levels by roughly 10 percent.
"Currently across the state, (snowpack) ranges from 70 to 105 percent of normal," Abramovich said.
At Heise, below Palisades Reservoir, an important point for determining Snake River water rights that marks where the system stops accumulating significant amounts of water, snowpack was 77 percent of normal.
Steve Howser, general manager of eastern Idaho's Aberdeen-Springfield Canal Co., said the Heise runoff forecast is near his "anxiety point." Though he's helped by strong carryover from last season, he'll likely require slightly more notice for members' water deliveries, hoping to achieve a 15-25 percent reduction in unused water leaving his system.
"While I think I've got a good chance of having a sufficient water supply, I think it will only be sufficient if I manage more tightly than I would in a normal water year," Howser said.
A gradual release of snowpack is likely this spring. Though Abramovich expects mid-March weather reaching 62 degrees will "ripen" snowpack for melting below 6,000 feet, he expects higher snowpack to remain intact. Based on three similar water years, Abramovich said the long-term weather outlook calls for a cool but dry spring.
He said it's also good news that strong base flows that started in April 2009 appear to be continuing this season, and American Falls Reservoir in southeast Idaho is forecast to fill by early April.
Washington NRCS water supply specialist Scott Pattee said long-term predictions call for below-average precipitation in Northern California, Oregon and Southern Idaho, with Washington listed as having equal chances of above- or below-average moisture. Pattee said a cool spring will likely be followed by a warmer-than-normal summer, which could have ramifications for storage water carryover.