Mountain snowpack levels throughout Idaho entered January well below normal, but irrigators can breathe a bit easier thanks to a recent turn toward wetter weather and strong reservoir carryover.
“It’s kind of a mixed bag of conditions,” said Danny Tappa, supervisory hydrologist with the Natural Resources Conservation Service’s Idaho Snow Survey, which is part of USDA. “The good news is that we have above-normal reservoir storage across essentially the entire Snake River Plain. The Owyhee, Salmon Falls, Oakley, Boise River, Upper Snake and Eastern Idaho reservoir systems are all above normal.”
The combined storage in Palisades Reservoir and Jackson Lake is about 140 percent of average, Tappa said.
“There’s a pretty good buffer in the system,” he said.
However, Tappa emphasized that the outlook is a little more concerning to irrigators who have natural-flow water rights, reliant on the current year’s runoff.
Tappa said Central Idaho— including the Weiser, Payette, Boise, Wood River and Lost River basins — has the lightest snowpack, ranging from 60 to 70 percent of normal. Total precipitation for the water year is even worse in that region, ranging from 50 to 60 percent of normal due to a November that was one of the driest month’s on record statewide.
The mountains south of the Snake River — including the Owyhee, Salmon Falls, Bruneau and Oakley basins — recorded near normal snowpack through Jan. 1.
The mountains in the Portneuf Valley had 60 to 70 percent of normal snowpack and water year precipitation, Tappa said.
Further north in Eastern Idaho, the Henry’s Fork, main-stem Snake River, Jackson, Wyoming, and above had about 75 percent of normal snowpack and water year precipitation.
The good news, Tappa said, is that January has started off wet. A large storm should hit much of Idaho this weekend and more wet weather appears to be on the longterm horizon.
“New Years Day brought in a decent amount of snow, and it looks like that will be topped by what’s headed our way on Friday and into next week,” Tappa said, adding cold weather should ensure the precipitation falls as snow. “But we’re so far below normal at this point we’re probably going to need some strong systems to come through. We’re closer to normal but at a point where our deficit is significant.”
Tappa said National Weather Service longterm forecasts have been indicating the regional pattern may be shifting toward wetter weather.
“We’re hopeful by Feb. 1 conditions will have improved relative to Jan. 1,” Tappa said.