BOISE, Idaho — Above-average mountain snow plus below-average temperatures equals the kind of weather forecast those concerned about Idaho’s water supply like to see in April, especially after much of the winter was dry.
However, what April has brought so far – and what’s coming – probably won’t be enough to fend off a drought this summer.
In a meeting of the Idaho Water Supply Committee, Troy Lindquist with the National Weather Service said Friday that the 8-to-14-day outlook favors below-normal temperatures and above-normal rain or snow for most of Idaho.
“I’ll take this any day over what we saw last spring,” Lindquist said.
The longer-range outlook, going into summer, is a different story. Lindquist said that favors hotter-than-average temperatures and below-normal precipitation, and continuing drought conditions through this spring.
“Not great news there,” he said.
As of Tuesday, April 12, the National Integrated Drought Information System’s U.S. Drought Monitor indicated more than 93% of Idaho was “abnormally dry” and more than 82% of the state was in some form of drought.
The Boise River basin is in the “moderate drought” category, but the rest of southern Idaho is already in severe drought, with impacts that include low river levels, possible curtailments of irrigation water and increased wildfire danger.
Snowpack is the biggest indicator of what kind of water supply to expect, according to Geoffrey Walters with the Northwest River Forecast Center. Walters said from a water-supply perspective, the recent snowfall around the Northwest is “kind of a blessing.”
“Every sports fan loves a fourth-quarter comeback,” Walters said, adding that a “comeback” to normal water-supply levels this year is unlikely. “It's going to take a lot more of what we've seen in the last week.”
Snowpack has been compared to Idaho’s water “bank account.” While anything helps, the reports presented at Friday’s Water Supply Committee meeting indicate things are going to be tight for Idahoans who need water in the summer, whether that’s for irrigating farm crops or boating on the reservoir.
In southern Idaho, snowpack for the Boise River and Snake River basins is well below normal, said Erin Whorton with the USDA’s Natural Resource Conservation Service, which conducts monthly snow surveys during the water year.
The Boise River basin snowpack is 65% of normal, and on track for the fifth-lowest water year in the past 40 years, Whorton said.
Jon Rocha with the U.S. Bureau of Reclamation’s Boise Office said “there’s not a strong likelihood” of any reservoirs in the Boise River basin filling up to 100% of capacity this year. Further north, in the Payette River basin, Lake Cascade has a “slightly better chance” than Deadwood Reservoir of filling this year, Rocha said. As of Friday, the Boise River system was at about 60% capacity, with reservoirs still filling. The Payette River system was at 62%; its reservoirs also were still filling.
The Snake River basin, at 75% of normal, will not have an adequate supply of irrigation water, and the Big Wood River basin, at 39% of normal, will “definitely” have water-supply issues this year, Whorton said. However, she added, “this year is better than last year.”
The amount of water stored in reservoirs can help offset the impacts of a low-water year -- if snowpack and runoff were more plentiful the previous year. That’s not the case in 2022.
Some farmers in eastern Idaho, a major potato and sugar beet growing region, “will run out of water this year,” said Jeremy Dalling, reservoir operations lead for the Bureau of Reclamation Upper Snake Field Office.
Dalling presented data showing the Snake River basin above south-central Idaho’s Milner Dam will have the third lowest water year in the past 25 years. In the worst years, Dalling said, canals – and irrigation season – closed early, sometimes in early September.
“We’re right on the borderline of those years when people are not able to finish out the season,” Dalling said.
The Idaho Water Supply Committee has another meeting scheduled for 9 a.m. Thursday, May 12, at the Idaho Water Center in Boise.
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