Early snowfall welcome, but a lot more needed

By Sean Ellis

Idaho Farm Bureau Federation

POCATELLO – Idaho’s new water year is off to a great start thanks to the recent snowstorms, and mountain snowpack levels in all Idaho basins are well above normal.

But it’s also really early in the water year, which began Oct. 1, and a lot more mountain snow is needed to ensure farmers, recreationists and others who depend on the state’s reservoirs have a decent water supply in 2023.

Idaho’s mountains typically don’t have a lot of snow this time of year so the current snowpack levels amount to a little on top of a little. That can deceptively make snowpack percentages seem enormous when compared to historical levels.

For example, collective snowpack levels in the Willow-Portneuf-Blackfoot basin were 498 percent of normal on Nov. 14, according to the Idaho SNOTEL report. 

In reality, measuring sites in that basins have a handful of inches of snow.

Snowpack levels were 153 percent of normal in the important Snake River basin, which feeds the critical Upper Snake River reservoir system, which holds 4 million acre-feet of water, enough to supply well over 1 million acres of farmland in eastern and southern Idaho with irrigation water.

That sounds like a huge amount of snow. But again, most measuring sites in the Snake River basin actually only had several inches of snow on Nov. 14. 

That’s a long way from what the Snake basin will need when Idaho’s typical mountain snowpack season ends April 1, said Tony Olenichak, watermaster for Water District 1, which is Idaho’s largest and encompasses the Upper Snake system. 

He said he usually doesn’t pay much attention to snowpack levels until about the first part of January but at the same time, this year’s early snowfall is certainly a good start.

“It really is too early to use the current snowpack as an indicator of how next year’s water supply will look … but it’s better than not having any at all,” Olenichak said.

Upper Snake reservoirs are very low right now and the basin will need an above-average snowpack this winter, he said. A wetter-than-average spring, which would delay the need for irrigation water to be released, would also help, he added.

“That’s the combination we’re looking for to have an average water supply next year,” Olenichak said.

Snowpack in the Boise River basin was 269 percent of normal on Nov. 14.

That’s certainly welcome news but the snow has to keep coming this winter to ensure a decent water supply for irrigators in 2023, said Bob Carter, manager of the Boise Project Board of Control, which provides water to five irrigation districts in southwestern Idaho.

“It’s an earlier start than normal, which is good,” he said. “We just need it to keep coming.”

Southern Idaho, where most of the state’s agricultural production occurs, is mostly a desert and farmers and ranchers there are dependent on Idaho’s reservoirs to get by during the hot, dry summer months.

Rainfall is great for improving soil moisture levels but it’s mountain snow that fill the reservoirs, which are the lifeblood of agriculture in southern Idaho.

During the Nov. 9 Idaho Water Supply Committee meeting, water exports said most basins in southern Idaho will need at least 100 percent of normal mountain snowpack this winter to fill nearly empty reservoirs. The driest basins will need 120-150 percent of normal snowpack.

The Boise basin is an exception and bright spot, they said, because Boise River system reservoirs ended the 2022 water season with good carryover. Because of that, the Boise reservoir system could potentially fill with at least 70 percent of normal snowpack this winter.

The Upper Snake reservoir system is currently at 19 percent capacity.

“The Snake (basin) will need 12 percent of normal snow to fill the system,” said Jeremy Dalling, a hydrologist with the U.S. Bureau of Reclamation’s Burley office.