Idaho’s snowpack is imperative to the growing season. Many producers are worried about how snowpack levels may affect water supply later in the year. Could Idahoans be facing another drought?
Jim Ekins, the area water educator at the University of Idaho, helps run The Confluence Project, a high school watershed science program. Multiple northern Idaho high schools send students to participate in the program, where they learn about jobs such as hydrologists and field technicians, while hands-on learning science practices. Ekins shares, “One of the activities is a field trip to Lookout Pass to dig snow pits and measure the snow-water equivalent. Last Thursday [Feb. 6] we were there, and they had around 140 centimeters of snow, with between 20 to 40 percent water, at 4,500 feet elevation.”
Along with observing current snowpack and snow-water equivalents, Ekins compares data from 40 to 75 years ago. There is a 40-plus-year trend of continuously decreasing snow-water equivalent in Idaho’s mountain snowpack. The Northwest and Intermountain West are receiving the average overall precipitation throughout the year; however, it is increasingly falling as rain, which results in not being stored as snowpack. The spring freshets, which occur from the spring and early summer snowmelt after the April 1 snowpack maximum, are happening about three weeks to one month earlier than it would have 50 to 75 years ago. Ekins states, “Our critical low and middle-elevation snowpacks are becoming less predictable, so managing water supply and maintaining water resilience for communities is becoming a more difficult balancing act.”
When asked about the levels of carryover water available from last year, Erin Whorton, the water supply specialist with the Natural Resources Conservation Service, shares that the Upper Snake reservoir system had about 250 thousand-acre feet (KAF) less water compared to last year and the Boise reservoir system had about 110 KAF less than last year. The Oakley, Magic and Mackay reservoirs all had more carryover water this year than the previous year, while the Salmon Falls and Little Wood reservoirs had less carryover than the previous year.
Image by Jim Ekins.
How do these statistics affect water users? It is more likely for water users who have carryover storage in their contracted space to see their storage contracts receive a full storage allotment during drought. However, if the reservoir system does fill, then all of the carryover from the season before is canceled and the contract holder receives a full allocation. Most of the time, the carryover storage is most useful when water users are entering into a drought, along with making the reservoir system easier to fill.
David Hoekema, a hydrologist for the Idaho Department of Water Resources (IDWR) shares, “The 2024 water year started off with average carryover in the Upper Snake Basin. Most of this carryover was positioned high up in the system, which is the optimal location for carryover storage. For example, because Jackson Lake was 77 percent full at the end of the water year, all the excess runoff in the system has been stored in Palisades, which is filling faster than normal. We are in a good position to face a drought year, which is becoming increasingly unlikely.”
Snowpack distribution varies across the different basins in Idaho. According to Whorton and the National Water and Climate Center snowpack map, the snowpack is highest in western to central Idaho, compared to the 30-year normal. The Weiser, Payette, Boise, Big Wood, Big Lost and Salmon basins have above-normal snowpack. The basins in southern and eastern Idaho have about normal snowpack, whereas the Coeur D’Alene – St. Joe basin has below-normal snowpack.
Hoekema explains, “Northern Idaho has been struggling with snowpack development. Because of the lower elevations in northern Idaho, they are more impacted by warming wintertime temperatures. Benewah County has had 90 percent of their typical precipitation, but the snowpack in mountains is bordering on moderate drought conditions.” The cold weather that has been occurring recently could help significantly in developing snowpack in those areas. Hoekema shares, “I think we have a good chance that this region will pull out of drought this year. Elsewhere, I don’t see any significant concerns related to the snowpack, given we are in the midst of an active weather pattern.”
Erin Whorton measures the snowpack in the Boise Basin. Image by Carly Whitmore.
Compared to last year’s snowpack, Kootenai/Pend Oreille, Lower Snake River and Middle Snake River basins are doing significantly better than last year, whereas the Upper Snake River and Bear River basins are fairly similar to the previous year. When asked about having any concerns for the 2025 growing year, Whorton says, “A wet spring is important for water supply in Idaho, so I am hoping that comes to fruition. I don’t have any particular concerns right now because the situation with our snowpack changed rather significantly compared to last week.” At the end of January, much of the state was in a snow drought, but that situation has positively changed.
Overall, most of the reservoir storage levels are currently near normal across Idaho. According to Hoekema, Big Lost basin is 111% of normal for this time of year and is 72% of the way toward its peak snowpack, which doesn’t typically occur for about another two months. One more big snowstorm could result in the Big Lost Basin having a snowpack in excess of the median peak. In contrast, Salmon Falls Creek will need a higher-than-normal snowpack in order to reach its normal reservoir storage level. It could be detrimental to the water supply if there is another prolonged dry spell like there was in January.
Hoekema notes, “We have almost two months until snowmelt is likely to start, so a prolonged dry period in March and April could result in drought. But generally, we are in a much better spot than last year and the probabilities, based on historical conditions, are leaning toward normal to pluvial conditions in southern Idaho and drought recovery in northern Idaho.”
All in all, as of the middle of February, things are looking more positive in regards to snowpack and reservoir levels. As far as snow-water equivalent decreases through the decades goes, Ekins states, “We are a resilient state and will find ways to figure out how to manage these into the future.” Let us all hope for another good snowstorm or two, and look forward to another prosperous growing year.
