The 2023 water year is off to a good start in Idaho, State Conservationist Curtis Elke and his team reported in their first snow survey of the year, released Jan. 10.
Snowpack through much of Idaho is already halfway to reaching normal peak snowpack conditions, the report states. But, it cautions, “last year serves as a good reminder that continued snowfall is required to reach normal peak snowpack conditions and ensure adequate springtime runoff.”
Likewise, the report’s authors point out in order for Idaho to fully recover from drought “we need ample snowpack to replenish depleted reservoirs and provide sufficient springtime natural streamflow.” An estimated 72 percent of land in Idaho is considered to be in a moderate to severe drought stage and the remainder of the state is abnormally dry, the report states. Precipitation for the winter needs to total between 120 and 160 percent of normal to end those conditions in the Upper Snake and Wood river basins, Elke’s team wrote. They’re optimistic that may happen this year.
According to the report, more than 70 percent of the surface water in Idaho comes from mountain snowpack, but the water supply also relies on the timing of snowmelt, soil moisture, spring precipitation and shallow groundwater conditions.
“The wet, cold start to ... winter gives us rose-colored glasses to be moderately optimistic for ample water supply conditions at this juncture,” the report states. The writers remind readers that reservoir storage is below average in much of Idaho and the effects of a multi-year drought linger in the state.
The National Oceanic and Atmospheric Administration’s Climate Prediction Center forecasts another La Niña winter, marking just the fifth time since 1910 for three consecutive La Niña winters.
“We will have to ride this triple-dip La Niña winter rollercoaster all the way to spring to find how conditions will pan out,” the report states.
Snowpack across Idaho is above normal, according to the report, ranging from 121 to 172 percent of normal. That’s due in part to the fourth-coldest November on record hitting a couple of months ago. Cold temperatures preserved early-season snowfall around Idaho, getting an early start to building snowpack.
Total precipitation for the water year to date is normal to above normal for all basins south of the Clearwater Basin, due to November snow and cold and a wet December. Precipitation is slightly below normal in the Clearwater and Panhandle basins.
Widespread rain at Christmas didn’t negatively affect mid- and high-elevation snowpack, the report states. “The snowpack was cold enough that any rain or meltwater generated during those storms refroze within the snowpack rather than being swept downstream.”
October brought cool, wet weather to the Salmon River Basin, which continued into November and December, resulting in total water year precipitation already reaching 100 percent of normal, the report shows.
Snowpack in the Salmon River Basin is 125 percent of normal and it’s been holding above normal since the first snow in late October. Basin-wide snowpack has reached 50 percent of the typical peak snowpack. “It’s a promising start to the snow season in the Salmon River Basin, but last year was a good reminder that quick starts don’t always yield optimal finishes,” the snow survey team wrote.
Plentiful precipitation arrived in the Lost and Wood river basins in the form of strong storms in November and especially late December, according to the report.
Like last year, these basins have received the most water year precipitation relative to normal in the state. Precipitation ranges from 120 to 145 percent of normal and snowpack ranges from 150 to 170 percent of normal. The typical peak snowpack occurs in April in these basins. If now continues to accumulate at above-normal rates it will help remedy drought conditions, the report states.
Mackay Reservoir storage is 97 percent of normal. The Little Wood Reservoir stands at 80 percent of normal while Magic Reservoir holds just 49 percent of its normal water.