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Storms continue to blast Idaho, Snowpack levels build to average-above average levels

By: Jake Putnam & Steve Stuebner
Published in Blog on  February 10, 2020

Boise--In the past 4 weeks, Mores Creek Summit gained nearly five feet of snow as storms hit with regular frequency since January 1st. Other parts of the state have seen even more snowpack the past few weeks.

Above-average precipitation in January and the first part of February has boosted Idaho snowpack levels to more than 100 percent statewide, except for the Big Wood, Little Wood, and Big Lost Basins. 

Good precipitation comes on top of high reservoir carryover across southern Idaho. The bump in precipitation, combined with strong reservoir carryover, caused agency officials to increase streamflow runoff predictions for the coming year. 

“We’ve had some big gains in the last 30 days,” said Troy Lindquist, a forecaster for the National Weather Service in Boise. 

Monthly precipitation ranged from 110-130 percent of normal in most of Idaho statewide, Lindquist said. 

The only basins that have below-normal snowpack (snow water equivalent SWE) are the Big Wood Basin 81 percent of normal, Little Wood 69 percent, and Big Lost 74 percent of normal. 

As of Feb. 1, Idaho normally has received 60 percent of the snowpack for the winter. 

Upper Snake snowpack is 

106 percent for the Henrys Fork Basin 

110 percent Snake River above Palisades Reservoir 

118 percent in the Bear River Basin 

Mid-Snake snowpack is well above-normal in the Goose Creek drainage 134 percent and Salmon Falls area 122 percent of normal. Owyhee Basin is 126 percent of normal, and the Bruneau is 119 percent of normal. That means the spring river floating conditions should be good in those two basins. 

Upper Snake Water managers say reservoir releases will begin out of Palisades later this month, and continue down the Snake River at American Falls and Minidoka, with about 1,200 CFS to be released below Minidoka, and those flows will be used by the Idaho Water Resource Board for recharging the Eastern Snake Plain Aquifer in recharge basins below Milner Dam in the Magic Valley region. 

Overall, coming into the winter and water year, beginning Oct. 1, soil moisture was at record low levels because of a dry November, officials said. That may affect runoff next spring. 

Upper Snake reservoir storage: 

136 percent of average and 96,000 a.f. above 2019, according to the Bureau of Reclamation. 

“We have extremely good storage in the Upper Snake,” said Jeremy Dalling of the BOR in Heyburn. 

Feb. 1 streamflow runoff forecasts call for 100 percent of average runoff on the South Fork Snake River at Heise or 3.6 million acre-feet. 

99 percent of normal runoff from Jackson Lake 

98 percent of normal runoff from Island Park Reservoir 

90 percent from Ririe Reservoir 

76 percent from the Little Wood 

Here’s the latest BOR teacup diagram for reservoir storage in the Upper Snake: https://www.usbr.gov/pn/hydromet/burtea.html

Boise-Payette reservoir system – Ryan Hedrick, BOR 

Forecasting 85 percent of normal runoff in the Boise River system. 

The reservoir carryover is 116 percent of average. 

Arrowrock is 85 percent full 

Anderson Ranch 67 percent full 

Lucky Peak 23 percent full … they keep Lucky Peak at a low level at the request of IDFG to allow elk to move through the area during the winter before filling the reservoir. Now that Arrowrock is almost full, they will be filling Lucky Peak. 

Carryover is high enough that they expect the Boise River reservoir system to fill. 

Cascade Reservoir is 62 percent full and Deadwood Reservoir is 59 percent full. BOR expects those reservoirs to fill. 

BOR teacup graphic on Boise and Payette reservoir operations: https://www.usbr.gov/pn/hydromet/boipaytea.html

Owyhee Reservoir has 147 percent of an average carryover “Great carryover” said Ryan Hedrick of the BOR. It’s 72 percent full now, and it’s expected to fill. 

Idaho Power officials said that cloud-seeding activities have been tracking above-normal this winter because of multiple storms and more cloud-seeding opportunities. They have had 36 active seeding days so far this year, and they typically average 10 days/month. 

Cloud-seeding operations may be suspended in the Upper Snake region in the next several weeks if snowpack remains high and precipitation stays above-normal … they will track suspension criteria and take action as necessary, Idaho Power officials said. 

Shawn Parkinson at Idaho Power would be the contact for more information about cloud-seeding. 

In Northern Idaho, there were record increases in snowpack seen in January, bringing the Clearwater Basin to 109 percent of normal, Spokane Basin 106 percent of normal and Northern Panhandle 116 percent of normal.

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