By Jim Stanford on May 27, 2012
Cold Wet Days has done it again, bringing a foot of snow to the high Tetons.
With the Jackson Hole Aerial Tram reopening for “summer” this weekend, skiers are carving powder in Cody Bowl and having a slightly better time than the kayakers paddling in the Wyoming Whitewater Championships.
The new snow will prolong what was shaping up to be a quick, early runoff on the Snake River. Mike Beus, operations manager for the U.S. Bureau of Reclamation, said Friday he will hold the release from Jackson Lake Dam at 5,000 cubic feet per second for another 10 days to 2 weeks.
“The plateau at 5,000 will last much longer than we had anticipated,” he said.
Beus had given a presentation in Jackson on May 17 in which he outlined a plan to scale back the release beginning this weekend. As of Saturday, Jackson Lake reservoir was filled to 96 percent of capacity.
Because of an unusually warm, dry spring, the bureau forecast a quick runoff and low flows on the Snake this summer. Beus compared this year to 2000 and 2010 and said it was likely that the dam release would be about 1,500 cfs from July through September — roughly half of what it was last year.
“What a difference a year makes,” he said, in comparing 2011′s massive runoff to this year’s early melt. Already in Idaho, he said, irrigation demand has been higher than at any point last summer.
Beus said he expects to drain American Falls and Palisades reservoirs downstream while storing as much water in Jackson Lake as possible.
During the meeting, fishing guides expressed concern that a hot, dry season could force the bureau to raise the release from Jackson Lake come August to meet irrigation needs — thereby hampering the fishing just as prime time for guiding arrives.
Beus acknowledged that possibility but said he would try to avoid a late-season bump in flows. “We share your concerns,” he said.
After Jackson Lake fills and runoff begins to subside, Beus will regauge his estimate of irrigation needs and try to set a constant flow for the summer, he said. He sketched out two scenarios in which the release could be higher than 1,500 cfs: a quick return to warm, dry weather, which would boost irrigation demand, or continued cold and snow, which would give him less time to draw down the reservoir to a required level for flood control.
On Friday, Beus said he does not expect the cold, wet weather to last long. The forecast calls for gradual warming, he said, which will moderate the runoff.
Barring a radical convergence of weather — hot temperatures mixed with heavy rain, for instance — it’s possible the Snake already has peaked for the year. The flow crested 9,000 cfs at Moose and 14,000 cfs in the canyon above Alpine on May 22 — little more than half last year’s peak.
In terms of total volume, 2011 was the third-highest runoff on the Snake in 100 years, trailing only 1997 and 1996, Beus said. Residual effects were felt throughout the winter, with increased soil moisture and recharging of groundwater. Springs had higher flows, putting more water in Jackson Lake.
Prior to this week’s cold spell, the snowpack at Lewis Lake Divide in Yellowstone — a key gauge for runoff — would have been depleted in five or six days, Beus said. However, the Buffalo Fork, an upper tributary of the Snake, was just beginning to rise, with nearly 16 inches of water remaining in the snowpack of its headwaters on Togwotee Pass.
Update 6/5: The snow, coupled with yesterday’s broiling heat, has fueled the runoff faster than anticipated, prompting the BuRec to raise the release at Jackson Lake Dam to 6,000 cfs. Flows today are 12,000 cfs at Moose and 18,000 in the canyon. The river ought to peak later today or tomorrow.