snowpack hits 169 percent of average

For a fourth straight year, boaters will enjoy high water on the Snake.

The water content of the snowpack in the Snake River basin has exceeded that of 1997, the year a record runoff surged through Jackson Hole, but dam managers say they have taken ample steps to control flooding.

The snow-water equivalent above Palisades Reservoir is at 168 percent of average, according to the Natural Resources Conservation Service. Above Jackson Lake, that figure is 169 percent, and for the entire basin above American Falls, the water content of the snowpack measures 172 percent of average.

Mike Beus, operations manager for the U.S. Bureau of Reclamation, says the snowpack in the upper Snake has more water than at this time in 1997. In May of that year, “we had a pretty good runoff going,” Beus says. By contrast, relatively little melting has taken place this spring, and inflows to Jackson Lake are at record lows because of continued cold weather.

Dam managers are “a little optimistic” they won’t have to raise releases much higher from Jackson Lake Dam to avoid a flood, Beus says. The agency has been releasing 5,000 cubic feet per second — far higher than normal — for about three weeks, freeing up storage space in the reservoir.

Reservoirs in the upper Snake River basin. The bureau plans to draw down Palisades to nearly empty to catch the runoff. Click to enlarge.

Once the runoff begins, the bureau may up the release to as high as 7,000 cfs, Beus says. But if temperatures don’t increase soon, the agency may have to cut back the flow to avoid releasing too much water too soon.

Beus will be in Jackson to give an overview of planned dam operations on May 19. The meeting starts at 7:30 p.m. at the Antler Motel conference room. River runners and anglers are encouraged to attend.

In June 1997, the second of back-to-back wet years, the Snake River peaked at 38,600 cfs in the canyon, the highest runoff in modern history. The bureau was slow to release water that spring and had to increase the flow rapidly to avoid overtopping the dam.

Last year the bureau also was slow to release water and was widely criticized when a flood ensued. This year managers have been much more aggressive, drawing down Palisades to near-empty and creating 400,000 acre feet of storage in Jackson Lake reservoir.

With the early releases from the dam, it's unlikely the Snake will rage at levels seen in 1996 and 1997. Here is the Canyon Club golf property in June 1996. "Trout Creek" may be floatable this year.

With a release of 7,000 cfs from the dam during peak runoff, the Snake likely wouldn’t come close to matching the floods of 1997, 1996 and 1986. But two key tributaries, the Buffalo Fork and Pacific Creek, could add a combined 10,000 cfs, pushing flows in Grand Teton National Park to nearly 20,000 cfs. In the Snake River Canyon, the runoff could exceed 25,000 cfs.

Much will depend on how fast the snow melts. The later the runoff occurs this spring, the more likely it will be sudden, Beus says.

“A steady warming progression would be really nice,” Beus says, echoing the thoughts of nearly everyone in Jackson Hole.

Although the bureau has taken steps to reduce flooding on the main stem of the river, several tributaries could pose problems for nearby residents. Landowners along Fish Creek have been worried about flood danger, and I seem to recall flooding from Lake Creek in 1997, too.

For geeks who like to keep track of snow stats, total precipitation for the water year, which includes rain last fall and snow this winter and spring, is still 12 to 15 inches below 1997, a sizeable amount, Beus says. More melting had occurred by this point in 1997.

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Posted under Environment, Sports, Weather

5 Comments so far

  1. Brian Remlinger May 6, 2011 8:06 pm

    Jim – Nice summary of the current water situation. I’ll paddle “Trout Creek” with you any day.

  2. js May 9, 2011 11:48 am

    Update 5/9 — Here’s the latest from the Bureau of Reclamation:

    “After rain/snow and warm overnight temperatures this weekend we are increasing the Snake River below Jackson Lake to 7,000 cfs today. This change is made to continue the draft of Jackson Lake and create more flexibility for potential relief from damaging floods that are increasingly likely as this extraordinary snowmelt season progresses. The changes will be staged as 500 cfs increments spaced at 2-hour intervals starting at 9:00 this morning.”

  3. Boat 1 Retired May 10, 2011 4:08 pm

    7000cfs release from the dam in early May! Yee haa! get out and ride that wave. Makes me miss my days on the river.
    Enjoy

  4. Aaron May 10, 2011 11:57 pm

    So we can fish the snake in October?

  5. js May 17, 2011 10:11 am

    The bureau is going up to 8,000 cfs release from the dam by tomorrow.

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