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The Sewell Ranch Levee held the Snake River at bay Monday evening as swelling runnoff caused the river to overflow its banks near the Sewell Ranch on Fall Creek Road south of Wilson. PHOTO COURTESY TETON COUNTY

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County residents dodged serious flooding Tuesday when releases from Jackson Lake Dam pushed the Snake River to the brink of levees where it stopped as tributaries receded.

A welcome dose of sunshine and clear skies – the first June day with no precipitation in Jackson Hole – helped steady the river level. Pacific Creek flows dropped 1,500 cubic feet per second and the Buffalo Fork dropped 1,000 cfs, helping the Snake level out at about 20,000 cfs at the Swinging Bridge gauge just south of South Park.

“It has been pretty concerning in terms of how fast the water came out,” Teton County Commissioner Hank Phibbs said of the runoff, spurred by rain. “Then, combined with increased flow coming out of the [Jackson Lake] dam, it gave us some pretty high water levels.”

Earlier in the day, county crews shored up a levee south of Wilson as Phibbs called the Bureau of Reclamation asking operators to shut dam gates, located north of Jackson in Grand Teton National Park. Instead, the flow in some tributaries went down and agency held dam releases steady.

Releases from the dam, boosted to a peak of 10,520 cfs on Monday, came as inflows into Jackson Lake reached the third-highest level ever. The reservoir behind the dam filled Monday, and even as dam tenders opened the gates then, the water behind it rose into a 1-foot surcharge level reserved for emergencies.

“We had no clue this was coming,” U.S. Bureau of Reclamation hydraulic engineer Art Hill, in Burley, Idaho, said Tuesday. “We started out the year at 50 percent of average snowpack.

“Then all of the sudden the cold weather came and it just held up there. Then it starts warming up and the rain on the snow brought it down.”

The reservoir level was “just a hair over” the “full” elevation of 6,769 feet above sea level, Hill said Tuesday afternoon.

The main flow into the lake, the Snake River draining southern Yellowstone and the Teton Wilderness, dropped dramatically from a high of 11,000 cfs on Monday to about 6,500 cfs on Tuesday. That appeared to reduce the possibility that the bureau would have to further increase flows from the dam, an eventuality that would have come within five days had Monday’s conditions persisted, Hill said.

The Snake washed away some big rocks on the face of the levees south of Wilson. County workers dumped loads of fill and boulders to reinforce the Taylor Creek Three and Sewell dikes.

County emergency personnel, Bridger-Teton National Forest and Grand Teton National Park officials were on alert Tuesday, and a Civil Air Patrol survey showed water lapping at the doorstep of a home off Meadow Road. A boulder rolled to a dangerous spot on the trail into Grand Teton’s Garnet Canyon, while float trip companies, worried about safety, canceled river trips.

“There wasn’t enough water to come beyond the big rocks, but it started some pretty significant erosion,” County Commissioner Leland Christensen said after spending the morning observing the work.

Water ran through cottonwoods and across Fall Creek Road in places near the Stanley Resor family’s Sewell Ranch. Corrals there flooded.

The county has hired extra workers to check on the levees around the clock. Despite the receding tributaries north of Jackson, the National Weather Service advanced hydrologic prediction service forecasts a peak at the Swinging Bridge gauge of about 23,000 cfs – above Tuesday’s high flow – for early today.

On the Bridger-Teton National Forest, officials reported no substantial flooding but did see extremely high, fast-moving water on the Greys River and some erosion that impacted the adjacent road.

“I was out in the field yesterday and this humongous boulder fell on the Greys River Road,” Bridger-Teton spokeswoman Mary Cernicek said. “We’re asking people to really reduce their speeds. There’s a lot of clay in the soil, and [the combination of moisture and traffic] really messes [the road] up.”

Cernicek warned drivers and hikers to be careful at creek crossings, because the water is so swift and deep it could be dangerous.

In Grand Teton National Park, officials issued a flood watch.

“We’re tracking the conditions, especially on the Snake River,” spokeswoman Jackie Skaggs said. “[The water] is up to the vegetation on the sides of the bank.

“Moose, that would be the place where we would likely see [flooding], because we’re in a bit of a low spot,” Skaggs said. “No other place in the park has the threat that Moose does.”

Engineers are also checking bridges at Moose, the Buffalo Fork and Pacific Creek in the park.

Thursday, park officials will temporarily close Garnet Canyon and Surprise/Amphitheater Lakes trail because of the threatening boulder. The trail will be closed from 8 a.m. until around noon.

“It’s a fairly good-sized boulder,” Skaggs said. “Because of melting and erosion [the boulder] let go and rolled downslope. We want to roll it on down the slope away from the trail so it doesn’t pose a safety hazard for hikers.”

The high water disrupted the valley’s river guiding industry. Some companies closed Tuesday, partly due to debris in the Snake. One company was offering whitewater trips but taking extra precautions.

Mad River Boat Trips senior guide Ian McIver said his company sent extra safety boats and kayaks downstream to catch any passengers who may go overboard.

“The current is moving real fast,” McIver said. “Our main concern with the temperature is if someone has a long swim, they might become hypothermic.”

On Monday, inflow into Jackson Lake reservoir, including Teton Range drainages that are not measured by instruments, averaged an estimated 15,661 cubic feet per second, Hill said.

Releases from Jackson Lake Dam should remain steady at 10,000 cfs for at least a few days, Hill said. Bureau officials want to lower water levels in the reservoir in case another heavy runoff from a storm occurs.

“We want to maintain some space [in the reservoir] in case we get a big run-off so we don’t have to increase flows like we did,” Hill said. “There’s still a lot of snow left on higher elevations.”

The full reservoir elevation is 6,769 feet above sea level. At that level, 41 feet of water is stored behind the dam.

Late Tuesday night, the reservoir contained 843,690 acre-feet of its 847,000 acre-foot capacity, according to a Bureau website.

The reservoir’s surcharge area adds an additional 26,000 acre feet, or 3 percent, of storage, Hill said.

The releases are drastically higher than the bureau forecast in May. Then, the bureau predicted a peak outflow of 5,000 cfs from the dam by June 13, which would slowly be reduced to a steady flow of 2,800 cfs for the remainder of the summer. Now, Hill said, river users can expect flows to remain around 5,000 cfs for several weeks even after reservoir levels are lowered.

“Then there’s no guarantee, but there’s a good chance they could stay higher than anticipated for rest of the month,” he said. “We’re going to have inflows coming all this month, but hopefully not like they are right now.”

Phibbs hoped for relief. “If [the dry weather] continues, I think we’re going to survive the runoff season intact,” he said.

Even though no rain fell in Jackson Tuesday, the National Weather Service issued a flood watch for the mountains and valleys of Teton County until Wednesday afternoon. A watch means conditions are favorable for flooding.

Sand bags are available to the public for pick-up at the Road and Levee facility in Adams Canyon.

The National Weather Service, meanwhile, is calling for at least a 40 percent chance of rain through Saturday.

The public can stay informed about the potential flooding situation by subscribing to the Nixle System, updated regularly by the county. To subscribe visit, www.nixle.com.

– Cara Rank and Cory Hatch contributed to this story.