Peak flow in 1997 pushed water over House Rock, challenging boaters like Kevin Kelleher.

Best the Crest

A contest of river intuition

Head scratching and guessing about when the Gallatin River will peak is a local pastime. This year, Gallatin River Guides is channeling everyone’s hydro-clairvoyance into its “Best the Crest” contest. Drop by the shop and guess the peak cfs (cubic feet per second) for $5 and the day it will peak for $15. All proceeds will be split with the Gallatin River Task Force.

     Predicting when and how big the Gallatin will crest is fun because the peak moment becomes a pivot point signaling the end of maximum runoff and the beginning of the summer flow. It sets the internal clocks of kayakers, anglers and guides. These people close to the river blend gut instinct, amateur meteorology and big water memories as they crunch snowpack numbers and consider average day and night time temperatures. 

     Here’s what we know: On Monday, May 14, the U.S. Geological Survey gauge showed the Gallatin River running at 2,830 cfs. It spiked on May 11, topping 4,000 cfs. 

     “That’s the highest it’s been on that day,” observed Bill Zell, owner of Montana Whitewater. He took this development as a sign the snowpack is diminishing at an impressive but steady rate. It’s not surging, but it’s putting a lot of volume downstream early. 

     His “Best the Crest” prediction: It will peak on May 30 and won’t go over 5,500. 

     “People think it’s going over House Rock. I don’t think it’s going to,” said Zell, who noted two epic years with runoff flowing over House Rock—1997 and 2011—included more snow. In mid-May ’97, remembered Zell, there was still lots of unmelted snow down low. And in ’11, it kept snowing well into May. 

     “It’s cooling off right now. I think the snowpack is not like 1997 or 2011. It really depends on the weather. That’s Mother Nature,” added Zell, admitting his guess about a 5,500 cfs peak might be wishful thinking. If the water gets too big, then Zell sees flooding at his business in Karst. 

     At Geyser Whitewater Expeditions, the other commercial outfitter operating on the Gallatin, Marina Clark and Glen Yetter spent part of a recent rainy afternoon talking cfs. They pay close attention to water levels, because once the river swells past 3,800 cfs, the company stops taking commercial trips down the House Rock rapid and the Mad Mile—a boiling snarl of water below the Lava Lake Trailhead. 

     “But we can certainly go down the upper, with some age limitations and other things. And then the scenic we can run,” said Clark. 

     At high water, Geyser offers scenic trips from the boundary with Yellowstone National Park to the takeout at Deer Creek. They also brave high-water all the way down to the Lava Lake Trailhead.

     “We can run the river at 3,500 cfs all the way up to almost 7,000,” said Yetter, a guide and the boat yard manager at Geyser. “If it gets above 7,000, we can’t fit under the bridges. If it gets above 6,500, we’ll go out there with tape measurers early in the morning and make sure it’s all safe to go.”

     When it comes to House Rock, once the river hits 6,000 cfs, Yetter said water “will be splashing a little bit over. At about 7,000, there’s a significant amount of current” going over the rock. 

     Yetter said when it comes to guessing peak flow, “Historically, the peak day is June 9. A lot of it depends on what the weather does in May.” 

     He added, “If it stays cold and crappy, then it gets hot in June, we might see 10 grand. I’d be surprised if we get over eight. I think we’ll see over seven within the first week of June.”

     Jimmy Armijo-Grover, general manager at Gallatin River Guides and a “Best the Crest” contest official said he blends some targeted web surfs with vivid memories of big water years when making his calculations about peak runoff. 

     “I use the USGS streamflow charts quite a bit to look at the data over time and based on experience over the years,” said Armijo-Grover, who also pulled up a long-term weather forecast looking toward the end of the month and into June. It showed no evidence of a sudden temperate jump on the horizon. 

     But, said Armijo-Grover, “I saw 84 in Belgrade one day, so maybe 70s up here.”

     Sunshine and temperatures above 60 degrees will increase runoff, driving up the Gallatin’s cfs. One “melt-off” factor could be the legacy of the devastating 1988 fires in Yellowstone, which roared through the Gallatin’s upper-watershed. Thirty years later, trees have returned, casting shade and protecting the snowpack from the sun’s glare. Will this be a factor? 

     Armijo-Grover won’t make a prediction, saying the “Best the Crest” contest is a new thing for Gallatin River Guides, though it’s been done before around Big Sky (including in the Lookout). He remembers the spring of 2011 when he lived in a cabin on the river near the Asbestos Mine Trailhead.

     That year, said Armijo-Grover, “Water touched the deck and was three or four inches from being in the cabin.”

     Lucas Zukiewicz won’t say whether or not cabins along the Gallatin are in for a drenching this year. The water supply specialist with the Natural Resource Conservation Service in Bozeman gets asked a lot about predicting peak flows. 

     He explained how the U.S. Geological Service maintains the Gallatin River’s gauge just below the confluence with Spanish Creek near the mouth of the canyon. It electronically transmits data to websites like waterwatch.usgs.gov, which is a bookmarked site for river guides and other Gallatin flow obsessives who check the river’s hydrograph the same way others click on their Facebook page. 

     When making predictions about peak flow and maximum cfs, Zukiewicz said, “I’m going to look at the relationship between how much snow is left and where the hydrograph is going. Every year it moves around. And this year, what’s surprising is how quickly the snow started coming off.”

     Like Zell at Montana Whitewater, Zukiewicz found the cfs data from Friday, May 11 telling. That day at 4 a.m., the Gallatin hit 4,090 cfs—the highest ever for that date. 

     “We moved a lot of water early,” said Zukiewicz. “We moved a bunch of snow melt down. That’s what makes peak forecasting that much more difficult. Is that going to lessen the peak we might have later in the year? It’s a really complex game. My guess is we’ll probably see a little bit lower peak.”

     Warm days and cool nights generally cause the Gallatin River’s hydrograph to stair step up this time of year. During the day, the total cfs rises and at night snow melt slows causing the cfs to drop. When the hydrograph spikes upward, that’s generally a “rain-driven peak” when rain on snow pushes more water downhill. Intensely bright sunny days can do the same thing. 

     “The dominant driver of snowmelt is solar radiation,” said Zukiewicz, noting how the air temperature might be the same on all sides of your house, but the aspects where the sun shines the most are where melting happens fastest. 

     When pressed to make a “Best the Crest” prediction, Zukiewicz hesitated, saying only he didn’t think House Rock would get covered this year. 

      “I’ve been asked so many times,” laughed Zukiewicz. “It’s tough man. It’s weather-based.”

More Information

Lone Peak Lookout

235 Snowy Mtn Circle
Big Sky, MT 59716
www.lonepeaklookout.com

Comment Here