Unusual breakup underway across the Interior  
5-7-07
Tim Bodony (KIYU) 

The terms “mush-out” or “thermal breakup” are being used to describe this year’s transition from ice to water on the Interior rivers.   

The tameness of this year’s breakup in the Interior stems largely from below-average snowfall this past winter.  Some communities, such as Bettles, set record lows for snow accumulation.  Galena only had a foot and a half of snow on the ground at most this winter – about half the usual amount – and that situation holds true for most communities across the Interior.  Satellite images used by the National Weather Service showed that almost all of the lower elevation snow cover was already gone by the end of April. 

With the high elevation snow pack just starting to melt away, the amount of water entering the Yukon, Tanana, and Koyukuk Rivers at this time is unusually low.   

At the early stages of breakup, ice jams usually present the greatest threat for flooding in river villages.  When a sudden surge of water pushes large blocks of solid ice downstream, conditions are right for that ice to get clogged, and form a dam that blocks the flow of water any further downriver.   

But the ice this year has been able to melt in place, helped by record high temperatures across the region at the end of April.  By the time it moves, it’s soft, and less prone to form a jam.   

Senior Hydrologist Dave Streubel, with the National Weather Service Pacific River Forecast Center, cites an example of this from the last few days at Hughes, on the Koyukuk River.  Last year, ice jam flooding damaged the runway, school, and some homes in Hughes…but this year, Streubel says, when ice blocked up in front of the village, there wasn’t cause for alarm.   

Streubel:  “talked to resident there, and they said there just wasn’t enough water in the system, and most of the water was just working its way under the jam, and they weren’t too concerned”  

Streubel predicts that a trouble free breakup will continue, as long as the water levels stay low. 

Streubel: “until we start getting some water coming in from the Canadian Yukon, and working its way through the upper Yukon river, the threat of any breakup related flooding due to ice jams is pretty small.”

Galena elder Paddy Nollner agrees.  He can vividly recall some of the Yukon’s most dramatic breakups, including the flood of 1945, when a long, cold spring quickly turned warm, and the sudden change triggered a massive flood in Galena.   

But this year, without a push of water to encourage it, the mushy river ice at Galena has been stubbornly anchored in place.  It’s a scenario that Nollner has never seen before. 

Paddy Nollner:    “I never did see anything like that in my life, being so low. I heard that from many older folks too.  That’s something that everybody is wondering about, what it’s gonna do…it don’t want to move.” 

Low water presents a challenge to boats and barges that will soon try to move along the rivers.  River villages are reliant on barges for the shipment of oversized freight and fuel.   

If the river levels stay unusually low, navigation this summer will be a serious challenge. 

Whether or not this will be a problem is only something at which Nollner can guess. 

Paddy Nollner: “Strange things happen. You never know if water will raise, it might start raining and rain for 40 days. But that is a good question.  Everybody’s wondering about the river channel. Sandbars are already sticking out, like fall time. I never did see anything like it.”