Record-high snowpack levels across the Yukon means keeping a close watch on spring and summer weather to determine flood risk, according to a local hydrologist.
That means the territory has a lot of snow on the ground, said senior hydrologist Holly Goulding of the Department of Environment by phone on April 12.
“I think that we have a sense that the flood potential is very high in the territory right now,” Goulding said.
Results of the Yukon government’s April 1 Yukon Snow Survey Bulletin and Water Supply Forecast show that snowpack levels are well above average throughout the territory, with 33 out of 57 stations challenging or exceeding their records for historical maximum snowpack.
This month typically records the highest snowpack in most parts of the territory, the bulletin notes, but there’s more snow this year than on average.
In the bulletin, most of the Yukon saw greater than normal levels of precipitation in March, which was a continuing trend, with the exception of Old Crow.
Goulding said pinpointing the timing and locations of where flooding hits will depend on how the spring weather unfolds.
“It’s too soon to say where we might see flooding or when we might see flooding, because it really is the weather in the next few weeks that’s really critical in determining how the snowmelt will play out,” Goulding said.
“It is gradual warming that we want to see, but also progressive warming throughout the summer period. So, the onset of snow melt and continued melting throughout the spring is really important, and that’ll reduce the likelihood that we’ll still have a large amount of snow on the ground later in the spring or early summer when higher temperatures can cause rapid melting and runoff.”
Observers should be keeping an eye on the cool conditions for the next little while.
“That’s not great news for potential and that’s something that we’re watching closely,” Goulding said.
The snow bulletin presents key findings related to the snowpack, weather and water levels or flows for 11 different basins across the territory.
In the bulletin, the highest basin snowpack levels on record occurred at eight of eleven monitoring stations: Central Yukon River Basin (Carmacks region), Lower Yukon River Basin (Dawson region), White River Basin, Liard River Basin, Teslin River Basin, Pelly River Basin, Peel River Basin and Stewart River Basin.
The remaining three – the Upper Yukon River Basin (Southern Lakes and Whitehorse), the Porcupine River Basin and the Alsek River Basin – were all above the historical median.
“The record-setting snowpack in many watersheds in the territory increases the probability of high freshet [also known as spring snowmelt] flows and lake levels. During the snowmelt period, small watercourses peak earlier than larger streams and rivers. Significant flows are expected in small watercourses during freshet across the territory, including many road crossings,” the bulletin reads.
“The timing and magnitude of peak spring freshet flows will depend on spring weather patterns. A sudden transition to warmer temperatures in April or early May could be conducive to ice jamming in some rivers. A delayed melt followed by a sustained rise in air temperature or significant rainfall could generate high runoff rates, resulting in high May and June peak flows in streams and rivers. Weather conditions over both the spring and summer will influence peak flows and lake levels in watersheds influenced by glacial melt.”
The bulletin notes the Yukon government will release flood warning messages during the flood season if needed.
No active flood warnings or advisories are in effect for the Yukon, according to the territorial government’s website.
The bulletin indicates the Upper Yukon River Basin, which includes Whitehorse and Southern Lakes, is seeing “significant snowpack” for the region.
In the bulletin, there is a “high potential” for water issues and ice jamming in several regions:
“Water levels in Carmacks-area rivers are likely to be well above average this spring and summer with a high potential for significant May and June peak flows, including in rivers and streams crossing the North Klondike and Robert Campbell Highways. A sudden sustained rise in air temperature in April or early May could be conducive to ice jamming.”
“The record-high snowpack in the Pelly Crossing watershed suggests a high potential for significant May and June peak flows, including in rivers and streams crossing the Robert Campbell Highway and Canol Road. A sudden sustained rise in air temperature in April or early May could also be conducive to ice jamming.”
“The record-high snowpack in the Stewart River watershed suggests a high potential for significant May and June peak flows, including rivers and streams crossing the Silver Trail Highway and other local roads. A sudden sustained rise in air temperature in April or early May could also be conducive to ice jamming.”
“The estimated Yukon River discharge at the White River is well above average. The well above median to record-high snowpack in upstream basins suggests a high potential for significant May and June peak flows, including rivers and streams crossing the Klondike, Dempster and Top of the World Highways. Prior to that, a sudden sustained rise in air temperature could be conducive to severe ice jamming. These statements also apply to the Klondike River.”
“The estimated Liard River discharge at Upper Liard is currently well above average. The record-high snowpack in the watershed suggests a high potential for significant May and June peak flows, including in rivers and streams crossing the Alaska and Robert Campbell Highways.”
“The estimated Peel River discharge is below average. The record-high snowpack in the watershed suggests a high potential for significant freshet flows, including in rivers and streams crossing the Dempster Highway.”
Contact Dana Hatherly at firstname.lastname@example.org