It is not only a worldview to consider that development is unsustainable when it attempts to control Nature rather than respecting it. For those who don’t believe in scientific knowledge and systematic observations, time will prove them wrong, and the cost for all of us will be higher. Isn’t it increasingly difficult to ignore the financial and human impact of climate change… wherever you are on the planet? It is also becoming evident that humans cannot simply engineer their way out of our various growth-related crises without protecting, and reinvesting in, our common environment and shared watersheds. Fortunately, there are years when Nature, through Water, seems compassionate about our historical mistakes, and this can be considered a worldview: Nature can give us a chance; a chance to adapt our infrastructure to our own historical mistakes. The 2024 hydrological year in Yukon was like that.
Winter concerns
From a flood potential perspective, two major concerns had been identified at the onset of snowmelt during the spring of 2024:
- A major freeze-up jam had formed in the Tr’ondëk (Klondike River) at the Klondike Highway bridge in Dawson (a recent analysis suggests that maximum water levels at breakup can only be higher than maximum water levels during the freeze-up event; see graph below based on Water Survey of Canada data). This freeze-up jam had the potential to cause an equivalent 2023 or a 2003 flood.
- The snowpack in the Ch’oodeenjìk (Porcupine River) watershed was well above average (this river generates floods relatively often – see second graph below mostly based on Water Survey of Canada data –, even when the snowpack is close to the historical average). This water would have to flow past the community of Old Crow in the coming weeks.
Spring scenarios
It turns out that the best possible scenario happened in both cases:
- Weather conditions during March and April near Dawson produced an impressive sequence of 46 consecutive days with an air temperature above 0°C during the day and below 0°C at night, what we refer to as thaw-freeze cycles. This sequence imposed a gradual snowmelt rate that attenuated the risk of ice jam formation and ice jam flooding. On the evening of April 29, the water level at the Klondike Highway bridge rose to the exact elevation as the freeze-up peak level, and the weakened freeze-up jam was lifted and pushed into the Chu kon’ dëk (Yukon River) with limited impacts on Dawsonites. The ice walls (called shear walls) left after the breakup show that ice pieces did not threaten the bridge structure (see photo below).
- Within less than 24 hours (May 16 to May 17), the discharge of the Ch’oodeenjìk rose from 30 m3/s (with an intact ice cover) to 3000 m3/s. This situation can easily lead to the formation of a significant ice jam at Old Crow. Fortunately, the ice run came with enough power to mobilize the ice cover over a long distance downstream of the community (it seems that a low freeze-up level contributed to this ideal breakup front progression). Only minor erosion was reported at the downstream end of the community (see second photo below). However, the snowpack was far from being depleted, and an open-water flood was expected. Luckily, colder weather reduced snowmelt rates, and the Ch’oodeenjìk discharge flirted with the flood level for about a week before dropping to levels that represented less of a concern for Vuntut Gwitchin people. Interestingly, the main flood consequence in Old Crow was attributed to a small creek whose flow was impeded by a culvert filled with ice.
In other areas of Yukon, a moderately intense ice jam was reported on the Ts’ekínyäk Chú (Pelly River) at Pelly Crossing. However, the generally average to below-average snowpack kept freshet flows close to or well below normal. This is the case at Łù’àn Män (Kluane Lake), that had record low summer levels since the 2016 A’ay Chu (Slims River) diversion into the Àłsêxh (Alsek River).
Additional 2024 stories about Water compassion
Southern Yukon debris flow: Two consecutive rainstorms, including convective episodes characterized by heavy rainfalls, caused a debris flow through a steep hillside gully that ends in a small culvert under the South Klondike Highway. This event forced the temporary closure of this important transportation link during the middle of the tourist season, and it also impacted the supply chain to Yukon (this is becoming a tradition). Why were we lucky? Because 1. No one was hurt and 2. The debris deposited directly at a lookout, allowing the partial reopening of the highway much sooner than if the process had taken place in a nearby stream. The event warrants exploring mitigation options for this type of extremely dynamic and hard-to-predict hazard, including identifying steep gullies and mountainside watersheds where debris flows could happen in the future and preventively closing segments of the Klondike and Alaska Highways when heavy precipitation is forecasted (or detected) while the ground is already saturated by snowmelt or a previous rain event.
Southern Lakes quasi-flood: The same sequence of late-July rainstorms caused a 0.5 m-rise of the Southern Lakes in 7 days, bringing their level dangerously close to flooding thresholds. By chance, weather conditions during August nicely collaborated, alternating between light rain and warmer periods. The glacier contribution to Mén Chó (Tagish) or Áa Tlein (Tlingit, Atlin Lake) and Tagish Lake peaked before mid-August, and no major flooding was reported in Southern Yukon. Those summer storms did cause flooding in the Gąąsé Tóo’e’ (Tagish) or L’ál Héeni (Tlingit) (Wheaton River) valley (Annie Lake Road), but only minor damage was reported. The graph below demonstrates that this event caused the highest summer flow (not snowmelt-related) on record at Water Survey of Canada 09AA012 (since 1966).
Eagle Gold heap leach failure: The most dramatic water-related event of 2024 in Yukon, which consequence will extend well beyond the calendar year and which lessons will hopefully be carried well past Yukon borders, is the failure of the heap leach facility (a pile of crushed rocks from which gold is diluted using chemicals) at the active Eagle Gold Mine located north of Mayo in central Yukon. No casualties among workers were reported and the landslide was contained upstream of Haggart Creek, which was initially positive for the environment. However, contamination of the Et’o Nyäk Tagé (McQuesten River) headwaters through the ground is now confirmed. This disaster is taking place on the Traditional Territory of the First Nation of Na-Cho Nyäk Dun, and their people are deeply concerned about the environment that they have been protecting for thousands of years.
Tŝilhqot’in (Chilcotin) River landslide and flood wave: A significant landslide blocked this river of central British Columbia for about a week at the end of July. It created a temporary reservoir while the downstream channel was essentially dry. The 30-m high dam caused by the landslide was eventually overtopped and quickly eroded, releasing the (120 million cubic meters of) stored water in a few hours. B.C. authorities managed the situation carefully, informing upstream and downstream populations about current conditions and possible consequences. Unlike what seems to be reported in the media, the flow in the downstream reach of the Tŝilhqot’in River was much higher than the normal snowmelt flow (by at least 10 times; the media were probably referring to flow in the receiving environment, the much larger ʔElhdaqox (Fraser River)), and this caused significant erosion. Luckily, the worst case scenario identified by the Government of B.C., in terms of water levels and subsequent landslides, did not materialize, and the direct impact on people and downstream infrastructure was relatively low. Nonetheless, the salmon run was potentially substantially affected (the fish would have to face extreme, unseen low flows followed by a wave representing 7,000 Megawatt-hour of waterpower), with important effects on the ecosystem and the local First Nations.
International perspectives
Millions of people have been affected by floods in 2024 and hundreds have lost their lives. The long list of affected countries includes Eastern Spain and Southeastern United States, countries that generally rely on robust hydraulic structures which design is based on construction codes developed by experts. Droughts have even greater impacts, although they are less shocking because they occur every day of the year. These water-related hazards were occurring well before climate started to be altered by human activities, but there is a consensus that their frequency and intensity is boosted by the increasing amount of heat trapped in our atmosphere. Nature cannot and will not be compassionate everywhere, every year.
Freeze-up outlook and 2025 Yukon perspective
Believe it or not, La Niña is back (at least temporarily). This usually means cool and moist conditions for at least a part of the Yukon. Nature does not care about statistics, but one must admit that the abrupt start to winter conditions near Kwänlin (Whitehorse) during the evening of October 16 corresponds to what climate scientists anticipated for the winter: snow. So far, precipitation has been well above average near Yukon’s capital. If this tendency persists for a few months, which is far from certain, Southern Lakes will receive significant attention next summer.
It was foreseen that wet fall conditions in some watersheds of central Yukon (Tr’ondëk and Nä`chòo ndek (Stewart River)) could lead to more intense freeze-up conditions than usual. However, mild air temperatures in late October and early November seem to have delayed river ice formation in most large rivers. This delay may be positive from a water level and spring flooding perspective, but it is starting to represent a concern for some Dawsonites. Our research group suggested a few years ago that a low discharge in the Chu kon’ dëk could favour the formation of ice congestion at the Tr’ondëk delta, upstream of Dawson, leaving open water at the ice bridge location. Since streamflow is declining daily, the sooner the Yukon River will freeze, the better (the freeze-up process has started downstream of the Forty Mile River, the usual location, on November 10, but the subsequent freeze-up pattern near Dawson remains uncertain).