From spiking temperatures during a heat dome in the summer, to a massive deluge from two atmospheric rivers in the fall, 2021 was a wild year for weather in the Pacific Northwest. In a new paper, a team of researchers from the University of Northern British Columbia examine the impact of these severe events on creeks, rivers and lakes and the aquatic species that call them home across the region.  

“Our work demonstrates that the extreme hydrometeorological events of 2021 induced drastic changes in water temperatures across the Pacific Northwest of North America,” says UNBC Environmental Science Professor Dr. Stephen Déry, the paper’s lead author. “As climate change amplifies, these types of extreme events may become more frequent, persistent and intense with potential deleterious impacts to water quality, aquatic species and their habitats.”

The paper, titled Extreme hydrometeorological events induce abrupt and widespread freshwater temperature changes across the Pacific Northwest of North America, is published in the journal Communications Earth and Environment. Déry collaborated with Faculty of the Environment colleagues Drs. Eduardo Martins, Philip Owens and Ellen Petticrew on the paper.

UNBC researchers were in the field in the traditional and unceded territory of the Nak’azdli Whut’en First Nation near Fort St. James, B.C. in late June 2021 when the heat dome saw air temperatures reach 38°C. Data collected showed water temperature in the Necoslie River rose by 6.2 C seven days after the heat dome began. In fact, for every 1 C in air temperature rise, the Necoslie River water temperature increased by 0.76 C.

“Spikes in water temperature can increase stress levels and cause mortality in cool- and cold-water adapted species, such as trout, char, and salmon,” Martins says.

Déry says there are different approaches policymakers can take to mitigate the impact of extreme temperatures, ranging from restoring or enhancing vegetation near waterways to provide more shade, to preserving or constructing wetlands by building beaver dam analogues. In cases where rivers are regulated, increasing the streamflow during periods of extremely hot weather can also lessen the impact.

Later that same year, atmospheric rivers caused severe flooding across southern British Columbia, resulting in five human fatalities, the loss of farm animals and damages to roads and bridges that are still being repaired. UNBC researchers found a spike in runoff and a surge in air temperature during the atmospheric rivers they studied, but water temperature only ticked up minimally due to the cloudy weather, increase in precipitation and the influx of alpine snow melt.

“Areas directly influenced by atmospheric rivers may not observe significant changes in water temperature despite surges in air temperature; however, areas in the warm sector of these storms may be more affected as observed in the mid-November 2021 atmospheric rivers.” Déry says. “Thus impacts to freshwater temperatures can be relatively remote from the storms themselves.”

This research was possible because of the ongoing research projects at UNBC that have seen the installation of weather stations, in-stream monitors and other equipment across northern British Columbia. 

“The contribution of data from all co-authors was central to this effort and all brought their different expertise to the preparation of the manuscript,” Déry says. “This was very much a team effort and a perfect example of the incredible and diverse expertise we have in-house at UNBC.”

Given the changing climate and increasing frequency of extreme weather events, such as the 2023 drought conditions, it is important for this type of research to continue. 

“There is an ever-increasing need to not only expand stream temperature monitoring across the Pacific Northwest of North America but also extend this study to encompass additional extreme hydrometeorological events including floods and droughts to mitigate their impacts on aquatic environments and ecosystems,” Déry says. “The UNBC research team is dedicating considerable effort to enhance monitoring of freshwater temperatures, and other variables, as extreme hydrometeorological events continue to afflict northern B.C.”

Primary funding support for the research came from the Natural Sciences and Engineering Research Council and Rio Tinto. Additional funding support came from Environment and Climate Change Canada, Eco Canada, the Nechako Environmental Enhancement Fund and Project Learning Tree Canada.