Finding the ‘cold’ in the Coldwater River
Oct 23, 2025|inBlog, Climate Adaptation Series, Salmon Steward
At-risk salmon in the Coldwater River are on the frontlines of climate change. Biologists and local Guardians are giving these fish a fighting chance.
What connects British Columbia’s lush west coast to the arid, dry Nicola Valley in the Southern Interior?
Look no further than the Pacific salmon migration.
As salmon travel from the coast into the Nicola Valley, home of the Nlaka’pamux and the Syilx Peoples, they bring an important pulse of nutrients inland.
The Coldwater River, the largest tributary of the Nicola River, is critical for both juvenile and adult salmon. Yet, the Committee on the Status of Endangered Wildlife in Canada has designated coho salmon that swim through the river as threatened, and Chinook and steelhead as endangered.
Locals have been living with the reality of salmon declines for many years.
“For decades, the community hasn’t had access to salmon for food,” says Nathan Lustig, fisheries biologist with Scw’exmx Tribal Council, which represents the Coldwater, Nooaitch, Shackan, and Upper Nicola bands. “To be able to fish, community members have had to go down to the Thompson or Fraser. But the long-term vision is for members to be able to fish for salmon at home.”
Photos by Nicole Van Zutphen/Raincoast Conservation
A buffer against climate change
In the Coldwater River, salmon are on the frontlines of climate change. The watershed’s already warm summers are getting hotter and drier.
Water temperatures as high as 27 °C in the Coldwater have been observed recently, well above the tolerable threshold for salmon. This year, adult salmon returning to the Coldwater faced unbearably warm waters and some died before they could spawn.
Fortunately, the river is naturally equipped with ‘thermal refuges’, or distinct patches cooler than surrounding waters. Thermal refuges often form where cool groundwater flows upward into a river or where a river meets a tributary. Salmon use these cool spots to find relief from thermal stress.
“It’s similar to air conditioning. When it’s hot out, people move inside to thermoregulate. Salmon do the same thing. They seek out these cool water areas to take a break from the heat,” says Auston Chhor, a salmon habitat biologist with Raincoat Conservation Foundation.
With support from the Pacific Salmon Foundation (PSF), the Scw’exmx Tribal Council, Citxw Nlaka’pamux Assembly (CNA), and Raincoast have embarked on a project to identify and map out thermal refuges in the 94-kilometre-long Coldwater River. Ultimately, they aim to protect and enhance these thermal refuges and help salmon increase their resilience against climate change.
Drones and snorkels
In the summer of 2025, biologists and local Guardians identified and mapped several thermal refuges along the Coldwater River.
This endeavour provided valuable insights into how the river’s dynamics have shifted since catastrophic flooding in 2021, which altered its course and displaced thermal refuges, raising ongoing concerns about impacts on fish habitat.
To locate the thermal refuges, they used a drone equipped with a thermal camera to produce a map of the river.
The researchers then conducted snorkel surveys at identified sites. They went underwater to record water temperatures, count fish, identify species, evaluate fish behaviour, and assess habitat features.
Snorkelling also provided the field team with much-needed breaks from the heat. “Swimming was an added bonus this summer,” says Chhor.
The team found that juvenile salmon, and other fish species, were actively using the cool water patches. However, the unexpectedly small size of the sites meant they were less suitable for larger adult salmon returning upstream.
As salmon were coming back in September, the team trialled low-tech methods to improve and expand these thermal refuge sites, such as shading the river to reduce temperatures, or constructing temporary rock weirs to prevent cool pools from mixing with warm waters.
“The salmon that are adapted to this area haven’t been able to keep up with climate change. We have an opportunity to protect thermal refuges and improve habitat to help salmon in the long term,” says Chhor.
Training the next generation of Indigenous Guardians
In the field, Chhor and Lustig were joined by two Indigenous Guardians from Citxw Nlaka’pamux Assembly.
The Guardians gained hands-on experience planning, collecting data, counting fish, and analyzing data.
A major goal of this project is to provide training in scientific protocols for the next generation of Indigenous Guardians, supporting their goal of increased leadership in conservation science.
“We would like to see this project flourish as the data that is being collected will significantly enhance our understanding of the watersheds in the Nicola Valley,” says Ariel Voght, Guardians Manager with CNA.
The Pacific Salmon Foundation supported this project through the British Columbia Salmon Restoration and Innovation Fund (BCSRIF) – a joint program from the Government of Canada and Province of British Columbia.
Through BCSRIF, PSF has collaborated with Dr. Eric Saczuk from BCIT’s Remotely Piloted Aircraft Systems Hub to train 10 Indigenous partners in the use of thermal drones to map and monitor salmon habitats.
Climate emergency funding
As of mid-October, PSF approved $855,180 in funding in 2025 to help salmon in response to extreme drought and other climate emergencies across the province. Local partners leveraged the funding to tag fish to assess salmon passage, improve river flows, and monitor conditions on the ground.
