New mapping reveals critical “cooling centres” for salmon in the warming Coldwater River
The salmon populations in the Nicola watershed are among the most endangered in BC. The Coldwater River provides critical spawning and rearing habitat for Interior Fraser Coho, Lower Thompson Chinook, and Interior Fraser Steelhead.
MERRITT, BC – As rivers across Western North America face climate change-driven record-breaking temperatures, Raincoast Conservation Foundation, in partnership with the Scw’exmx Tribal Council and nłeʔképmx Guardians from Citxw Nlaka’pamux Assembly, have released a groundbreaking study and map of “thermal refuges” in the Coldwater River.
The project identifies vital cold-water pockets where endangered salmon congregate to survive lethal summer heatwaves. These areas are known as “thermal refuges” by researchers. Using aerial thermal infrared imaging collected by a drone, researchers found that while the mainstem of the Coldwater River reached a staggering 27°C in the summer of 2024 – a temperature often lethal to salmon – certain groundwater-fed refuges remained up to 8°C cooler.
“Salmon are cold water species. In naturally hot and dry regions of our province, they are being pushed to the edge of their thermal tolerance by climate change,” said Auston Chhor, Salmon Habitat Biologist at Raincoast and project co-lead.
“You can think of thermal refuges as air-conditioning for salmon. When it gets hot, these areas are literally live-saving for these fish.”
By identifying and mapping thermal refuges, the researchers hope to restore habitat and plant shade-providing trees to ensure that these areas are suitable for salmon. They also aim to better understand how to protect groundwater, which creates thermal refuges when it seeps into the river.
Key findings from the research
- Critical Connectivity Gaps: The study identified three large “gaps” (roughly 4 km each) between thermal refuges. These gaps may act as heat barriers, preventing fish from moving safely through the watershed during extreme heat.
- The 2021 Flood’s Silver Lining: Analysis of historical satellite imagery revealed that the catastrophic 2021 floods may have increased the number of thermal refuges by reconnecting the river to its floodplain and opening new pathways for groundwater to enter the river.
“Ensuring salmon thrive in the Nicola watershed as they have for thousands of years is a moral, ecological, and cultural responsibility,” says Nathan Lustig, Fisheries Biologist at Scw’exmx Tribal Council and project co-lead. “People, wildlife, and even the plant communities depend on healthy salmon populations. Losing this resource would be catastrophic for the region.”
Citation
Chhor A, Lustig N, and Spahan B. 2026. Identifying thermal refuges for salmon in the Coldwater River. Raincoast Conservation Foundation. DOI: https://doi.org/10.70766/436.452
About Raincoast Conservation Foundation
Raincoast is a team of scientists and conservationists guided by an ethic of social and environmental responsibility. We dedicate our research to investigate and inform the protection of the lands, waters, and wildlife of coastal British Columbia.
About Scw’exmx Tribal Council
Scw’exmx Tribal Council (STC) is a non-profit organization located in Merritt, British Columbia, that serves as a central hub for the “People of the Creeks,” representing the Coldwater, Nooaitch, Shackan, and Upper Nicola Indian Bands. Dedicated to protecting the Nlaka’pamux and Syilx heritage, the Council provides advisory services and leadership in areas such as resource management, land stewardship (Tmixʷ research), and title and rights to ensure the long-term prosperity and self-sufficiency of its member communities.
About Citxw Nlaka’pamux Assembly
Citxw Nlaka’pamux Assembly (CNA) is a non-profit organization that manages and administers agreements related to the Highland Valley Copper Mine on behalf of eight Participating Bands, ensuring that resource development respects Nlaka’pamux Title and Rights. A vital component of their work is the nłeʔképmx (NLX) Guardians program, which serves as the “eyes and ears” of the territory; these boots-on-the-ground stewards monitor wildlife, water quality, and land use while bridging the gap between traditional knowledge and modern environmental management to protect tmixʷ (the land) for future generations.