Drought jeopardizes salmon in the Nicola watershed
New research highlights the threat of climate change to the Nicola and the importance of streamflows to salmon.
Streamflow in the Coldwater River, a major salmon-bearing river within the Nicola Watershed near Merritt, BC, is not meeting minimum ecological requirements for salmon.
A new collaborative study released by researchers from Raincoast Conservation Foundation and Scw’exmx Tribal Council determined that streamflow in the Coldwater River is too low to support a healthy salmon population. The multi-disciplinary research team also included nłeʔképmx Land Guardians from Citxw Nlaka’pamux Assembly.
The Nicola Watershed is one of BC’s most vulnerable regions to the effects of climate change, particularly as it relates to drought. The cumulative impacts of logging and agricultural water withdrawal, coupled with increasing water scarcity, are a serious threat to the persistence and recovery of Nicola salmon populations.
There were two significant findings from the study:
- Optimum flows are much higher than flows that are currently being observed in the Coldwater River.
- The relationship between salmon habitat and stream flow follows a negative exponential trend. As streamflow approaches zero, salmon habitat is lost at an increasing rate.
This new research adds to the growing work centered in the Nicola to build the resilience of salmon populations against drought.
The field-based study was co-led by Raincoast salmon habitat biologist Auston Chhor and Scw’exmx Tribal Council fisheries biologist Nathan Lustig, who measured streamflow and river depth at nine sites throughout the Coldwater River from July-September, 2024.
“As a region the Nicola is getting less snow in the winter and less rain in the summer due to climate change, which has increased the risk of drought each year dramatically,” says Nathan. “Understanding how much water salmon need helps water managers set a target flow that can balance water requirements for both humans and fish.”
“Our results really highlight the importance of acting proactively to protect streamflows when they are still high, earlier in the season,” says Auston. “Too often water managers wait until droughts are well underway before taking action, and our data shows that the longer you wait, the more damage is done.”
The pair used a novel methodology –known as the Okanagan Weighted Usable Width method–developed by the Okanagan Nation Alliance in 2020 to model the relationship between streamflow, depth, and salmon habitat based on species (coho, chinook, or steelhead) and life stage (juvenile or adult).
These relationships are presented as curves and allow for the determination of the optimum flow for each specific species and life stage.