A century’s worth of data collected from sites across BC’s Fraser River Basin indicates we may be seeing much more of the intense flooding the province is experiencing this spring. According to a study by University of Northern British Columbia (UNBC) researchers published this week in the prominent international journal Environmental Research Letters, the increase in extreme fluctuations is negatively affecting salmon returns, water quality, and the safety of residents in affected regions.
 
“If rivers are the veins of Canada, we’re having some pretty dramatic blood pressure fluctuations,” says the study’s lead author, UNBC Environmental Science and Engineering professor Stephen Déry. “What we used to consider once-every-hundred-years flooding may now be happening more frequently, perhaps once every 10 years or so. On the opposite end, we are also seeing extremely low water flow years in some parts of the Fraser River Basin, which are also detrimental.”
 
In the study, 2012: A century of hydrological variability and trends in the Fraser River Basin, streamflow data from 139 sites situated across the Fraser River Basin from 1911 to 2010 were extracted and analyzed for patterns in water runoff. The results revealed greater runoff productivity and lower runoff variability in headwater and coastal catchments compared to those in the central portions of the Fraser River Basin.
 
“What we found was increased variability in annual streamflow over time, with more prominent changes in spring and summer across the basin,” says Dr. Déry, who is also a Canada Research Chair in Northern Hydrometeorology. “As BC’s climate continues to warm, greater variability in streamflow may influence ecological processes and how the Fraser River Basin is used in the 21st century.”
 
In addition to climate change, Dr. Déry points to factors such as the recession of BC’s glaciers and the loss of water retention resulting from the loss of millions of hectares of trees from the mountain pine beetle outbreak as factors exacerbating the situation.
 
The Province of BC issued high streamflow advisories this month for multiple rivers in the Basin including the Fraser, Nechako, Quesnel, Shuswap, and Thompson Rivers and a number of evacuation orders due to flooding.

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