Fraser Freshet Happening Earlier Says Study
Prince George, B.C.- A new study by researchers at UNBC warns of dangers to salmon migration and future drought along the Fraser River all because of climate change.
The report, “Impacts of a Rapidly Declining Snowpack on Streamflow Timing in Canada’s Fraser River Basin” analyzed data from 1949 to 2006. What they discovered is that warmer temperatures have changed the kind of precipitation, resulting in reduced snowpacks and more rain which mean the spring melt is happening earlier.
UNBC Professor of Environmental Science, Dr.Stephen Dery, is one of the co-authors of the report which has been published by the Nature Publishing Group’s journal Scientific Reports.
Dr. Dery says the total amount of precipitation remains about the same, but the mix of snow and rain to that total has shifted “Over the period of study, the contribution of snow to the Fraser River flow has declined between 20 to 25%” says Dr. Dery. “So we have less snow to melt and it’s melting earlier, so that melt water reaches the Fraser River earlier than it used to in the past, so the spring freshet has advanced by about 10 days.”
Earlier peak flows could spell lower than normal flows and warmer than normal water temperatures by the time the salmon are migrating up the Fraser River.
Lower water levels can translate into warmer water temperatures. “20 degrees is really the critical temperature for salmon” says Dr.Dery, if the water is above 20 degrees C, fish may become susceptible to a disease called columnaris, and can become confused about where they are supposed to go. “Certainly for a couple of summers in the Nechako River, water levels have reached that level if not above, so certainly not good conditions for the salmon in that system.”
Then there’s the potential for drought. “Lower flows definitely are an indication of dry conditions. Certainly for the past couple of summers here in Prince George, we have seen these very dry summers. Just looking into the future, we believe this is going to be a more frequent occurrence in the Fraser River Basin.”
“Unfortunately, I think conditions may be exacerbated in the future” says Dr. Dery, ” I guess one option is that we increase releases from the Nechako reservoir during that critical (salmon migration) period in the summer.”
Dery says it’s not the end of the world “We will still see some summers with above normal precipitation, but it’s certainly a trend we are seeing now based on our results.”
Dery says some “adaptation strategies” may have to be considered, such as increased water restrictions or closures of fishing seasons “The Fraser River is still a very large river, so it’s not going to go bone dry, so there will still be lots of water in there, even in the dry summers, but certainly we may have to consider such options.”