A presentation from Rio Tinto Alcan outlined concerns about flooding due to high levels of snowpack unusual for this early in winter, the District of Vanderhoof heard at its January 11 meeting.
“Snowpack levels are reaching historical maximums,” Alcan representative, Justus Benckhuysen told mayor and council as he showed graphs, including satellite real-time data measurements made over the couple of weeks prior to the meeting.
While reservoirs are capable of holding large influxes, even major discharges to relieve the buildup from local watersheds could still see reservoirs remaining filled to the brim by spring the hydrographer warned.
“Based on the where Vanderhoof and are are now and the natural drop we would expect as the winter gets colder, we can expect the inflows for the year to be 156 per cent of the long-term average,” Benckhuysen noted.
The Alcan presentation showed the effect of what it might look like if the pattern were to continue, “even while some of this has to do with the warmer temperatures that we’ve been experiencing,” he said, while snow continues to accumulate.
He showed the flow conditions of the Nechako River to include a model of maximum flow scenario at more than double the average as the region has been experiencing so far this winter.
With the average precipitation and snowmelt we can reasonably expect Benckhuysen observed, along with the maximum volume of water that can be discharged from the reservoir, (some 80 cubic metres per second,) it would be just short of being filled to the brim.
“The reservoir would not quite fill up. We would reach one foot from capacity,” Benckhuysen said.
But he also noted that this means we would still be needing to let go the maximum discharge from out of the dam’s spillway as the warmer months progressed to keep up with the agressive flow.
“We would need to let go as much water as we can all spring and summer,” Benckhuysen said.
He added that water flows can be hard to predict, observing, “It’s not always possible to match trends and this can only be seen in hindsight.”
Fire and rescue chief, Joe Pacheco said they are revamping their rescue plan just in case. Mayor Gerry Thiessen ended the discussion by requesting Benckhuysen to return in two weeks to give an update of the situation.