BC Hydro has extended its public safety notice advising residents to stay away from the Puntledge River until Feb. 12, saying river flows will remain high and dangerous.
“Last week was challenging with the three successive atmospheric rivers bringing almost 300 mm of rainfall and major snowmelt within the upper Puntledge River watershed,” said BC Hydro spokesperson Stephen Watson. “We entered the wet week in a great position with a lower than normal Comox Lake Reservoir level for this time of year, at 132.7 metres above sea level. We started pre-spilling at Comox Dam in the evening of Jan. 24. With the heavy rain and snowmelt, and backing off for the high ocean tide for four hours every morning, the reservoir level peaked on Feb. 1 at 135.46 metres. That’s a 2.75-metre water level increase and a level not reached since Nov. 2016.”
According to BC Hydro, the five-day period from Jan. 29 to Feb. 2 had the second-highest water inflow average, at 291 m3/s, on record into the Comox Lake Reservoir. The highest was 301 m3/s in 2011. (Records go back to 1963.)
The peak hourly inflow rate into the reservoir was around 500 cubic metres per second (m3/s) while downstream flows from the Comox Dam were as low as 50 m3/s during the high tide. Discharges at low tide were as high as about 230 m3/s. The high flows from the dam that started on Jan. 24 will end the evening of Feb. 5.
“As is the case for each storm event, the risk of isolated downstream flooding much depends on the timing of the peak flows from the Browns River and Tsolum River, the high tides, and any storm surge from winds,” explained Watson. “Thankfully, the tides were on the lower side last week and the natural flowing rivers didn’t have peak flows during the high tides. It was a bit tenuous at times and there was good co-ordination with Comox Valley Emergency Management (CVEM). With the higher-than-normal reservoir level, in co-ordination and led by CVEM, there was reservoir level monitoring in place, though the levels ended up being about 30 centimetres below potential impacts along the reservoir shoreline.”
The reservoir has moved down to the current water level of 134.55 metres.
“We will lower the Puntledge River flow to normal conditions on Feb. 5 and 6, to be able to provide ideal steelhead migration and spawning flows. However, river flows will be back up to about twice the normal flow rate to about 70 m3/s on Feb. 7,” said Watson.
Danger safety signage will be updated with the Feb. 7-12 dates. This will good timing for the next weekly fish migration flow on Feb. 13 and 14, and also allow BC Hydro staff to move the reservoir level downward to prepare for the final set of ocean king tides on Feb. 10-14. These tides will be up to half a metre higher than the tides from last week.