Seasonally high temperatures have sped up the rate of snowmelt above the Comox Lake Reservoir and that means BC Hydro will release high volumes of water downriver to keep the lake level from going too high.
BC Hydro will increase the Puntledge River flow by about 50 per cent Wednesday night, return to normal flows by Thursday morning, then increase the river flow by about threefold starting Thursday night and hold at that level through Tuesday.
The public is advised to stay out of the river during these potentially dangerous water releases. Safety signage will be posted along the river.
On Monday, BC Hydro increased the river flow by about 40 per cent but within the limits before public river safety notification is needed. The moderate increase has not been able to keep up with water inflows into the lake.
It was a drier-than-normal winter and a bit of a challenge for BC Hydro to conserve water for downstream fish habitat. For 2013, the lake level and river flows have been on the low side.
Things began to improve in April with a few storm systems and warmer weather, causing some snow melt. The lake level and river flows moved higher.
However, the water abundance has certainly increased in recent days with the record and near-record temperatures for this time of year causing snowmelt. Rising by about 10 centimetres per day, the lake level is now at 135 metres, about 30 centimetres from spilling over the Comox Dam.
BC Hydro had been releasing about 32 cubic metres per second (m3/s) from the dam for the power generating station and river fish habitat flows until it increased the discharge on Monday to about 46 m3/s.
Beginning at about 10 tonight to about 8 a.m. Thursday, BC Hydro will increase the river flow to about 70 m3/s before reducing back to the 46 m3/s level.
Then beginning Thursday night and by Friday morning, the river flow may be as high as 110 m3/s through to Tuesday. Water inflows into the lake have been around 70 m3/s. Browns and Tsolum river flows enter the river system downstream.
The high release of water from the dam will first and foremost control reservoir levels, and secondly, allow the Vancouver Island Whitewater Paddling Society to utilize the water abundance with ideal kayaking conditions.
These experienced kayakers are familiar with the fast moving water conditions, and the water is still cold. Tubers should not enter the river.
BC Hydro has also discussed operations with Fisheries and Oceans Canada and will keep river flows below 110 m3/s out of consideration for young salmon fry.
BC Hydro plans to lower the reservoir level by mid-next week so it can absorb more inflows as the snow melt season progresses.
There is no risk of downstream flooding. For BC Hydro-operated facilities on Vancouver Island, the flood risk is only within the fall to winter timeframe.
This year’s spring to summer water supply inflow forecast into Comox Lake is about average, at 99 per cent. This BC Hydro forecast considers snowpack, rainfall and historical records. The forecast variation is 12 per cent should the forecast turn dry or wet.
— BC Hydro