A moderate storm is expected to hit the North Island region on Saturday.
However, there is a chance the system could shift south and stall over central Vancouver Island, Stephen Watson of BC Hydro said Thursday in a news release. There is also potential storm activity around the middle of next week.
The Comox Lake Reservoir was at 134.4 metres Thursday morning, and just beginning to hold at that level.
"With the forecast, and also receiving more water runoff from the weekend storm than forecast over the past few days, we are uncomfortable in having less room to absorb future storms for downstream flood risk management," he explained.
"BC Hydro now has less than a metre of reservoir water storage room left before it spills over the dam (135.3 metres). Normally as we enter the fall and winter season BC Hydro prefers the reservoir near the 133.5 metre level. Weather conditions can change quickly."
Through Thursday, BC Hydro has in place the chinook salmon migration and spawning flow.
The chum salmon fishery is open and weekend river access for fishers is of interest. Kayakers have good river flow conditions at about 110 cubic metres per second (m3/s).
Lastly, when the reservoir moves higher, there are considerations for wave action erosion around the shoreline. With all these water use interests it is a challenging water management balancing act for BC Hydro, though flood risk management and public safety are BC Hydro’s highest priorities.
Beginning Thursday at 8 p.m., BC Hydro will once again increase the river flow by about fourfold to 110 m3/s and hold at that level throughout Friday. BC Hydro will lower the discharge to about 40 m3/s for Saturday morning and keep it at those levels during the day.
Then on Saturday night and Sunday night, BC Hydro will once again increase the river flow to up to 110 m3/s. The timing of those releases will be from 8 p.m. to 7 a.m. The river flows Monday onward should be around 40 m3/s or normal flow levels.
With this modified operation BC Hydro forecasts the reservoir level likely being below 134 metres by Monday.
BC Hydro will review operations and the weather conditions daily for potential operational adjustments as needed.
The public is advised to stay away from the Puntledge River on Friday due to the high and dangerous water flow conditions.
Current conditions pose no risk of flooding downriver, Watson added.
— BC Hydro