Submitted by Stephen Watson
BC Hydro
The wet weather continues.
Just how wet was October? We set a new precipitation record in the upper Puntledge River watershed for the month of October. Our precipitation records go back 36 years. The new record is 537 mm or almost 54 cm, breaking the previous record of 506 mm.
As well, it was the second highest total water inflows for the month of October into Comox Lake reservoir. That record goes back 49 years.
So far we have been able to manage through this very wet period quite well with the reservoir level not getting too high, but also holding back water at key times for downstream flood risk management. The reservoir is slowly moving upward after each storm though we try to move it down again between storms. Since yesterday, we have been able to pull down the reservoir level by nearly 50 cm and it continues to drop with our Comox dam spillway gates wide open. This will be harder to do this week based on what’s forecasted, with the reservoir storage filling up; this may be a concern for full flood risk management capabilities for a potential storm at the end of week.
The month of November is off to a very wet start. Storm activity began Tuesday evening and was expected to peak Wednesday, with precipitation totals on Wednesday forecast (at press time) to be near 80 mm. This will be the most significant storm this week.
Precipitation rates on Thursday to Saturday may be 30 to 40 mm per day. It may be hard to lower the reservoir over this period with the constant water inflows. There is the potential for another large storm hitting the area on Monday and Tuesday.
The way the storms tracked in October and are forecasted to track this week, the mid-Vancouver Island and Comox Valley area has had more than its share of rain. A bit of a bulls-eye seems to be painted on the area.
BC Hydro will continue to release maximum water levels from Comox dam downstream for likely the next two weeks. We will once again back off on the discharges for the high tides. Discharge rates from the dam may go as high as 200 m3/s this week as the reservoir water level increases from the storms.
The Comox Lake reservoir is currently at 133.65 metres.
Please stay away from the Puntledge River through this week and next week. River flow rates may reach the highest level so far for this fall storm season, and will be very dangerous.
Through this week, there may be the potential for isolated downstream flooding on Wednesday during the high tide, which is at 4.7 metres at 8:42 am. It will depend on when and how high the Browns and Tsolum rivers peak. Winds look to be out of the southeast and may cause some storm surge. There is a low downstream flood risk from Thursday to Sunday. Monday and Tuesday next week would be the next focus.