A simple word of explanation on what happened since Monday into today is that we got walloped with rain.
The Puntledge River watershed has seen massive amounts of rain and subsequent run-off into the Comox Lake reservoir and downstream river systems. On Monday, 100 mm of rain fell above the Comox Lake reservoir and now into Tuesday, from 12:00 am to 10:30 am, 94 mm of rain has fallen. That’s basically 200 mm in 36 hours.
The water inflows have been massive. The Cruikshank River hit a high of 530 m3/s this morning and is coming off that peak. The peak water inflows into the reservoir hit about 1000 m3/s – that’s the equivalent of the water within an Olympic-sized swimming pool entering the reservoir every 2.5 seconds. The water inflows will be very high through today.
The Comox Lake Reservoir has risen about 1.5 metres in the past 24 hours to noon Tuesday. At the current rate of rise, we see it beginning to free spill over the dam tonight. As the reservoir level increases, BC Hydro’s downstream operational flexibility diminishes.
BC Hydro proactively lowered the reservoir in advance of this storm. With the very high water flows downstream, as per normal protocol, BC Hydro decreased the water release from the dam from about 180 m3/s to about 32 m3/s in advance of the high tide this morning.
BC Hydro spokesperson Stephen Watson..
A water survey gauge at the 5th Street Bridge reached a maximum of 4.61 m at 8:30 am around the peak tide before slowly receding. Isolated flooding can begin at 4.2 metres. As the tide moved out, BC Hydro increased water discharges from the dam to maximum to move water out of the reservoir. This was delayed by one hour in consideration of what was happening downstream, which were followed by gate operations issues that limited our ability to release planned water volumes downstream. The current rate of discharge from the dam is about 200 m3/s. The water inflows into the reservoir upstream of the dam have been four to five times that amount.
BC Hydro will reduce flows from the Comox dam during tomorrow morning’s high tide.
The Tsolum River just hit a high of 282 m3/s which is a new record, but now starting to recede, and the Browns River hit a high of about 250 m3/s and is receding – 133 m3/s as of now.
BC Hydro is in close coordination with the City of Courtenay and emergency response agencies will continue discussions as needed over the next few days. This will be a multiple day event. A new storm, with up to 70 mm of rain is forecasted to hit the area tomorrow morning.