This storm system is ending up being a one in two-year event.
An atmospheric river has provided rainfall amounts from Wednesday afternoon of 180 mm, plus about 20 per cent more water from snowmelt.
BC Hydro is advising a high river flow advisory from Friday at 6 p.m. through Tuesday morning and for the public to stay away from the Puntledge River. BC Hydro will increase the Puntledge River flow by up to 500 per cent.
A thin but long strip of precipitation known as an atmospheric river hit the West Coast on Thursday and went right over the Ash and Puntledge river watersheds. This watershed took a direct hit and more heavy rain may fall until noon Saturday before dissipating.
Hourly peak inflows into the Comox Lake Reservoir have hit 360 cubic metres per second (m3/s) yet BC Hydro has been releasing just 40 m3/s downstream of the Comox Dam.
The Browns (84 m3/s) and Tsolum (209 m3/s) rivers that feed into the Puntledge downstream also hit fairly high levels.
Flooding in the Courtenay River can begin with a total flow of about 400 m3/s but this depends on high ocean tides and storm surge from winds.
BC Hydro was able to absorb the storm but the reservoir level increased by about 1.2 metres in about 36 hours, and it will continue to rise. It was at 134.4 metres early Friday afternoon and will reach around the 135-metre range or even higher before trending downward.
Water free-spills over the dam at 135.3 metres
BC Hydro has modified its operations given the larger storm event than forecasted. Beginning at 6 tonight, river flows will increase to almost 200 m3/s.
BC Hydro will hold at this level for several days with the exception of high tides; and will lower the flow release to as low as 50 m3/s four hours in advance of the high tides, and once the tide moves out, will go back to about 200 m3/s release.
River flows as a result will go up and down significantly.
The weather forecast looks drier but still wet through early next week. BC Hydro is monitoring a storm system that could be significant and hit on Tuesday. The current track is further to the south but the track could change given it is four days out.
BC Hydro will advise of any further operational changes. There continues to be no risk of downstream flooding through Monday.
— BC Hydro
