There was finally a shift to wet weather on Dec. 24. Since then, the Comox Lake Reservoir has risen about three metres. With the continued wet and mild weather forecast, BC Hyrdo needs to release extra water down the Puntledge River. Hydro is issuing a public safety notice to stay away from the river with the high and dangerous flows from the evening of Jan. 6 through 13. Temporary safety signage has been placed along the river.
“We’ve moved from very low water conditions to flood risk management operations in 14 days,” said Stephen Watson of BC Hydro.
With improved water storage conditions, Hydro began to generate electricity from the Puntledge powerhouse last week. The current discharge from the Comox Dam is about 40 cubic metres per second (m3/s), with the powerhouse running at full capacity and some extra water within public safety thresholds being released down the Nymph Falls section of the river. Through most of December, Hydro was releasing only about 8 m3/s from the dam.
The reservoir level hit a low of 130.92 metres on Dec. 23. The level is currently at 133.92 metres. Hydro generally likes to see it at or below 134 metres at this time of year for flood risk management considerations and being able to hold back water during high tides. The reservoir generally operates between 131 and 135.3 metres.
Beginning Friday night, Hydro will increase water release from the dam from about 40 m3/s to 90 m3/s and plan to hold it at that flow rate through the weekend. The 90 m3/s flow rate is for expert kayakers who for the first time this fall/winter will have ideal Puntledge River kayaking conditions. The wider public is advised to stay away from the river flow.
From Monday to Friday next week, discharges from the dam may be within the 45 to 110 m3/s range to help control the reservoir level. Hydro will closely watch the tides, and the downstream Browns and Tsolum river flows, and may reduce discharges for about four hours prior to the high ocean tides, which are 5.0 metres this week. Puntledge flows may be moving up and down each day.
The snowpack is about 60 per cent of normal for this time of year though lots of time to recover. The snowpack typically peaks in April.
“We are always looking at the near-term and long-term weather forecasts, current snowpack conditions, hydrologic forecasts, and are conservative in our decisions for environmental and social considerations while generating clean power,” Watson said. “Upon reflection, we managed through this past fall as well as possible. Salmon were able to spawn and we tried to keep those salmon eggs covered with water.”
The December and upcoming January ocean king tides
It’s always a tenuous time during the ocean king tides. Over that time, possible storms and how the Browns and Tsolum react and if they peak during the high tide, possible ocean storm surge from winds, and the water releases from the Comox Dam. There are many variables that go into the potential of isolated flooding in the Courtenay area. There was a close situation Dec. 26 and 27 during the king tides. The total river flow under the 5th Street Bridge was about 270 m3/s and about 180 m3/s on those days, respectively, while the discharge from the dam over those two days was around 8 m3/s – far less than what Hydro may be providing in normal storm conditions when the releases may adjust from about 30 to 200 m3/s or higher during low tides. The record low reservoir level for this time of year and the ability to absorb all those inflows was fortunate. The height of the water level around the Courtenay River by the estuary was near the brim over those two days. Generally, about 400 m3/s of river flow can potentially cause isolated flooding, though under this close king tide and storm scenario it was at a significantly lower flow rate and still close.
There was good communication between BC Hydro, City of Courtenay, and the Comox Valley Emergency Program during the December storms, and that continues into January. The final set of king tides, at the 5.3 to 5.4 metre level, is Jan. 22 to 26.