BC Hydro update: Puntledge River Operations and Forecasted Storms

October 12, 2016

From BC Hydro:

"A bit of an update as we seemingly quickly transition from our summer season operations to fall operations, and the upcoming storms.

Throughout the summer, we were able to provide minimum fish habitat flows down the Puntledge River system and also generate some power while doing it. We operated the generating station at 20% of capacity for most of the summer and until last week. That’s the first time we’ve been able to do that since 2013 so it was pretty good for fish and power generation, as well as CVRD domestic water supplies. 

The Comox Lake reservoir hit its lowest point of the summer/early fall on October 4, at 132.76 m. The reservoir generally fluctuates between 131 m and 135.33 meters.

A bit of a surprise storm hit the watershed last Thursday and into Friday, where we measured 60 mm of rain falling over about a 12-hour period in the upper Puntledge River watershed. This provided good inflows into the Comox Lake reservoir and since that time, the reservoir level has increased from 132.9 metres to 133.4 metres. With the improved water abundance situation, last Friday, we were able to increase power generation to full capacity. We will likely continue operating at that level through the fall. We are currently releasing about 32 m3/s from Comox dam.

Last Friday, the Tsolum River hit a peak of 238 m3/s from 15 m3/s as a result of the storm. A high flow rate considering no snow was in the mountains; it was all rainfall. The Browns River did not really react at all. It was just the way the storm hit the area.

That first fall storm was a good chance for BC Hydro to reach out to community emergency response leaders and get prepared again for the upcoming storm season, particularly on communications. We have already reached out to those leaders in advance of these more significant storms, culminating on Saturday with the remnants of a typhoon potentially hitting the area with heavy rainfall and high winds. 

We are monitoring the three storms that are forecasted to hit the area on Thursday through Sunday, potentially dropping over 200 mm of rain in the upper watershed. The reservoir is well positioned and has room to absorb much of these water inflows.  However, we will need to spill water and will do so this evening by ramping up the water discharge from the dam from around 35 m3/s to about 110 m3/s – a three-fold increase. The spill volumes will likely fluctuate as needed well into next week, and will also be lowered for the high tides.

It is a good time to start paying attention to river flow rates and the flood risk management considerations, such as higher tides and storm surges from winds, in the months ahead. The tide is quite high on Saturday at 4.9 metres and there is a potential for significant ocean storm surge up the estuary from the strong winds.

For public safety, please stay away from the Puntledge River system through next week with the high and changing river flows.

BC Hydro will provide an update on an as needed basis as we try to manage through these storm systems."