BC Hydro Puntledge River Operations
March 9, 2016
From BC Hydro:
Yesterday morning, we identified the potential for all the ingredients to add up to potential isolated flooding in the lower areas near the Puntledge River within the City of Courtenay. We immediately reached out to the City and other key emergency response leaders to provide a heads up on the potential risk, understanding forecasts are subject to change.
Today’s forecast has worsened a bit for the storm that’s about to hit the area. Given the storms tracking, we are looking at perhaps 100 to 140 mm for the Cruikshank River side of the Comox Lake reservoir through Thursday. There is also a fair amount of precipitation at lower levels, with our Comox dam forecasted to get around 75 mm. Freezing levels are going up 1800 m briefly for a few hours before coming back down to the 1500 m range. The upper elevations will get a good amount of snow.
There is particular focus around the high tide tomorrow morning. The higher than normal tide at 5.0 metres, significant storm surge from winds perhaps adding another 0.6 of a metre, and the Browns and Tsolum rivers, as well as other tributary water inflows, peaking near the 6:30 am high tide have all the ingredients in providing downstream flood risk.
BC Hydro has been aggressively moving the Comox Lake reservoir level downward the past few days, after that week of rain, and it is now well positioned to hold back as much water as we can during the sensitive high tide period, and potentially beyond. The two spillway gates at the dam have been fully opened for days. The potential for isolated flooding will be the result of downstream conditions. The City of Courtenay’s deployment of the aqua dam was a prudent measure to prepare for this event. Communications between the various parties continue.
The good news is the weather forecast then turns showery with no significant storms through the weekend, and then to a drier trend next week.
We ask the public to continue to stay away from the Puntledge River, given the high and fluctuating water flows, through Monday.
Previously from BC Hydro:
March 7, 2016
An update from last week. About 275 mm of precipitation has fallen in the upper Puntledge River watershed so far this month. Since March 1, while there has been high snow accumulation in the upper elevations, a lot of this precipitation has fallen as rain and provided significant water inflows into the Comox Lake reservoir.
How much water have we had? Water inflows this month have been about 350% of normal. The water inflows the last 6.5 days would equate to the Comox Lake reservoir rising by 3.6 metres, or filling over 80% of BC Hydro’s available reservoir water storage (from 131 metres to 135.3 metres). The vast majority of this water has been safely passed downstream for flood risk management.
The reservoir level is currently at 134.55 metres. That’s 0.5 metres higher than where it was on February 29.
BC Hydro has been spilling maximum water levels at low tide and backing off for about four hours for the high tide. This operational manoeuver will likely continue through to next Tuesday. Discharges from the Comox dam have ranged from about 190 m3/s to about 50 m3/s at high tide.
The good position we were in with the low ocean high tides a week ago has shifted to very high tides this week. They have moved upward each day from 4.2 metres and will hit 5.0 metres on Wednesday through Saturday before moving downward again. There is also forecasted to be some ocean storm surge from winds that will slightly raise the tides.
We continue to advise the public to please stay away from the Puntledge River through to next Tuesday. The danger safety signage continues to be in place throughout the river system.
We are following some storm activity forecasted for Wednesday but much of this storm has shifted farther south. There is also a potential significant storm on Saturday. At this time we do not see any downstream flood risk though this will be more dependent on Tsolum and Browns river flows timed with the high ocean tides.