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Puntledge River flows drop to a trickle: BC Hydro

We are in a level of dryness for this time of year in the Comox Valley that no one could have imagined. The water inflows into the Comox Lake reservoir have now dropped to basically a trickle. BC Hydro’s main focus is the late summer and having enough water in the reservoir for September and even October, so more action is being implemented to protect the water storage we have.

After operating the Puntledge River hydroelectric system at only about 20 per cent of capacity in May to keep key fish habitat covered, in my May 22 community update, BC Hydro communicated a proactive and responsible operational plan in consultation with government fish agencies for water discharges through September. And as planned, BC Hydro shut down power generation on June 16 and has been providing a water release of only 12 m3/s down the river system. That plan is now obsolete given the stunning drop in water abundance.

We have come through the lowest snow pack on record and have had the double-whammy of a record dry May and June. Over those two months, we had about 15 mm of precipitation. Water inflows into the reservoir in May were 29% of normal, and this month, 17% of normal.

BC Hydro spokesperson Stephen Watson…

Since June 8, this extremely dry situation has come to roost with water inflows going from 8-9 m3/s, to about 3-4 m3/s range, to about 1 m3/s late last week. There’s little water coming into the reservoir; where there is some, the surface evaporation rates are eliminating most of it. To put it in perspective, the previous record low water inflow rate into the Comox Lake reservoir for this time of year was 10 m3/s back in 2009. Our records go back 52 years and to break it in such a manner is hard to believe.

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From now until September 30, BC Hydro is modelling an average water inflow rate of only 1 m3/s – an absolute worst-case scenario. And from that standpoint, we have modelled out various discharge scenarios to determine the best course of action to not run out of available reservoir storage. The current reservoir level is 133.92 metres, about a metre below the historical average for this time of the year.

Tomorrow, BC Hydro is moving to the extreme conservation flow of 8.5 m3/s versus the earlier plan of going to that level on August 1. That flow rate has been initiated only a few times before, and unlike those situations, this is being done not at the end but at the beginning of the summer. In addition, with further government fish agency discussion planned next week, we may likely be moving the Puntledge River flow down to 7.5 m3/s in mid-July – a discharge rate BC Hydro has never implemented before. By reducing our operations, even to these extremely low river flow rates, the Comox Lake reservoir may be forecasted to be around 130.8 metres by September 30. The threshold level where uncertainty begins on how much water can be released from the dam is at 131 metres. The Comox dam is located about 200 metres from the outlet of the reservoir, and it becomes a river channel from the reservoir to the dam.

BC Hydro took advantage of the low reservoir conditions last year to conduct lake bottom slope and depth readings in the event dredging may be required in front of the dam in the future. We are now focusing our attention on that raw data to determine what the potential flow rates may be from 131 to 130 metres. This will greatly assist in planning for emergency instream dredging works should that situation come to pass in late September or October. The goal is to never get to that point.

BC Hydro has reached out to the CVRD throughout the spring on the drought situation and that happened again late last week. The CVRD has employed measures for the five reservoirs it has across the Comox Valley to limit the peak CVRD instantaneous withdrawal from the BC Hydro penstock, and therefore lesson BC Hydro’s buffer flow to maintain about 8.5 m3/s in the river for fishery and water licence reasons. The less the CVRD draws on the penstock, the less of a water flow buffer BC Hydro needs to provide to maintain the targeted river flow.

BC Hydro weather forecasters, as well as provincial and federal forecasters, are unanimous that the summer will be hotter and drier than normal. While the odd small storm system this summer will be of welcome relief for all, there is nothing yet on the horizon.

To learn about one of the main causes of this weather phenomenon the last two years that’s causing low snow pack and dry conditions, check out the Blob that began forming in the Pacific Ocean in 2012/2013. This large area in the ocean has temperatures about 3 degrees warmer than normal. See link:

(BC Hydro)

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