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Record low flows on Puntledge River

On Thursday, given the continued dry summer conditions, BC Hydro will move the Puntledge River down to the lowest flow rate ever recorded in BC Hydro’s 52 years of data. The water release from the Comox dam will go from 8.5 m3/s to 7.5 m3/s.

The normal river flow rate for this time of year is around 25 m3/s.

The region is in extreme drought and adjacent river flows into the Puntledge River are at all-time lows. The Brown River and Tsolum River are at flow rates that are close to zero. The water inflows into the Comox Lake reservoir have been around 2 m3/s for some time. The small amount of rain over the weekend, up to 20 mm over the watershed, was nice to see but did not change the overall conditions. If not for the Comox dam and BC Hydro’s ability to manage a sustainable downstream flow, the natural flow down the Puntledge River would only be around 2 m3/s.

BC Hydro continues to work closely with Fisheries and Oceans Canada and the Comox Valley Regional District. BC Hydro communicated in our June 29 community update that there was a good likelihood the water release from the dam would be reduced by a further 1 m3/s to conserve water for the months ahead. The 7.5 m3/s flow may be the lowest river flow level BC Hydro may provide this summer, as this new flow rate positions us well to maneuver through this extreme weather drought into October.

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BC Hydro spokesperson Stephen Watson…

The CVRD’s summer instantaneous peak withdrawal from the BC Hydro penstock can be as high as 1.2 m3/s. In order to bring down that flow rate, the CVRD has restricted flows into its reservoirs. The lower, more consistent withdrawals from BC Hydro’s penstock enable our operators to more efficiently maintain minimum river flow requirements.

Because of the reduction in domestic water consumption, the CVRD instantaneous withdrawal peak is now at 0.65 m3/s. The CVRD has water for fire protection and sufficient water system pressure. Close coordination between BC Hydro and the CVRD allows BC Hydro to be aware of the CVRD withdrawal rates so that BC Hydro can refine the amount of water released from the dam to provide the targeted fish habitat flow. It also keeps just a bit more water in the reservoir for storage, and in the river for fish.

At the end of last week, the Comox Lake reservoir was at 133.65 metres, dropping from 133.92 on June 29. Over the past three or four days the reservoir has been holding steady at that level with the modest rain and will now begin dropping by about 2 cm per day as it has been doing over the past month.

BC Hydro has only been running the four hydroelectric systems on Vancouver Island at about 10-15% of capacity. BC Hydro has been closely monitoring and anticipating a dry spring and summer, although the extent of these current drought conditions is remarkable. BC Hydro’s proactive flow adjustments on Vancouver Island are to ensure sustainable water flows for fish, local energy reliability requirements, and domestic water supplies in the event this drought last into the early fall.

BC Hydro has the benefit of an integrated hydroelectric system of reservoirs, dams and generating stations in different climactic zones across the Peace, Columbia and South Coast regions.

This allows BC Hydro to manage its operations with various degrees of flexibility during unusually dry or wet conditions. Currently, BC Hydro is forecasting to have more than enough energy to meet provincial demand during this fiscal year. It just means more electricity is being supplied to Vancouver Island through our undersea cables that connect to the provincial grid.

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