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Comox Lake inflows lowest in 50 years

The dry and cool fall season has provided record low water runoff for this time of year into the Puntledge River hydroelectric system.

Water inflows into the Comox Lake Reservoir from Oct. 9 to date have been the lowest in 50 years of record. BC Hydro is operating the 24-megawatt Puntledge River generating station at 25 per cent of capacity to conserve water.

This is normally a time of year when we are running our Vancouver Island hydroelectric facilities near full capacity and have a careful eye for flood risk management. Not this year.

The Puntledge River is flowing at about a third of normal for this time of year and the reservoir is at about 132.3 metres and dropping slowly. The reservoir is about 1.4 metres below normal and the fourth-lowest on record for this time of year.

The reservoir level where things may become more critical for meeting downstream river flows is around 131.3 metres. 135.33 metres is considered full.

BC Hydro was running the generating station at full capacity as a result of the significant storm at the end of September, but following that event and the dry weather setting in, generation output was dropped to 40 per cent on Oct. 22, and to 25 per cent on Nov. 28 to manage the conditions.

The forecast is somewhat unsettled this week and will make little difference in the situation. The weather next week is forecast to be relatively dry.

BC Hydro has been working with Fisheries and Oceans Canada and the Ministry of Forest, Lands and Natural Resource Operations in keeping them apprised of the conditions.

The Puntledge River is flowing at about 16 to 17 cubic metres per second (m3/s) and this is just enough to keep the river margins and salmon eggs fully covered with water. The inflows into the reservoir upstream have only been about seven m3/s and the reservoir has been dropping about three centimetres per day.

The longer-term concern is the potential for winter drought-like conditions that happened from mid-December through to spring last year, where the cool and dry conditions made it challenging for BC Hydro to meet downstream environmental flows for fish.

The reservoir level was higher last year, meaning we have less water storage this year should this dry pattern continue. However, one large storm system could quickly change the water abundance conditions.

There is no concern for meeting domestic water supply withdrawal requirements for the Comox Valley Regional District.

BC Hydro may provide further operational updates to the community in the future.

The nearby Campbell River system is also operating to conserve water, and is running at about 50 per cent of power generation capacity to also keep salmon eggs in that river system covered with water while managing upstream reservoirs.

Fish screen cleaning

Fish screens positioned in the penstock or pipeline at the Puntledge Diversion Dam requires two cleanings per year.

This dam is where the water is pulled from the river, about 3.7 kilometres downstream of the Comox Dam, into a pipeline that travels five kilometres to the generating station and back into the river.

The purpose of the screens is to screen fish that get pulled into the intake back into the Puntledge River. The annual spring cleaning has been in April each year. Grasses, algae and debris gets lodged into the screens.

For 2014, in working with Fisheries and Oceans Canada, and seeing the 2013 outmigration of salmon happening earlier in the season, BC Hydro has moved the cleaning up to February so it is more effective.

BC Hydro has set Feb. 3 to 5 to dewater the pipeline and clean the screens. During those three days the Comox Valley Regional District will be required to pull water from the Puntledge River and not the BC Hydro pipeline.

— BC Hydro

 

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