BC Hydro is reducing the Puntledge River flow from about 12 cubic metres per second (m3/s) to 8.5 m3/s, or by about one quarter, out of concern for the ongoing and unprecedented dry weather.
“The last time BC Hydro did this was in October 2006 when dry conditions lasted well into the fall, and matches the lowest river flow in recent history,” said Stephen Watson in a press release.
BC Hydro’s water supply year is measured from October to September, and with a few weeks to go and the forecasted dry weather, 2013/2014 will become the driest year in 51 years of BC Hydro record.
BC Hydro has been monitoring the forecast and there was some hope for a weather transition this week to some stormy conditions. That system has now shifted north and following that, a high-ridge pressure is likely to form again.
“The Comox Lake Reservoir has been dropping by about four centimetres per day, and recently, is nearing five centimetres per day,” said Watson. “The current reservoir level is now 131.95 metres and at the previous discharge rate, we would run out of water be early October – the caveat being the natural water flow entering the reservoir would then pass downstream. Right now that’s around 2-3 m3/s versus the 12 m3/s we had been releasing below the dam. By moving to about 8.5 m3/s, it pushes out the length of time we can maintain that river flow to around October 21.”
The 24 megawatt Puntledge River generating station has been out of service since June with the dry conditions. Since then, BC Hydro has been managing downstream flows for fish habitat, water supply for the Puntledge River Fish Hatchery, and water that’s extracted from the penstock or river for domestic water use by the Comox Valley Regional District.
In June, with the depletion of the snow pack and low water abundance conditions, BC Hydro determined with a 95 per cent probability that the 12 m3/s release would last through the summer and early fall until the fall rains arrived.
“That five per cent chance of not making it has risen its head and BC Hydro must take further action,” said Watson. “On September 15, BC Hydro held a conference call with Fisheries and Oceans Canada and the Ministry of Forests, Lands and Natural Resource Operations. There was agreement on the change in operations given the unprecedented conditions and lack of water. BC Hydro has also been in contact with the Regional District.
“BC Hydro is very concerned that even with the 8.5 m3/s flow there is still a chance the dry conditions could make things even more severe. Conversely, all we need is one good storm event.”
Should conditions change BC Hydro will provide further updates.