BC Hydro update: Record low water inflows into Comox Lake reservoir

October 6, 2017

From Stephen Watson, Engagement Advisor at BC Hydro:

It may be a surprise to learn that the September water inflows into the Comox Lake reservoir were the lowest on record for that month. Our records go back to 1963. Only July 2015 had a lower cumulative monthly total. The month of October is also starting at a record low water inflow volume level and the forecast looks dry for the next two weeks.

Total inflow volume for September was 42% of normal and October is starting off  very low. This also follows a dry July and August when inflow volumes were 65% and 52% of normal, respectively.

We had been fortunate to have some rain and mostly a good snowpack that led to good water abundance in the Puntledge River system through the spring and summer.  But the continual dry weather is catching up to us and we are beginning to see impacts.

BC Hydro has kept the Puntledge River flow at the minimum fish habitat flows of about 16 m3/s through the summer.  However, after seeing the dry weather looking to continue, we dropped the discharge from the Comox dam down to 13.5 m3/s on September 20. We had done this change just prior to the active salmon spawning season so fish eggs may not be dewatered, and mainly, to have better certainly of maintaining  that flow rate until the fall rains arrive. We lowered the river flows in consultation with government fish agencies.

The dry weather looks to continue and further action needs to be taken.

Into October, we have had daily water inflow averages around 1-2 m3/s, while we release up to 14 times that volume downstream for fish habitat and domestic water supply. The generating station has been shut down to conserve water.

BC Hydro and the Comox Valley Regional District are always in close communication and the regional district is doing its part to stabilize and minimize water flows taken from the BC Hydro penstock. With historical swings of around  1 m3/s coming out of the penstock to fill their six water reservoirs around the Comox Valley, the regional district has made improvements on how they pull water from the penstock. Over the past two weeks they have seen a maximum withdrawal of about 0.3 m3/s. This better precision and lower threshold of water withdrawals was in response to previous years of extremely dry weather conditions where river flows have been low. This water efficiency improvement allows BC Hydro to provide less flow buffer in the river to maintain our conservation flow for fish habitat. A difference of 0.7 m3/s or more that is now not needed as extra buffer in the river for potential water supply withdrawals can add up over time in the Comox Lake reservoir level.

The Comox Lake reservoir is currently at 132.0 metres and has been dropping by about 3-5 centimetres per day. The reservoir is considered full at 135.3 metres. When the level approaches 131 meters we begin to get concerned about providing water flows down the Puntledge River.

BC Hydro and government fish agencies just completed another round of discussions and tonight we will be reducing the Puntledge River flow down to 12 m3/s. The goal is to not approach the 131 metres reservoir level threshold.

BC Hydro may provide a community update as the conditions change.