The Campbell River overflowed its banks in a number of places along Highway 28 on Saturday.

High water flows start to abate

BC Hydro is finally able to turn the tap down as a period of intense rainfall eases off.

“We finally have the extended weather break we were all looking for,” BC Hydro spokesperson Stephen Watson said on Monday. “The continuous storm activity has finally come to an end, at least for now, with only sporadic showers in the forecast for this week.”

The upper Campbell River watershed received the normal amount of precipitation for the whole month of November (400 mm) in the first eight days of the month. From a water inflow perspective, in the six weeks since the start of October, Upper Campbell Reservoir/Buttle Lake received the runoff volume that normally would occur between October to mid-January.

“We were very concerned about the potential water inflows from the Friday to Saturday and Sunday storms but the precipitation rate wasn’t too bad,” Watson said.

With the promising weather forecasts the past day or two for drier conditions for the near term, Watson said, BC Hydro was able to drop discharges through the system and below their three dams from the 600 cubic metres per second release that was put in place last Wednesday. On Saturday, Hydro reduced the discharge to 500 cubic metres per second, and Sunday evening, the company reduced it further to 350 cubic metres per second.

“We had notified the City of Campbell River of the risk for potential flooding last week and that notification was rescinded on Sunday, at least for the near term,” Watson said. “It was nice to see how the city coordinated with BC Hydro and prepared the community, including the city working with property owners in case the water inflows rose and corresponding releases from our dams caused isolated flooding to take place.

“We need to remain diligent as the reservoir is high and we are now hitting mid-November which is typically when storm season starts. The weather over the next week looks relatively benign with lower freezing levels. It will take some time for the upstream reservoirs to gradually lower to more normal conditions.

There are many variables that can lead to downstream flooding, Watson said.

“Somewhat remarkably, those variables fortunately did not line up over the weeks of record storm run-off to cause any significant downstream flooding,” he said. “When the Quinsam River did peak, it peaked at times that were manageable. The high tides were lower the past three weeks than they are now, now that the King Tides have begun this week. It’s all about timing. The winds did not cause too much storm surge by pushing water up the estuary. And BC Hydro was able to hold back water at key times to limit downstream effects, such as for four hours during the daily high tide.

“To go through such an extremely wet period and essentially have very limited impacts from a flood risk management perspective was very fortunate.

“The reservoir was at about 215.5 metres in mid-October when these storms increased and we were pleased that our operations were able to keep back the majority of the large inflows that were coming into the reservoirs; this was the benefit of upstream attenuation and regulation from our dams.”

The Upper Campbell Reservoir/Buttle Lake hit a high of 221.2 metres last Wednesday and is now at 219.9 metres. It came up very slightly with the Sunday storm.

“We will continue to gradually reduce the river flow this week to minimize fish stranding as flow is reduced in areas that are not normally covered with water,” Watson said. “These very high flows had the potential for gravel movement within the Campbell River. When inflows and water releases return to normal, we will be working with government fish agencies and stakeholders to assess impacts to fish habitat.”

BC Hydro will maintain a flood risk management spill rate likely through this week and will reduce flows in coordination with river monitoring.

There is potential for a wetter weather pattern to develop by next weekend, albeit with lower and more seasonal freezing levels, so flow in the Elk Falls Canyon will probably not get all the way down to its minimum base flow of four cubic metres per second this week.

People are being reminded to stay away from the river through this week with the high flow rates.

By this coming weekend the Upper Campbell Reservoir/Buttle Lake may be around 219.5 metres.