Cowichan Lake had just 16.5 per cent water storage capacity as of Aug. 13 as the recent hot spell, which saw temperatures in the region go above 30C, began to die down.
Brian Houle, environment manager at the Domtar Crofton mill, which owns and operates the weir at Lake Cowichan, said the regulators of the watershed decided to reduce water flows from the lake over the weir to 4.5 cubic metres per second beginning on Aug. 13.
He said the flow reduction will be done in two stages, dropping to 5.0 cms on Aug. 13 and then to 4.5 cms on Aug. 14 and that flow will hold until the rainfall returns this fall.
“The weather forecast shows rain coming, and there is possibility that this rainfall will be significant,” Houle said. “Domtar is coordinating that 20 large water pumps will again be rented and delivered to the weir area in advance of needing to use them to sustain the base flow in the river. The pumps are expected to be needed on or about Sept. 15, depending on the weather in the coming days.”
After a severe drought that struck the area in the summer of 2023, Domtar had to use 20 pumps for more than a month in September and October of that year to pump water over the weir to sustain water levels in the river.
Houle said that on Aug. 12, the average water temperature in Cowichan River was 22.9C during the heat wave, but noted that it’s expected that the water temperatures in the river will drop in coming days as the forecast is calling for cooler temperatures.
“Water quality in the river has improved, and solar gain is reducing each day now, with fall coming soon,” he said.
The drought in 2023 lowered water levels in Cowichan Lake and the Cowichan River dramatically and impacted water quality, which resulted in the deaths of approximately 84,000 fish in the river.
Houle said that, as water flows are reduced to the river, Domtar will have qualified professionals in the river helping to salvage fish stranded in pools, as well as measuring water quality.
“Water quality measurements are very important now to understand fish-habitat health as flow is reduced,” he said. “Weekly calls with the regulator and stakeholder group will continue next week as we may have the opportunity to increase the river flow if the rainfall that is being forecast raises water levels in the lake in the coming days.”
