North Cowichan Approves Further Action to Improve Water Quality of Quamichan Lake

(North Cowichan, BC) – Findings from the year-long water sampling program on Quamichan Lake were presented at the July 17 Council meeting where Council unanimously agreed to take further action toward improving the health of the lake.

Dr. Dave Preikshot was contracted by North Cowichan to conduct the water sampling program on Quamichan Lake with the goals of: 1) establishing the current state of lake water quality, 2) identifying the specific causes for the presence of blue-green algae, and 3) identifying potential management options to improve lake quality. Key findings of the study show that the primary cause of blue-green algae is the phosphorus that has accumulated in the lake over the last 150 years, that reducing the phosphorus load into the lake will require a long-term strategy, and that agricultural activity is a more significant source of phosphorus than residential development around the lake.

After receiving Dr. Preikshot’s report, Council decided to expand the monitoring program and act on a number of Dr. Preikshot’s recommendations, including:

  • Taking a sediment core under the lake to determine the internal versus external phosphorus loads;
  • Installing temperature and dissolved oxygen meters in the lake to track changes on an hourly basis;
  • Monitoring weekly for pH, turbidity, conductivity, chlorophyll, and blue-green algae;
  • Monitoring monthly for phosphorus and other nutrients;
  • Treating upstream tributary streams and ditches with zeolite and limestone; and
  • Undertaking a feasibility study for constructing wetland areas.  

The next key milestone will be taking a core sample of lake sediment and presenting the findings back to Council. Ongoing monitoring will ensure that an accurate baseline state is documented so that results can be measurable over time, and will help North Cowichan hone in on the most suitable treatment processes to pursue.

“The actions approved by Council mean that remediation of Blue-Green Algae in Quamichan Lake will begin immediately,” says Dr. Preikshot. “These first steps will address phosphorus entering the lake from adjacent properties via surface runoff. In the coming year, the approved research and monitoring work will be used to develop a cost-effective management approach to deal with the legacy phosphorus already in the lake.”

“Protecting and enhancing the environment, including Quamichan Lake, is one of Council’s key strategic priorities,” says Mayor Al Siebring. “Our focus is currently on establishing an accurate picture of baseline conditions and beginning to use that data to inform our remediation plans and spending decisions.”

The health of Quamichan Lake has been a focus for North Cowichan since concerns were raised during a blue-green algae bloom in the summer of 2016. While blue-green algae is not uncommon in shallow urban lakes and has been present in Quamichan Lake since at least the 1930s, in recent years the blooms have become more intense and longer in duration.


For more information, please contact:
Al Siebring, Mayor
Municipality of North Cowichan
T 250.710.3416