Quamichan Lake - Blue Green Algae

Blue-Green Algae - Frequently Asked Questions 

Update: July 17, 2019 Regular Council Meeting

Findings from the 2018 water quality sampling program on Quamichan Lake were presented at the July 17, 2019 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.

A copy of Dr. Preikshots report can be found by clicking the following link  "Management Options and Monitoring Programs for Persistent Blue-Green Algae Blooms in Quamichan Lake"  [PDF - 23 MB]

Background Information

In response to a toxic blue-green algae bloom that occurred in the summer of 2016, North Cowichan established the Quamichan Lake Water Quality Task Force. The task force was composed of concerned residents, neighboring local government representatives as well as local and provincial experts specializing in lake health. The group was asked to recommend treatment strategies to the BC government in order to improve water quality in the lake. After several meetings and a lot of research on behalf of the group, the task force produced a report to the Mayor and Council at North Cowichan recommending that the Municipality:

  1. Implement a water quality monitoring program
  2. Inspect the outflow of the lake annually
  3. Provide a report to Council on how to establish a program to manage and reduce nutrient loading into the lake. 
  4. Install permanent signage at the public access points to the lake to advise the public of the potential for toxic algae blooms.

Progress To Date

Since the recommendations from the task force were passed by Council, staff have completed the following:

  • Installed permanent signage at all public access points
  • Inspected the outlet of the lake annually
  • Worked with a local consultant to develop an appropriate sampling regime to monitor water quality throughout the summer and fall of 2018.  
  • Coordinated the local consultants work with a professor and prospective master’s student from the Ecological Restoration Program at British Columbia Institute of Technology (BCIT). Throughout 2018, they will be sampling and analyzing various water quality parameters in order to develop strategic recommendations to improve conditions in the lake. The full report will be posted here upon completion.
  • Updated neighboring governments, stakeholders and the Quamichan Lake Water Quality Task Force on progress to date, the sampling methodology and anticipated recommendations to improve lake health. 

The meeting minutes from each of the task force meetings can be viewed by clicking the links below:

December 20th, 2016 May 25th, 2017
June 26th, 2017 March 16th, 2017
June 13th, 2017 January 19th, 2017


See our Blue-green Algae - Frequently Asked Questions page for more information