Quamichan Lake Health


Blue-Green Algae - Frequently Asked Questions  Actions To Date
Background Information and Reports  Waterfowl Impacts


Quamichan lake has been subject to undesirable blooms of Blue-Green Algae since at least the 1930's.  In the past two decades, the blooms have become longer and more intense.  The root cause of these algae blooms is the high concentration of phosphorus in the lake which is largely due to phosphorus that has been stored in the lake after 150 years of runoff from forested, farmed and developed lands in the Quamichan watershed.  As a result of a toxic algae bloom in 2016, Council set up a task force to research ways to reduce the prevalence of toxic algae blooms in the future. 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 improve water quality in the lake.  The Task Force recommended that Council direct staff to set up a water quality sampling program study in 2018.

Findings from the 2018 water quality sampling program on Quamichan Lake were presented to Council in 2019 and they unanimously agreed to take further action toward improving the health of the lake.  Key findings of the study show that the primary cause of blue-green algae is the phosphorus load that has already accumulated within the lake and that agricultural activity is currently a more significant source of phosphorus than residential development around the lake.  After receiving results from the water quality  report, Council decided to expand the monitoring program and act on a number of the recommendations, including:

  • Taking a sediment core from the lake bottom to determine the internal versus external phosphorus loading;
  • 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  streams and ditches that feed into the lake with zeolite and limestone; and
  • Undertaking a feasibility study for constructing wetland areas. 

Ongoing monitoring will ensure that an accurate baseline state is documented to accurately assess improvements over time.  This will also help North Cowichan hone in on the most suitable management options in the future.

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]