Advisory for QUAMICHAN LAKE, British Columbia

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QUAMICHAN LAKE

Type: Water Quality Advisory  -  Active

Issued: 6/27/2025

Details:

QUAMICHAN LAKE (North Cowichan) – (WQA/BGA) June 27 Permanent Advisory has been in place for 10 years as a result of ongoing high bacteriological counts and frequent toxic algae blooms.

Quamichan Lake has been subject to cyanobacteria (blue-green algae) since the 1930s. In the past two decades, the blooms have become longer and more intense. The root cause of these blooms is high concentration of phosphorus, which is largely due to excessive nutrient loading that has accumulated in the lake sediment over 150 years of runoff from forested, farmed and developed lands in the Quamichan watershed. 

Human activity since the turn of the last century has elevated nutrient levels in Quamichan Lake such that it is now considered a Highly Eutrophic Lake; dissolved oxygen has depleted to the point where the aquatic life begins to die off. Due to this predisposition, Island Health no longer tests the water and has a permanent advisory in place.