CHLORIDE: Spare the Salt
It's often the algae blooms on Nepahwin's surface or Eurasian water-milfoil that draw attention to the changing lake water quality, but it's what we can't see that is causing the decline of our lake.
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Road salt is a major culprit. It can be highly disruptive to the balance of a healthy aquatic ecosystem, and we are seeing its effects locally. Common road salt crystals contain sodium (and often calcium and/or magnesium) chloride. When the crystals dissolve on our driveways and roads, chloride enters storm drains that flow directly to the lake. Urbanization of the watershed over the past ~30 years and its associated increase in surface and storm system runoff into Nepahwin has led to concerning levels of chloride.
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The Canadian Water Quality Guideline for chloride to protect aquatic life is 120 mg/L.
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Chloride levels in un-impacted Canadian Shield Lakes are 1-7 mg/L.
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Nepahwin Lake Chloride Level in 2021: 154.0 mg/L.
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Above 120 mg/L, zooplankton (microscopic organisms that graze on algae) can decline. Combine fewer 'algae grazers' with increasing phosphorus levels and higher water temperatures, and it's the perfect environment for increased algae blooms, excessive eurasian water-milfoil growth, beach closures and yucky shorelines.
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Why and how to spare the salt?
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Road salt harms concrete, car exteriors, hydraulic brakes, mufflers & exhausts, boots & pet paws, vegetation, soils and our lakes!
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It is important to maintain safety from slips, falls and skids but there are alternative ice melts and traction aids to road salt that achieve a safe driveway and road surface.
RESOURCES:
The CGS Salt Management Plan has been developed to mitigate the impact of road salt on the environment by minimizing its use of salt while still maintaining safe roads. The map below shows salt routes prior to the fall of 2023. In the fall of 2023, CGS changed ~9.7 lane km of salt routes to sand routes in the Nepahwin Lake Watershed, including Loach's Rd, Algonquin Rd, MacIsaac Dr., Maki Ave, a small segment of Nepahwin Ave and a section of Latimer Cres. More detail can be found at CGS 2023 Salt Route Changes
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Sources:
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Canadian Council of Ministers of the Environment.2011. Canadian water quality guidelines for the protection of aquatic life: Chloride. In: Canadian environmental quality guidelines, 1999, Canadian Council of Ministers of the Environment, Winnipeg.
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Lake Partnership Program, Ministry of Environment and Parks, accessed November 2023. https://foca.on.ca/lake-partner-program/