Water Quality FAQ

The Greater Bobs and Crow Lakes Association receives many inquiries about water quality each year.   Here is a sample of some of the questions along with our response.

  1.  What is Blue Green Algae and its health risks? 

Blue Green Algal bloom

Blue-green algae are microscopic, plant-like organisms that occur naturally in rivers, lakes and streams. Exposure to this algae can cause rashes, skin and eye irritation, allergic reactions and gastrointestinal upset. 

Blue-green algae are not normally visible in the water, but populations can rapidly increase to form a large mass called a bloom when conditions are favourable.   Blooms most commonly occur in late summer and early fall and thrive in areas where the water is shallow, slow moving and warm.  Algae blooms also pose a risk to fish and other aquatic species, because as algae dies off it sinks to the bottom and decomposes.  This decomposition process reduces oxygen levels in the water, limiting the available habitat for aquatic life.  Simple steps to prevent the growth of blue-green algae are:

  • use only phosphate-free products
  • avoid using natural or store-bought fertilizers on lawns
  • reduce runoff by maintaining vegetation 20 meters from the  shoreline
  • Pump out the septic tank every 3-5 years and inspect regularly

If you spot blue-green algal blooms, call:  416-325-3000 or 1-800-268-6060

2.  What is E Coli?

E.coli bateria

Coli refers to a group of bacteria commonly found in the intestines of humans and animals. While most strains are harmless, some strains can cause severe stomach cramps, diarrhea and vomiting. On Bobs and Crow lakes, the presence of E. Coli is below the Provincial Water Quality guidelines at all monitored sites.  The West Basin did report a higher average result than other monitored sites in 2014.   This was due to an elevated sample in August, however the previous sample in June was well below the guideline.   While this site has exceeded guidelines standards in the past (Oct. 2003), this is most likely indicative of a temporary contamination (i.e. waterfowl, other wildlife), given the productive habitat associated with the site.

3.  How do zebra mussels affect water quality?

Zebra mussel shells are very sharp and can easily cut through skin

Zebra mussels are an invasive species that has spread throughout the great lakes and most inland lakes in Ontario.  These mussels cause damage to the lake ecosystem plus their sharp shells can easily cut bare feet.    Although Bobs and Crow lakes have zebra mussels, they remain part of a declining group of water bodies that do not have established zebra mussel populations.  This is partially due to the lower calcium content in the lake, which is a result of the geology of the lake rather than human influences.    To further reduce the risk of introducing additional mussels to the lakes, boats, fishing gear, and other recreational equipment entering from a different water body should always be cleaned and inspected before entering the lake.

4. What are the main sources of phosphorous in the lake?

Excess phosphorous runoff from farms is a major source or algal blooms in western Lake Erie

Most phosphorus in a lake comes naturally from the soil, plants, animals and precipitation in and near the lake. But human activity can significantly contribute extra phosphorus to a lake.   The common sources of phosphorus, which can be controlled or influenced by lake residents:

  • Fertilizers: neither chemical nor natural fertilizers (manure) should be used near the lake or other water such as creeks. These fertilizers contain phosphorus as one of their components.
  • Soaps and cleaners: many soaps and cleaners contain phosphorus (ie. phosphate). Buy only phosphate-free products. 
  • Septic tanks: Maintain your septic system and remember to have your tank pumped out every 3 to 5 years. 
  • Stormwater and erosion: Make sure that your property has as little hard surface as possible.  Maintain vegetation like trees, flowers and shrubs  within 20 meters of the shoreline to absorb rainwater runoff before it enters the lake. 

5.  What can I do about too many weeds in the water?

Dense growth matt of Eurasian Milfoil

Excessive growth of aquatic plants on Bobs and Crow lakes is usually from invasive plant species such as Eurasian Milfoil.   During hot sunny and dry summers, the outbreaks are worse due to rapid growth combined with lower than average water levels.  Swimming, boating and other water activities are severely hampered.

The unfortunate reality is that cutting or harvesting these invasive plants can actually accelerate its spread to other areas of the lake.   Commercially sold rakes can "manage" the weeds in favourite swimming and boating areas, but that is the extent of it. 

Flooded Septic Field