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Your Link to Muskoka's Water!


Monitoring Parameters 

The following parameters are often monitored to provide an indication of water quality.


Water Clarity & Secchi Depth

secchiThe Secchi disk is an 8-inch (20 centimeter) diameter, black and white disk attached to a dowel rod, PVC pipe, rope or chain. Inch or centimeter intervals are marked on the rod, pipe, rope or chain with permanent ink, paint or clamps.

This very simple sampling technique gives a good reading of water clarity.

The sampling methods and interpretation of the results are provided by the Ministry of the Environment.



Phosphorus is the nutrient that controls algal growth in many of Ontario's lakes. In general, more phosphorus means more algal growth.

Regular testing will identify changes in the nutrient status and/or the water clarity of the lake due to the impacts of shoreline development, climate change and other possible stresses.


Dissolved Oxygen

Dissolved oxygen measures the amount of oxygen dissolved in water that is available for use by aquatic plants, shellfish, fish, and other animals. Oxygen gets into the water by diffusion from the surrounding air and as a waste product of photosynthesis. Sufficient oxygen levels are required in order to provide for life forms. Where there is low dissolved oxygen concentrations, aquatic animals are more vulnerable to adverse effects of other stressors.

Lake trout are the most sensitive local species and require a minimum of 6 mg/L dissolved oxygen to thrive.

In lakes that go anoxic (lose all oxygen) at the end of the summer or winter, phosphorus can be released from the sediment and may result in a late summer algae bloom.



Temperature affects many aspects of a lake, including:

  • The solubility of oxygen in water
  • The rate of photosynthesis by algae and higher plants
  • The metabolic rates of aquatic organisms
  • The sensitivity of organisms to toxic wastes, parasites and diseases
  • Life cycle rates of aquatic insects
  • Whether cold-water species or warm-water species are present

thermometerConsiderable increases in water temperature may decrease cold-water species populations (such as such as trout and stonefly nymphs), and increase large plant growth, thereby contributing to eutrophication.



pH is a measure of the acid concentration in a water sample. A pH of 7 is neutral. Values above 7 are basic and values below 7 are acidic. Lakes in Muskoka tend to be slightly acidic. Although this tends to be a natural condition, many lakes have experienced acid stress as a result of acid precipitation. These lower pH values strain fish and other aquatic animals and habitats.



Conductivity is a measure of the ability of water to conduct an electrical current. It is measured by the amount of electrical current passed through a water sample. Water conductivity is closely connected to the amount of dissolved substances in water. Conductivity can indicate the degree to which a watershed's bedrock and mineral soil resists erosion. Typically, low-conductivity streams have less groundwater input than high-conductivity lakes.



The following may be involved in testing for bacteria:

  • District Municipality of Muskoka - tests municipal drinking water systems for bacteria.
  • Homeowners - can take samples of water from a private drinking water system to the Health Unit for testing.
  • Health Unit - tests public beaches classified for recreational use.
  • Lake Associations - may carry out monitoring programs to test for E. coli in their lake.


The Ontario Provincial Standard for E. coli in:

  • Drinking water is 0 E. coli per 100 ml
  • Recreational water (for swimming) is 100 E. coli per 100 ml


The Muskoka Watershed Council has developed guidelines for collecting bacteria data in recreational waterbodies.



Benthic monitoring involves collecting benthic macroinvertebrates (otherwise known as benthos), which are mostly aquatic insects or the aquatic stage of an insect. These insects live in, crawl upon, or attach themselves to the bottom of the waterbody.

caddisflyBenthic monitoring can provide an understanding of a waterbody's condition because these organisms are sensitive to the smallest changes in chemical and biological factors. Their presence or absence provides valuable information about a waterbody's health over time. Benthic macroinvertebrates are relatively inactive, inexpensively sampled, and fairly easy to identify.

Reference Condition Approach (RCA)

The reference conditon approach (RCA) to bioassessment involves the use of a set of minimally impacted reference sites to evaluate the condition of subsequent test sites. Test site data is compared to reference sites and an assessment of the level of impairment is produced. There are seven steps involved in applying the RCA to bioassessment:

  1. Minimally impacted reference sites spanning a range of physiographic conditions are selected (ideally, this is done randomly), and sampled.
  2. Biological conditions of these sites are summarized and are then grouped according to the similarity of their biological features.
  3. Niche variables are identified.
  4. A model that predicts a test site's reference group membership is built using niche variables.
  5. Biological, habitat and physiographic data associated with a test site are gathered.
  6. The test site is matched with its predicted reference site group.
  7. Statistical tests are applied to determine if the test site falls within the normal range of biological condition defined by its matched reference site group.

(Ontario Benthos Biomonitoring Network Protocol Manual, Version 1.0, May 2004)

Once reference site data from minimally impacted sites across the province are collected and entered into a database, test sites will then be able to input data and generate an impairment value for their lake, stream or wetland. The Ontario Benthos Biomonitoring Network is currently in the process of developing this database, and requires more baseline data from minimally impacted sites to improve the accuracy of the database-generated assessments of impairment values.