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Lake Joseph North Association

Water Quality

No doubt, the one thing that brings all the residents of Lake Joseph North together is the lake itself. We enjoy it in many ways from swimming to boating, water skiing to canoeing and much, much, more. And the best part? The water quality at the north end of Lake Joseph is the greatest in Muskoka! Couple this with the remarkable clarity and minimal presence of algae and aquatic vegetation along the shoreline and you can see why this lake is holds a special place among its residents, cottagers and visitors.  

In order to appreciate the importance of water quality and to understand the issues, here are some key insights that residents should be aware of and that LJNA takes seriously:


There are a couple reasons why the water quality is so high in the north end of Lake Joseph including the lake’s location at the top of the watershed and the fact that until relatively recently, the north end of Lake Joseph was rather undeveloped compared with the south end of the lake and the other two big Muskoka lakes (Rosseau and Muskoka). This began to change with the completion of the 400 series highway up the west side of the lakes during the late 1990s and early 2000s. The historical high quality standard is a big reason why cottagers and residents at the north of Lake Joseph remain vigilant regarding water quality.


Lake Joseph, like most lakes located on the Canadian Shield, is oligotrophic - meaning the lakes have a naturally low nutrient level. This gives the lake its clarity and accounts for the minimal presence of algae and aquatic vegetation along the shoreline. Yet, the low-nutrient status of Lake Joseph also means that the aquatic ecosystem is also very sensitive to slight fluctuations in phosphorous content.

Phosphorous is the limiting nutrient in oligotrophic lakes. The low concentration of phosphorous in the lake translates into low levels of ‘food’ for aquatic plants. If more phosphorous is added, more aquatic plants will grow, reducing the oxygen content and disrupting the ecosystem conditions that most species of invertebrate and fish rely on.

Compounding the issue is the fact that the water in Lake Joseph changes very slowly, taking several years to entirely flush out. In other words, any extra phosphorous that is added to the lake can only be removed through natural processes very slowly. It is therefore critical that cottagers and residents on Lake Joseph carefully monitor the concentration of phosphorous in the lake and strictly manage the amount of phosphorous entering the lakes.

Testing for water quality

In 2002, the Muskoka Lakes Association (MLA) began sampling sites in Hamer Bay as part of their Water Quality Initiative. Testing for phosphorous and bacteria (especially E. coli) has continued in the bay every year since. In 2004, sites in Gordon Bay were sampled and has since continued intermittently as needed. Sampling was also started in Stanley Bay in 2004, and has been continued every year since.

Copies of the MLA’s Water Quality Reports can be obtained at PDF downloads from the MLA’s website.  

Program to monitor Benthic invertebrates

The health of a lake is very much dependent on, and reflected by, its benthos which is the biological community in the bottom seiment of a lake or river. The abundance and diversity of this living community in the littoral zone (shallow water nearest to dry land) can be indicative of the overall health of a lake. This zone is especially important to lake quality and is impacted by snowmelt, property runoff, and sedimentation.

Beginning in August 2021, LJNA volunteers are sampling at one of more locations on the lake to establish representative trends. Working with a Biomonitoring Technician with the District of Muskoka, the team of 4 to 6 volunteers collect and classify "bugs in the mud". All are welcome and it is a fun and educational few hours in the sun.

Learn more about the LJNA Benthic program HERE

To learn more about the District of Muskoka program click HERE

Invasive species warning: Starry Stonewort - CLEAN DRAIN DRY

Lastly, the Ontario Federation of Anglers and Hunters (OFAH) have raised the alarm regarding the invading macroalgae starry stonewort. It forms dense mats and competes aggressively with native plants. It is spread primarily by boating and boaters must be vigilant in reducing its transport to various waterbodies. For more information, check out:


The LJNA is also very eager to enlist more volunteers in the water testing program. If you are available to collect water samples one weekend per month between May and August, please contact us at

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