Water Quality

ML Water quality update May 2025

Jenny Fairbrass is managing the Eurasian Water Milfoil program.  This invasive species is arguably one of the most significant threats to our lake.  Volunteers are needed to help.

Marco Pescantin has taken over the Lake Steward – Environmental role. Pete LeMoine will assist and represent the MLRA at the Muskoka Watershed Council. 

Love your Lake surveys were completed in 2022.  These surveys of every waterfront property highlight how important a natural shoreline buffer is to lake health and how you could make minor changes to provide major benefits.  See our website for all the positive impacts of a natural shoreline.  Natural Shorelines — Morrison Lake

The Lake Partner Program has been providing decades of water quality results due to the efforts of many ML volunteers. There are 3 test sites on the lake for spring sampling and bi-weekly clarity measurements.  The sites are at the north end near the inlet river, at the deepest spot (55 feet, 17 metres) south of Bell Island and near the outlet river Morrison Creek.

In 2024 the TP (total phosphorus) levels at the 3 sites were similar.  The average of the sites is 8.5 ug/l.  The average over the past 18 years is 8.5.  In most of the lakes in Muskoka, the TP readings have been dropping – improving due to better environmental practices such as zero phosphate cleaning products and upgraded septic systems. TP of less than 10 ug/l is considered low nutrient level which is good.  Some years we have exceeded this so we should not relax our positive actions.

Calcium levels were destroyed by acid rain.  The major industrial changes made decades ago have resulted in current rain in Muskoka being 40 times less acidic than it was!  It takes a long time to recover calcium levels, but we are doing OK.  ML calcium level is just under 4mg/l, less than 2.5 is bad.

Salt is a significant problem in many lakes and in Gravenhurst Bay.  Primarily due to road salt application on roads, driveways and commercial lots.  Our readings are 6.2 mg/l. our 10-year average is 5.9 so let’s not keep increasing.  Greater than 10 mg/l can harm the very small creatures important to lake ecology.

To learn about how to help enhance and protect our water quality review the Environmental section on our website. If you have ideas for improvement and/or want to get involved contact us at mlraexecutive@gmail.com

Every cottage should have a copy of the Living in Cottage Country book on their coffee table.  They are available here for $20.