Connecting Lake Simcoe's Community


By John Hicks

The probable cause for the increasing numbers of dead fish (fish kills)
in Lake Simcoe’s bays and canals this year (and the Maskinonge River
last year), is likely due to the process of Thermal Stratification in combination
with the infiltration of excess nutrients. (See illustration below.)

The surface layer of the lake (called the epilimnion) experiences wind and wave action
which encourages oxygen in the air to dissolve and be dispersed throughout the water
column of the lake. The spring sun gradually warms the surface water and thermal
layers begin to form in the lake. Immediately below the top layer (epilimnion), a separate layer of water exists (called the thermocline) where the most rapid drop in temperature
occurs and where oxygen begins to deplete. With just a few degrees Celsius between
the two layers, the natural mixing of water stops, and de-oxygenation occurs.
The organisms in the lower layers begin to consume what little oxygen is left in the water, which now cannot be replenished without circulation.

If the temperature layering continues long enough, coupled with excess nutrients entering the lake (from sewage treatment plant outfalls, farm run-off, septic beds, soil loss from subdivision re-grading, fertilized lawns etc,) toxin-producing algae, coupled with the lack of oxygen can result in a massive fish kill.  In this situation, the microscopic plants and animals (called phytoplankton and zooplankton) begin to die along with the larger organisms which feed upon them (i.e. fish), ultimately producing a fish kill. Foul odours and floating dead fish are a sure give-away to thermal stratification and deoxygenation.

The situation is worse in the canals and swampy bays of the lake, where another, deeper poisonous layer exists, (the benthal layer) on the bottom. The benthal layer is the result of decaying vegetation and anaerobic bacteria (bacteria not requiring oxygen), which form an “ooze” or sludge on the bottom. An event known as the “Spring Turn-Over”, which is caused by periods of strong winds and persistent rainfall, can occur which mixes the benthal layer with the upper layers of the lake spreading its decaying material and deoxygenating the whole water column above. Fish gasping for air on the surface are often indicative of this situation. In early years on the lake, it was rare to see a fish kill like we see today, and it’s not because of thermal stratification alone, but aggravated by the continuous infiltration of excess nutrients. The lake will surely express its stress many more times severe than we now see it unless we stop this infiltration. Development pressures and poor land use practices are the root problems which provoke this phenomena. We need to take charge of this situation quickly or the lake will deteriorate.
Already hosting taste and odour algae, its south portion is losing its appeal for swimming.

An extract from my new book covering the planning, design and management of small
lakes and ponds to be released this summer by Fitzhenry & Whiteside, Toronto.




Source Protection Plan Now Available for Public Comment

The South Georgian Bay Lake Simcoe source protection committee is seeking public input into its recently released draft proposed source protection plan and explanatory document. Members of the public will find the documents on the website at They are also available for viewing in hard copy at the following locations during regular business hours:

- Lake Simcoe Region Conservation Authority, 120 Bayview Parkway, Newmarket

- Nottawasaga Valley Conservation Authority, 8195 Concession Line 8, Utopia
- Severn Sound Environmental Association, 67 Fourth Street, Midland

The policies were drafted with the input of a variety of different stakeholder groups such as municipalities, the business community, agriculture, environment, public health and First Nations.

“Members of the source protection committee and its “policy and planning work group” have been working for the past two years on researching and developing these draft policies. We’re now at the point where we want to hear from the public,” says source protection committee chair Lynn Dollin.

“Reference to drinking water threats does not suggest there is an immediate risk to drinking water on a landowner’s property”, says Mike Walters, Project Manager. “Use of the word threat indicates one of 21 land use activities, such as a septic system or home heating oil, that has the potential, in certain circumstances, to pose a risk to municipal drinking water sources, if not properly managed.”

The local committee is sending formal notice of the draft policies to municipal administrators, First Nations, and owners of properties where potential significant drinking water threats may exist. There is also the opportunity to meet with staff and committee members to discuss the policies and provide their input through one of four public Open Houses.

Monday, April 16, 2012 5:30pm to 8:30pm, Brooklea Golf & Country Club, 8567 Highway 93, Midland

Thursday, April 19, 5:30pm to 8:30 pm, Holiday Inn Express, 100 Pony Drive, Newmarket
Saturday, April 21, 2012, 11am to 2pm, Liberty North, 100 Caplan Avenue, Barrie
Tuesday, April 24, 2012, 5:30pm to 8:30pm, Best Western Mariposa Inn, 400 Memorial Avenue, Orillia

The committee has addressed risks to drinking water supplies using a variety of tools such as education and outreach, financial incentives, land use planning changes, risk management plans, provincial prescribed instruments, and in some cases, prohibition of future land use activities. Landowners can take positive action now to review the policies and provide their feedback to the committee before the deadline of May 25, 2012.

Comments must be submitted in writing, either in person, by mail, fax or e-mail:

Source Protection Committee

c/o Lake Simcoe Region Conservation Authority
120 Bayview Parkway, Box 282
Newmarket, ON  L3Y 4X1
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
fax: 905-853-5881

Some people are having problems seeing the Winter 2011/2012 issue due to a technical glitch. 

While we are getting this sorted out, you can still see the Winter 2011/2012 issue by clicking on this link!

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