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Back Roads Bill: What gives Windex lakes their colour?

This week Bill tells us why those lakes have those green-blue colours and where you can find some of them

They are often referred to as 'Windex' lakes. These Caribbean blue-green-turquoise-aquamarine-coloured lakes dot the landscape of Northern Ontario.

Some have natural reasons as to why and some have been affected by humankind.


John Gunn, is the Canada Research Chair in Stressed Aquatic Systems at the Vale Living with Lakes Centre, School of Natural Sciences at Laurentian University. He explains the colour range of lakes found in and around the City of Greater Sudbury region including the La Cloche Range. They extend roughly from La Cloche Provincial Park, south of Massey, to Killarney Provincial Park, southwest of Sudbury. The communities of West River, Willisville and Whitefish Falls are located directly within the range.

“Like the ocean, perhaps in the Caribbean, the colour is due to the depth to which light penetrates into the Killarney water without being altered or scattered by particles in the water ( because nothing much dissolves from the hard quartzite) or affected the typical tea colour substances called Dissolved organic carbon (DOC) coming from wetlands in many lakes.

“The quartzite and the rather wetland-free watersheds of Killarney combine to affect the spectral image of the light bouncing back from great depth in the clear dilute Killarney giving us these magnificent colours. The decades of acid rain also enriched the colour by destroying the DOC in the water. Now with air pollution controls the "natural colour is coming back" but the colours still remain spectacular.”

Some of the clearest lakes are OSA and Nellie Lakes within Killarney Provincial Park.


It was Ontario Parks’ Superintendent (Fushimi, Nagaagamisis and René Brunelle Provincial Parks) Kevin Wilson who first directed me to the Windex lakes near Hearst.

“I am not a geologist…but yes Rabbit is beautiful, and lots of lakes like this around Hearst to Hornepayne. I believe it’s because they are all spring fed and has something to do with glaciers when they retreated.”

It is thought because there may be no drainage in and out, there is an unusual input of water loaded with iron and particulate organic matter. The slight amount of suspended silt particles refract blue light.

“Most of these lakes are stocked with Splake and some with Rainbows," Wilson said. “You will see a lot of the lakes are just north of Nagagamisis Provincial Park and also a bunch north of Constance Lake.”

Sudbury Geologist Mark Hall said these are not alpine lakes found at high altitudes in a mountainous zone fed from glacial melt. These have the characteristic bright turquoise or green colour as a result of glacial flour, suspended minerals derived from a glacier scouring the bedrock.”

“Good thing you did not ask this question in winter or I would be longing to travel,” Hall said when asked about the lakes.

We have to go back to high school chemistry to understand how the Windex lakes get their colour, he said.

“So that (lack of turbulence) gets the mud out of the water. Next, there are all the little critters and plants that like to drift around in the water as well, which can affect the clarity. If the pH (indicating basicity or acidity of a solution on a scale of 0 to 14) is high or low, the aquatic life has a harder time of living in the water.”

“The clarity of the Windex lakes is, like the Caribbean or Georgian Bay, mainly due to the lack of 'stuff' in the water," he said. "In the case of the oceans or the Great Lakes, the suspended sediment (clay, silt particles etc.) have had the opportunity to settle out of the water. As the sediment enters the larger body of water, the turbulence of the water decreases, and consequently the ability of the water to keep small particles suspended. As the speed, movement and turbulence of the water decreases, the particles settle to the bottom of the lake, to form layers of clay/silt/mud. These can be seen in the rocks or soils as 'varved' clays."

"This happens in acidified lakes around Sudbury, such as Wolf Lake, that you are familiar with. But you do get naturally occurring high/low pH lakes. This may be due to the mud in the lake, or the host geology.

“In Northern Ontario, I have always preferred high/low pH (a measure of how acidic/basic water is. The range goes from 0 to 14, with 7 being neutral) for the basis for Windex lakes as quartz can come in many colours but mainly white or clear which does not in my mind give a blue colour, even if finely ground. He said if it was glacial silt one expect to see some of that colour in the fine-grained sediments deposited in winter.

“So high/low pH kills off the algae and you are left with the lovely blue also seen in Lake Huron caused by the natural colour of the water.”

For the Hearst area, he said, “I would think that the bedrock being effectively glass that there is a severe lack of nutrients, prohibiting abundant plant, algae growth. No or limited life, no tannins, no algae so the water has only its natural colour of blue like icebergs.


Nazneen Mehdi is a locum nurse who has resided and returns to Hearst to regularly visit one of the local Windex lakes.

“Rabbit Lake is like our good ‘ole swimming hole but it is more than that," Mehdi said. "Locals find it cool and refreshing and on the days with the marshmallow-cumulus clouds, the range of colours change dramatically right before your very eyes. There is some sort of natural magnetism to this colour spectrum. On my way to Constance Lake First Nation I would routinely go out of my way to see this natural phenomenon.”

She said not everyone would feel this way but after a six-year year absence this summer she returned.

“It is truly magical here, almost sacred, there is something about the emerald-sapphire colours of the forest background meeting the water on their own terms. There is a connection, you can breathe in the hues, shades and tones," she said. "Nothing had changed and my wish came through that it remains a gem.”

For people driving the long stretches of Highway 11, it is a stop to recharge and be with Nature.” There is no sign on the highway, but the map link below will help.

This year also marks Hearst’s 100th anniversary. If you visit stay over at nearby Fushimi Provincial Park and find out about its history.

The Blue Lagoon, another colourful destination, was featured in a Back Roads Bill video and a recommended, short-duration canoe and easy to do is the Chiniguichi-Wolf-Dewdney-Matagamsi route (including the Blue Lagoon).

Find one of these swimming holes on the map and take in these vibrant tinctures on the back roads.

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Bill Steer

About the Author: Bill Steer

Back Roads Bill Steer is an avid outdoorsman and is founder of the Canadian Ecology Centre
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