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Biology, Dragon boat, Everyday science experiments, Sustainability, Uncategorized

Why is the water so brown?

When you’re used to clear water coming out of the tap it’s easy to make assumptions about how clean a water body is based on how clear it is. This means that most people assume that the North Saskatchewan River through Edmonton, Alberta, Canada is pretty dirty, particularly in the spring.

A muddy bank leads to a dark river. Two bridges are in the distance
Looking out on the North Saskatchewan River

The visible brown colour of the water is from sediment that gets washed into the water and churned up from the bottom by the faster water in the spring. This sediment is things like dirt, sand, and silt. Material that is light weight and easily picked up by the moving water. By contrast, rivers that have rocky bottoms tend to look much clearer because the rocks and pebbles can’t be picked up by the water.

At one point, most cities and towns would dump things like sewage directly into the water and Edmonton was no different. We also used to build our garbage dumps right next to the river. Fortunately, this has changed and the river has steadily improved since the 1950s. There is mercury in the river, leading to recommendations regarding limiting fish consumption from the river. However, most of the mercury is from natural sources such as leaching out of rocks.

Today most contamination happens through runoff. The snow melt and rain that runs over land and into the river either directly or through the storm sewers. This runoff can pick up things like bacteria, fertilizers, pesticides, soaps (if you wash your car in your driveway for example), and other contaminants. Of course these contaminants are largely invisible in the water so it’s harder to know they are there.

The sand and silt will eventually settle out of the water but many of the contaminants above are much harder to get rid of and affect the health of the river system. You can help by breaking up hard surfaces (e.g. use paving stones instead of cement), installing rain barrels, dispose of paint and chemicals properly, clean up after your pets, use environmentally friendly soaps on your car or go to a car wash, and use slow release fertilizers and never fertilize before it rains.

With all that being said, Edmonton’s North Saskatchewan River Valley is an incredible place to be. Let’s help keep it clean and healthy.

About Tai Munro

I am passionate about making science, sustainability, and sport accessible through engaging information and activities.


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