Mosaic

Not worth its salt?

We have lots of water in Toronto, but it's too polluted

Image of concrete channel with water flowing

In Toronto, the local water supply is good. But we’re destroying it with pollutants, especially salt.

Salt is the most popular de-icing element for keeping Canadian roads safe for cars and pedestrians. That salt is then flushed into our groundwater and aquifers, contaminating our lakes and our drinking water.

UTSC environmental science researchers Mandy Meriano and Carl Mitchell are conducting two separate hydrology projects assessing the movement of water.

“We look at water flows, chemistry and factors related to pollution,” Mitchell says.

He’s studying the watershed at Mimico Creek, in the west end of Toronto. “The biggest pollutants in urban systems are easy to measure but hard to control, like salt,” Mitchell says. In winter, salt concentration in water systems is higher, and that is linked to the use of road salt.

Meriano’s project looks at the impact of urbanization on waterflows, both on the surface and in aquifers—the underground layer of water-permeable rock—in the Frenchman’s Bay watershed in the eastern GTA. As the area was urbanized, it was expected that there would be a lot more water runoff, since cities set out to convey water in a direction away from where we live. But, Meriano says, “what we found was very exciting. The aquifer system receives just as much water as it did before urbanization.”

Although the quantity of water didn’t change, quality did. With urbanization comes more cars, more buildings and more pollutants being flushed into the groundwater. As the city ages, its surfaces become more pervious, allowing more water to seep through so the slow groundwater system becomes a reservoir for contaminants.

“There used to be a time when we used aquifers for drinking water. We can’t do that anymore because the water is too salty. If we can’t drink the water, animals like fish and birds can’t either. Maybe you and I aren’t really going to feel that impact,” Meriano says, “but future generations will.”