Skip to content

How 'weather whiplash' is affecting water quality in Lake Simcoe watershed

Nine municipalities within the watershed rely on the lake for their drinking water supply.
06-14-2018-climate change
Dana Eldon, outreach co-ordinator with the Lake Simcoe Regional Conservation Authority, with climate-change materials available at the Bradford West Gwillimbury Public Library. Miriam King/Bradford Today

The climate is changing.

According to Environment Canada’s senior climatologist Dave Phillips, we are experiencing “weather whiplash” — warmer summer temperatures extending into the fall, periods of drought, more intense storms resulting in heavy downpours, and more unpredictability in the weather.

In the Lake Simcoe watershed, the impact of climate change is complicated and magnified by rapid development and population growth, said Dana Eldon, education outreach co-ordinator with the Lake Simcoe Region Conservation Authority.

Eldon was at the Bradford West Gwillimbury Public Library on June 11, outlining the complex picture of the effect of climate change on Lake Simcoe and its watershed, meaning an area of land where all the surface water drains into the same place.

The key is water quality, she said.

It is the water that sustains the diversity of life, fisheries, and recreation-based activities that add an estimated $200 million per year to local economies, she said.

There are also nine municipalities within the watershed that rely on the lake for their drinking water supply.

And now, said Eldon, with changing conditions, “there are places in the lake where young fish can’t survive anymore.”

Warming water temperatures put cold-water fisheries at risk and reduce the amount of oxygen in the water, she said.

Runoff spikes in urban areas

The watershed population is expected to double within 30 years to more than 800,000 residents, Eldon said.

That means more rooftops, more roads, driveways, parking lots and shopping malls, and less opportunity for rainwater to soak into the ground.

Instead, the water runs into the storm-sewer system, carrying fertilizers, pesticides, oil, gas, and salt and sand from roads and parking lots.

The use of the term “storm sewer” is misleading, Eldon said, noting it suggests there is some kind of treatment of the stormwater, when in fact there is none.

“For the most part, storm drains go out into the nearest stream,” or into stormwater management ponds, which are designed to manage the volume of water, not its quality, she said.

Everything dumped or flushed into storm sewers ends up in nearby rivers, and eventually, in Lake Simcoe.

To paint a picture of this, Eldon said 10-20 per cent of rainwater in a natural environment will become runoff, with 80-90 per cent soaking into the soil, eventually reaching groundwater.

In a subdivision, however, the split between runoff and absorption is 50/50, and the runoff increases to 90-100 per cent of rainwater in a fully urban environment, she said.

That becomes a problem when an area receives “almost a month’s rain in one or two storm events,” Eldon said. “That’s a lot of water in a very short time.”

Severe storms can easily overwhelm stormwater management systems, leading to serious flooding.

Road salt in waterways

The expected increase in the number of freezing rain events and ice storms in winter may also contribute to another problem: increasing use of salt on winter roads that eventually finds its way into waterways.

The conservation authority has 80 monitoring stations to check up on conditions in the watershed.

Among its findings: the period of warming is now 28 days longer than it was when monitoring began, and the salt level in runoff has increased from 10 milligrams per litre in the 1970s, to 47 milligrams per litre now.

Green rooftops, rain gardens needed

Growth is happening, but it needs to be sustainable growth, Eldon said.

The conservation authority is working with developers to promote “low impact development” — using permeable pavement, green rooftops, rain gardens and swales (low, marshy tracts of land) to increase the opportunities for rainwater to soak into the ground instead of running off.

Rainwater management and harvest are back in vogue, and retrofitting of existing stormwater ponds and neighbourhoods “is a really critical part of sustainable development,” Eldon said.

Instead of catch basins, some municipalities are installing curb cuts (ramps graded down from sidewalk to street level) and landscape elements called bioswales designed to concentrate or remove debris and pollution out of surface runoff water.

The goal is to reduce runoff and flooding, improve water quality, and create communities more resilient to climate change.

“It’s a very real threat to watershed residents, and to our way of life,” said the conservation authority’s CEO Mike Walters. “What we do over the next 100 years is going to be very important.”


Miriam King

About the Author: Miriam King

Miriam King is a journalist and photographer with Bradford Today, covering news and events in Bradford West Gwillimbury and Innisfil.
Read more

Reader Feedback