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Water Today Title October 30, 2020

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Update 2018/3/2


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By Stuart Smith

After three years of drought, dams supplying the Western Cape in South Africa are at 24%. The largest of which, the Theewaterskloof, is at 11.1% (with the last 10% unrecoverable). What's worse, is that the levels are still falling. It is a dire state for Cape Town and the surrounding area to be in.

We see droughts in Canada as well, although not nearly to the same effect as in Cape Town. But could this change with altered temperature and precipitation patterns due to global warming? In our previous article, Preventing a Cape Town Crisis in Canada, Barrie Bonsal, a research scientist from Environment and Climate Change Canada, explained that on the whole Canada will get slightly warmer and probably wetter.

He stressed, however, that regional variation is significant, and that different seasons may change in different ways. In addition, we do not yet know how extreme climate change will be, because GHG emissions depend on the result of global political initiatives and socioeconomic changes. The 2015 COP 21 Paris Agreement corresponds with RCP 2.6 (negative net emissions from 2070 onwards), but public policy is still on track for RCP 8.5 - the business as usual scenario.

So let's zoom in. What are specific Canadian cities doing to address the risk? Each municipality will manage its water storage and distribution slightly differently, so we chose three cities: Toronto, Calgary, and Vancouver, to investigate how they keep the water flowing during times of drought.

The City of Vancouver purchases water from wholesaler Metro Vancouver, who sources water from three natural reservoirs: the Seymour, Capilano, and Coquitlam (which is shared with B.C. Hydro). Each one provides one third of the 390 billion litres demanded per year by the 2.5 million people in the Metro Vancouver Regional District. Because their operation relies on precipitation and snowmelt refilling the reservoirs annually to supply the summer season, it is very important to know how the climate will change.

"Climate change has been a really important consideration for all the plans we have for the past fifteen years", explains Greg Valou, Media Relations Officer at Metro Vancouver. In this region they expect warmer temperatures, longer dry spells in summer, and a decrease in snowpack. But they also predict more precipitation during the rest of the year and more intense extreme weather events. Brent Burton, Lead Senior Engineer of Water Services at Metro Vancouver, explains they can therefore continue to expect the dam will refill annually.

However, he says, to ensure supply during the drier, longer summer months, they will need to increase storage capacity at one of their reservoirs. In 2015, the low snowpack and low spring/summer rainfall left the region with unseasonably high water demand and record low reservoir inflows. This triggered Stage 2 and Stage 3 water restrictions which prohibit most non-essential uses of water.

The solution, Brent explained, will be a second intake for the Coquitlam reservoir. This will allow access to a total of 250 billion litres per year, more than double what the dam currently supplies. This extra intake should ensure supply close to the end of the century, despite the significantly reduced snowmelt, the drier summer, and the additional one million people expected to move to the region.

In Toronto, there is a very different response to drought. It too is expected to get warmer, with fewer snow days and more rainy days. Here though, precipitation is expected to increase for all seasons, not just the non-summer months. And as all Toronto's water comes from Lake Ontario, which is in no danger of running out of water, the changes in climate are even less important.

In fact, explains Kris Scheuer from City of Toronto, the only time they have had to ask people to conserve water was a decade ago - and it was voluntary - due to insufficient pumping capacity to meet demand. Nowadays, she estimates pumping stations could double their rate if demand were to require it - partly because demand is considerably down, and partly because they have significantly expanded and improved their infrastructure.

However, there are ways for droughts to happen even with plenty of water. Toronto's extreme precipitation events are expected to increase in intensity, and ironically, this can lead to water shortages. Gary Wheeler from Ontario's Ministry of Environment and Climate Change, explains: "The ministry does not have any evidence that climate change will cause taps in Ontario cities and towns to go dry," but "extreme events such as heavy rain can cause turbidity to increase, particularly in river systems." This extra, intense rainfall "can cause clogging issues in filtration systems," meaning that without proper forecasting and management, heavy rainfall can be the cause of a water shortage by shutting down the municipal filtration system.

Gary assures us though, that "operators of such systems pay close attention to weather forecasts and will ensure that reservoirs are filled enough to allow closing of intakes until the turbidity decreases to levels that the filtration system can manage."

Over in Calgary the situation is different once again. It relies on water direct from Bow river, as well as from Glenmore reservoir (which is fed by the Elbow river). As with the other two municipalities, they do not rely on groundwater.

Twyla Kowalczyk, a climate change engineer with Calgary's Water Utility points out that Calgary is in a semi-arid region and is already prone to droughts. "We will see hotter temperatures and longer growing seasons, which will drive demand up...but we haven't had a severe drought for a very long time. We are prone to it, but the way we manage water and the storage we have in place has been managing quite well."

To prepare for climate change, they are still in the process of analysing river and water supply flows: "It is a paradigm shift. We rely, as engineers, on historical data. With climate change we are going to have to make predictions and capital decisions which extend outside of that data."

They already know that rising temperatures will affect the water quality in the rivers and will decrease the size of glaciers reducing the amount of water available to supply the river. But the specifics will be decided once understanding of how the watershed will change has improved. Regardless the predictions, she is certain of one thing: "water storage is very critical for drought."

The other half of the equation involves regulating demand. Cape Town has done a good job of this recently, with effective media campaigns, strict enforcement and harsh punishments for those who use more than the mandated 50 litres a day. It is going some way to avoiding the much dreaded "Day 0", when municipal water supplies will be turned off and residents will queue daily for a 25L ration.

All of the Canadian municipalities, to some degree, are promoting water conservation. Even Toronto, which does not need any extra supply, is still keen on reducing the amount used. In 2014, 41% of Toronto's energy use went to water and wastewater management, and reductions in water use will directly decrease greenhouse gas emissions as well as reducing cost.

In Calgary, Twyla explained they are trying to hold water consumption at 2003 levels (despite population growth) but achieving this will require an improved balance between urban and agricultural water use, especially with the predicted lengthening of the growing season. And another avenue she says they are keen to explore is water reuse, whether from storm water, effluent or grey water, though "there are still a lot of policies and water quality questions that need to be addressed with that."

Metro Vancouver found that revising its lawn sprinkling played a huge role in reducing water use in the area. And during the drought of 2015, a combination of communications about water conservation and municipal enforcement brought down water use from a peak of 1.7 billion litres per day, to 1.2 billion litres per day.

The big picture is reassuring for Canadians. The municipalities that we talked to were planning infrastructure and policy well into the century. It is unlikely, even with the predicted changes to our climate, that Canadian cities will end up in a situation close to Cape Town's. But we should all still do our bit and be clever with our water use, especially in summer. For the sake of the environment, and for our wallets.


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