I started walking around Toronto over 6 years ago, well before I started this site. As I started covering more of the city, I had a vision for what a top-tier trail system could look like, using and connecting the city’s ravines, utility corridors, shoreline and other open spaces. And I was groundtruthing how many of these links didn’t exist.
So 2 years ago, I made a map. This map was my vision, and an atlas of problems and opportunities for Toronto’s trail system.
Urban experts will tell you all the benefits of having a high-quality and fully-integrated trail network. It encourages more active transportation use, reduces emissions, improves cardiovascular health, etc.. Any well-planned major urban centre should have something like this.
For me, it was a little more philosophical. I believe waterways and the natural space along them is a public right. I believe that the best trips are point-to-point, and not doubling back the way you came. I believe networks should exist to encourage residents and visitors alike to go beyond the known, and explore new places.
But overall, generally, it provides more open space for people in a large, noisy, bustling city. That’s a good thing. And it’s critical on a normal day.
Leave it a pandemic to show us how critical it is.
The spread of COVID-19 and the need to protect the vulnerable is putting pressure on local parks. Playgrounds, dog parks and anything else involving touching or close proximity is closed. The remaining space is what’s left for dense populations to enjoy themselves while practicing physical distancing.
This is where large parks and corridors are a benefit. This is where a narrow and disconnected system is a risk.
At the time of writing, it’s been 18 days since COVID-19 was declared COVID-19 a pandemic, and 12 days since Ontario ordered a shutdown. It seems like many people are doing well to self-isolate and physically distance themselves (with a few idiots amplified by isolated people posting and sharing on social media from their homes). As the weeks of continued shutdown continue, I worry about people getting cabin fever and open spaces becoming crowded, fueling a second wave.
But I hope anyone who can’t find enough space in their local ‘hoods can find some inspiration, and go explore other less-trodden paths. I also hope, once we get through this, that we do not forget this lesson and make better open space networks. For the normal days, and if we’re unlucky, the next pandemic.
Disclaimer: This piece is a data analysis and open discussion regarding Lake Ontario levels. The conclusions are not definitive and are editorial in nature. The matters before the Supreme Court of the State of New York are unproven and may be tested in court through rigorous argument, expert testimony, and applicable law.
Significant unregulated flow into Lake Ontario from Lake Erie;
Significant unregulated flow into the St Lawrence from the Ottawa River; and,
Restricted outflow from Lake Ontario to compensate for the Ottawa River.
It was the coming together of a bunch of factors. There was so much water rushing into the system, and not enough capacity going out, that it filled like a clogged bathtub. New York State, however, thinks that more could have been done. They’re suing the IJC, the bi-national agency in charge of operating Lake Ontario’s outflows at Moses-Saunders Dam near Cornwall.
So I’ve decided to pick up from my previous post, and look at some of the claims.
The Records and the Damage Done
As I wrote previously, Lake Ontario hit a new record monthly average lake height of 75.91 metres (Note 1) last June. That’s 10 cm above the previous record set in June 2017, 15 cm above the record set in 1952, and 1.15 metres above average (Note 2). So in 2017 and 2019, these record high levels caused flooding and erosion on both sides of the lake, including a whack of property damage on upstate New York’s shoreline.
This damage is not just because the lake is generally high. There’s also:
Lake surge (or wind set-up), which is a significant tilting of the lake due to wind (see diagram below); and,
Waves, which are self-explanatory.
On top of lake levels being a half-metre above average levels, surges and waves can add well over an additional metre of height to the water, and that’s a powerful force to be reckoned with, causing devastating flooding and erosion during a single storm.
“In the event of extremely high water levels in Lake Ontario, the IJC’s Dam operation protocol requires the Commission to operate the Dam to provide ‘all possible’ flooding relief to riparian property owners along Lake Ontario upstream of the Dam, subject only to protecting owners downstream of the Dam. During the severe flooding in 2017 and 2019…the IJC chose not to implement its flood relief protocol, which required the Commission to increase outflows through the Dam to the maximum extent possible.”
I don’t know about you, but it seems to me NY State undercut that second sentence with the first one.
The IJC’s ‘Dam operation protocol’ is called Plan 2014, and in a nutshell, when Lake Ontario reaches a certain height, the IJC is able to take certain actions to provide relief to Lake Ontario. This upper trigger varies every “quarter-month” or 7-8 days. Looking at last year’s data, it is true the dam wasn’t opened to full capacity when it reached the upper trigger; between May 7 and June 21, 2019. But again, providing “all possible” protection to Lake Ontario shoreline property upstream of the Dam is subject to protecting downstream properties on the St. Lawrence.
Opening up the Taps
Ignoring the downstream, what difference would it have made to open the dam to max capacity? Would it have been significant? If New York says not opening it up was negligent and the IJC says there was just too much bloody water, this is a good hypothetical scenario to test that.
Under Plan 2014, Lake Ontario would have hit the Upper Limit Trigger on May 7, when it surpassed 75.53 metres. Now, it would have fallen below that the very next day, as the trigger increased to 75.56, and the lake level was 75.55. But I’m going to ignore that. I’m also going to ignore the fact that, in this hypothetical situation, the hypothetical lake level resulting from max outflow bounces above and below the Plan 2014 trigger.
Let’s just assume that, on May 7, 2019, the IJC ignored all downstream impacts and opened up the Moses-Saunders Dam to its max capacity of 10,400 cubic metres a second. What difference would it have made?
31 centimetres, or a standard school ruler. That’s how much lower it would have been between June 21 and August 21, when the dam was opened to max capacity anyway, and less so from May 7 to June 21. The lake would have still been 55 cm above average, and it’s insignificant relative to surge and waves (Note 3).
Remember this is a scenario that would have devastated Montreal, which was already grappling with floodwaters, as well as other communities along the St Lawrence downstream of the dam.
What Arguments Hold Water
The theoretical scenario above illustrates a simple fact: there was a lot of water in the system. There’s no way to control how much water comes into Lake Ontario, from Lake Erie and all of the rivers and creeks on both sides of the border. This theoretical scenario also ignores other considerations the IJC has to make, such as potential downstream impacts, ice, hydroelectric plant equipment, and shipping / navigation.
This is consistent with the IJC’s position. From my viewpoint, New York State has a tough case in front of them. As a start, they have to prove that a) opening up the dam to its fullest extent would have made a significant enough difference to the property damages they faced, and b) it would not have significantly impacted downstream communities.
In the face of that challenging argument, it’s hard to see why New York State has gone through the trouble of this lawsuit. Giving them the benefit of doubt, perhaps they do have convincing data to show that extra discharge at the dam would have made a difference. Being really cynical, perhaps they don’t care how downstream communities in Quebec are impacted (the dam is about where the New York border turns east from the river).
But I think it’s political, and I say that with respect.
Paragraph 74 of the lawsuit argues the IJC was negligent because “Among other things, the IJC…chose to prioritize commercial shipping interests over riparian property owners.” That would have been crazy to say back in the 19th and early 20th centuries, when marine shipping was still a major way of transporting goods. But in the 21st century when we have other means to move goods by road, rail and air, I think it’s a fair question to ask if accommodating ships during critical lake conditions is reasonable.
Maybe that still wouldn’t make a huge difference, but it’s a difference nonetheless. And perhaps that’s one reason amongst others to step back, look at the bigger picture, and have a political discussion about how to manage flooding and flows in the Great Lakes basin.
That discussion should also include how New York manages it’s shoreline development. The best way to avoid a flooding or erosion hazard is to avoiding or mitigating the damage before development occurs. How much damage could have been prevented has been the burning question for me.
Note 2: Averages are for 1917-2016 (100 years). The annual lake average was 74.76 m. Monthly averages are different and vary month-to-month.
Note 3: This is a calculation based upon a surface area of 18,960 km². The difference between the max outflow from the Moses-Saunders Dam and the last outflow change for the dam was applied for each day (i.e. outflow in M3/s, multiplied by 86,400 seconds in a day), for a total volume of discharge for that day. This was then calculated as a height (volume ÷ area), and subtracted from the previous day height. The actual height change that occurred that day was also subtracted to account for inflows and evapotranspiration.
It’s been half a year since I picked up from Toronto, the big city, and moved to the more affordable pastures of Kitchener-Waterloo-Cambridge (“the Tri-Cities”). I’ve covered less than a tenth of what I walked in the T dot, but it’s given me enough time and distance to reflect on how these two regions differ, how the metroscapes have changed.
Toronto was founded as the Town of York in 1793, and has since been a focal point for development as the capital of Ontario, and an economic epicenter of the country. Waterloo County (the predecessor to the Regional Municipality of Waterloo) was settled around the same time, but Kitchener served as the administrative a rural seat for the area. It would be the mid 19th century before they became towns, and the 20th before they were cities.
As such, Toronto has deeper rooted intersections between the natural and built environments. This time piece is critical; the natural environment gets a lot more protection and attention in development planning than it ever did. New development is mostly prohibited where there are wetlands, waterways, floodplains and valley slopes, mostly to protect people or their property from flooding and erosion. But Ontario’s regulatory regime only became strong in the wake of Hurricane Hazel and it’s devastating effects in 1954. Even then, it was mostly focused on waterways and floodplains until encompassing valley slopes and wetlands towards the turn of the century.
This has created a swath of legacy development in Toronto, where houses and commercial/industrial operations had either buried and filled in ravines, or significantly encroached on them before regulation in place. The Tri-Cities on the other hand were more rural in character for some time, took longer to develop, and did so at a lower density and scale. This left more relatively more natural areas intact or unadulterated, at least until more robust protection of ravines was in place.
That’s development. Then there’s infrastructure, which is given more priority and leeway to encroach into or near natural areas. It’s still shaped by the same increasing environmental standards over time, but depending on how important that infrastructure is and how much demand there is for it, there may be more money available to make it happen. Toronto’s capital status and greater population and larger economy put it under greater pressure to provide sufficient roadways, highways, subways, railways; ways across and through natural areas. That hasn’t occurred to the same intensity in the Tri-Cities, but it’s there.
The key is that this infrastructure happened earlier in history, and at a larger scale. Massive infrastructure filled in ravines, or led to the complete burial of creeks. By today’s standards, it’s either not worth the cost of the infrastructure required to cross a natural area, or it’s avoided altogether.
Each metroscape also has one major difference: land availability.
There are historic shots of mid to upper parts of Toronto on either side of Yonge Street that seem unreal; the city was still quite rural in the mid-20th century. But by the 70’s and 80’s, new development was punching up to the city’s north border along Steeles Avenue.
Walking in the Tri-Cities in 2020, there are still plenty of rolling farmer fields and freshly carved woodlots on the frontier of development. There are approximately 47 km² of land that are considered “greenfields” within the current urban boundary. This is ignoring development outside of KWC proper, in places like Breslau, the Stockyards, and Mannheim, and it’s entirely possible that these borders could change with annexation. The pressure will only continue to grow as the Tri-Cities grow, and more people like me flock from the GTA in search of more affordable housing.
So the effects are obvious to me when I go exploring the respective metroscapes. Toronto has more natural spaces that have been covered up, constrained, engineered, fractured and/or half restored. This can often make them more interesting; they may be mysterious from an aerial perspective, and hold more surprises when explored in person. Add this to the fact that Toronto has a lake shore and the Tri-Cities does not, and there’s a clear difference in variety.
These unique metroscapes exist in the Tri-Cities too, but significantly modified natural spaces are fewer and farther between. It’s a bit of a double edged sword. Finding an unadultered natural refuge in the Tri-Cities is easier to do than in Toronto. Yet when you find it in a choked, noisy, concrete jungle, that’s what makes it more remarkable and more special. And when you find spaces that are modified to some degree by the built environment, it gives them character, and makes them unique.
This doesn’t make my walks in the Tri-Cities less interesting. There is a moment during every walk, something that raises an eyebrow and makes you smirk. It’s a snapshot that sticks with you, and it adds to your self-constructed image of the city.
That’s why I urge my readers and followers to go beyond living vicariously through me. Go explore these places yourself. Find your moment. My role is to be a guide and inspiration for where to start.
2019 marked a milestone in exploring local metroscapes. 2018 was the first full year under the new brand, and when my walk planning was starting to get really organized. So this past year was about covering as much ground as I could; I was in the groove, but I had the inkling that this may be my last year in Toronto. I tried to cover off all that I could, but it’s hard being a father and working full time.
I did not top 2018’s total walking distance, but considering everything going on in my life, I still covered a good amount of ground.
Over 26 walks, I covered 407 kilometres (321 km Toronto / 86 km KWC), a little longer than driving between Niagara Falls and Kingston. This is a decrease of 150 km from 2018.
The average walk was 15.6 km, an increase of 1.7 km from 2018. This is the same distance as walking between Keele and Main Street subway stations in Toronto, or between Conestoga Mall and Mill Stations in KW.
The longest walk was the last one of the year (December 7), coming in at 23.7 km. This was following the proposed ION Stage 2 route, which is longer than the actual route because of the detours.
Most months were an average of 30 km total, the outliers being March (57 km) and June (77 km).
There were 118 Toronto neighbourhoods covered in 2019, 84 of them which were truly walked through, down from 166 and 143 last year, respectively. Half decent coverage of the city, especially Etobicoke and west Toronto-East York North York was a bit of a void. 2 walks went beyond the City of Toronto borders, 3 of them in the Pearson airport area.
As for the tri-city, in which I completed a neighbourhood project for, I covered 41 neighbourhoods, 32 which were truly walked through. Many of them are concentrated along the regional north-south spine, as this happened to be the features I explored. 1 walk went beyond the borders of the tri-cities, when following the Grand’s west bank technically took me through North Dumfries.
Note: A watersheds project for Kitchener – Waterloo – Cambridge is still in progress, so this only reflects watersheds for Toronto walks. This section will be updated once KWC Watersheds is completed.
Last year, I was able to cover all 7 watersheds in Toronto. This year, I technically walked through all of them again, but fewer of my walks traced watercourses.
I covered 9 first-order rivers and creeks of 4 main watersheds (Lower / West Etobicoke, Lower / West / East Humber, Lower / West / East Don, East Highland).
10 second-order or lower streams were followed (Black, Lavender and 4 tributaries, Mud, Curran Hall, West Hill and tributary).
1 lost river was traced: Russel Creek, which drained straight into Lake Ontario.
Looking ahead to 2020
2020 will be a big year for exploring the metroscapes of the tri-city. I have lots of opportunities to go beyond the spine I’ve covered so far, and hit the far reaches of each city. In total, I have almost 500 km of walk plans. This includes:
16 in riverine systems
6 in hydro corridors
3 along rail corridors
2 along highways
In addition to that, I still have some unfinished business in Toronto, so I may fire down to the T Dot a couple times to try and cover more ground. This includes checking out some new stuff, such as Garrison Crossing and the new East Don Trail.
Aside from the walks, I have a lot of project work to do as well, and for starters I will finish and publish KWC neighbourhoods. I also have to get my head around KWC watersheds; it’s a bit of a different beast from Toronto, as it will be a number of subwatersheds of the Grand River.
I also hope to figure out a better mapping solution. I have been using Google My Maps as a primary tool, and MapHub for posting and sharing screenshots (since it’s open source). They’re free, which is the primary reason I’ve used them, but both are becoming limited in the scale and capacity I want to use them. I may move to a GIS tool if I have the time and energy amongst the rest of life’s demands.
My suggestion for Scarborough Waterfront West has been adopted;
The future Leaside South connection has been illustrated;
The Weston North Humber Connection gap was recognized; and,
The Finch Hydro Corridor trail will be kept within the corridor across the Metrolinx Uxbridge Subdivision.
It definitely feels good that I was able to lean on my walking experience and create some change in a major planning document. This will help create continuous trails along the waterfront, Humber River and Finch Hydro Corridors. Furthermore, some of the things I raised were (relatively) small scale details that I’m not too worked about.
That said, I am a bit disappointed that three of my large scale suggestions were not taken up.
The Crosstown Southwest corridor is the biggest disappointment for me, and is somewhat baffling. It is a natural corridor that would be richer than the bike lanes on Bloor. Furthermore, the middle part between Davenport and St Clair is a formally recognized project by the city, and there is about a kilometre and a half of existing trail west of that. I thought filling in the gap in the Stockyards area and continuing the line past Rockcliffe Boulevard to Etobicoke Creek was a good idea.
A trail through Black Creek Ravine also seems like a relatively feasible project, as pretty much all of the approximately 6 kilometre trail would be on existing, publicly owned parkland and open space. The only exception would be a half-kilometre stretch under the Highway 400 / Jane Street interchange, which is still public land, making access negotiable.
North Scarborough has this ginournous gap in north-south connectivity. Once again, there are existing segments of trail and most of the ravine is intact. It may be constrained in spots where wetlands are present and a meander belt is protected for, but I think a link to Scarborough Centre should be worth the effort.
Progress is slow and steady sometimes, and the fate of these potential trails is not sealed. So I will take this as a win, and I hope Torontonians will continue pushing for a better trail network.
A reflection on my walks in Toronto, both in 2019 and as a whole for the past 6 years.
A massive valley with towering apartments on the top of the slope.
The remnance of where a river swept an entire crescent of houses away.
Thick forest followed by a massive train trestle overhead.
A sweeping shoreline leading to a downtown core.
These were the sights along my first walk after moving to Toronto, from Cruickshank Park to the lake. While this was something to occupy myself for the weekend, it started a fascination with how Toronto’s natural and built environments collided.
That said, the walks were aimless and kinda shallow. It wasn’t until November 2017 that it became a brand, and a focused effort to document Toronto’s best walks and biggest opportunities. All in all, from what I could remember back to April 2016, I racked up over 1,300 kilometres over 111 walks.
I thought it worthwhile to take a look back, and make some initial reflections.
2019 in Toronto
2019 was a pretty fruitful year. Despite only completing half as many walks as last year (306 km, or a drive from Toronto to Chatham), I did go further on average (16.4 km; a Lakeshore West GO train ride from Union to Dixie Road). More important than the stats, however, is that I feel like I went on some particularity special walks.
One was certainly the Leslie Spit. Dreary weather can make for a dreary day, but sometimes it makes the colours in the landscape pop a little more. That certainly was the case with the Spit’s brick-laden shores, wetlands in their infancy, tall barren trees and still harbour waters. There’s nothing else like it.
Finally, there was walking the Beltline, which was a bit of coming full circle. It mixed the midtown trail that was an integral part of my last 4 years in Toronto, and the valley that fills faint memories from the first 6 years of my life. It’s objectively beautiful without context, but it was a very spiritual trip for me.
Looking Back and Forward
I can’t pick those three walks and say they were my top 3 for 2019, or that any of them were the best of all time. Even when I have an incident(e.g. heat exhaustion, falling through ice, or getting lost), every walk has its moment. Despite my bitterness with the circumstances I had to leave under, these adventures will stick with me for years to come.
I’m just happy that I’m able to share all of this. Whether it’s looking up ideas for your own walks, referring to older pictures as the city continues to grow and change, or using analysis to further improve the walking environment of the city, I will strive to maintain this website as a resource for current and future Torontonians.
That said, the Toronto section of the site is not going to be completely static going forward. I still have work to do in the Projects section, and I will return to the city on occasion to visit and take care of some unfinished plans.
So this isn’t goodbye Toronto. More like “See you later.”
Note: This post was first published on June 1, 2019 with data available from May 30, 2019. It was updated on June 3, 2019 with the latest data available, and improved graphs. It was updated again on June 5, 2019, July 2, 2019 and February 17, 2020 to reflect new height records and revised data from sources.
In June 2017, Lake Ontario rose to a height not seen in the last 100 years of recorded history. The pictures of how this impacted Toronto were dramatic; flooding parks, eroding shorelines, and boardwalks, beaches and the Islands underwater.
Two years later, we broke records again. Once again, it’s a shocking scene.
The height of water in a lake fluctuates naturally. The amount of rainfall flowing into it, and the rate at which it drains through an outlet (if it has one) is a major determinant. However, it can also be affected by temperature, sunlight, formation / melting of snow and ice, and wind.
But how have we hit crazy high levels within the last two years? Rain, and how much and how hard it falls, is definitely a huge factor. But you may be surprised to learn that its less about the rain that falls onto Lake Ontario’s surface and shores or how hard it fell, and more about what’s happening to the east and the west.
This is a look at where water in Lake Ontario comes from, and where it goes.
First, let’s set this up with some historical context on Lake Ontario’s water level (Note 1).
Prior to 2017, Lake Ontario had only gone above a height of 75.7 metres twice in the last century: 1952 and 1973. It has also only gone below 73.8 metres twice during the same period: 1934 and 1936. Otherwise, Lake Ontario has varied in height within this 1.9 metre range from year-to-year, and season-to-season.
Then in 2017, the previous record set in 1952 was broken by 5 centimetres, with the lake reaching a monthly average height of 75.81 metres above sea level. It was dramatic and visually striking, flooding the Toronto Islands and other shoreline areas on the mainland. The capital repair costs to the city were estimated to total $15.6 million.
This year, the high lake levels are repeating themselves. Most days in June 2019 broke Lake Ontario’s previous daily height record of 75.88 m set in 2017. June 2019 also saw a new record average lake height of 75.91 m, or 10 cm above the previous record set in June 2017.
Looking back makes you realize that in Lake Ontario’s history, a couple pairs of high level years occurring in close vicinity is not unprecedented. 1929 + 1930. ’43 +’ 47 + ’52. ’73 + ’74 +’76. Keep the last two sets in mind next time you’re looking at imprints on Toronto’s bridges and culverts. Same story goes for sets of years with record lows.
What causes the changes in Lake Ontario to swing so much? Do I really need to bust out that graphic from your high school science class showing the water cycle? No? Good.
But as I alluded to, Lake Ontario’s water level isn’t affected as much by the rain that falls near the lake. Below is a chart showing the water balances for the Great Lakes.
As you can see, Lake Ontario’s levels are highly dependent on upstream inflow and downstream outflow (79% and 95% of total inflows and outflows, respectively). The remaining 21% of the total inflow is from water fed from rivers and streams, and 5% of the total water is evaporated (Note 2).
Upstream inflows come from the other Great Lakes, which are fed by rainfall and streamflow. So technically, it makes it an indirect impact. But it’s an important distinction to make. A closer look at where Lake Ontario’s water comes from and where it goes will make it clear why.
Ontario: Last Stop Before the St Lawrence
Lake Ontario is impacted by the fact that it is part of Great Lakes-St Lawrence River system. This means it is fed by water from (going upstream):
Lake Erie via the Niagara River;
Lake St Clair, via the Detroit River;
Lake Huron / Georgian Bay, via the St Clair River;
Lake Michigan, via the Straits of Mackinac; and,
Lake Superior, via the St Mary’s River.
Water from Lake Erie flows down the Niagara River, and its mostly unregulated, meaning it flows without anything really holding it back (i.e. a dam). Two exceptions are hydroelectric power plants on both the Canadian and American sides, as well as the Welland Canal. However, the power plants are restricted in how much water they take in; the International Join Commission (IJC) is a bi-national agency that has rules to ensure there is enough water flowing over Niagara Falls, so they look pretty and aren’t a pathetic dribble.
The Welland Canal is another pathway for water between Lakes Erie and Ontario. It isn’t a huge factor either; it’s 8.5% of what flows through the Niagara River (Note 3).
Continuing upstream, Lake Huron and Lake Michigan are technically one lake, as they are hydraulically connected through the Straits of Mackinac and generally sit at the same level. The water from them flows unregulated through the Lake St Clair and the St Clair and Detroit Rivers.
Lake Superior is the one major upstream part of the basin that is regulated. Outflow is controlled via three power plants and a 16-gate dam on the St Mary’s River. However, the outflow of Superior pales in comparison to other inputs to Lakes Michigan, Huron and Erie, and even then, any water held back would be a percentage of that outflow.
All that to say Lake Ontario is fed by the other lakes and the rainfall that feeds into them, and there’s really nothing holding it back. So when all of the lakes are up, it can mean a significant cumulative height difference for Lake Ontario.
Outflow: A Balancing Act
Lake Ontario, and all of the water fed into it, flows into the St Lawrence River, and eventually the Atlantic Ocean. But it’s not as simple as draining a tub.
While the eastern end of Lake Ontario is defined as being at Kingston (where it passes both sides of Wolfe Island), there are locks and dams along the way, which widen the St Lawrence River behind them and form ‘lakes.’ These lakes are:
Lake St Lawrence, between Kingston and Cornwall
Lake St Francis, between Cornwall and Melocheville
Lake St Louis, along the west end of Montreal Island.
The key outlet is at Cornwall, between Lake St Lawrence and Lake St Francis, where the Moses-Saunders Dam controls the flow of water. How much water is released is once again determined by the IJC, but unlike the Niagara River, that goal is not making pretty waterfalls. Nor is it just contingent on what is happening to the west. The IJC has to play a balancing act between the height of Lake Ontario and how high the St Lawrence is downstream.
Lake Ontario is 19,000 km² and an average depth of 86 m. Lake St Francis and Lake St Louis on the other hand are…not so big. I couldn’t find the figures I was looking for, but it’s in the ballpark of 400 km² and an average depth of 10-20 m (if you got better numbers give me a shout). But the magnitude speaks for itself; the same amount of water has a disproportionate impact on water levels.
Even if Lake Ontario is really high, increasing outflow to reduce its height by a couple centimetres could send downstream communities underwater. So even if the Toronto Islands are underwater and our shorelines are being eaten away by erosion, it’s a small cost relative to the damage that could occur down in Quebec.
Another complicating factor is that the Ottawa River meets the St Lawrence at Lake St Louis. It is a very large river basin which is also relatively unregulated, and it can significantly alter the height of the St Lawrence at Lake St Louis. If there are already high flows coming down the Ottawa River, this put extra restrictions on the flow out of the Moses-Saunders Dam so that flooding in Montreal and other Quebec communities downstream doesn’t occur or isn’t worsened.
One mitigating factor in all of this is the evaporation off of the lakes. One would think that warm temperatures mean big thunderstorms, and that is a major pathway for moisture to be carried out of the lake. Well, actually it’s quite low.
Just as snow melt starts entering the system and the rain begins to fall, evaporation rates nosedive, and whatever goes through a lake’s outflow is the only output of the system. When you put the plug in the tub while the water’s still pouring in, it’s gonna fill up.
The manner in which snow falls and melts can also have an impact on the system. I reached out to a friend who is more academically trained in earth and atmospheric sciences to expand on these effects of seasonal change on lake levels.
“A late start to spring and extended cold weather can delay local vegetation’s break from dormancy. This has the effect of reducing evapotranspiration rates early in the season. As plants take up water, they remove some moisture from the ground which would otherwise end up in local river systems, and eventually through to the St. Lawerence River.
An extended winter may also delay snow melt timing, resulting in a greater surge of water into the Great Lakes, as opposed to the longer, drawn-out thaw that we are typically used to.
Downstream damming and excessive rainfall are much more significant contributors to lake level issues. Still, evapotranspiration and snow melt play an important part in our water cycle, and all of these factors together may have helped pushed things over the top this year.”
Putting it all together, you get an idea of why 2017 and this year saw crazy high water levels in Lake Ontario.
Extended winter and late spring
Significant spring rain
Significant unregulated flow into Lake Ontario from Lake Erie
Significant unregulated flow into the St Lawrence from the Ottawa River
Restricted outflow from Lake Ontario
And when you put this in chart form, with the lake level put against the rates of inflow and outflow, it becomes clear how restrictions at the Moses-Saunders Dam can play a large part in raising Lake Ontario’s height.
Between April 18 and May 21, 2019, there was an average of 114.85 million m³ more water flowing into Lake Ontario than flowing out each day. Over 34 days, that makes for a total of 3.9 billion m³ of water. If you didn’t account for elevation, that would be enough to cover the city of Toronto in 6.2 metres of water (Note 4). Accounting for elevation however, that’s enough water to flood downtown Toronto, East York and south Etobicoke (up to the old Iroquois shoreline) with as much as 50 metres of water (Note 5).
So, a lot of water. Spread out over the entirety of Lake Ontario however, it rose 70 cm, which is enough to impact the entirety of Toronto’s 111 km of shoreline, and thousands more kilometres of shoreline across the rest of the lake (Note 6).
So what are the odds of this happening again? I can’t tell you exactly. I have delivered simplified numbers here, and don’t have a good enough understanding of inter-year and inter-seasonal effects on basin supply and drain.
So perhaps it’s time to talk about how we manage the inflows and outflows of the Great Lakes. Should we be taking steps to regulate flows out of Lakes Michigan, Huron and Erie? Should we begin to deregulate flows out of Lake Ontario and find another way to mitigate flooding in the St Lawrence?
That discussion would be a geographical (upstream and downstream) and impact-based (net natural, social and economic) balancing act. And that’s way beyond a single blog post or a single year of records.
1. Lake height measurements are from the National Oceanic and Atmospheric Administration’s master gauges (Superior – Marquette C.G., Michigan – 9099018 | Michigan-Huron – Harbor Beach, MI – 9075014 | Erie – Fairport, OH – 9063053 | Ontario – Oswego, NY – 9052030) and are based on the International Great Lakes Datum, 1985. Monthly/annual maximums, averages and minimums available here.
4. Not accounting for elevation, Toronto has an area of 630.2 km² (per StatsCan); taking the volume (of water in lake Ontario) and dividing it by area (of Toronto) equals height (3.9 million km³ / 630.2 km² = 6.2 m).
5. I obtained a simplified line drawing of the shore from BlogTO, eliminated the segment east of Scarborough Heights Park, and converted into a polygon (area is 152 km²). I then employed simplified math to illustrate how much water there is; assuming that this area was a triangular prism, with a height equal to point where the slope starts a significant elevation increases (~130 m above sea level, near Yonge Street and Woodlawn Ave; difference from the lowest point in Toronto of 76.5 metres of 53.5 metres from the shore). The volume of this perfect triangular prism is therefore area * height divided by 2 (152 km² * 53.5 m = 4,066 km³). To reverse-calculate how high the water would be for a different volume of water (e.g. the net flow into Lake Ontario; 3.9 million km³), you can multiply the volume by 2, and divide by the area ([3.9 million km³ * 2] / 152 km² = 51.4 m).
6. Toronto’s shoreline length is calculated based on my previous #shorelineTO work. Lake Ontario’s shoreline length is quoted as 1,020 km, however, this measurement may be subject to the coastline paradox to a greater degree than my measurements in Toronto.