Lake Ontario and St. Lawrence River Levels Rise Following April Rains

By Jacob Bruxer, International Lake Ontario-St. Lawrence River Board

A series of storm events passed through the Lake Ontario-St. Lawrence River system from April 4-10, resulting in significant precipitation across the region. Some eastern parts of the Lake Ontario basin received as much as 80 millimeters (3.2 inches), while areas around the St. Lawrence River near Montreal saw as much as 90 mm (3.5 inches) during the same series of events.

Total precipitation accumulation, April 4-10. Credit: Environment and Climate Change Canada
Flooding near Rideau River, Ottawa, Ontario, on April 10. Credit: David Fay, IJC

With the ground already fully saturated, the recent rain, coupled with snowmelt in some areas, resulted in high amounts of runoff and rapidly increasing streamflows across the basin. Flood warnings were issued by many agencies in Canada and the US, and many reports of localized flooding have since been received.

Daily Lake Ontario levels. Credit: International Lake Ontario-St. Lawrence River Board
Daily Lake Ontario levels. Credit: International Lake Ontario-St. Lawrence River Board

The wet conditions have resulted in rapidly rising water levels throughout the Lake Ontario and St. Lawrence River system. Lake Ontario’s level has risen approximately 19 centimeters (7.5 inches) since April 4, increasing the risk of storm damages and leading to concerns among many lake riparians.

Daily St. Lawrence River levels at Lake St. Louis. Credit: International Lake Ontario-St. Lawrence River Board
Daily St. Lawrence River levels at Lake St. Louis. Credit: International Lake Ontario-St. Lawrence River Board

Downstream of Lake Ontario on the St. Lawrence River, levels at Lake St. Louis near Montreal, Quebec, have risen almost twice that amount during the same period, by about 37 centimeters (14.6 inches), due to rapidly rising Ottawa River and other local tributary flows. To prevent Lake St. Louis levels from rising further and causing more extensive damage, the International Lake Ontario-St. Lawrence River Board reduced outflows from Lake Ontario in accordance with Plan 2014, in effect since January.

Lake St. Louis flooding begins at a level of 22.19 m (72.80 feet), on April 17, 2008. Credit: Rob Caldwell, International Lake Ontario-St. Lawrence River Board
Lake St. Louis flooding begins at a level of 22.19 m (72.80 feet), on April 17, 2008. Credit: Rob Caldwell, International Lake Ontario-St. Lawrence River Board

Plan 2014 sets flows to balance the risk of flood damages, both on Lake Ontario and the St. Lawrence River downstream, by keeping the level of Lake St. Louis below a given threshold for a corresponding Lake Ontario level. As the level of Lake Ontario rises, the threshold level on Lake St. Louis also rises, allowing more water to be released from Lake Ontario.

Recent water levels of Lake Ontario and Lake St. Louis in comparison to Plan 2014’s tiered “F-limit” rule. Plan 2014 prescribes outflows from Lake Ontario that attempt to balance the impacts of high levels both upstream on Lake Ontario and downstream on the St. Lawrence River. Credit: International Lake Ontario-St. Lawrence River Board
Recent water levels of Lake Ontario and Lake St. Louis in comparison to Plan 2014’s tiered “F-limit” rule. Plan 2014 prescribes outflows from Lake Ontario that attempt to balance the impacts of high levels both upstream on Lake Ontario and downstream on the St. Lawrence River. Credit: International Lake Ontario-St. Lawrence River Board

However, it’s important to note that while Plan 2014 tries to balance these impacts, it cannot and does not eliminate the risk that high levels may occur during periods of extreme weather like we’ve experienced recently. In fact, no regulation plan can do so.

To illustrate the limitations of regulation, consider that it would have taken an increase in outflow of more than 6,000 cubic meters per second (211,900 cubic feet per second) above the average flow since April 4 of 7,010 cubic meters per second (247,600 cubic feet per second) to have maintained Lake Ontario at a stable level. A flow increase of that magnitude would be nearly impossible to achieve, physically. It also would cause levels at Lake St. Louis to rise more than 1 m (3 feet), resulting in catastrophic flooding throughout the lower St. Lawrence River.

Extremely high water levels are a concern to all riparians throughout the Lake Ontario-St. Lawrence River system. While impossible to avoid entirely, balancing the risk of high levels and associate impacts, both upstream and downstream, is a key aspect of Plan 2014.

Jacob Bruxer is the alternate regulation representative of the International Lake Ontario-St. Lawrence River Board and senior water resources engineer at the Great Lakes-St. Lawrence Regulation Office, Environment and Climate Change Canada, Cornwall, Ontario.

15 thoughts on “Lake Ontario and St. Lawrence River Levels Rise Following April Rains”

  1. So what level do we expect on Lake Ontario this spring. Our high risks and associated impacts are already causing sewer systems to fail at Sodus Point. This is not balanced.

  2. A State of Emergency was declared on 4/20/17 by the Mayor of Sodus Point due to the Lake Ontario water levels.

  3. Where are the high water levels coming from? There was little snow in Western New York. Oak Orchard Creek 11″ higher, docks AT water level now, and expecting 11 more inches in the next few weeks. Something has to give.

  4. How about comparing what the actions would have been in December, January, February and March based on 1958 DD specs. That would really tell what Plan 2014 is doing to us!

  5. High water levels have occurred throughout the Lake Ontario and St. Lawrence River system during recent weeks, a direct result of the extremely wet weather received across the basin so far in April. Precipitation has been well above normal this month throughout the system, with large areas receiving more than twice what they normally do on average. Water supplies to Lake Ontario and Ottawa River flows into the lower St. Lawrence River have both been above record highs recently. Emergency measures have been taken in many local jurisdictions across the basin, and flooding has been reported on Lake Ontario, the St. Lawrence River, and on many inland local tributaries, including the Ottawa River.

    Lake Ontario outflows continue to be adjusted according to Plan 2014 in order to minimize and balance flooding on Lake Ontario and along the St. Lawrence River in the Montreal area. This is essentially all that can be done under any regulation plan during such extreme weather conditions. While it is nearly 25 years since we have seen water levels this high, the current conditions on Lake Ontario and the St. Lawrence River have occurred in the past and will occur again. The current high water levels have not been caused by Plan 2014. Lake and river levels would have been almost identical this year under the previous regulation plan.

    For more information, please see the International Lake Ontario – St. Lawrence River Board’s latest media statement at: http://ijc.org/en_/islrbc/news?news_id=597

    Or check its Facebook page at: https://www.facebook.com/InternationalLakeOntarioStLawrenceRiverBoard

  6. Data exists to determine exactly what lake levels would have been under the old plan… We hear terms like “levels would have been nearly the same”… Why not just publish a daily comparison of levels and actions so this debate can end and perhaps something could be learned…

    1. Eddie Wilson makes an excellent point. Anyone have access to that data ? Blaming the new water level plan only makes sense if it is indeed the only factor which is causing this situation. Frustrating as it may be, the discussion needs facts not emotions.

      1. I own property on Oak Orchard Creek 1/2 mile from Lake Ontario. My docks are under water – the first time since I bought the place in Sept 2000. Something doesn’t add up right.

    2. This is what needs to be published – publish the last 10 years levels and show us how we compare…..day by day since Jan of each year. Then we can draw our own conclusions.

  7. Just find it wierd that Moira River watershed wasn’t flooding as per normal and yet Lake Ontario Levels flooding surrounding area in Bay of Quinte. Yet people says it’s due to spring rain? Wierd.

  8. I am an aquatic biologist, an Emeritus Prof at UWO. I’ve “done” lakes, streams, rivers, drainages, runoff and flooding throughout my half-century career, so I know something about this subject. I am on Presqu’ile Point on the shore of Presqu’ile Bay at Brighton Ontario. I bought my property in 1997, and I have never seen Spring water levels this high. Others on Presqu’ile Point are not so lucky – their basements are flooding and their sump pumps are not keeping up. My house is probably high enough to be safe. I don’t have a sump pump because it’s downhill from the basement floor to the Presqu’ile Bay water level. Water in the basement goes out through a pipe and runs down to the Bay, and the Presqu’ile Bay water level would have to come up quite a bit before that would change enough to be a serious problem. However I am concerned about shoreline erosion. Most of my shoreline has got young trees (e.g. cedars) growing. In all previous years their bases and roots have been above the water level even at the high water time (usually June-July). This year the water level is part-way up the trunks. Some shoreline stretches are open and exposed. We are fairly protected, part-way up an inlet with marsh across from us. Properties further out Presqu’ile Point (to the east of us, toward open Presqu’ile Bay and – at the lighthouse – open Lake Ontario) are less protected and more vulnerable to storms and to shoreline erosion. With the water as high as it is (and perhaps not at its peak) I am worried about shoreline erosion at our place. Now that flooding has peaked in the Montreal area and water levels are falling, I am hoping that Lake Ontario water will more seriously be “bled off” and allowed to run down through the St. Lawrence Seaway locks. I feel for the Montreal area people but soon the IJC should move to alleviate the threat to the people on the shorelines (both the ON and the NY sides) of Lake Ontario. There is nowhere for the rising Lake Ontario water to go other than down the St. Lawrence River, so sooner or later it has to go that way. I hope sooner.

  9. It is May 16th and I was checking the Lake Ontario water levels and had a sense that the level was still increasing but that the rate of increase was tapering off. So I fit a simple model to the May data (May 01 to May 14) and found that that was the case. A quadratic equation is the simplest model and the fitted line is Lake Ontario level (feet) = 247.8 + 0.1482(date) – 0.004478 (date-squared). It is a very good fit, with r-squared = 98%. I have a graph of the data with the fitted curve. More to the point, the quadratic term (indicating that the rate of lake level increase is dropping off) is highly significant at p=0.001. Beyond that I wouldn’t get too excited about it. With only 14 points and the vagaries of weather and how smoothly (linearly) the water will come down from the upper Great Lakes, any attempt to predict the peak water level date would be silly. If our region gets another period of heavy precipitation, things would look worse. But, conversely, if the IJC folk start releasing more water through the St. Lawrence Seaway locks, which they should do soon with the improvement of the Montreal area flooding situation, the peak water level and the timing of it would only get better (lower peak water level and sooner).

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