Water levels slowly declining on Lake Ontario
Some flooding relief as outflows continue
After reaching a high of 75.92 metres in June, water levels on Lake Ontario are starting to decline with the recent warmer, drier weather but the lake remains 84 centimetres above its average for this time of year.
As of Sunday, the lake level sat at 75.85 metres, just below the record peak set in May of last year at 75.88 metres.
Lake levels are measured according to how high they are above sea level.
Even as the levels start to decline, the International Lake Ontario–St. Lawrence River Board continues to release water at a record outflow 10,400 cubic metres per second from the Moses Saunders Dam between Cornwall, Ont., and Massena, N.Y.
In a release, the board, part of the International Joint Commission, said it decided to maintain the current outflow, which is 200 cubic metres per second higher than the maximum safe navigation limit that would normally apply.
It said both the Canadian St. Lawrence Seaway Management Corp. and U.S. St. Lawrence Seaway Development Corp. implemented mitigation measures, including no wake and no passing zones, to allow for safe navigation to continue at the higher flows.
The agency said it looked at several lake outflow strategies above the current record-setting flow but determined any additional increase would require the Seaway shut down shipping on the St. Lawrence River between St. Lambert and Cape Vincent.
“The economic costs for disrupting the supply chain of the Great Lakes-St. Lawrence economy is estimated at $50 million per day,” it said in the release.
It added additional impacts were also expected for recreational boating and downstream shoreline property owners, including resumed and additional flooding in areas of the lower St. Lawrence River just upstream of Montreal.
An increase in the lake’s outflow would also have environmental impacts on fish, wildlife and waterfowl habitat and breeding grounds.
“The board has also agreed to maintain the flow at 10,400 cubic metres per second for a longer duration than in 2017 until water levels on Lake Ontario drop more than 30 centimetres and fall below 75.50 metres.”
Current forecasts, it said, suggest that drop may occur around mid-August, depending on water supplies.
In addition, the board said it notified both seaway corporations that it will continue to set outflows at approximately 200 cubic metres per second above the normal safe navigation flow limit into the fall to continue lowering Lake Ontario levels at an accelerated rate.
“These enhanced outflow measures will help to provide both immediate and longer-term relief to all impacted upstream shoreline residents and property owners due to the high water levels. The intent of the board is to lower water levels as much as possible prior to winter,” it said, adding it only controls the outflow of the lake, not what flows into it.
The board added that while the higher outflows will accelerate the rate of lowering that would otherwise occur, it is not possible, this year or any other, to lower Lake Ontario to a predetermined ‘safe water level by the onset of winter.
Water levels on Lake Erie continue to remain above average, with a reading from a water level monitoring station in Port Colborne showing the lake was 1.51 metres above its 173.50-metre level.
It reached a high of 1.81 metres above and a low of 1.41 metres over a 24-hour period.
The high waters level on the lake can easily be seen at the boat launch at H.H. Knoll Lakeview Park in Port Colborne, where the centre launch ramp is partly underwater and the east launch ramp and part of the walkway on the dock is completely underwater.