Lake Ontario-St. Lawrence River board continues to maximize outflows from Lake Ontario

The International Lake Ontario-St. Lawrence River Board agreed to continue releasing an outflow of 10,400 cubic meters per second (m3/s) or 367,300 cubic feet per second (cfs), as conditions allow, to help lower the level of Lake Ontario and provide all possible relief to riparian residents while considering the impacts throughout the Lake Ontario-St. Lawrence River system. This outflow continues to be the highest ever released from Lake Ontario on a sustained basis.

The board reviewed current conditions and despite efforts to provide relief by releasing record-high outflows, recent wet conditions continue to sustain high water levels, causing continued severe impacts to Lake Ontario and St. Lawrence River property owners, recreational boaters, businesses and tourism. Lake Erie remains well above average, and combined with significant rainfall during the past month, the total inflow to Lake Ontario was the second-highest recorded in the month of June since 1900. Yet despite the near record-high inflows and notwithstanding a slight rise in levels following especially heavy showers and thunderstorms on June 22, Lake Ontario levels fell 9 cm (3.5 inches) overall last month, 8 cm (3.1 inches) more than average and the 11th largest decline in June since 1918.

On the St. Lawrence River, levels near Montreal and further downstream had been declining in general, but rose to near-record highs in recent days following a series of storm events. The board continues to monitor and assess conditions in consideration of the impacts that these exceptionally high levels and flows are having in Lake Ontario and the upper and lower St. Lawrence River on all stakeholders, including commercial navigation.

Furthermore, based on information provided to the board by the St. Lawrence Seaway on navigation conditions at high flows, the board concluded that an outflow of 10,400 m3/s (367,300 cfs) is the maximum outflow that can be released from Lake Ontario with present river levels that would still allow continued, though restricted, safe commercial navigation in the St. Lawrence River. The board noted that while wet weather has maintained high levels recently, warmer and drier summer conditions are likely to return and allow water levels throughout the system to resume their decline. As levels decline, a gradual reduction in outflows will be required to prevent the velocities in the St. Lawrence River from exceeding the limits for safe navigation. However, the board expects the flow of 10,400 m3/s (367,300 cfs) can safely be maintained for some time to come and will continue to re-evaluate this on a daily basis at least until its next meeting.

Outflow changes, photos and graphs are posted to the board’s Facebook page. More detailed information is available here.

Maritime Editorial