Why wasn’t more water released from Lake Ontario in the spring of 2017?
Since flooding was occurring above and below the dam in spring 2017, Lake Ontario outflows were set to balance upstream and downstream flooding impacts.
Why wasn’t more water released in 2016 when downstream flooding was not an issue?
The Board saw no reason to release more water since Lake Ontario was below its long-term average from May through December 2016 and because the basin experienced severe drought during late summer and fall of that year. The capability to predict whether conditions would be wet or dry in the following year does not exist.
For example, Lake Ontario was at the same level at the end of March 2017 as it was at the end of March 2016. An extreme drought followed in 2016 while extremely high rainfall followed in 2017. Neither scenario could have been predicted, nor were they.
Would the Board have had more flexibility to release water if Plan 1958DD had been in place in 2017?
While the Board would have had greater authority to deviate and release flows other than those prescribed by the plan, this greater authority may not have been exercised during the extreme weather conditions in 2017, including highly variable temperatures and ice conditions in the St. Lawrence River in winter and the extreme rainfall and flooding conditions upstream and downstream in the basin during spring. Therefore, it likely would have made little or no difference if the Board had been operating under Plan 1958DD.
For example, while the Board had the authority to deviate from Plan 2014 flows when Lake Ontario reached its high water trigger level on April 28, the Board chose to follow Plan 2014 until May 24 to balance the flooding that was occurring simultaneously both upstream and downstream. The outflow decisions that the Board made once it began to deviate from the Plan 2014 flow may have been the same outflow decisions it would have made under the Plan 1958DD because the Board would have been faced with the same considerations.
Why were flows reduced for navigation?
The Board’s priority in 2017 was to reduce the impacts from high water upstream and downstream. However, in setting the outflow, the Board must consider the degree of relief that can be provided as well as the consequences to all interests. Higher flows than those set by the Board would have increased currents in the international section of the St. Lawrence River to an extent that would have effectively forced the stoppage of commercial navigation. This would have further impacted people’s lives and the economy throughout the Great Lakes region by disrupting the transport of raw materials and finished products, without providing a great deal of relief on Lake Ontario.
Starting on May 24, as flooding conditions subsided downstream, outflows were increased above the flows that would otherwise have been prescribed by Plan 2014. In fact, outflows exceeded the highest flows ever previously released on a sustained basis, and these unprecedented outflows were maintained from mid-June into August. To maintain safe conditions for navigation during the sustained, record high flows, the Seaway entities imposed speed limits, no passing restrictions and other mitigation measures.
The gradual decline of Lake Ontario through the summer months caused the velocity in the upper St. Lawrence River to gradually increase. This presented additional challenges, and eventually, maintaining record high flows was no longer safe for navigation. As a result, starting in August, flows had to be gradually reduced in order to ensure safe conditions and allow ship transits to continue.
In summary, outflows were set at or near the maximum possible rate consistent with safe navigation from the end of May through December in order to lower Lake Ontario levels as quickly and safely as possible.
Why did the Board not set flows at a rate that would have resulted in temporary navigation stoppages, such as those that occurred in 1993?
The interruptions of Seaway operations in 1993 were a short-term, experimental measure and removed just over an inch of water from Lake Ontario. In 2017 Lake Ontario outflows were comparable to, or higher than, those released in 1993 on a weekly basis and were sustained over an extended period while balancing all interests in the system. This resulted in record releases and a greater rate of lowering of Lake Ontario than that which was achieved in 1993, and with fewer impacts on other stakeholders. In the four months following the peak water level (June through September), Lake Ontario dropped a record 93 centimeters (36.6 inches); the next largest decline during this period was 86 centimeters (33.9 inches) in 1993.
Why were flows reduced in October for boat haul out?
The extremely high outflows, especially after Lake Ontario reached lower levels in August, reduced the level of Lake St. Lawrence just above the dam at Cornwall, Ontario and Massena, New York. Levels there were lower than they had been since 1987, leaving many boats grounded, and many marinas and boaters were unable to remove their vessels prior to winter. Reducing the outflow for one weekend in the fall (October 7-8, 2017) raised the level of Lake St. Lawrence sufficiently to assist with boat haul out without any significant impact on the level of Lake Ontario. In any case, the effect on Lake Ontario was subsequently removed by releasing slightly higher flows over the following weeks.
What actions can be taken to lower water levels and prevent a flood in 2018?
As the end of 2017 approached, Plan 2014 continued to specify very high outflows, but whether or not a flood occurs during the spring of 2018 will depend on weather conditions and water supplies over the winter and spring months, not the regulation plan. While the Board and the Plan are doing all that can be done, no flow management plan can eliminate the risk of future flooding.
Why not draw Lake Ontario down each fall so that there is sufficient storage to prevent flooding in the spring?
The physical capacity simply does not exist to prevent flooding in years when water supplies upstream and downstream are as extreme as those experienced in 2017. Previous IJC studies have shown that it is not possible to prevent all flooding on Lake Ontario, even if this was the only objective of the regulation plan. Furthermore, the impacts that can occur to other interests, such as navigation and recreational boating, during low water years must be considered. For example, if there is a drought in the following spring, drawing down Lake Ontario as much as possible each fall would result in significant economic impacts to other interests, which may actually exceed the reduction in economic damages to Lake Ontario shoreline property. Lastly, fall drawdowns are also known to have detrimental impacts to environmental restoration interests as well.
How did outflows under Plan 2014 during fall 2017 differ from those that would have occurred under Plan 1958DD?
This cannot be determined with exact confidence since decisions that may have been made by the Board in this situation under Plan 1958DD are not entirely predictable and, hence, are unknown. However, from April through August 2017, the Board had authority to deviate from Plan 2014. It did so, starting at the end of May as downstream flooding subsided, and released the maximum flow possible while maintaining commercial navigation in the St. Lawrence River throughout the summer. Starting in September, the Board returned to following Plan 2014 which continued to set outflows at the maximum that could be released while maintaining commercial navigation operations in the upper St. Lawrence River throughout the fall and until ice formation began in late-December. Had outflows been increased further, whether under any regulation plan or through deviations, it would have increased the risk to ships and may have suspended commercial navigation operations in the St. Lawrence River. Finally, Lake Ontario water levels are primarily influenced by natural water supplies, whereas outflow regulation has a lesser influence. Especially under extreme conditions, one can expect the same extreme water levels to occur under either regulation plan.