A thorough six-year review of how Lake Ontario outflows are regulated when water supplies are extreme is nearing completion.
Outflows from Lake Ontario into the St. Lawrence River are regulated at the Moses-Saunders Dam in accordance with an International Joint Commission (IJC) regulation plan. The review of Plan 2014, the current regulation plan, was originally scheduled to be conducted by 2031. However, the IJC ordered an expedited review after record-setting floods in 2017 and 2019 caused widespread damage across the Lake Ontario-St. Lawrence River system.
The review has been led by the IJC’s Great Lakes-St. Lawrence River Adaptive Management (GLAM) Committee. The IJC applies an adaptive management strategy to monitor and assess the effects of Lake Ontario outflow regulation over time and explore ways to improve its implementation. The GLAM Committee reports its findings to the International Lake Ontario-St. Lawrence River Board, the body responsible for overseeing the operation of Plan 2014.
The Expedited Review of Plan 2014 was conducted in two phases. The first phase, completed in November 2021, focused on providing detailed information on high water impacts. The purpose was to support real-time decisions when Lake Ontario rises to certain high-water trigger levels and the board has authority to deviate from the rules of Plan 2014. Phase 2 evaluated the rules of Plan 2014 itself and explored whether modifications could improve longer-term outcomes.
In seeking improved outcomes, the GLAM Committee’s experts gathered data and modernized the tools used to assess potential modifications to the regulation plan. One team considered plausible future water supply scenarios. Another team refined the models that simulated how modifications to the regulation plan would affect water levels and flows throughout the system.
A different group improved the performance indicators, which are a tool to measure how water levels and flows impact a specific interest. In the case of the expedited review, these are utilized to estimate how uses and interests would be affected, including shoreline property owners, municipal water intakes, commercial navigation, recreational boating, hydropower production and ecosystem health. Yet another team devised an evaluation and ranking framework so that assessing the different options would be consistent and transparent.
A major project was the Integrated Social, Economic, and Environmental (ISEE) System. An earlier version of this system was previously used by the IJC successfully during the Lake Champlain-Richelieu River flooding study. This powerful computational tool brings data sets on land elevation, land use and other features together with performance indicators to simulate how a particular interest might be affected by water level and flow changes. The ISEE system includes a geospatial system built on a high-resolution grid that can display performance indicator results at different scales on an interactive map, showing changes, week by week over a 60-year simulation.
Throughout the expedited review, the GLAM Committee sought feedback from its binational Public Advisory Group made up of 18 members from shoreline communities, business sectors, local governments, agricultural interests and environmental advocacy groups. The diverse membership brought a range of views and concerns that deepened the GLAM Committee’s understanding of the impacts of extreme water levels and flows. Relationships with Indigenous Communities were also initiated through a series of listening sessions and other gatherings. Finally, the expedited review’s methods and findings were scrutinized by an Independent Peer Review Group.
The GLAM Committee explored a wide range of modifications to Plan 2014’s various components. These included the rule curves used to calculate outflows, the flow limits that protect downstream interests and navigation, and the trigger levels that authorize the board to deviate from the regulation plan rules.
While thousands of plan modifications were tested, none of the alternatives would eliminate flooding. This is because the effects of natural factors such as water supply trends and sustained winds far outweigh the influence of Lake Ontario outflow regulation. However, the GLAM Committee did identify regulation plan changes that marginally reduce flooding impacts in certain areas.
The board has the responsibility of recommending what modifications to Plan 2014 should be made. After inviting public comment, the board will present a final report with recommendations to the IJC. The IJC will then undertake its own engagement process prior to making decisions on the board’s recommendations.
More information about the GLAM Committee’s work on the Expedited Review of Plan 2014, including fact sheets that explain different aspects of the study, can be found at https://ijc.org/en/glam/phase2.
