Graph for Lake Ontario/St. Lawrence

The model integrates results and allows a comparison of how performance indicators (PIs) respond to alternative management plans.

Water quality at Blue Plains

spacerFacebook LinkedIn Twitter

Success Story

Water level and Flow in Lake Ontario/St. Lawrence System

Since 1959, the St. Lawrence Seaway has modified the natural dynamics of water level fluctuation in Lake Ontario, the St. Lawrence River, Lake St. Lawrence, and associated wetlands. The International Joint Commission established the Lake Ontario-St. Lawrence (LOSL) Study Board to investigate water level/flow changes and determine new water-level regulation criteria that would protect ecosystem resources without significantly impacting other interests, such as commercial and recreational navigation, hydropower, and riparian landowners. LimnoTech’s contributions to the project team advanced the understanding of water levels and flow in the LOSL system and helped link these issues to ecological impacts.


A key concern addressed was that existing water-level regulation criteria were contributing to undesirable ecological impacts, including effects on wetland habitat quality and quantity, fish species utilizing ecological services provided by nearshore and wetland habitats, terrestrial fauna that inhabit shoreline habitats in the system, endangered species, and water quality. An Environmental Technical Work Group (ETWG) was formed to identify and quantify the effects of water levels and flows on key ecological performance indicators.


Working closely with ETWG scientists, LimnoTech built a model to quantify the relative long-term response of ecological indicators when subjected to alternative regulation plans over a 50-year period. The model helped identify 32 key Performance Indicators representing the overall health and integrity of the LOSL ecosystems.


The LOSL Study Board used the model to compare alternative plans and their impacts on all of the interests being considered, including the environment, and to recommend the best plan. The development and application of the model was a major advancement in understanding how the flora and fauna components of wetlands and coastal zone ecosystems of lakes and rivers respond to fluctuations in water level and flow.