A translation by Judith Turcotte.
Climate change causes extreme conditions: on one hand, torrential rains provoke floods and force the expansion of flood zones and on the other, long periods of droughts lower the level of the St. Lawrence River as is currently the case. We should be worried about floods but the decrease in the level of the St. Lawrence is equally damaging.
In a recent article, the Journal de Montréal informed us that according to the pilots who guide the ships, the level of the St. Lawrence has not been this low in 15 years. The level is 70 cm lower than normal. As we all read in the media, this decrease in the level of the river disrupts commercial navigation and water activities. These disruptions are easy to see with a glance at the shorelines; however, other consequences are not as obvious such as the decrease in the dilution of pollutants, the increase in the cost of the treatment of drinking water without forgetting the environmental impact on the aquatic plants and the wildlife.
According to Ouranos, a consortium on regional climatology and the adaptation to climate change, two water treatment plants along the St. Lawrence are vulnerable and could see their production capacity limited. The increase in water turbidity could also cause a rise in production costs for all of the municipalities who take their water from the river.
The decrease in the level of the river has an impact on its ecosystem. The decrease disrupts the reproduction cycle of numerous species and limits the available habitats for the aquatic plants and wildlife. The wetlands, such as aquatic herbaria, decrease in size resulting in the loss of necessary spawning habitats and food supply for the fish and birds.
In the assessment of this subject, we must remember that the Great Lakes represent the principal source of the water of the St. Lawrence River. The river’s water level is controlled by the International Lake-Ontario-St. Lawrence River Board under the authority of the International Joint Commission (IJC). The IJC is a Canada-American structure that implements the management plans of the river’s level according to binational agreements. The Great Lakes have recorded water inputs lower than the average with the result that during the summer of 2025, there was a reduction in the water inputs of the Great Lakes towards the St. Lawrence River. The waters that reach the river come from Lake Ontario and must pass through the Moses-Saunders dam where the flow rate of the water is regulated. If the drought continues, which seems to be the case, the flow rate towards the St. Lawrence River could be reduced again. For now, on the 18th of October, the dam will let water reach the St. Lawrence, to help with the situation. This policy will lower the level of Lake Ontario by one third of a centimetre but will help solve problems in the St. Lawrence but on a temporary basis.
The decrease in the level of the St. Lawrence River, which affects us today is considered as a temporary and cyclical phenomenon although its frequency and severity are on the rise due to climate change. The St. Lawrence River’s situation could deteriorate further with the arrival of Trump in power.
The subject of my next blog.