During the summer, The duty crosses the waters of the St. Lawrence River, this giant “almost ocean, almost Atlantic” that Charlebois sings. Today, we take stock of his state of health.
It originates in the largest lake system in the world, the Great Lakes, and drains their 23,000 km3 freshwater to the Atlantic Ocean. Along the way, he collects the waters of dozens of rivers. Its watershed represents a quarter of all the fresh water reserves in the world. For millennia, it has fed and transported the humans who live on its shores and those of its tributaries. The vast majority of the populations of the two most populous provinces in Canada, namely Quebec and Ontario, and part of the population of the United States, live in this watershed, draw their drinking water from it and… discharge their sewage there. . The St. Lawrence River, which stretches over nearly 1,200 km and crosses southern Quebec from west to east, is the vital, sentimental, ecological and economic link of our beautiful province.
Several invasive species have been introduced over time, including zebra mussel, round goby, Asian carp. These new species introduced by human activities change the ecosystem and food webs and bring permanent changes to the river. These introductions can also complicate the ecological balance for certain species unique to our environment and threatened — such as the copper redhorse.
We thought for a long time that with such a volume and such a flow of water, we could release almost anything into the river, that all this water would dilute the pollution and that we would not see any impact. It was said (and we still hear…) that the solution to pollution is dilution! Thus, until the 1970s, almost no effluent, municipal or industrial, received the slightest treatment before flowing into the St. Lawrence. Fortunately, since those not-so-distant years, a collective awareness has made it possible to put in place a legislative and financial framework for municipalities and industry to equip themselves with treatment systems for their effluents.
We treat more and better, but…
Today, the majority of effluent receives at least primary treatment before discharge, but there is still a long way to go to remove contaminants at source. Indeed, if the level of wastewater treatment varies from one treatment plant to another, the majority is still limited to the elimination of suspended particles and the control of phosphorus.
In addition, several municipalities still have wastewater collection systems that pass through the same pipes as rainwater to the treatment plant, which treats all this water together before it is discharged. All it takes is a heavy rain for the treatment plants to be literally overwhelmed and discharge their effluents directly into the river without treatment.
Too often, wastewater treatment does not include disinfection steps and does not at all target the removal of emerging contaminants like pharmaceuticals (antibiotics, antidepressants, pain relievers), hormones, plastic by-products and other chemicals. We can even measure, for the poly and perfluorinated (PFAS) family, concentrations about twice as high in the St. Lawrence River as in other waterways.
PFAS come from various domestic or industrial uses (used as anti-adhesives, water repellents, flame retardants, in fire-fighting foams, etc.). These compounds and hundreds of others degrade so slowly that they can persist in the environment and in living organisms for decades after they are banned.
While agricultural activity has greatly intensified over the last century in Quebec, agricultural pollution is first and foremost an issue for the tributaries of the St. Lawrence River, and near their mouths. Nevertheless, we find traces of pesticides in the river and we still know very little about their impact on the fauna and flora. Traces of pesticides have been detected even in the drinking water of municipalities that use them. Concentrations of atrazine (a herbicide to kill weeds) occasionally exceed European standards (but meet the much less restrictive North American criteria).
In addition, large quantities of nitrogen, phosphorus and organic matter of agricultural origin, but also municipal and industrial, are released, which causes measurable eutrophication downstream, as in Lake Saint-Pierre and into the estuary of the river, where we have observed for several years a deep zone almost devoid of oxygen, and therefore inhospitable for aquatic fauna.
A jewel to preserve
The microaggressions on the river are multiplied through chemical pollution, the destruction of habitats, the installation of dykes to build in flood-prone areas that serve as refuge and breeding ground for the river’s fauna, and thus eliminates buffer zones that purify the water and also absorb large volumes of water during spring floods.
For several decades, we have been aware of the importance of preserving the St. Lawrence River, our Quebec jewel. Our efforts, combined with those of the inhabitants of the Great Lakes watershed, have not been in vain. In fact, the quality of the water in the river, upstream from Montreal and downstream from Trois-Rivières, has improved over the years, to the point where we see more and more beaches open to swimming. There remains, however, much to do everywhere, from Montreal to Lake Saint-Pierre and throughout the watershed of our river.
Our river is entitled to protection standards inspired by the precautionary principle, to ensure that the health of its ecosystems and that of its residents will be protected for generations to come. We must, and we can, bequeath to our children a healthier river than the one we inherited. It remains to want it collectively. Beyond the legal implications, giving our St. Lawrence a legal personality, as other communities elsewhere in Quebec and around the world have already done for other rivers, would, in our opinion, be a source of collective pride. .