I am interested in Lake Saint-Pierre because it is part of the St. Lawrence River. The St. Lawrence has the second-largest discharge among North American rivers. The St. Lawrence flows through a series of fluvial lakes; Lake Saint-Pierre is the last of these. Currently, water quality in the St. Lawrence, especially downstream of Montreal and in Lake Saint-Pierre, is very poor. I am interested in finding out why water quality is so terrible in this environment. Water quality in the St. Lawrence has been rather bad for a long time. I would say easily for the past 50 or 60 years. It has somewhat improved over the past few decades. The causes of the problem have also changed. Water quality problems in Lake Saint-Pierre stem from three main causes. First, the sewage treatment technology used in the Montreal area. The cities of Montreal, Longueuil and Laval have sewage treatment techniques dating back to the last century and are not at all helpful in preserving water quality in Lake Saint-Pierre.
Lake Saint-Pierre also has problems because of non-sustainable agriculture. You can’treally be against agriculture, but you can disagree with the way it is currently practiced. Currently, there is very little concern for water quality in receiving bodies of water. If you take a look at the Yamaska, Richelieu and Saint-François Rivers you can see that they have terrible water quality.
The third cause of problems in Lake Saint-Pierre is the waterway in the middle of the lake. Because of this ship channel, all the clean water coming from the Great Lakes and Lake Ontario flows rapidly through the centre of Lake Saint-Pierre and does not help clean out or dilute the polluted waters from Lake Saint-Pierre’s agricultural tributaries, such as the Yamaska and the Richelieu.
The combination of these three issues – outdated treatment of sewage water upstream, agricultural pollution from non-sustainable farming techniques and the presence of the ship channel – results in very poor water quality in Lake Saint-Pierre.
We have found that water quality in approximately 40 % of the surface area of Lake Saint-Pierre, an area of over 100 km2, water quality does not even meet the Ministry of the Environment’s Water Quality Guidelines for the Protection of Aquatic Life. Lake Saint-Pierre is thus so badly polluted that aquatic life in the lake is not being properly protected.
Lake Saint-Pierre has other problems as well. Because of the ship channel running through its centre, the lake experiences rapid siltation. I think there must be other ways... Commercial shipping isn’tthe problem;it’s the way that we practice it. I think it is a very bad idea to bring ocean vessels all the way up the river to Montreal and the Great Lakes. On most other large rivers around the world, barges are used; a barge has a much shallower draught than an ocean vessel. This allows them to travel through much shallower channels. This concept could easily be applied to Lake Saint-Pierre.
We are discovering that Lake Saint-Pierre has a special configuration. There is the central ship channel, that quickly drains water from the Great Lakes and the heavily polluted waters from the agricultural tributaries, which carry high phosphorus and nitrogen loads, as well as large amounts of suspended matter, which is deposited on the bottom of Lake Saint-Pierre. In some parts of the lake, especially the upstream areas, the upstream half of the lake, we are observing very rapid siltation. If you factor in the expected decrease in the St. Lawrence River’s water volume, the rapid siltation we have observed together with the decreased water volume leads us to believe that Lake Saint-Pierre as we know it, with its current surface area, will be a thing of the past within a few decades. This means that the lake is rapidly silting up, it is rapidly filling, especially in the southern section and also in some shallow areas of the northern half of the lake that now support thick growths of aquatic plants, which promote sedimentation. There are problems with contamination, not only by pathogenic micro-organisms, phosphorus and nitrogen but also by other substances, including pharmaceuticals and hormones, that are having noticeable effects on biology in the St. Lawrence River and Lake Saint-Pierre. For example, we have observed abnormal male/female ratios with negative effects on the reproductive capacity of some species of fish and amphibians in the ecosystems of the St. Lawrence River and Lake Saint-Pierre.