Montreal is surrounded by water: the St. Lawrence River to the south, the Rivière des Prairies to the north, Lake Saint-Louis to the southwest, and Lac des Deux Montagnes to the west. These water bodies, which provide most of the drinking water used by Montrealers, follow ancient rift zones that formed when the continent broke up, 600 million years ago. The main water intake is located upstream of the Lachine Rapids, in the centre of the St. Lawrence River, and supplies water to two treatment plants. Water at the Atwater plant, the older of the two, is routed via the Aqueduct Canal, an 8 km long water artery. The treated water is stored in several tanks, a number of which are located right in the heart of Mount Royal. Waterways around Montreal have many uses, including recreational fishing and swimming.
The Aqueduct Canal channels water toward the city. (Courtesy of P.Bédard(UQAM))
Monitoring the Resource For the past several years, the Port of Montreal has been affected by particularly low water levels in the St. Lawrence River. Unusually dry climatic conditions and an increase in the amount of water removed from the river upstream of Montreal have resulted in record decreases in water levels and flow rates. This situation is of concern to all and has significant negative impacts on aquatic ecosystems, wetlands, shoreline erosion, and commercial shipping.
Water Right Under Our Feet!
Although it cannot be seen from the surface, groundwater underlies the entire Montreal region, primarily in the fractured rocks of the St. Lawrence Platform. In quarries and other deep excavations, such as those created for urban infrastructures, groundwater must be continuously pumped out. On Montreal Island, groundwater is not heavily used for human consumption, and only a few hundred homes at the west end of the island are supplied from this source. Around Montreal Island, groundwater is used for various purposes, including as a source of drinking water and for crop irrigation, fish farming, and commercial ends. Water bottled from a groundwater source in the Mirabel area is known throughout North America for its quality.
Groundwater reaches the surface. (Courtesy of P.Bédard(UQAM))
At the beginning of the sixteenth century, Jacques Cartier must have been taken aback by the churning waters of the Lachine Rapids, and had to abandon his dream of discovering the Northwest passage. To bypass this obstacle to navigation, the Lachine Canal was completed in 1829, linking Lake Saint-Louis and Montreal. Widened several times since it was first constructed, the Lachine Canal facilitated trade with the interior of the continent and fostered the industrial development of the region. In 1959, the St. Lawrence Seaway replaced the Lachine Canal, which was later closed to navigation.
The first of the Seaway locks is located at Saint-Lambert near the Victoria Bridge. The Côte-Sainte-Catherine and Beauharnois locks raise and lower ships through a total elevation change of 38.6 m, over a distance of a few tens of kilometres. The Seaway brought world trade into the interior of North America and made Montreal a key transfer point for transatlantic cargo.