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Proactive disclosure Print version | A change in the wind: Climate Change in Québec The St. Lawrence has its ups and downs
The St. Lawrence River is the dominant feature of the Quebec landscape. It flows a total distance of 1500 km, and over 70% of Quebec's population lives along its 4200 km of shoreline. The St. Lawrence is not a homogeneous unit. It is divided into three sections, (1) the freshwater reach, (2) the estuary, and (3) the gulf, on the basis of its natural characteristics: tides, salinity, vegetation, and sources of water. Reduced flow of freshwaterThe freshwater reach is fed by the Great Lakes basin and two large tributaries - the Ottawa River and the Saint Maurice River, and extends from Cornwall to Lake Saint-Pierre. This freshwater reach has no tides. The impact of climatic changes on this ecosystem may be felt on several levels, including a drop in water flow, which would affect access to quality water, and modification of wetland areas. The very low water levels observed in 1998-1999 in the freshwater reach caused, among other things, a change in available habitat area, leading to an invasion of opportunistic land plants on bare and dry ground. The ecosystem was impoverished, notably because these species are of little interest to the fauna of the St. Lawrence - fish, ducks, amphibians, and reptiles. Invasion of opportunistic land plants Alain Armellin, St. Lawrence Centre Examples of potential impacts in the freshwater reach:
Pointe-aux-Trembles marsh
Did you know? Rising sea level
Between Lake Saint-Pierre and the Atlantic Ocean, the estuary and the gulf are sectors with tides in which the water ranges from fresh (upstream of Île d'Orléans) to brackish and saline. The saltwater portion of these reaches is being affected by increased erosion that climate warming could worsen. General circulation models (GCM) are very imprecise at regional scales, although they all predict to varying degrees atmospheric warming above the Gulf of St. Lawrence. The main impacts likely to be felt in the estuary and gulf are a reduced flow of fresh water from the freshwater reach, an inflow of colder fresh water from Labrador, and an increase in ocean levels. Examples of potential impacts in the estuary and gulf:
Too little water or too much? The main impact of climate warming on the St. Lawrence River would be the fluctuation in water levels. Whether they are fresh, brackish, or saline, the waters of the St. Lawrence River will either rise or fall. These fluctuations will affect various riparian and aquatic habitats, as well as biophysical and socio-economic aspects. ReferencesHudon, C., 1997: Impact of water level fluctuations on St. Lawrence River aquatic vegetation; Canadian Journal of Aquatic Science, v. 54, p. 2853-2865.
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