How will Climate Change affect Canada’s water resources?

Global climate models indicate that future changes in temperature will be greatest at high latitudes. Therefore, the magnitude of climate change in a northern country, such as Canada, will be greater than in southern countries. 

In general, we are likely to see changes in our ability to grow food and potential costly changes to the methods we use to do it. Warmer temperatures could create conditions for more severe weather events, including thunderstorms and an increased frequency of tornadoes, with attendant risk to life and property. Drier conditions and warmer temperatures could also cause more frequent forest fires. More frequent heat waves could affect the health of Canadians, especially in cities. 

Higher air temperatures and removal of the insulating vegetative cover could lead to a melting of permafrost in the Arctic. This could cause more landslides in some areas, and problems for the construction and maintenance of pipelines, roads, and bridges. Glaciers could retreat more quickly because of higher air temperatures, resulting in less late season runoff, and placing fish habitats and water supplies in dependent communities at risk. As water plays a central role in many economic and societal functions, the implications of climate change for water resources are key to defining overall impacts. Water resources in all regions of Canada will be affected to differing degrees.

British Columbia:

• Sea level rise and flooding could create drainage problems and over- whelm municipal sewage systems in coastal communities, resulting in water contamination.
• Sea level rise could also cause saltwater to intrude into the groundwater, making it unfit to drink
• Increased precipitation is predicted to occur in winter which could promote landslides and local flooding
• Warmer river temperatures could cause severe pre-spawning mortality in anadromous fish, such as Pacific salmon.
• Increased temperatures cause glaciers to melt more quickly, initially, providing more water, however over time as glaciers retreat there will be less runoff and lower flows - leading to warmer water temperatures and declining water quality.

The Prairies:

• Periodic droughts may become more severe and more frequent due to higher temperatures and increased evapotranspiration.
• Increased irrigation, where water was available, could bring more soluble salts to the surface, degrading the soil
• Summer precipitation is projected to decline 10–20 per cent and evaporation is expected to increase.
• Severe weather conditions, such as extremely heavy rainfalls and storms ranging from winter blizzards to summer tornados, could become more prevalent.

Ontario:

• Decreased runoff during summer is likely to lead to reduced water quality, increased water treatment costs, and greater competition and conflict for reduced water supplies during drought periods.
• Higher air temperatures and increased evapouration will cause the Great Lakes’ levels to drop much lower than they are now,

         o    decreasing the flow available for the generation of hydroelectric power, and
         o    reducing the amount of cargo ships could carry per trip.

• Water users dependent on groundwater for their supplies may expect increased costs because of a need to drill deeper wells.
• In rural areas, the frequency of shallow wells drying up may increase.
• Changes to wetland form and function may be expected as groundwater discharge decreases.
• Stress on fish habitat is likely to increase as water temperature increases and flows decrease.
• Increased water temperatures also create a more favourable environment for microbial and algal blooms, further reducing water quality.

Quebec:

• The St. Lawrence River’s annual flow rate could decrease by as much as 40 percent in Montreal and 30 per cent in Quebec.
• The St. Lawrence River is a source of drinking water for 45 per cent of Quebecers. This decrease, and subsequent water quality issues, would severely impact a large proportion of Quebec’s population.
• Extreme weather events could become more frequent in Quebec as the climate changes.

Atlantic Canada:

• Increase in the occurrence of storm surges and flooding due to sea level rise, more heavy storms and the occasional hurricane. The subsequent saltwater intrusion may result in contamination of groundwater aquifer supplies and rivers.
• Warmer climate may encourage the growth of toxic algal blooms, these pose a serious threat to both fish and human populations.

The Arctic and Far North:

• Gradual melting of permafrost will change the water drainage patterns.
• Increase precipitation, particularly in fall and winter, would result in a greater accumulation of snow, although over a shorter season, and the possibility of extensive and earlier flooding in the spring.
• Higher precipitation could increase the net water supply to northern watersheds.

These kinds of impacts illustrate ways in which global climate change creates local problems that stakeholders in each province will have to confront.

For more information on Climate Change, and Climate Change and Water Resources see Pollution Probe's Climate Change and Human Health Primer and Mainstreaming Climate Change in Source Water Protection Primer.