Changes to water quantity: drivers and impacts

Canada is a water-rich country. It has only 0.5% of the world's population, but its landmass contains approximately 7% of the world's renewable freshwater supply. That being said, most of Canada's population resides in the south while much of the water flows north.

Key drivers of changes to water quantity

Multiple factors influence the amount of water found in Canadian lakes, rivers, wetlands and groundwater aquifers. Although the amount of water available for human use is strongly linked to climate and weather, water use depends on population levels and individual and industrial activity.

Weather variability: Water levels and flows in rivers, lakes and reservoirs generally follow changes in temperature, rainfall and snowfall throughout the year. In general, the landscape is wettest right after snow melt in the early spring and gradually dries out through the late summer and early fall. In any given year, high levels of precipitation increase the amount of water in rivers, lakes or reservoirs, whereas warmer temperatures and less rainfall or snowfall than normal mean less water.

Climate change: Climate change is expected to result in shifts in the location and timing of rain and snow across Canada. The intensity and frequency of floods are projected to increase. Drought is expected to increase in areas prone to receiving less snow and rain, such as the Prairies.Footnote 1 Higher temperatures associated with climate change are already causing glaciers to recede, which will also result in long-term changes to the amount of water flowing in some major Prairie rivers.

Human development: Human development impacts the amount of water in lakes and rivers by affecting how water moves across and through the landscape. Expanding cities remove natural vegetation cover and replace it with surfaces that water cannot penetrate, such as roads and parking lots. This development reduces the amount of water available to replenish groundwater and to provide soil moisture. It also increases the amount of water running directly into storm sewers, lakes or rivers, triggering erosion and flooding when rivers are overwhelmed by a sudden influx of water.

Water demand: Many industrial processes depend on water, such as electricity generating plants which use water for cooling and to produce steam to drive the turbines to produce electricity. Water is also used for irrigation, for cleaning, and in chemical processes. Municipalities distribute water for both residential and commercial uses, including drinking, cooking and bathing.

Key impacts of changes to water quantity

Depending on where you are in Canada, changes to the amount of water in rivers, lakes, wetlands and groundwater aquifers will have widely differing effects on the environment, human health and the economy.

Environmental impacts

  • Periods of higher water quantity have the beneficial effect of replenishing water resources in wetlands, lakes and rivers and recharging groundwater aquifers. It is also during these periods that rivers move sediment and nutrients onto agricultural land, helping to restore degraded soils
  • Excessive water flow through a river channel can increase soil erosion resulting in deteriorating water quality and destroying plant and animal habitat
  • Drier conditions affect the food webs of aquatic ecosystems by reducing survival and reproduction of aquatic species, including fish
  • Dry conditions can increase the number and frequency of wildfires resulting in losses of wildlife and vegetation
  • Groundwater supplies can also be impacted when water levels decrease as people become more dependent on groundwater when surface supplies dry up.Footnote 2 Over the long term, removal of the groundwater can cause the land surface to sink

Human health impacts

  • Major flooding may result in loss of human life and increase the risk of waterborne diseases
  • Wetter conditions can lead to more frequent flooding of basements and public places and cause mould to grow in buildings
  • Increased dust in the air during drier conditions can affect people with respiratory conditions

Economic impacts

  • Flooded agricultural lands can result in delayed or no planting of crops. On the other hand, droughts, and efforts to alleviate their effects, cost Canadians many millions of dollars every year in lost crop production, insurance claims as a result of crop failure, and associated food price increases. It is estimated that the 2001-2002 drought on the Prairies cost approximately $3.6 billion in agricultural production and caused the gross domestic product to fall an estimated $5.8 billionFootnote 3 
  • Floods cause damage to infrastructure, such as roads, bridges, and buildings. This damage has a direct economic impact associated with the costs of replacing the damaged infrastructure. Indirect economic impacts include losses due to inactivity for a prolonged period of time caused by, for example, the inability to commute, broken communication networks and reduced tourism. In the past 20 years, flooding in Canada has cost upwards of $8.3 billion, with the June 2013 flood in Alberta the most costly to date at an estimated $2.7 billion.Footnote 4 More recently, a 2-day atmospheric riverFootnote 5 that swept across southern British Columbia in mid-November 2021 caused multiple evacuations and is likely to be the costliest natural disaster in British Columbia's history with insured damages estimated at $450 million. Given the scale of the disaster, it is expected that overall economic losses will be much higher than the insured lossesFootnote 6 
  • Seaways, such as the Great Lakes-St. Lawrence system, are affected by changes in water levels. Low water levels mean ships must carry less to avoid running aground. It is estimated that ships navigating the St. Lawrence Seaway can lose 20 to 100 tonnes of cargo capacity per centimetre of lower waterFootnote 7 at a great economic cost 

Ways to reduce pressures on water quantity

Treating our freshwater as a precious resource that deserves protection and careful stewardship will help lessen the effects of changing water quantity. The first step to preserving this natural resource is for governments, businesses and individuals to take steps to use it more efficiently. Actions can range from installing low-flow toilets in households to choosing drought-tolerant crops in agricultural areas prone to dry spells, to improving flood predictions so that people can avoid losses to their households.

The Federal Sustainable Development Strategy is the Government of Canada's primary vehicle for sustainable development planning and reporting. It sets out the Government's sustainable development priorities, establishes goals and targets, and identifies actions to achieve them. The Strategy outlines the actions toward sustainability that the Government will take in collaboration with partners within Canada and internationally, including actions related to reducing pressures on freshwater. 

For more information on how individual Canadians can help to reduce their impact on water quantity, consult Things you can do to help the environment.


Agriculture and Agri-Food Canada (2016) Lessons Learned from the Canadian Drought Years 2001 and 2002.

Environment and Climate Change Canada (2015) Water quantity.

Environment and Climate Change Canada (2004) Threats to water availability in Canada.

Government of Canada (2019) Causes and effects of climate change.

Insurance Bureau of Canada (2021) British Columbia floods cause $450 million in insured damage. Retrieved on February 18, 2022.

National Oceanic and Atmospheric Administration (NOAA) (2022) What are atmospheric rivers? Retrieved on February 18, 2022.

Public Safety Canada (2019) The Canadian Disaster Database.

Related indicators

The Water quantity in Canadian rivers indicators provide a summary of trends and the status of water quantity in rivers at the national, regional and local levels.

The Canada's water use in a global context indicator reports on the amount of water removed from the environment per person per year for use in agriculture, manufacturing and in homes, and as a percentage of each country's total renewable water supply for nine countries, including Canada.

The Water availability in Canada indicator compares the amount of fresh water withdrawn from rivers for human use to the volume of water in Canadian rivers.

The Residential water use indicator reports how much water is used in homes across Canada.

The Water withdrawal and consumption by sector indicator shows how much water is used by 7 economic sectors in Canada.

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