Hydrology of Canada


Canada’s surface water resources are considerable, an estimated 7% of the world’s renewable water supply. The location and average flow of Canada’s largest rivers are presented on the map of Streamflow. This map indicates that approximately 60% of the country’s freshwater drains to the north, away from the 85 percent of the population living within 300 kilometres of our southern border.

Canada’s Hydrologic Diversity

The diversity of Canada’s hydrology is a reflection of its bio-physical diversity, which can be generalized by the fifteen Terrestrial Ecozones.

The relatively wet, mountainous Montane and Boreal Cordillera and Pacific Maritime ecozones covering British Columbia, southwestern Alberta and much of the Yukon Territory form the western fringe of the country. High runoff from these ecozones drains westward into the Pacific Ocean - exceeding 3,000 mm annually in some coastal areas - and eastward into the vast, dry Interior Plains. The latter region comprises the flat, fertile Prairies ecozone in the south and the Boreal and Taiga Plains ecozones to the north. Generally, runoff on the Plains averages well under 200 mm per year, especially in the south where it can average less than 50 mm.

Most of central and eastern Canada is covered by the rugged Boreal and Taiga Shield and Southern Arctic ecozones, for which annual runoff trends from 100 mm in the northwest to 800 mm in the southeast, to over 1000 mm along the Atlantic coast. Surrounded by the Shield, the extensive wetlands of the Hudson Plains ecozone drain northward into Hudson and James bays.

The humid Mixed Wood Plains ecozone of the Great Lakes-St. Lawrence River Valley encompasses the heavily populated area of southern Ontario and southern Quebec. Annual runoff ranges from as low as 200 mm in the southwest to over 600 mm in the northeastern end of the ecozone. To the east of the Mixed Wood Plains lies the rugged, wet Atlantic Maritime ecozone which covers all of the provinces of New Brunswick, Nova Scotia and the Atlantic provinces and a portion of eastern Quebec. Runoff increases significantly from west to east, varying from 600 mm annually in the western part of the ecozone to 2000 mm along the Atlantic coast.

In the far north, the desert-like Northern Arctic ecozone straddles the Northwest Territories and Nunavut. Few data on runoff are available in this ecozone, but in view of the very low precipitation (100-200 mm annually) annual runoff is considered to be very low also. Even less is known about runoff from the glaciated, mountainous Arctic Cordillera ecozone, most of which covers Nunavut’s east coast.

The climates of Canada range from continental in the south to boreal or subarctic in the mid-latitudes and arctic in the north. Maritime influences modify both the west and east coast climates, the east coast less, because of the predominantly eastward movement of interior air masses. Permafrost occurs throughout the mid- to northern latitudes. Annual precipitation varies from 50 mm in the far north to as much as 4000 mm on the Pacific Coast.

Regional Water Issues

The hydrologic and socioeconomic diversity that characterizes Canada makes understanding and managing its water resource and its aquatic environment a great challenge. The federal-provincial/territorial water quantity agreements were developed in response to the needs of water management and environmental issues in each region. The accompanying table summarizes the hydrologic characteristics and related issues in each province and territory. Data and information collected under the cost-sharing agreements are essential to those who must make decisions concerning these issues.

Water issues in Canada's provinces and territories
Province/Territory Hydologic Setting Water Issues
British Columbia
  • Climate and physiography highly variable: perhaps the most hydrologically complex region
  • Elevations from sea level to over 4000 metres
  • Precipitation extremely variable: potential annual runoff of
    over 3000 millimetres in coastal basins but under 100 millimetres in some interior basins
  • Population concentrated in the SW, in the lower Fraser Valley
  • Quantity: water rights licensing, flooding, irrigation, hydro power
  • Quality and waste management
  • Resource development: forestry, fisheries, mining
  • Integrated watershed management, erosion
  • Generally mountainous with a subarctic climate
  • Annual runoff to over 500 millimetres in east but under 100 millimetres in the north
  • Very low population
  • Placer mining
  • Fisheries
  • Water quality
  • Waste management
  • Water rights licensing
  • Varied hydrology, due to mountains in west, prairie in south, Mackenzie Lowland in the north
  • Dry continental climate
  • Annual runoff from mountains to over 600 millimetres, but generally under 100 
    millimetres, especially in the southeast Population concentrated in the prairie region
  • Water supply, irrigation, hydro power, flood control, erosion
  • Instream flow
  • Water quality
  • Hydrology influenced by flat prairie in south, rugged Shield in north
  • Precipitation 200-300 millimetres
  • Annual runoff under 50 millimetres in south, to 200 millimetres in north
  • Population concentrated in the prairie region
  • Apportionment (transboundary streams), irrigation, water rights
  • Water supply: wildfowl habitat
  • Resource development: mining, forestry
  • Shield dominates the north and east, prairie to the south and southwest
  • Continental climate; annual precipitation 200-400 millimetres, drier in north
  • Annual runoff from under 50 millimetres in the flat, pervious southwest to 300 millimetres in the northeast
  • Population concentrated in the prairie region
  • South: water supply, agriculture, water quality, wildlife
  • North: hydro power, environmental assessment
  • Rugged Shield and marshy Hudson Plains in north and centre, humid and fertile in heavily populated south
  • Generally continental climate, although modified by Great Lakes in south
  • Precipitation increases from northwest to southeast
  • Annual runoff increases northwest to southeast, from 200 to 600 millimetres
  • Flood alerts
  • Water quality
  • Hydro power
  • Fish and wildlife habitat Irrigation
  • Transboundary (International Joint Commission)
  • Shield except for fertile Mixed Wood Plains in heavily populated south, and Atlantic Maritime in southeast
  • Continental climate in south, subarctic in north
  • Generally wettest in southeast, driest in north
  • Annual runoff follows precipitation trend, from 200 to 600 millimetres
  • Toxic chemicals, agricultural pollution
  • Environmental impact assessment, fish habitat
  • Hydro power
  • Flooding
  • Transboundary
  • Navigation (Seaway) irrigation
  • Transboundary
  • Water quality
New Brunswick
  • Entirely within rugged Atlantic Maritime ecozone
  • Climate more continental than maritime due to eastward-moving air masses
  • Relatively high precipitation, especially in south
  • Annual runoff from 600 to 1000 millimetres
  • Population distributed throughout province
  • Pollution abatement
  • Hydro power
  • Flood forecasting
  • International cooperation
Nova Scotia
  • Entirely within Atlantic Maritime ecozone
  • Major maritime influence on climate
  • High precipitation
  • Annual runoff from 800 millimetres to nearly 2000 millimetres in east
  • Population distributed throughout province
  • Watershed and fishery habitat management
  • Industrial withdrawals
  • Harbour and estuary pollution cleanup
  • Pesticide infiltration of groundwater
  • River recreational uses
  • Hydro power
Prince Edward Island
  • Hilly, part of Atlantic Maritime ecozone
  • Major maritime influence on climate
  • Annual precipitation of l000 millimetres results in runoff of 600 to 800 millimetres
  • Rural, small population
  • Sizing of instream structures
  • Irrigation, stock watering, land drainage, soil erosion and nutrient losses
  • Wastewater discharges
  • Salt storage and snow disposal
  • Rugged topography on island and mainland
  • West coast of Newfoundland has elevations over 800 metres
  • Labrador climate generally continental, that of Newfoundland highly influenced by ocean currents
  • Annual precipitation much higher on the island, especially in the south
  • Annual runoff to 600 millimetres in Labrador; on the island from 600 to over 1000 millimetres
  • Population concentrated on the island
  • Hydro power
  • Water control structures
  • Municipal and industrial supply
  • Urban drainage systems, pollution
  • Floods
  • River management for wildlife and recreation
Northwest Territories
  • Climate from arctic to subarctic
  • Permafrost common throughout
  • Precipitation very low, especially in far north
  • Annual runoff generally under 200 millimetres but may reach 500 millimetres in west, in Cordilleran Region
  • Hydrology of dry, frozen far north not well known
  • Population sparse throughout
  • Mining, oil and gas pipelines
  • Navigation, hydro power
  • Fisheries, tourism
  • Covered by Northern Arctic and Arctic Cordillera ecozones
  • Climate from arctic to subarctic
  • Permafrost common throughout
  • Precipitation very low, especially in far north
  • Annual runoff generally under 200 millimetres
  • Hydrology of dry, frozen far north not well known
  • Population sparse throughout
  • Mining, oil and gas pipelines
  • Navigation, hydro power
  • Fisheries, tourism



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