Hydrology of Canada
Canada’s surface water resources are considerable, an estimated 9 percent of the world’s
renewable water supply. The location and average flow of Canada’s largest rivers are
presented on the accompanying 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. The pattern of distribution of Canada’s
freshwater resources is further described by the accompanying map of
Average Annual Runoff.
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
in the
accompanying map.
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.
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Province/Territory
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Hydrologic Setting
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Water Issues
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British Columbia
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Climate and physiography highly variable: perhaps the most hydrologically
complex region
Elevations from sea level to >4000 m
Precipitation extremely variable: potential annual runoff of
>3000 mm
in coastal basins but <100 mm in some interior basins
Population concentrated in the SW, in the lower Fraser Valley
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Quantity: water rights licensing, flooding, irrigation, hydro power
Quality & waste management
Resource development: forestry, fisheries, mining
Integrated watershed management, erosion
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Yukon Territory
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Generally mountainous with a subarctic climate.
Annual runoff to >500 mm in east but <100 mm in the north
Very low population
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Placer mining, fisheries, water quality, waste management, water rights licensing
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Alberta
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Varied hydrology, due to mountains in west, prairie in south, Mackenzie
Lowland in the north
Dry continental climate
Annual runoff from mountains to
>600 mm, but generally
<100 mm, especially in the southeast Population concentrated in the prairie
region
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Water supply, irrigation, hydro power, flood control, erosion
Instream flow
Water quality
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Saskatchewan
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Hydrology influenced by flat prairie in south, rugged Shield in north
Precipitation 200-300 mm
Annual runoff <50 mm in south, to 200 mm in north
Population concentrated in the prairie region
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Apportionment (transboundary streams), irrigation, water rights licensing
Water supply: wildfowl habitat
Resource development: mining, forestry
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Manitoba
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Shield dominates the north and east, prairie to the south and southwest
Continental climate; annual precipitation 200-400 mm, drier in north
Annual runoff from <50 mm in flat, pervious SW to 300 mm in NE
Population concentrated in the prairie region
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South: water supply, agriculture, water quality, wildlife
North: hydro power, environmental assessment
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Ontario
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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 NW to SE
Annual runoff increases NW to SE, from 200 to 600 mm
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Flood alerts, water quality, hydro power, fish & wildlife habitat,
irrigation, transboundary (International Joint Commission)
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Quebec
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Shield except for fertile Mixed Wood Plains in heavily populated south, and Atlantic
Maritime in SE
Continental climate in south, subarctic in north
Generally wettest in SE, driest in north
Annual runoff follows precipitation trend, from 200 to 600 mm
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Toxic chemicals, agricultural pollution
Environmental impact assessment, fish habitat
Hydro power
Flooding
Transboundary
Navigation (Seaway) irrigation
Transboundary
Water quality
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New Brunswick
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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 mm
Population distributed throughout province
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Pollution abatement, hydro power, flood forecasting, international cooperation
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Nova Scotia
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Entirely within Atlantic Maritime ecozone
Major maritime influence on climate
High precipitation
Annual runoff from 800 mm to nearly 2000 mm in east
Population distributed throughout province
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Watershed & fishery habitat management
Industrial withdrawals
Harbour & estuary pollution cleanup
Pesticide infiltration of groundwater
River recreational uses
Hydro power
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Prince Edward Island
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Hilly, part of Atlantic Maritime ecozone
Major maritime influence on climate
Annual precipitation of l000 mm results in runoff of 600 to 800 mm
Rural; small population
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Sizing of instream structures
Irrigation, stock watering, land drainage, soil erosion & nutrient losses
Wastewater discharges
Salt storage and snow disposal
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Newfoundland-Labrador
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Rugged topography on island and mainland
West coast of Nfld. has elevations >800 m
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 mm in Labrador; on the island from 600 to >1000 mm
Population concentrated on the island
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Hydro power
Water control structures
Municipal & industrial supply
Urban drainage systems, pollution
Floods
River management for wildlife & recreation
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Northwest Territories
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Climate from arctic to subarctic
Permafrost common throughout
Precipitation very low, especially in far north
Annual runoff generally <200 mm but may reach 500 mm in west, in
Cordilleran Region
Hydrology of dry, frozen far north not well known
Population sparse throughout
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Mining, oil & gas pipelines
Navigation, hydro power
Fisheries, tourism
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Nunavut
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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 <200 mm
Hydrology of dry, frozen far north not well known
Population sparse throughout
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Mining, oil & gas pipelines
Navigation, hydro power
Fisheries, tourism
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