Water in Canada

Information on this page has been reproduced from Government of Canada’s Environment and Natural Resources portal. Please visit canada.ca to see original content.

Is Canada a "water-rich" country?

Assessing the "water-richness" of Canada is a complex process involving many geographic, physical, economic, and social issues. Canada's fresh water can be found in the form of rivers, lakes, groundwater, ice, and snow. Considering that on an average annual basis, Canadian rivers discharge close to 7% of the world's renewable water supply, Canada appears to have a generous water endowment. Aggregate measures, however, can be deceiving.

Some areas in the interior of British Columbia, the southern Prairies, and the high Arctic experience arid or semi-arid climates (less than 35 centimetres of annual precipitation). In these areas, the water supply is further limited because the groundwater tends to be salty and unsuitable for many uses.

Approximately 60% of Canada's fresh water drains to the north, while 85% of the population lives within 300 kilometres of the Canada-United States border. Many areas have restricted water supplies, and water availability constitutes a major concern for water management. Even in the Great Lakes basin, the world's largest freshwater lake system, some off-lake areas in southern Ontario experience periodic and even chronic water shortage, and groundwater "mining" takes place (i.e., more water is taken out of the aquifer than is being recharged). In this region, a significant increase in the consumptive use or a reduction in the supply of Great Lakes waters would result in a lowering of long-term mean levels of the lakes.

1 cubic metre per second (m3/s)

= 31 536 cubic decametres per year (dam3/yr)

= 86 400 cubic metres per day (m3/d)

Fills 2000 backyard swimming pools per day

Fills 1000 rail tank cars per day

In many of the settled areas of the country, water is extremely polluted and is either unsuitable for human, animal, and industrial use or usable only at a relatively high cost of treatment.

Figure - water flow comparisons


How do you measure water in lakes and rivers?

Environment Canada's Water Survey of Canada, along with many contributing agencies, presently measures the rate of flow (discharge) in rivers and records the levels of lakes and rivers at more than 2900 locations in Canada.

  • Water levels are read manually by gauge readers or continuously recorded either electronically or on graph paper or in digital form.
  • Rate of flow (or discharge) requires multiple measurements of channel depth, width, and flow velocity to yield the average discharge in the stream crossing for a given water level. Measurements can be made electronically from a bridge, by wading into a stream, by boat, or from a cableway strung across the river. In winter, the measurements are made through the ice.
  • With sufficient measurements of flow over a variety of water levels (including extreme lows and highs), a water level-discharge relationship is established at each location so that the discharge can be computed from measured water levels.
  • Historical records from over 8000 active and discontinued sites permit the estimation of streamflow at ungauged locations.

This table shows typical river flows in meters cubed per second. The annual average, as well as the highest and lowest daily averages are also indicated.



Annual average

Daily average



Prince Edward Island

Dunk River at Wall Road





Qu'Appelle River near Lumsden




New Brunswick

Lepreau River at Lepreau





Manigotagan River near Manigotagan





Rideau River at Ottawa





Gander River at Big Chute


1 170



Athabaska River at Hinton


1 200



Yukon River at Whitehorse





South Saskatchewan River at Saskatoon


3 940



Rivière aux Outardes à la Centrale de Chute-aux-Outardes


2 830


New Brunswick

Saint John River below Mactaquac


11 100



Ottawa River at Britannia

1 180

5 060



Churchill River above Upper Muskrat Falls

1 740

6 820


British Columbia

Fraser River at Hope

2 720

15 200



Niagara River at Queenston

5 880

9 760

2 440


St. Lawrence River at Cornwall

7 350

10 700

4 500

Northwest Territories

Mackenzie River at Norman Wells

8 480

33 300

1 680

Note: This table is based on historical data to 1999, extracted from the national HYDAT database.


Why do you need to know how much water Canada has?

Water level and discharge information is essential for the wise management of Canada's water resources. For example,

  • to allocate water between various users
  • to manage water resources or minimize the impacts of extreme flows (e.g., flood protection, floodplain mapping, diversion canals, and irrigation)
  • to design and construct bridges, canals, culverts, roadways, water supplies, irrigation facilities, and countless other structures
  • to plan and conduct environmental programs and assessments related to water quality, fisheries, and wildlife habitat
  • to ensure that the nation's water resources are developed in a manner that conserves and protects the environment.

Which are the largest bodies of water in Canada?

Our rivers and lakes situated north of 60 degrees latitude constitute some of Canada's largest water bodies. The Mackenzie River, for example, is over 4000 kilometres long and is the country's largest river. Great Bear Lake, Northwest Territories, is the world's ninth largest lake (by area). The St. Lawrence-Great Lakes drainage basin is the largest in southern Canada.

Longest rivers in Canada. The illustration shows that the longest rivers in Canada are as follows: Albany River: 980 kilometres; Severn River: 980 kilometres; Assiniboine River: 1070 kilometres; Liard River: 1120 kilometres; Yukon River (Canadian portion): 1150 kilometres; Athabasca River: 1230 kilometres; Ottawa River: 1270 kilometres; North Saskatchewan River: 1290 kilometres; Fraser River: 1370 kilometres; Peace River: 1540 kilometres; Churchill River (Saskatchewan): 1610 kilometres; Nelson River: 2580 kilometres; St. Lawrence River: 3060 kilometres; Mackenzie River: 4240 kilometres.

*Canadian portion only. Note: Numbers have been rounded

Largest lakes in Canada. The illustration shows that the largest lakes in Canada are as follows: Lake Melville, Newfoundland: 3200 square kilometres Amadjuak Lake, Nunavut: 3200 square kilometres Lake of the Woods, Ontario and Manitoba (Canadian portion): 3300 square kilometres Dubawnt, Northwest Territories: 3800 square kilometres Lake Winnipeg, Manitoba: 4800 square kilometres Lake Nipigon, Ontario: 4900 square kilometres Lake Winnipegosis, Manitoba: 5400 square kilometres Nettilling Lake, Nunavut: 5800 square kilometres Smallwood Reservoir, Newfoundland: 6700 square kilometres Reindeer Lake, Saskatchewan and Manitoba: 6800 square kilometres Lake Athabasca, Saskatchewan: 7800 square kilometres Lake Ontario, Ontario (Canadian portion):10 200 square kilometres Lake Erie, Ontario (Canadian portion): 12 800 square kilometres Lake Winnipeg, Manitoba: 24 200 square kilometres Great Slave Lake, Northwest Territories: 28 500 square kilometres Lake Superior, Ontario (Canadian portion): 29 800 square kilometres Great Bear Lake, Northwest Territories: 31 400 square kilometres Lake Huron, Ontario (Canadian portion) : 38 300 square kilometres Note: Numbers have been rounded. The total area includes islands.

*Canadian portion only. Notes: Area in km2 x 1000. Total area including islands. Numbers have been rounded


What percentage of Canada's fresh water is found in the Northwest Territories and Nunavut?

The Northwest Territories and Nunavut cover 34% of Canada's land mass, and have 18% of its lake area. Average annual runoff produced within the two territories is 18% of the total for Canada, and another 5% of that total flows into this area from the south.

The Northwest Territories' and Nunavut's portion of Canada's fresh water must be estimated on the basis of the total mean annual flow of rivers, as accurate data on water stored in its lakes, under the ground, and in glaciers are unavailable. However, northern runoff is less significant than commonly perceived because the North is a cold desert. Relatively little water is actually circulating in the hydrologic cycle, due to permafrost conditions, seasonal storage of water in snow, and long-term storage in glaciers.


What is meant by sustainable development of water resources?

Many Aboriginal peoples of Canada believe that one must consider the impact of any decision on one's children, grandchildren, and great grandchildren seven generations hence to ensure that their needs can be accommodated in the future. Sustainable development has been defined by the Canadian Council of Ministers of the Environment as "development which ensures that the utilization of resources and the environment today does not damage prospects for their use by future generations". For example, industrial development on a river may involve activities that seriously damage our soil, water, and atmospheric systems.

To make the development "sustainable", environmental, social, and economic planning cannot proceed independently of each other. They must be integrated. Our water resources must be developed in harmony with the natural ecosystem so that neither the water resource nor the plant and animal life dependent on it are depleted or destroyed for short-term gain and at the expense of future generations. Long-term economic growth depends on a healthy environment.


Is the water that flows into the oceans from lakes and rivers wasted?

Not at all. It is an essential part of the global hydrologic cycle. This water is vital to navigation, recreation, fish and wildlife support, and waste dilution, and so sustains the lifestyles of large and small communities across Canada. Even in the least populated northern reaches of this country, the seasonal fluctuation of high and low flows strengthens a stable relationship among natural forces such as climate, sediment transport, and freshwater discharge to the marine environment. For example, the Mackenzie River system has two inland deltas and one of the world's largest marine deltas, the Mackenzie Delta. (A delta is sediment deposited where a river discharges into a lake or ocean.) Most of the birds using the western flyway make their home in these deltas or use them to rest and feed on their long migrations. Northern rivers flowing into the Arctic Ocean are an essential component of the hydrologic cycle and contribute to this large aquatic ecosystem.

Mackenzie River basin. Map of the Mackenzie River basin showing its major deltas: the Slave River delta at Great Slave Lake in the Northwest Territories; the Peace-Ahtasbasca delta at Lake Athabasca in Alberta; and the Mackenzie delta where the Mackenzie River enters the Beaufort Sea.


Information on this page has been reproduced from Government of Canada’s Environment and Natural Resources portal. Please visit canada.ca to see original content.