The Human Activity and the Environment (HAE) publications (Statistics Canada) bring together a collection of environmental statistics from many sources, and paint a statistical portrait of Canada’s environment. Special emphasis is given to the relationship of human activity to air, water, soil, plants and animals. This analytical article “Freshwater Supply and Demand in Canada” provides information on Canada’s freshwater supply as well as the demands placed on it.
- Canada’s average annual renewable freshwater supply, or water yield, is 3,472 km3. To put this in perspective, this water yield amounts to almost as much water as there is in Lake Huron (which contains 3,540 km3).
- This abundance in water yield is distributed unequally across the country. With an average annual water yield per unit area of 1.54 m3/m2, the Pacific Coastal drainage region has the highest water yield per unit area in the country. It is followed by the Newfoundland and Labrador and the Maritime Coastal drainage regions which have average annual yields per unit area of 0.86 m3/m2and 0.85 m3/m2 respectively. Drainage regions in the Prairies and north of the Prairies produce the least water, with yields between 0.02 and 0.07 m3/m2.
- The southern part of the country, where 98% of the population is located, is responsible for 38% of the water yield or 22,661 m3 of renewable freshwater per capita. In the North, water yield per capita is 185 times greater, or 4,193,014 m3.
- The average annual water yield per unit area for the Prairies is 0.05 m3/m2, less than that for either Australia or South Africa. This is equivalent to 12% of the yield of the Great Lakes drainage region, 6% of the yield of the Maritime Coastal drainage region and only 3% of the Pacific Coastal drainage region.
- Brazil, which has the highest total water yield of any country in the world, provides 43,756 m3 of water per person per year, 40% of the almost 110,000 m3that is annually available per person in Canada.
- While total water yield is comparable between the United States and Canada, the amount of renewable freshwater per American is only 9.1% of that per Canadian because the United States has a much larger population.
Trends in Water Supply
- From 1971 to 2004 water yield in Southern Canada decreased an average of 3.5 km3 per year, which is equivalent to an overall loss of 8.5% of the water yield over this time period. This average annual decrease of 3.5 km3 is almost as much as the 3.8 km3 of water that is supplied to the residential population of Canada in a year.
- The area in Canada that had the lowest water yield, and the highest variability in water yield between 1971 and 2004, was the Prairies.
- From 1971 to 2004, water yield for the Prairies decreased by 0.56 km3/yr. In perspective, this volume represents about 80% of the total volume of water that was produced by drinking water plants in these five drainage regions in 2005. Over the 34-year period, this represents a total reduction of 20 km3 of water yield, equivalent to roughly half of the long term, average annual water yield for the Prairies.
- For most of the country the bulk of the water yield is produced in April, May and June, as snow and ice melt, and precipitation increases. In the North this peak occurs in late spring and early summer. In the South, where the preponderance of Canada’s economic production takes place, water yield is highest in the spring. As spring turns into summer, yield declines and demand for water related to human activity increases.
- In 2005, an estimated 42 km3 of water were withdrawn from the environment and used in household and economic activities in Canada. About 14% of this water flowed through the public utility water system, while about 86% was extracted from the environment directly by the end user.
- More than 90% of the water that was withdrawn went to support economic activity, and about 9% was used directly by the residential sector. The residential sector used 56% of the water that was supplied by the public utility water system. The sector that used the most water overall, by a considerable margin, was Thermal-electric power generation.
- Overall it is estimated that 25% of Canadians rely on groundwater as a source of drinking water. This varies depending on the region of the country: the population in the Saint John–St. Croix drainage region is the most reliant on groundwater, whereas the population in the South Saskatchewan drainage region is the least.
- The agricultural sector was responsible for 4.6% (almost 2 km3) of total water withdrawals in 2005. The bulk of this water was used to irrigate crops, with a balance of 16% going to support livestock production.
- In 2005, the precipitation that supported crop growth was roughly twice the volume of water that was withdrawn annually by all sectors of the economy.
- Canada is one of the largest producers of hydro-electricity in the world, and the volume of water involved in hydro-electric generation in Canada is many times larger than all other uses of water in the country combined. In 2005 hydro-electric generation in Canada made use of approximately 3 trillion m3 of water—more than 100 times the volume of water used by the Thermal-electric power generation sector, and just over 70 times the total volume of all water used in Canada in 2005.
- More water is embedded in forest products than food. When precipitation was included, the production of exported lumber, wood pulp, paper, and other forest products required seven times more water than the production of exported agricultural commodities.
- The production of exports required the largest share of the water use required to satisfy final demand, accounting for 66%, while personal expenditures accounted for 16%.
- When precipitation was excluded in the calculation of the water use required to satisfy final demand, personal expenditures were the largest contributor, accounting for 47% of water use, while exports accounted for 37%.
- The Virtual Water Project would like to show the world how much freshwater is used to produce selected products— hoping for people to rethink their consumption patterns.
Supply and Demand
- In 2005, total water withdrawals in Canada amounted to 1.2% of the average annual renewable water resources. More pressure however, is placed on water resources in some areas of the country than in others, with this pressure peaking in summer.
- In August 2005, more than 40% of the water yield in the Okanagan–Similkameen drainage region and the Prairies was withdrawn by agriculture, industry and households. In the Prairies, where stocks are limited, water demand must be met primarily by renewable water, and water shortages are evident when demand exceeds the renewable supply.
- The North Saskatchewan drainage region does not show a similar demand to supply ratio to that of the South Saskatchewan drainage region for August 2005, because it has a higher water yield, a smaller population and less irrigation.
- In August 2005 more than 40% of the water yield was also withdrawn in the Great Lakes drainage region in Canada. The Great Lakes themselves, however, contain more than 6.5 times Canada’s annual water yield. Therefore, low summertime water yield in that drainage region has less potential to impose a constraint on human activities.
The supply of freshwater, or Canada’s renewable freshwater resources, is represented by water yield. Water yield is the amount of freshwater derived from unregulated flow measurements for a given geographic area over a defined period of time and is an estimate of the renewable water.
Water intake is used as a proxy for demand. Water intake refers to the total amount of water added to the water system of an establishment or household to replace water discharged or consumed. It may be broken down into the amounts withdrawn from various sources (for example, surface water or groundwater) and the amounts used for various purposes, or end uses. It is often also referred to as water withdrawal.
These, and other important terms, are defined in the USGS Water Glossary.