Section 1: Introduction

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Water is fundamental to the survival of every individual, species and ecosystem on Earth. Canada—more than most countries—benefits from readily available sources of freshwater. Freshwater is used to produce electricity, grow food, supply drinking water, as well as for transportation and recreation. How we use water, and how much of it we use, exerts pressure on water resources. When demand for water increases, ecosystem function can be impaired, and activities of communities can face limits.

Canada is often presented as a water-rich nation, and this notion is easy to understand: we do have one of the largest renewable water supplies in the world (Table 1.1) and have access to a considerable portion, perhaps as much as 20%, of the world’s stock of surface freshwater.

Stocks of freshwater, in the form of lakes, rivers, wetlands and groundwater, are the quantities of water that have accumulated in the environment. Renewable water resources correspond to the amount of water that is supplied to the environment, primarily as precipitation. Water yield is an estimate of these renewable water resources (see Section 2). ¹  For water use to be sustainable, water withdrawals must not exceed renewal over a given time period, and there must be sufficient water of appropriate quality to satisfy ecological requirements.

The amount of water that is available to ecosystems and citizens across the world varies widely (Map 1.1, Table 1.1). Expressed as a depth, the average annual water yield of Brazil is 967 mm. Accumulated, this water would reach the waist of most adults, while the yield of South Africa, at 41 mm, would barely wet one’s feet. In Canada, at 348 mm, the accumulated annual water yield would almost reach the knees.

Put another way, Canada’s average annual water yield per unit area is 0.348 m³/m², or 348 litres of renewable freshwater for every square metre of the country (Table 1.1). This yield is substantially higher than the yield in drier countries such as Australia and South Africa that have one-fifth and one-eighth of this amount, respectively. Brazil, a tropical country with significant precipitation, has 0.967 m³/m², almost triple the production of water per unit area in Canada (Textbox: “Selected units of measure for water”).

This measure of water abundance is estimated on a national scale; however on a regional scale, there is as much disparity within Canada as there is between countries (Map 1.1). A lot of water is produced on the coasts, while the Prairies in particular, are relatively dry. Moreover, 98% of Canadians live in the southern part of the country which is responsible for only 38% of Canada’s renewable freshwater. ² 

Water yield is also unequally distributed throughout the year. In much of Canada the bulk of the water yield comes in spring and greatly declines through the summer months. Demand, however, increases through the summer, with the highest demand in July and August.

Countries are often compared in terms of water production per capita, but expressing the information this way partially obscures the productive capacity of the land by tying it to its population. Comparing the water yield of a variety of geographic areas, and at different scales, allows us to evaluate the ability of the land, and its water resources, to support a population and its economic activities.

It is important to monitor water resources because climate change is having numerous water-related impacts. Precipitation patterns and surface water flows are being altered. ³  Extreme weather events, including severe droughts and floods are becoming more frequent: glaciers are melting more quickly and sea levels are rising. ⁴ 

In 2005, an estimated 42 km³ of water were withdrawn and used in Canada (see Section 3). This represents about 1.2% of our annual national water yield. More than 90% of the water that was withdrawn went to support economic activity, and about 9% was used directly by households. The sector that withdrew the most water overall, by a considerable margin, was Thermal-electric power generation. The bulk of the water withdrawn by this sector is returned to the environment close to where it was extracted. The sector that consumed the most water, also by a considerable margin, was Agriculture.

Further analysis into water use went beyond traditional sector breakdowns with the examination of the end users of Canada’s water resources. Water is used both to satisfy the demands of our domestic economy, and to produce goods for export. Excluding water involved in the production of hydro-electricity, and including water supplied by precipitation, 66% of water was used to produce goods for export and 34% supported domestic demand in 2005. If precipitation was also excluded, 37% of water was used to produce goods for export and 63% was used to satisfy domestic demand. The importance of precipitation to the production of forestry and agricultural products, and the prevalence of these products in Canadian exports, explains why a greater proportion of water is directed towards exports when precipitation is included.

Section 1 of this article compares Canada’s renewable water resources to those of other countries, introduces key highlights and presents a short water primer. Section 2 quantifies Canada’s renewable water resources (annual water yield), shows how water yield has changed from 1971 to 2004, and presents graphs of water yield by month for four regions of the country. Section 3 quantifies economic and residential water use in Canada and concludes with an analysis of the relationship between supply and demand. A glossary of terms used in the publication is available in Appendix A.

The scope of this article does not include water quality. The Canadian Environmental Sustainability Indicators project (CESI), a co-operative venture of Environment Canada, Health Canada and Statistics Canada, addresses this important topic, and information on this project is available at www.ec.gc.ca/indicateurs-indicators/default.asp?lang=En.

Geography used in this analysis

Flows of water in Canada occur within five ocean drainage areas: the Pacific Ocean, the Arctic Ocean, the Atlantic Ocean, Hudson Bay, and the Gulf of Mexico. These drainage areas are further subdivided into 25 drainage regions (Map 1.2). This geography is Statistics Canada’s standard drainage area classification, ⁵  and many of the statistics provided in this report are classified according to this geography.

Water primer

Approximately 70% of the surface of the earth is covered by water, and over 97% of this water is contained in saltwater oceans and seas. Freshwater, which is found in lakes, rivers, ice, snow and aquifers, constitutes the remaining water—but the greater portion of this is held in glaciers and permanent snow cover. It is generally understood that less than 1% of all the water in the world is present in freshwater ecosystems. Saltwater can be treated to make it suitable for drinking water and other purposes, but water is not desalinated in any appreciable quantity in Canada.

Freshwater plays an integral role in ecosystems. Rivers and lakes serve as habitat for fish and other aquatic species. Wetlands filter nutrients and bacteria, improving water quality, and help to temper the effects of flooding. The Great Lakes moderate the climate in Southern Ontario. Clouds, ice and snow reflect energy from the sun back into space, thereby influencing the climate.

Water is the only substance on Earth that occurs naturally in the three different states: liquid, solid and gas. Water passes through these states as it cycles in a continuous pattern called the hydrological cycle. Evaporation from the oceans and land, sublimation from ice and snow, evapo-transpiration from plants and transpiration from animals, create water vapour. This water vapour rises in warm air, condenses as the air cools, and forms clouds. Water is discharged from the atmosphere as precipitation—rain, snow, dew, fog or hail. When precipitation lands on the ground it is absorbed by soil particles (turning into soil moisture); is taken up by plants and animals; infiltrates through the ground to become groundwater; flows into rivers, lakes, or oceans; or evaporates back into the atmosphere. This process, fuelled by the heat of the sun, maintains water movement and renews freshwater resources.

The portion of precipitation that is stored in the soil or that temporarily stays on top of the soil or vegetation and eventually evaporates or transpires through plants is referred to as ‘green’ water. Green water is available to be taken up by crops for crop growth. ⁶  The portion of precipitation that runs off on land or recharges groundwater is referred to as ‘blue’ water. It can be found in freshwater lakes, rivers and aquifers. Blue water can be used for a variety of purposes including navigation, irrigation, and as a source of drinking water.

Whether green or blue, water is present in all aspects of our lives, and is embedded in the goods and services that we rely on continuously. This embedded water—also referred to as the ‘virtual’ water content—refers to the water used to make a product, including the generation of the energy used in manufacturing, as well as all the water in all the inputs used in production. For example, it takes approximately 15,500 litres of water to produce a kilogram of beef. ⁷  This includes the water used to grow the grains and roughage the cattle consume, the water the cattle drink, and other water needed for livestock rearing, such as washing. ⁸ 

The concept of a water footprint takes the virtual water content of a product into account but also considers what source of water is used, when the water is used, and where the activities take place. ⁹ 

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