Section 2: Freshwater supply and demand
Canada is the second largest country in the world and has the third largest renewable freshwater supply worldwide (Table 2.1). Among developed countries, its water resources per capita are exceeded only by Iceland’s.Note 1 However, this freshwater is not always easily available for use since it is unevenly distributed across the landmass and its supply varies from month to month and year to year.
Water use per capita is also among the highest in the world—it is surpassed only by the United States. As a proportion of the total renewable freshwater resource, Canadian water withdrawals for industry, households and agricultural use are relatively low (1%). However, challenges in balancing supply and use can still be an issue due to the temporal and regional variation of water supply and demand.
Water use and other human activities can also have impacts on the quality of freshwater resources and the health of ecosystems. Monitoring changes in water resources, their quality and use is important, particularly given the changing demand for water resources due to demographic and economic factors, resource development, as well as ongoing changes in precipitation and temperature patterns and extreme weather events.
2.1 Renewable freshwater in Canada
Canada’s many different landscapes and climate regions result in considerable challenges when measuring when, where, and how much freshwater is provided to ecosystems; how much is available for human use; and if the rate of renewal may be changing over time. As well, water quality varies naturally and can be degraded by human activities (Textbox 2.1).
Water yieldNote 2 is an estimate of freshwater runoff into streams and rivers and provides information on Canada’s renewable freshwater supply. The average annual water yield for Canada from 1971 to 2013Note 3 was 3,478 km3 or 0.349 m3/m2, equivalent to a depth of 349 mm across the extent of the country. Overall, this yield corresponds to renewable freshwater resources of 103,899 m3 per person (Table 2.2).
The distribution of water yield varies widely across the country (Map 2.1).Note 4 The Pacific Coastal drainage region in British Columbia had the highest water yield per unit area in the country at 1.5 m3/m2. On a per capita basis, an average of 339,002 m3 of renewable water were produced per person in this drainage region.
The lowest yields were found in the Prairies—the average annual water yield per unit area for the Missouri, Assiniboine–Red, South Saskatchewan and North Saskatchewan drainage regions was 0.05 m3/m2. Average water yield per capita was also comparatively low—an average of 5,689 m3/person.
Monthly water yield
Water yield varies throughout the year. In a typical year, most renewable freshwater is produced in spring and early summer, with the peak occurring later in some northern and snow and glacier melt-driven systems. By late summer and fall, water yield typically decreases significantly; however, much of the country experiences the lowest yields in winter. The median monthly water yield from 1971 to 2013 in southern CanadaNote 5 reached a peak of 218 km3 in May, dropping to 76 km3 in August, with a low of 50 km3 in February (Chart 2.1).
Water yields in the Okanagan–Similkameen and the Assiniboine–Red drainage regions are the most heavily dominated by spring flows—in these areas the median water yields in April, May and June accounted for 75% and 77% respectively of the annual flows over the 1971 to 2013 period (Maps 3.3.3 and 3.3.12). In contrast, peak median water yields occurred later in the year and declined more gradually in the South and North Saskatchewan drainage regions due to the contribution of snow and ice melt.
The peak water yields occurred in April in the Great Lakes and the St. Lawrence drainage regions, with spring flows in March, April and May accounting for close to half of the annual volumes. Median water yield in the drier summer months of July, August and September accounted for 10% and 14% of the annual flows in these two regions (Maps 3.3.19 and 3.3.21).
Depending on the region, the monthly water yield can also be quite variable from year to year. Water yields are the most variable in the prairie drainage regions (Map 2.2).Note 6 The Assiniboine–Red has the highest variability index for monthly flows (Table 2.2) followed by the Missouri, Okanagan–Similkameen and the South Saskatchewan drainage regions. Variability of water yield in the Prairies may result in challenges in satisfying the various demands for water.
Changes in water yield over time
The water yield varies throughout the year and by geographical area. It also fluctuates over time.Note 7 Climate change further alters the regional and temporal characteristics of hydrological conditions (Textbox 2.2).Note 8
The annual water yield fluctuated from a high of 1,544 km3 in 1974 to a low of 1,165 km3 in 1987 in southern Canada (Chart 2.2). The water yield decreased from 1971 to 1987 and then began a gradual recovery to 2012, with a dip in the late 1990s to early 2000s. Similarly, annual fluctuations are common for individual drainage regions (Charts 2.3, 2.4 and 2.5).
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Canada’s large land mass, complex hydrological conditions, changing climate and human activities not only impact the quantities of water yielded by the environment, but also the quality of its waters. This, in turn, impacts the capacity of ecosystems to deliver the services society depends upon—for example, fish, clean water and healthy habitats.
Water quality refers to the physical, chemical and biological properties of water. These properties vary naturally according to environmental factors such as geology, soils and flow rates, which affect the type and quantity of substances dissolved or suspended in the water. Water quality can also be degraded by human activities occurring in the surrounding, upstream and even distant environments. Societies modify the land cover, dam and divert rivers changing the hydrology and emit pollutants directly into water and indirectly via air emissions.
The Freshwater quality in Canadian rivers indicator, produced as part of the Canadian Environmental Sustainability Indicators, provides information on the ability of ambient water to support aquatic life and covers selected rivers at risk of being impaired by human activity. For drainage regions with more than five sites tested, more than 70% include sites with poor or marginal quality (Table 2.3).
Surface water sources used to produce drinking water for communities are monitored so that drinking water plants can ensure appropriate water treatment including filtration and disinfection. One important measure of the quality of source water for drinking water treatment plants is turbidity, which refers to the relative cloudiness of water, caused by suspended particles in the water. These particles can include clay, silts, metals, organic matter and microorganisms.Note 9
There is a considerable range in the level of suspended sediment that occurs naturally.Note 10 These levels vary between watersheds and seasonally within watersheds, generally increasing during spring runoff and declining during summer low-flow periods. Since turbidity can be affected by runoff and erosion, it can therefore be affected by human activities that disturb land, such as construction, logging, mining, farming, as well as many others. Sudden increases in turbidity in water bodies that are normally clear can indicate a water quality problem.
In 2013, the Survey of Drinking Water Plants collected information on monthly maximum turbidity values for surface water sources. These values were highest in the Lower Saskatchewan–Nelson, North Saskatchewan and Assiniboine–Red drainage regions in the Prairies and in the St. Lawrence drainage region, while the lowest levels were seen in drainage regions in British Columbia and the Atlantic provinces (Map 2.3).Note 11 Results were similar for 2011.
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Scientific evidence indicates that the hydrological cycle is impacted by climate change.Note 12 Impacts include increases in water temperatures and evapotranspiration, and variations in precipitation patterns. These variations may include changes in the magnitude, duration, frequency and timing of events such as droughts, storms and floods, and also changes in the regular provision of water.Note 13
The water environment of individual biomes is also impacted by these changes. For example, air temperature increases are resulting in permafrost melting, modifying the hydrology of northern areas.Note 14 Water quality characteristics are also impacted by a changing climate, for example as a result of the influence of temperature increases on water-born nutrients or storm intensity on turbidity.Note 15
Temperature change and evapotranspiration
A recent study of the 1948 to 2015 period demonstrates that average air temperatures have increased in all eleven climate regions of the country, with the most prominent increases occurring in some of the northern climate regions.Note 16 These temperature increases also contribute to the warming of marine surface waters. Ocean surface temperatures have increased from 1.0°C to 2.6°C along the Atlantic Coast and 0.7°C to 1.1°C along the Pacific Coast from 1901 to 2014 (Map. 2.4). Warmer oceans further intensify climatic events.Note 17
Evapotranspiration—the combined processes of evaporation from land surfaces, water bodies and transpiration from plants—provides the atmospheric water vapour required for precipitation. Solar radiation, air and water temperature, soil moisture, air humidity, wind speed, vegetative cover and root depth, among other factors, influence the amount of water transferred from the surface of the earth to the atmosphere.
Significant amounts of freshwater can be lost to evapotranspiration, particularly during the hot summer months, reducing the amount of surface runoff and the volume of water stored above ground. Subsurface water assets are also impacted with a diminished groundwater recharge and loss of soil moisture. In Canada, an estimated 2,257 km3 of water is transferred to the atmosphere each year by these two processes.Note 18
The highest average annual volumes of water lost to evapotranspiration occurred in the Great Lakes, Saint-John–St. Croix, Maritime Coastal, Ottawa, Okanagan–Similkameen, Columbia, Winnipeg, Assiniboine–Red and St. Lawrence drainage regions (Table 2.2 and Map 2.5). The lowest values occurred in the North.
Climate change, permafrost and peatland ecosystems
One type of ecosystem already affected by climate change is peatlands. Canada has over 1.1 million square kilometres of peatlands, covering 12% of its total land area.Note 19 These organic wetlands provide valuable ecosystem services by storing carbon, providing unique habitats and regulating water flow. More than one-third of Canada’s peatland area is frozen throughout the year as permafrost. These frozen peatlands store large quantities of water in their soils.
The Mackenzie and Northwestern Forest climate regionsNote 20 of north-central Canada contain approximately 462,117 km2 of peatlands, 58% of which are permafrost (Map 2.6).Note 21 In these peatland-dominated climate regions, average annual temperatures have increased by 2.6°C and 1.9°C respectively from 1948 to 2015,Note 22 resulting in thawing permafrost. Temperature changes are even larger in the winter.Note 23
These changes have resulted in increased fire susceptibility;Note 24 increased emissions of greenhouse gases such as carbon dioxide, nitrous oxideNote 25 and methane;Note 26 increased groundwater recharge and surface water flow;Note 27 and modification of plant and animal habitat.Note 28
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2.2 Water demand
Water withdrawn from water bodies provides drinking water and water for other uses around the home, but also supports economic uses including thermal-electric power generation, manufacturing, agriculture, mining and oil and gas extraction. Important instream water uses also include shipping, fishing and recreational activities, while water also supports ecosystem functions, vegetation, fish and wildlife (Textbox 2.3).
Information on the volume and timing of water withdrawals, the type and location of source water bodies and the amount of water returned to water systems are important in order to understand potential pressures on ecosystems and difficulties in balancing competing water demands. Understanding the contribution water users make to the economy is also helpful in understanding the value of water.
In 2013, 37,892 million m3 (37.9 km3) of water was withdrawn from the environment and used in economic and household activities in Canada.Note 29 The majority of this water—87%—was self-supplied, for example by industry or households that took water directly from rivers, lakes and groundwater. The production of potable water by drinking water plants accounts for the remaining 13% of water intake.Note 30
While some of this water was consumed—for example, lost to evaporation, transpiration or included in products—the majority was returned back to the environment after use.
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Although the water use data presented here focuses on water withdrawals, total water abstraction in the System of Environmental–Economic Accounting includes the much larger amounts of precipitation and soil water used to support agricultural and timber production, as well as the vast amounts of water flowing through turbines to generate hydro-electricity.Note 31
Previous estimates of water abstraction indicate that in Canada, in 2005, irrigation represented less than 2% of total water abstracted for agricultural production, forest land required more than 500 billion m3 of water to support timber production and water abstracted for hydro-electric generation was in the range of 3 trillion m3.Note 32
Estimates of water abstracted for hydro-electric power generation or rain-fed agriculture and timber production are not aggregated with other water use data presented in this report, which focus on water that is withdrawn from the environment.
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Water use, by industry and households
The main water users in 2013 were electric power generation, transmission and distribution;Note 33 manufacturing; households; agriculture; mining and oil and gas extraction; and natural gas distribution, water, sewage and other systemsNote 34 (Chart 2.6). These industries, which use both self-supplied and publicly-supplied water, contributed 22% of total gross domestic product and 14% of employment in 2013 (Table 2.4). All other industries combined accounted for only 3% of water use in 2013.
The utilities sector, which includes the electric power generation, natural gas distribution and water, sewage and other systems industries, depends on large amounts of water. Hydro-electric power plants store vast quantities of water behind dams in reservoirs and use it to drive turbines.Note 35 Thermal power plants withdraw water from water bodies and use it mainly for cooling purposes before returning it to the environment. Together, the electric power generation industry produced 628 million megawatt hours of electricity in 2014, with hydro-electric stations accounting for 60% of electricity production, followed by thermal-electric plants at 37%. Alternative power generation sources, such as tidal, wind, solar, represented 2% of production (Table 2.5). In 2014, 91% of electric power generated was used domestically.Note 36 The remaining 9% represented 0.6% of total exports value.Note 37
Thermal-electric power generation used 25,635 million m3 of water in 2013.Note 38 This represented 68% of total water use, though the majority (98%) of this water was discharged back into the environment after use, with small amounts lost to evaporation.Note 39 Natural gas distribution and water, sewage and other systems used 885 million m3 of water—2% of total use.
The majority (88%) of water used by thermal-electric power plants was self-supplied freshwater from surface water bodies, with the rest originating from tidewater and other saline water sources.Note 40 Thermal-electric power plants in Ontario were responsible for 81% of water withdrawals by the industry, followed by those in the Atlantic provinces (10%) and the Prairie provinces (9%) (Chart 2.7).Note 41
The industry’s average monthly water use from 2007 to 2013 was highest in July and AugustNote 42 due to higher demand for power in summer. In 2013, total water use for thermal-electric production was down 8% from 27,834 m3 in 2007.
The thermal-electric power generation industry spent $172 million on water in 2013, half of which was for water acquisition, 30% was for intake water treatment and the remainder was related to water recirculation and discharge treatment.Note 43
Overall, the manufacturing sector used 3,954 million m3 of water in 2013—10% of total water use.Note 44 The largest amounts were used by the paper manufacturing (1,537 million m3) and primary metal manufacturing (1,142 million m3) industries. Of manufacturing’s total water intake, 90% was eventually discharged back to the environment.Note 45
Most (88%) water intake by manufacturing was self-supplied and 95% of the total intake was freshwater (Table 2.6). More than one-third (35%) of water intake by manufacturing industries occurred in the Great Lakes drainage region, followed by 18% in the St. Lawrence, 8% in the Pacific Coastal, 7% in the Fraser–Lower Mainland and 6% in the Maritime Coastal drainage regions (Chart 2.8).
Average water intake by the manufacturing sector was highest in summer (Chart 2.9). Overall, water intake for manufacturing has declined 13% from 4,573 million m3 since 2007. Annual sales of manufactured goods declined 11% from 2007 to 2013.Note 46
The manufacturing sector spent a total of $1.2 billion on water including acquisition ($465 million), intake treatment ($198 million), recirculation ($97 million) and discharge treatment ($447 million) in 2013.Note 47
The household sector used 9%—or 3,239 million m3—of the country’s total water use in 2013, including both publicly-supplied water and estimates for households on wells.Note 48 While some of these household uses of water are consumptive, an estimated 90% of water withdrawals are eventually discharged back into the environment after treatment by municipal wastewater treatment plants.Note 49 See Textbox 2.4 for more information about household water use and conservation practices.
Drinking water plants produced 5,059 million m3 of potable water in 2013, with 39% (1,978 million m3) consumed by the residential sector (Chart 2.10).Note 50 However, the sector of use was unknown for 21% of publicly-supplied water and distribution system losses accounted for another 13%.
Surface water accounted for 88% of potable water processed by drinking water plants in 2013, followed by groundwater (10%) and groundwater under the direct influence of surface water (2%).Note 51 Water withdrawals by drinking water treatment plants peak in summer (Chart 2.11) and were highest in the Great Lakes and St. Lawrence drainage regions.Note 52 Households spent $3.2 billion for delivery of publicly-supplied potable water in 2013.Note 53
Most homes in Canada are connected to a municipal water supply. In 2015, municipal water was the main source of water for 89% of households.Note 54 Homes not connected to a municipal water supply most frequently had a private well as the main source of water. The proportion of households using a non-municipal supply was highest in the Maritimes—51% of dwellings in Prince Edward Island, 48% in New Brunswick and 41% in Nova Scotia relied on non-municipal water.
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Residential water use includes indoor water use from toilets, faucets, showers, baths, clothes washers and dishwashers, as well as seasonal outdoor use such as lawn watering. Toilet flushing, faucets and showers account for the largest proportions of indoor water use.Note 55 Many factors can account for differences in water use, including pricing and billing practices, conservation measures, demographics, dwelling types, economic activities, the state of infrastructure and climate. Outdoor water use is particularly variable.
Household water use in Canada has declined in recent years. Total household water use in 2013 was down 16% compared to 3,875 million m3 in 2005,Note 56 while on a per capita basis water use has dropped from approximately 330 L/person/day to 250 L/person/day.Note 57
For households served by public water utilities, per capita daily residential water use in Newfoundland and Labrador, Yukon, British Columbia, Prince Edward Island, Quebec, Northwest Territories and New Brunswick was above the Canadian average (Chart 2.12). Residents of the three Prairie Provinces and Nunavut had the lowest per capita usage.
These trends are consistent with the results of other studies, which have also found large decreases in household daily water use for many cities throughout North America.Note 58 These changes were attributed mainly to water use efficiencies in toilets and clothes washers. Other studies indicate that water metering and volume-based pricing tools can be used to reduce residential water use.Note 59
According to the 2015 Households and Environment Survey, 51% of households in Canada reported having a low-volume toilet, 62% reported having a low-flow shower head, while 43% of households reported that they had a water meter.Note 60 Outdoor water conservation tools include the use of water barrel or cistern to store water, used by 15% of households in 2015.Note 61 As well 32% of households using lawn sprinklers to water their lawn used a sprinkler timer.
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In 2013, the value of Canadian agricultural production was $55.2 billionNote 62 and farm, fishing and intermediate food products made up 6% of exports.Note 63
Crop and animal production was responsible 5% of total water withdrawals in 2013—a total of 2,007 million m3. This water was used mostly for irrigation and livestock watering.Note 64 Crop production accounted for slightly more than half (53%) of this total.Note 65 While a portion of irrigation water is taken up and incorporated into plants or transpired, water is also lost to evaporation and can percolate or run off fields.Note 66
Farms spent $21.1 million to purchase water or water rights for irrigation purposes in 2013.Note 67 The amount and timing of water used for irrigation depends on crop type, as well as local temperature and precipitation patterns.
According to the Census of Agriculture, 7% of farms in Canada irrigated their land in 2011.Note 68 By area, field crops including grain, oil and seed crops such as wheat, barley, corn and canola, represented the largest irrigated crop type (60%), followed by alfalfa, hay and pasture land (29%) and vegetables, fruit and other irrigated areas (11%).Note 69
In 2014, farms in Canada used 1,679 million m3 of water to irrigate 585,870 ha of farmland.Note 70 As a percent of irrigation water, the main water sources included off-farm water sources (71%), on-farm surface water (21%) and on-farm groundwater sources (7%).Note 71 The largest irrigation volumes were used in the South Saskatchewan drainage region—this drainage region accounted for 78% of the annual irrigation volume, followed by the Fraser–Lower Mainland drainage region (11%) (Table 2.7).Note 72 Water use for irrigation is highest in July (Chart 2.13).
Mining, quarrying and oil and gas extraction
Crude oil and natural gas represented 78% of primary energy production in Canada in 2013,Note 73 with 76% of crude and 52% of natural gas production going for export.Note 74 Energy products excluding electricity represented 24% of exports in 2013, while metal ores and non-metallic minerals accounted for 4%.Note 75
Together, mining and oil and gas extraction used 982 million m3 of water in 2013—under 3% of total water use.Note 76 While the oil and gas industry reuses much of its water intake, the vast majority of this water use is consumptive—for example, it may be lost to steam, injected into oil reservoirs or held in tailings ponds after use.Note 77
For mining and quarrying (excluding oil and gas), the total water intake was 599 million m3, with the highest water use resulting from metal ore mining (373 million m3 of water or 62%), non-metallic mineral mining and quarrying (134 million m3 or 22%) and coal mining (92 million m3 or 15%).Note 78 Water discharges from the mineral extraction industries were 675 million m3 in 2013 with the majority (71%) released to surface water, followed by tailings ponds (13%) and groundwater (8%).Note 79
Self-supplied surface freshwater made up 73% of total water intake for mining and quarrying, followed by groundwater (12%) and other self-supplied freshwater sources (9%).Note 80 Mining and quarrying operations in the Atlantic provinces were responsible for over one-third of water intake, followed by operations in Quebec (22%) and the Prairies (21%) (Chart 2.14). The majority (71%) of water use was process water while 5% was for cooling, condensing and steam.Note 81
The mineral extraction industries spent $179 million on water in 2013, 70% of which was paid by the metal ore mining industry. Water acquisition costs represented 19% of total costs, while discharge costs represented 45% of the total.Note 82
Water use by final demand
Another way to look at water use is from the final demand perspective, which attributes water use related to the production of goods and services to the end-user of that product rather than to the producer. For example, water used for power generation is attributed to the businesses or households that use electricity.
From this perspective households were the main water users in Canada. When including both direct water use in the home including cooking, drinking, cleaning and watering, as well as the indirect water use required to satisfy household demand for goods and services such as electricity and food, households were responsible for 53% of total water use in 2013 (Chart 2.15).Note 83 The production of goods and services for export was the second highest final demand category at 30% of water use in 2013.
Competing water demands
In certain areas of the country, concerns have been raised about the allocation of water among competing water demands including drinking water, agriculture, manufacturing and other industries during periods of water scarcity.Note 84 Lower than normal streamflows can have significant economic effects on agriculture, fisheries, municipalities and industries including electricity production, while also impacting water quality, aquatic habitat and opportunities for recreation.Note 85
Balancing the demand for water from these different sectors may be more challenging during the summer months, which often coincide with increased demand for irrigation and municipal water, while at the same time water supplies are at a low.Note 86
Ratios of surface freshwater withdrawals to the water yield for August 2013Note 87 were above 40% in the Assiniboine–Red and in the Great Lakes drainage regions, while they were between 20% and 40% in the South Saskatchewan drainage regions and Okanagan–Similkameen (Map 2.7). These higher ratios point to a higher possibility for water shortages, conflicts between competing uses and the potential for insufficient instream flows for ecosystem requirements.Note 88
The high intake to water yield ratios in the Great Lakes and Assiniboine–Red drainage regions were largely attributable to withdrawals for thermal-electric power production. The majority of this water was eventually released back to the water body from which it was taken.
Water withdrawals for irrigation accounted for the majority of the total water intake in the South Saskatchewan drainage region and over 40% in the Okanagan–Similkameen.Note 89 Little water withdrawn for irrigation is returned to the water source.Note 90