Measuring renewable water assets in Canada: Initial results and research agenda
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François Soulard and Mark Henry, Environment Accounts and Statistics Division
Water is a basic necessity of life—access to clean water in sufficient quantity is an integral part of our well-being. It has had a strong influence on Canada's development as a country and it remains a precious part of our natural wealth. However, owing perhaps to a general but misleading impression of abundance, few attempts have been made in the past to measure Canada's assets of renewable fresh water.
These attempts to measure renewable water assets have been produced using a variety of methods and do not generate results that can be compared over time and space. However, this information is necessary to manage water resources adequately. This is especially true in a context where water resources are affected by competing uses and changes in the climate.
This article describes the results of a research study estimating Canada's annual average water renewal. The estimate, the Fresh Water Yield for Canada, is coherent through space and time, and will allow further study of the monthly regional renewal of water resources. For information about the methodology used, please see "The Water Yield for Canada as a Thirty-year Average (1971 to 2000): Concepts, Methodology and Initial Results." 1
A new measure of Canada's renewable fresh water assets
Canada's renewable water assets can be measured as the water that flows in the network of streams, rivers and lakes. A portion of this water originates from groundwater as it flows back to the surface. However, most of it is created when rain and melted snow flow over the ground, eventually reaching a surface water body.
Map 1 shows the distribution of average runoff across Canada. The national estimate of the volume of water runoff is calculated to be, on average, 3,435 km3 per year. To put this number in perspective, experts estimate that, worldwide, irrigation consumes 2,664 km3 of water each year.2 Or, as another example, Lake Huron contains 3,540 km3 of water.3
This result could seem to indicate that Canada's water resources are abundant and do not present an environmental, social or economic barrier. Indeed, the water yield for Canada is equivalent to approximately 100,000 cubic meters per capita. The Canadian economy withdraws only about 1.4% of this volume annually—industrial activities such as energy generation, mining and manufacturing withdrew 40 km3 in 2005;4 agriculture, an estimated 4 km3 in 2001;5 and Canadian households, institutions and services, roughly another 4 km3.6 Moreover, much of these withdrawals are not for consumption: with the exception of agricultural water use, water is withdrawn from the aquatic environment and discharged back, generally in the same watershed.
However, these national figures do not capture two important dimensions: the location and the timing of the withdrawals, and the location and the timing of the availability of water resources.
A first attempt at mapping the relationship between the availability and demand for water in Canada demonstrated that water used by the Canadian economy could represent more than 40% of the water flows in some areas of the country, on an average annual basis.7 For instance, the water intake to streamflow ratio reached 43% in the South Saskatchewan, Missouri and Assiniboine – Red drainage region. Water intake was also a high proportion of streamflow in the North Saskatchewan drainage region and in the Great Lakes/ St. – Lawrence drainage region.
The availability of Canada's renewable water assets therefore needs to be examined on a regional basis, for specific time periods. By creating a model that produces data that can be compared spatially over time, the Water Yield Model will allow Statistics Canada to evaluate water withdrawal in reference to water availability at that exact time period.
For example, Map 2 displays the variability of renewable water assets over time. The variability is calculated as the average annual departure8 from the long term average. The map points to a spatial trend in the variability of water availability over time, with the Prairie Provinces and parts of central and south-east British Columbia representing the areas of highest variability. This variability will be the subject of future study, in order to analyse it in the context of changing, and often competing, demands for water resources.
Next steps: Determining water yield trends
One major benefit of this work is the development of a robust methodology producing consistent national estimates of Canada's renewable water assets. Further research in the Water Yield Model approach will determine the degree to which the model produces statistically significant results for various regions, including drainage regions, ecozones, parks, climate regions, and the like. Last, but not least, the model will be tested against its capacity to produce water yield trends for the aforementioned areas. These results might provide fresh insights with regards to the challenges and opportunities of adapting to a changing climate.
- R. Bemrose , L. Kemp, M. Henry, and F. Soulard, 2009, "The Water Yield for Canada as a Thirty-year Average (1971 to 2000): Concepts, Methodology and Initial Results," Environment Accounts and Statistics Analytical and Technical Paper Series, Statistics Canada Catalogue no. 16-001-MWE2009007, (accessed June 4, 2009).
- FAO, 2006, AQUASTAT database, www.fao.org/nr/water/aquastat/dbase/AquastatWorldDataEng.xls (accessed March 10 2009)
- United States Environmental Protection Agency, 2006, Great Lakes Fact Sheet, http://epa.gov/grtlakes/factsheet.html (accessed March 10, 2009.
- F. Soulard and A. Shinnan, 2007, "The cost of water in the manufacturing sector," EnviroStats, Fall 2007, Statistics Canada Catalogue no. 16-002-X, accessed March 10, 2009).
- F. Soulard, M. Beaulieu and C. Fric, 2008, "Agricultural water use in Canada," EnviroStats, Spring 2008, Statistics Canada Catalogue no. 16-002-X, (accessed March 10, 2009).
- Statistics Canada, 2003, Human Activity and the Environment: Annual Statistics 2003, Catalogue no. 16-201-X, (accessed March 10, 2009).
- Statistics Canada, 2004, "Map B.1: Water use and availability, by drainage area," Human Activity and the Environment: Annual Statistics 2004, Catalogue no. 16-201-X, accessed June 4, 2009); reproduced by Environment Canada, (accessed March 10, 2009).
- Average annual departure is measured as the standard deviation.