Annual water yield for selected drainage regions and Southern Canada (38100283)

This table provides annual estimates of renewable freshwater for selected drainage regions and Southern Canada beginning in 1971.

Water yield is an estimate of freshwater runoff into streams and rivers and provides information on Canada’s renewable freshwater. It is derived from data on the unregulated flow of water in rivers and streams in Canada.

To estimate water yield, a database of natural streamflow observations was compiled from the Water Survey of Canada HYDAT database. The streamflow values were then converted to a runoff depth and interpolated using ordinary kriging to produce spatial estimates of runoff. These spatial estimates were then scaled to create annual estimates at the drainage region level.

Drainage regions are a variant of Statistics Canada’s official classification of drainage areas, the Standard Drainage Area Classification (SDAC) 2003. This classification groups 974 sub-sub-drainage areas representing all land and interior freshwater bodies into 25 drainage regions, which can be further grouped according to their outflow into one of 5 ocean drainage areas: the Pacific Ocean, Arctic Ocean, Gulf of Mexico, Hudson Bay or Atlantic Ocean. Southern Canada is a statistical area delineated by a boundary separating the northern from the southern portion of the country.

Results are included where data points are dense enough to support estimation and sufficient data are available for validation. Few northern results are included because northern networks are generally sparse, with fewer stations available across larger distances.

The water yield was modelled to the international border and includes areas not covered by some versions of the drainage region boundaries. These areas extend the boundaries to the Canadian portion of all freshwater bodies and include the Canadian portion of the Great Lakes and the St. Lawrence River as far east as the Île d’Orléans, near Québec.

Although the water yield provides an estimate of renewable freshwater, it can include some water that is considered non-renewable (e.g., meltwater from receding glaciers). Unregulated flow is prioritized, and most stations are selected on this basis but because human influence on regulation is constantly changing, it is a challenge to keep this status up to date. To compensate for some of this uncertainty, the Reference Hydrometric Basin Network (RHBN) of the Water Survey of Canada network is used as a complementary data source. The RHBN is a set of stations with minimal human influence.

For a more comprehensive review of the methodology, including the validation steps, refer to Statistics Canada, 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, Catalogue no. 16-001-M, no. 7.

Data sources include the HYDAT database and the Reference Hydrometric Basin Network.