Water Quantity in Canadian Rivers
In 2010, 16 drainage regions were classified as having normal water quantity; four had higher-than-normal water quantity; and one had lower-than-normal water quantity. Over the past decade (2001–2010), Canada’s rivers typically contained a normal quantity of water. Higher-than-normal water quantity was observed in six drainage regions in 2005, a particularly wet year in central Canada. Five drainage regions had lower-than-normal water quantity in 2001, a year with lower-than-usual rainfall and snowfall in central Canada.
Water quantity in Canada’s drainage regions, 2001 to 2010
Note: Normal water quantity is based on the amount of water observed at water quantity monitoring stations from 1978–2007 for Canada’s 25 drainage regions. For the period 2001 to 2007, there are not enough data to describe water quantity for three drainage regions; data for four drainage regions are missing for 2008–2010. Normal water quantities are specific to each region and do not refer to the same amount of water in each drainage region (e.g., normal water quantity on the Prairies is different from normal water quantity in the Maritimes).
Source: Water Survey of Canada, Environment Canada (2012) HYDAT Database. Retrieved on 4 July, 2012.
Canada is a water-rich country, with its rivers and lakes accounting for 7% of the world’s renewable freshwater. However, even with all this water, shortages are a serious problem for regions of Canada where natural water supplies do not always meet human needs. Normal water quantity does not mean that there are not areas within the drainage region with too much or not enough water for some period of the year. Natural changes in temperature, rainfall and snowfall can cause water quantities in rivers, lakes and reservoirs to rise and fall throughout the year. These weather fluctuations can result in flooding or water shortages.
The water quantity category given to a drainage region is based on the water level or flow classification most frequently observed at water quantity monitoring stations within that region. The water quantity for a station is classified as low, normal or high in relation to the quantity typically observed each day of the year at that station compared to values collected from 1978 to 2007.
 A drainage region is an area of land where all the water under and on it drains into the same lake, wetland or ocean. Stations within a drainage region are connected by a common water source.
 Renewable freshwater refers to the total amount of freshwater available for use in Canadian rivers. It is calculated as the total volume of water flowing in a river plus the volume of water returned to it from groundwater, rainfall and snowfall, plus water originating from outside the country.
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