Local Water Quantity in Canadian Rivers

In 2010, higher-than-normal water quantity was more frequently observed in Manitoba, south-central Saskatchewan, southeastern Alberta, the southern Northwest Territories, eastern Ontario and northern New Brunswick than in other parts of Canada. Lower-than-normal water quantity was observed more frequently at monitoring stations in the Yukon, northwestern Alberta, the Great Lakes and the St. Lawrence River than in the rest of Canada.

Water quantity at monitoring stations, Canada, 2010

Water quantity at monitoring stations, Canada, 2010

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How this indicator was calculated

Note: The 2010 water quantity classification for a station is based on a comparison of the most frequently observed condition in that year, with typical water quantity at that station between 1978 and 2007. 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). Natural stations are those where human activity upstream of the station has little impact on water quantity. Regulated stations have water withdrawals, dams, diversions or other structures upstream that may change the water quantity in the river. Water quantity data for seasonal stations are only collected for part of the year. The water quantity for the Great Lakes drainage region is based on rivers draining into the Great Lakes and not on the Great Lakes themselves.
Source: Water Survey of Canada, Environment Canada (2012) HYDAT Database. Retrieved on 4 July, 2012.

Natural changes in temperature, rainfall and snowfall cause water quantities in rivers to rise and fall throughout the year, resulting in flooding or water shortages. Where water levels and flows are classified as low, drought conditions likely exist. In Canada, droughts normally last for one or two seasons and can be very damaging. Sectors relying on water, such as agriculture, industry and municipalities, are especially affected by long-term droughts. Droughts can also affect lakes and rivers, causing reduced fish survival and reproduction rates.

High water quantity at a water quantity monitoring station indicates a wet year, but does not mean flooding occurred. In Canada, floods are most commonly associated with the spring runoff, although they can occur year-round due to storms and ice jams. Floods may cause soil erosion, destroy infrastructure, threaten life and contaminate water sources by soaking agricultural lands or causing water in municipal wastewater treatment plants to flow directly into lakes or rivers. Annual floods bring benefits, such as helping to replenish groundwater supplies and making soil more fertile by providing nutrients. Floods tend to be short-lived, lasting on average about 10 days[1], and may not change the water quantity rating in this indicator. For example, in 2010 the southern prairies started the year in drought and by mid-June had record rainfalls, yet there was minimal flooding that year.

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Other information

[1] Dartmouth Flood Observatory (2004) Interannual Evolution of Flood Duration (since 1985). Retrieved 8 August, 2012.