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Lakes and Rivers

Trends in minimum river flow in natural rivers

Graphic thumbnail: Trends in minimum river flow in natural rivers

This map of Canada with ecozone+ boundaries shows trends in minimum river flow for 172 natural (unregulated) rivers from 1970 to 2005. The lowest annual flow increased significantly over this period at 13% of the sites. These sites were predominantly in the northern Montane Cordillera, Boreal Cordillera, Taiga Plains, Taiga Shield, and Arctic ecozones+. Twenty-eight percent of the sites had significant decreases in minimum flow, generally in the southern Pacific Maritime, southern Montane Cordillera, Boreal Shield, Mixedwood Plains, Atlantic Maritime, and Newfoundland Boreal ecozones+.

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Trends in maximum river flow in natural rivers

Graphic thumbnail: Trends in maximum river flow in natural rivers

This map of Canada with ecozone+ boundaries shows trends in maximum annual river flow for natural (unregulated) rivers from 1970 to 2005. Almost 20% of the sites showed a significant decrease in maximum flow. These sites were distributed across almost all ecozones+. About 5% of rivers showed an increase in maximum flow, mostly in the Atlantic Maritimes, but also in the Taiga Shield and the Montane Cordillera.

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Summer flow of four rivers in the Prairie Provinces

Graphic thumbnail: Summer flow of four rivers in the Prairie Provinces

This graphic contains line graphs displaying summer flow trends for four prairie rivers over scales of decades. Flow values are plotted as the percent of the flow at start of timeline for each of the four rivers. The graphs each show annual fluctuations overlain by a trend line. The overall trends show reduction in summer flow in each of the rivers. The trends for the four rivers are described in the point form in the text below the graph.

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Water levels in prairie closed-basin lakes

Graphic thumbnail: Water levels in prairie closed-basin lakes

This series of 8 line graphs displays changes in water levels in prairie closed-basin lakes from as early as 1910 to 2006. Dashed lines connecting widely separated data points indicate possible trends for years without data. All lakes experienced overall declines in water levels with the exception of Waldsea Lake.

Each graph is described in the following set of points:

  1. In Muriel Lake, water level declined approximately 3 metres from 1967 to 2006.
  2. In Little Fish Lake, water level declined approximately 6 metres from 1939 to 2004.
  3. In Manito Lake, water level declined approximately 7 metres from 1919 to 2006
  4. In Redberry Lake, water level declined 9 metres from 1918 to 2006. Four data points are marked as records that were recovered by means of air photos or survey notes.
  5. In Waldsea Lake, water level increased approximately 4.5 metres from 1964 to 2006.
  6. In Big Quill Lake, water level declined approximately 3 metres from 1919 to 2006.
  7. In Oro Lake, water level was measured using three data points from air photos or survey notes and three samples. Water levels increased approximately 3 metres from 1947 to 1981, and then declined approximately 2 metres by 2006.
  8. In Kenosee Lake, water level declined approximately 6 metres from 1938 to 2006. Four of the data points are based on records from air photos or survey notes.

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Southern Saskatchewan and southeastern Alberta

Graphic thumbnail: Southern Saskatchewan and southeastern Alberta

Two maps show the location of the lakes included in the study across southern Saskatchewan and southeastern Alberta.

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Change in freshwater discharge into the Arctic and North Atlantic

Graphic thumbnail: Change in freshwater discharge into the Arctic and North Atlantic

This graphic consists of a bar chart and an associated map. The bar chart displays the percent change in freshwater discharge into the Arctic and North Atlantic from 1964 to 2003. The associated map displays the five watersheds draining into these northern ocean regions. The map also shows locations of major river mouths and indicates, by means of symbols, whether the discharge decreased or increased during the study period. Percent changes in freshwater discharge are shown on the bar chart, by drainage basin. These are: 1) discharge to the Labrador Sea decreased by 10.6%; 2) discharge to eastern Hudson Bay decreased by 11%; 3) discharge to western Hudson Bay decreased by 13%; 4) discharge to the Arctic Ocean increased by 2%; and 5) discharge to Bering Strait decreased by 4.8%. The total decrease in freshwater discharge from 1964 to 2003 was 10%.

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Loss of variability in Great Lakes water levels

Graphic thumbnail: Loss of variability in Great Lakes water levels

This graphic consists of line graphs showing trends in water level variability in the five Great Lakes from 1918 to 2007. Water levels are plotted as metres in relation to a lake reference point. All lakes displayed seasonal fluctuations, but the patterns of year-to-year variation differed among lakes. Lake Erie, Lake Michigan, and Lake Huron all showed strong year-to-year fluctuations over the period from 1918 to 2007. Lake Ontario displayed this pattern of strong year-to-year fluctuation from 1918 until 1960, from which point fluctuations were predominantly seasonal. Lake Superior showed little year-to-year variability over the period of record.

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