Water quantity in Canadian rivers

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Canada is a water-rich country. However, too much or too little water can lead to serious problems. When there is too little water, there may not be enough water to irrigate farmland and there may be drought. When there is too much, rivers may flood. These indicators provide information about water flows across Canada.

National results

National key results

  • From 2001 to 2017, most Canadian rivers had normal water quantity
  • Since 2010, there has been an increase in sites with a higher-than-normal water quantity
  • The percentage of stations with a lower-than-normal water quantity has declined since 2001

Water quantity at monitoring stations, Canada, 2001 to 2017

Water quantity at monitoring stations, Canada, 2001 to 2015 (see long description below)
Data table for the long description
Water quantity at monitoring stations, Canada, 2001 to 2017
Year Total number of stations High quantity
(percentage of stations)
Normal quantity
(percentage of stations)
Low quantity
(percentage of stations)
2001 1 241 5 68 27
2002 1 237 5 79 16
2003 1 254 2 76 21
2004 1 253 9 85 7
2005 1 247 22 74 4
2006 1 242 11 78 11
2007 1 248 12 80 9
2008 1 245 10 86 4
2009 1 256 8 82 10
2010 1 252 20 73 8
2011 1 226 26 68 7
2012 1 279 17 70 13
2013 1 224 26 68 6
2014 1 212
31
61
8
2015 1 119
23 64 13
2016 1 009
31 56 13
2017 766
26 68 6

Note: Percentages may not add up to 100 due to rounding.

Download data file (Excel/CSV; 1.63 kB)

How this indicator was calculated

Note: The water quantity classification for a station is based on a comparison of the most frequently observed flow condition in a given year with typical water quantity at that station between 1981 and 2010. Data from Northern Quebec are missing for 2016 and 2017 and from the Arctic Coast-Islands for 2017 because of delays in getting data into the database. The results for this indicator vary slightly from those in the Regional water quantity in Canadian rivers indicator because of differences in the methods used to calculate the indicators. For more information, please see Data sources and methods.
Source: Environment and Climate Change Canada (2019) National Water Data Archive (HYDAT).

More information

In 2017, there were 766 water quantity monitoring stations located across 23 of Canada's 25 drainage regions.Footnote 1 Overall, water quantity at 26% of the stations across Canada had a higher-than-normal water quantity, 6% had lower-than-normal quantity and 68% had normal quantity.

Water quantity in Canadian rivers is measured as water flow, or the volume of water moving over a point, over a fixed period of time. Water flows in rivers generally follow changes in temperature, rainfall and snowfall throughout the year. More precipitation increases the amount of water in rivers, whereas warmer temperatures and less rainfall or snowfall will result in less water.

Generally, water flows are highest right after the snow melts in the early spring and gradually dry up through the summer and fall.

Over longer time scales, the amount of water in rivers is also affected by weather patterns and ocean surface temperatures which interact to influence the amount of rain or snow that falls. For example, extended summer droughts on the Prairies tend to take place when the southern Pacific Ocean warms during El Niño Southern Oscillation events. In an El Niño year, lower-than-normal water flows are generally seen on the Prairies. The Prairies experience more rain and snow when the ocean cools during La Niña events.Footnote 2 When this happens, higher-than-normal flows are found in the Prairies. Climate change may increase the strength and occurrence of the El Niño Southern Oscillations.

Regional results

Regional key results

In 2017, at the drainage region level,

  • water quantity conditions in 16 of the 23 drainage regions monitored were normal
  • higher-than-normal water flows were observed in northern British Columbia, much of the Prairie provinces, northern Ontario and southern Quebec
  • there were no drainage regions with lower-than-normal water quantity

Water quantity status of drainage regions, Canada, 2017

Water quantity status of drainage regions, Canada, 2015 (see long description below)
Data table for the long description
Water quantity status of drainage regions, Canada, 2017
Drainage region number Drainage region name Water quantity classification
1 Pacific Coastal Normal
2 Fraser–Lower Mainland Normal
3 Okanagan–Similkameen High
4 Columbia Normal
5 Yukon Normal
6 Peace–Athabasca High
7 Lower Mackenzie Normal
8 Arctic Coast–Islands n/a
9 Missouri Normal
10 North Saskatchewan High
11 South Saskatchewan Normal
12 Assiniboine–Red Normal
13 Winnipeg Normal
14 Lower Saskatchewan–Nelson High
15 Churchill High
16 Keewatin–Southern Baffin Normal
17 Northern Ontario High
18 Northern Quebec n/a
19 Great Lakes Normal
20 Ottawa High
21 St. Lawrence Normal
22 North Shore–Gaspé Normal
23 Saint John–St. Croix Normal
24 Maritime Coastal Normal
25 Newfoundland–Labrador Normal

Note: n/a = not available.

Download data file (Excel/CSV; 1.86 kB)

How this indicator was calculated

Note: The 2017 water quantity classification for a drainage region is based on the category (low, normal, high) for the most downstream monitoring station in the drainage region with more than 30 years of data. The flows are for the Canadian portions of the drainage regions. There are not enough data to describe the Arctic Coast-Islands (8) and Northern Quebec (18) drainage regions. The results for this indicator vary slightly from those in the Local water quantity in Canadian rivers indicator because it uses data for the most downstream site in the drainage region. For more information, please see Data sources and methods.
Source: Environment and Climate Change Canada (2019) National Water Data Archive (HYDAT).

More information

To characterize water quality at a regional level, monitoring stations for the most downstream site in the drainage region are used. In 2017, 324 of the 766 monitoring stations are included to analyse the water quantity level.

Every year in Canada is marked by weather extremes and 2017 was no exception. These extreme events do not always translate into major changes in seasonal or long term water quantity. For example, British Columbia experienced record dry summer conditionsFootnote 3  but over the whole year water quantity in the province was mostly normal. By contrast, eastern Ontario and Quebec experienced record spring flooding and rain fallFootnote 3  that did result in higher-than-normal water quantity over the year in those regions.

Although lower-than-normal flows were observed in some monitoring stations in 2017, the flows did not represent a large enough percentage of the drainage region to result in a low water quantity classification for the region.

Local results

Local key results

In 2017, looking across the 766 monitoring stations included in the indicator,

  • higher-than-normal water quantity was more frequent at monitoring stations in southern British Columbia, Yukon, central Alberta, Saskatchewan and Manitoba, and southern Ontario
  • lower-than-normal water quantity was seen more frequently at monitoring stations in southern British Columbia and Alberta, and New Brunswick

Water quantity at monitoring stations, Canada, 2017

Water quantity at monitoring stations, Canada, 2015 (see long description below)
Long description

The map shows the water quantity classification (low, normal or high) at Canadian monitoring stations in 2017 for both natural and regulated stations monitored on a yearly or seasonal basis.

Navigate data using the interactive map

How this indicator was calculated

Note: The 2017 water quantity classification for a station is based on a comparison of the most frequently observed condition in that year with the typical water quantity at that station between 1981 and 2010. Normal water quantities are specific to each region and do not refer to the same amount of water in each drainage region (for example, the normal water quantity on the Prairies is different from the normal water quantity in the Maritimes). Natural stations are those where human activity upstream of the station has little impact on water flows. 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. Data for 2017 for Northern Quebec and Arctic Coast-Islands are missing because of delays getting data into the database. The results for this indicator vary slightly from those in the Regional water quantity in Canadian rivers indicator because of differences in the methods used to calculate the indicator. For more information, please see Data sources and methods.
Source: Environment and Climate Change Canada (2019) National Water Data Archive (HYDAT).

More information

Local changes in temperature, rainfall and snowfall cause water levels in rivers to rise and fall throughout the year. These changes can sometimes result in flooding or water shortages.

Where water quantity is classified as low, drought conditions likely exist. In Canada, droughts normally last for 1 or 2 seasons and can be very damaging. Agriculture, industry and municipalities are especially affected by long-term droughts because they rely on water. Droughts can also affect water quality in lakes and rivers, and threaten fish survival.

High water quantity at a water quantity monitoring station indicates a wet year, but does not mean flooding has occurred. Floods tend to be short-lived, lasting on average about 10 days,Footnote 4  and may not change the water quantity classification in this indicator.

An exception to this was the spring flooding experienced in eastern Ontario and Quebec in 2017. Unusually heavy rainfall, coinciding with melting snow that had already saturated the ground and swollen waterways, generated record volumes and major peak water levels in the Ottawa River and its tributaries, exceeding those set in 1974 and 1976.Footnote 5 

About the indicators

About the indicators

What the indicators measure

The national indicator provides a summary of trends in water quantity in rivers across Canada from 2001 to 2017.

The regional and local indicators present the status of water quantity at monitoring stations across Canada in 2017. At the drainage region and monitoring station level, the indicators provide an illustration of whether water flows were normal, low or high in 2017.

A station's water quantity status is the category most often observed for a given year. Daily water quantity classifications are determined by comparing the measured value for a date to the flow observed at that site for 1981 to 2010. A station described as having a low water flow on January 31, for example, had a measured value ranking among the lowest 25% of values observed for each January 31 from 1981 to 2010. A station described as having a high water flow had a measured value ranking among the highest 25% of values observed on that date.

A drainage region was classified as having a low, normal or high water quantity by examining the water quantity classification at the most downstream monitoring station in the drainage region. Where more than 1 most downstream station was identified for a drainage region, such as in coastal areas, the classification representing the greatest percentage of the drainage region was used.

Why these indicators are important

Canada has 0.5% of the world's population and approximately 7% of the world's renewable freshwater supply. Canada may have a lot of water, but water is in short supply in some parts of the country. Humans use a lot of water in agriculture, in industry and in their homes.

These indicators provide information about the state of the amount of surface water in Canada and its change through time to support water resource management.

Federal Sustainable Development Strategy icon. Pristine lakes and rivers.

Pristine lakes and rivers

These indicators support the measurement of progress towards the following 2019 to 2022 Federal Sustainable Development Strategy long-term goal: Clean and healthy lakes and rivers support economic prosperity and the well-being of Canadians.

In addition, the indicators contribute to the Sustainable Development Goals of the 2030 Agenda for Sustainable Development. They are linked to the 2030 Agenda's Goal 6: Clean water and sanitation.

Related indicators

The Canada's water use in a global context indicator reports on the amount of water removed from the environment per person per year for use in agriculture, manufacturing and in homes, and as a percentage of each country's total renewable water supply for 9 countries, including Canada.

The Water availability in Canada indicator compares the amount of fresh water withdrawn from rivers for human use to the volume of water in Canadian rivers.

The Water withdrawal and consumption by sector indicator shows how much water is used by 7 economic sectors in Canada.

The Residential water use indicator reports how much water is used in homes across Canada.

Data sources and methods

Data sources and methods

Data sources

Water flow data across Canada for 1981 to 2017 are taken from the Water Survey of Canada's National water data archive (HYDAT).

More information

For 2017, the indicators include data from 766 yearly and seasonal stations across Canada. At yearly stations, water flow data are collected 365 days per year. In general, seasonal stations operate 6 months of the year for a maximum of 217 days per year. Both natural and regulated rivers and all basin sizes were included (Figure 4).

Figure 1. Location of water quantity monitoring stations used for the Water quantity in Canadian rivers indicators, 2017

Location of water quantity monitoring stations used for the Water quantity in Canadian rivers indicators, 2015 (see long description below)
Long description

The map shows the location of each of the 766 Canadian water quantity monitoring stations used in this indicator.

Note: Natural stations are those where human activity upstream of the station has little impact on water flow. Regulated stations have water withdrawals, dams, diversions or other structures upstream that may change the quantity of water in the river. Water quantity data at seasonal stations are only collected for part of the year.
Source: Environment and Climate Change Canada (2019) Water Survey of Canada.

Data completeness

Water flow data from each monitoring station are managed by their respective Environment and Climate Change Canada regional offices and stored in the federal HYDAT database. The data used in the indicators are subject to quality assurance and quality control procedures to ensure they adhere to Environment and Climate Change Canada's national standards.

There are gaps in the water flow datasets due to periodic instrument failure. Where possible, regional offices use standardized protocols to estimate flow data to fill these gaps. Estimated flow values are considered to be reliable and are included in the calculation of the water quantity indicators.

Only when data cannot be estimated are they considered missing. A complete dataset was defined as missing no more than 20% of the year: 73 days out of 365 for yearly stations and 43 days out of 217 for seasonal stations. Stations not meeting these criteria for a year were not included in the calculation of the indicators.

Data for stations in the Arctic Coast-Islands and Northern Quebec drainage region were unavailable for 2017.

Data timeliness

Data for this indicator were taken from the July 2019 version of HYDAT.

There is a time lag of about 2 years between the last year reported and the publication of the indicators. This time lag is due to several factors, including the time required to verify the raw data, compile the data at the national level from all partners, and analyze, review and report the data.

Methods

The water quantity at a station is classified as low, normal or high by comparing daily water flow values for each station to the 30-year normal values for that station. The station's status for the year is the category most often observed for that year. For the national indicator, the percentage of stations in each category is calculated and then presented for each year from 2001 to 2017. For the regional indicator, the water quantity in Canada's 25 drainage regions is classified by assessing water quantity at the most downstream station in the drainage region. Drainage in coastal regions requires more than one station to characterize flow in these areas.

More information

Data extraction

Basic station information and water flow data were extracted from HYDAT according to input parameters, such as record length, data type, and drainage area. An R script was used to set the parameters for running statistical calculations and to calculate the percentiles.

Categorizing water quantity at a monitoring station

Water quantity at a monitoring station is classified based on historical data recorded at Water Survey of Canada hydrometric stations. To start, frequency distributions for each day of the year were calculated using water flow data collected from 1981 to 2010 at each monitoring station. A 30-year period is used to provide a picture of the hydrologic characteristics of a station, while maximizing the number of stations included in the indicators.

Water quantity categories were defined from the frequency distributions:

low < 25th percentile

25th percentile ≤ normal ≤ 75th percentile

high > 75th percentile

Daily water quantity records for 2001 to 2017 were categorized as low, normal or high by comparing the measured value to the percentiles calculated for the corresponding station and day of the year over the normal period. Accordingly, a station described as having a low water flow on January 31, for example, had a measured value ranking among the lowest 25% of the values observed for each January 31 from 1981 to 2010.

A station's status for a year is the category most often observed (the mode) at a given station in a given year. Thus, a low classification does not mean that water quantity was consistently low throughout the year; it only means that low water quantity conditions were most often observed.

Table 1. Number of water quantity monitoring stations used in the national and local indicators grouped by drainage region, 2017
Drainage region Number of stations
Pacific Coastal (1) 66
Fraser–Lower Mainland (2) 32
Okanagan–Similkameen (3) 6
Columbia (4) 45
Yukon (5) 18
Peace–Athabasca (6) 18
Lower Mackenzie (7) 19
Arctic Coastal–Islands (8) n/a
Missouri (9) 41
North Saskatchewan (10) 18
South Saskatchewan (11) 59
Assiniboine–Red (12) 56
Winnipeg (13) 16
Lower Saskatchewan–Nelson (14) 37
Churchill (15) 30
Keewatin–Southern Baffin (16) 2
Northern Ontario (17) 14
Northern Quebec (18) n/a
Great Lakes (19) 158
Ottawa (20) 18
St. Lawrence (21) 5
North Shore–Gaspé (22) 1
Saint John–St. Croix (23) 21
Maritime Coastal (24) 35
Newfoundland–Labrador (25) 51

Note: n/a = not available.

For 2017, there were not enough data to represent water quantity for the Arctic Coast-Islands (8) and Northern Quebec (18) drainage regions.

Calculating the Regional water quantity in Canadian rivers indicator

The regional indicator generalizes the water quantity classification across Canada's drainage regions representing major Canadian rivers. For this indicator, where possible, the most downstream monitoring station of an inland drainage region was chosen to determine the water quantity category for that drainage basin.Footnote 6  Where more than 1 most downstream station was identified for a drainage region, the classification representing the greatest percentage of the drainage region was used. For example, 8 water quantity monitoring stations were necessary to characterize water quantity in the North Saskatchewan drainage region in 2017 (Figure 5). Since the monitoring stations with higher-than-normal water quantity cover a greater percentage of the drainage region, the North Saskatchewan drainage region is assigned a high flow for that year. Using the most downstream stations to classify water quantity for a region resulted in data from 324 of the 766 stations to be included in the indicator for 2017 (Table 2 and Figure 6).

Although all water flowing from a drainage basin may not be captured by this collection of long-term stations, the percentage area of the basin gauged provides an estimate of the level of certainty associated with the results.

Figure 5. Illustration of regional station selection

Illustration of regional station selection (see long description below)
Long description

The map illustrates how 8 water quantity monitoring stations at the most downstream point of the North Saskatchewan drainage region are used to characterize water flowing out of this drainage region.

Table 2. Number of most downstream, long-term water quantity monitoring stations used to classify water quantity for each drainage region, 2017
Drainage region Regional water quantity category Number of monitoring stations used Percentage of drainage region area gauged
Pacific Coastal (1) Normal
41 43
Fraser–Lower Mainland (2) Normal
19 44
Okanagan–Similkameen (3) High 2 99
Columbia (4) Normal 3 100
Yukon (5) Normal 2 83
Peace–Athabasca (6) High 7 32
Lower Mackenzie (7) Normal 10 33
Arctic Coastal–Islands (8) n/a n/a n/a
Missouri (9) Normal 7 60
North Saskatchewan (10) High 8 69
South Saskatchewan (11) Normal 2 88
Assiniboine–Red (12) Normal 5 78
Winnipeg (13) Normal 3 94
Lower Saskatchewan–Nelson (14) High 7 95
Churchill (15) High 2 93
Keewatin–Southern Baffin (16) Normal 2 8
Northern Ontario (17) High 9 37
Northern Quebec (18) n/a n/a n/a
Great Lakes (19) Normal 93 33
Ottawa (20) High 3 67
St. Lawrence (21) Normal 3 19
North Shore–Gaspé (22) Normal 1 1
Saint John–St. Croix (23) Normal 18 50
Maritime Coastal (24) Normal 32 19
Newfoundland–Labrador (25) Normal 45 14

Note: n/a = not available. The percentages of the drainage regions gauged are based on the number of long-term, water quantity monitoring stations with more than 30 years of data used for this analysis and do not reflect the actual percentage of the drainage region gauged by Environment and Climate Change Canada's water quantity monitoring network. Values are based on the Canadian portion of the drainage basins only.

Figure 6. Location of water quantity monitoring stations used to calculate the Regional water quantity in Canadian rivers indicator, 2017

Location of water quantity monitoring stations used to calculate the Regional water quantity in Canadian rivers indicator, 2015 (see long description below)
Long description

The map shows the location of each of the 324 Canadian water quantity monitoring stations used to characterize water quantity in each drainage region.

Note: Natural stations are those where human activity upstream of the station has little impact on water flows. 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.
Source: Environment and Climate Change Canada (2019) Water Survey of Canada.

Recent changes

The water quantity classifications for 2014 and 2015 have been revised to include missing data from Quebec and British Columbia. The data were not available in past reporting of the indicator due to delays in submissions to the HYDAT database.

Caveats and limitations

Large-scale events of short duration, such as a flood, may not influence the final classification of a station. Changes to seasonal flow patterns will also affect final classifications.

There are not enough stations in areas such as the North to compute complete, nationally representative indicators.

The status of water quantity assessed by the present indicators is a reflection of the 30-year time period used for the calculations and does not necessarily reflect longer-term trends at the station.

Water flow data collected at a monitoring station are representative of the average conditions of the upstream drainage area. Professional judgment is used to determine whether there were enough stations to describe water quantity in a drainage region.

More information

Extreme short-term events may not be detected with the indicators, since the focus is on frequency of observations in different categories through the year.

Water quantity generally follows a predictable seasonal pattern with natural, year-to-year variability. The indicators compare daily values to the 30-year normal and assume that water quantity is approximately the same from one year to the next for the same calendar day. A shift in the predictable seasonal pattern (the hydrograph) for one year will influence the results.

Most water quantity monitoring stations in Canada are located in populated areas and do not represent the country's entire geographic extent or all its watersheds.

While 30 years represent a long time series for water quantity data, it represents a relatively short historical time frame for a given river and does not account for all natural variability in a river system.

The variability of conditions across a drainage region may not be reflected, and water quantity classifications of tributaries may differ from that described by the indicators.

The number of water quantity monitoring stations included in these indicators fluctuates from year to year because stations may be closed as monitoring networks are optimized. Whether or not the data have been verified and uploaded into HYDAT by the time the data are extracted to calculate the indicator also influences whether the station is included in the calculation that year.

The water quantity for the Great Lakes drainage region is based on rivers draining into the Great Lakes and not on the water contained within the Great Lakes themselves.

Resources

Resources

References

Environment and Climate Change Canada (2019) Real-time Hydrometric Data. July 2019 version. Retrieved on September 23, 2019.

Environment and Climate Change Canada (2019) Water Survey of Canada. Retrieved on September 23, 2019.

Statistics Canada (2003) Standard Drainage Area Classification. Retrieved on September 23, 2019.

Related information

Changes to water quantity: drivers and impacts

El Niño

Large-scale climate oscillations influencing Canada

Ratio of surface freshwater intake to water yield

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