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Measuring river flows
Environment Canada's Water Survey of Canada  , along with many contributing agencies, presently measures the rate of flow (discharge) in rivers and records the levels of lakes and rivers at more than 2600 locations in Canada.
How do you measure water in lakes and rivers?
- Water levels are read manually by gauge readers or continuously recorded either electronically or on graph paper or in digital form.
- Rate of flow (or discharge) requires multiple measurements of channel depth, width, and flow velocity to yield the average discharge in the stream crossing for a given water level. Measurements can be made electronically from a bridge, by wading into a stream, by boat, or from a cableway strung across the river. In winter, the measurements are made through the ice.
- With sufficient measurements of flow over a variety of water levels (including extreme lows and highs), a water level-discharge relationship is established at each location so that the discharge can be computed from measured water levels.
- Historical records from 5000 active and discontinued sites permit the estimation of streamflow at ungauged locations.
This table indicates typical river flows at various locations in Canada: 
Water level and discharge information such as this is essential for the wise management of Canada's water resources. For example, the information can be used
- to allocate water between various users;
- to manage water resources or minimize the impacts of extreme flows (e.g., flood protection, floodplain mapping, diversion canals, and irrigation);
- to design and construct bridges, canals, culverts, roadways, water supplies, irrigation facilities, and countless other structures;
- to plan and conduct environmental programs and assessments related to water quality, fisheries, and wildlife habitat; and,
- to ensure that the nation's water resources are developed in a manner that conserves and protects the environment.
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