Rideau Valley Conservation Authority

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Streamflow and Water Levels

Click to view the streamguage locations along the Rideau River

In this section near real-time streamflow and water level data at various locations are presented. The intention is to give the viewer an indication of continuous stream conditions in the watershed and to make the public aware of potential flood or drought conditions. Various agencies (Parks Canada - Rideau Canal Office, Environment Canada - Water Survey Division, Ministry of Natural Resources, and RVCA) are involved in the collection of the data presented here. Please note that the data presented have not been subjected to quality control checks. Thus the data you see on this site are only provisional; RVCA does not guarantee data accuracy; and the user should assure themselves of the appropriateness of data for their intended use.

Streamflow and water level data are used to monitor flood and drought events. They are also used to monitor water supply for lake operation and navigation. This information is used to determine flood risk, support land use planning, assess fish habitat and for water quality analyses of contaminant loading.

Click here to view cross-section.

Direct measurement of streamflow is done at a section of a river that is reasonably stable, straight and has a relatively obstruction free bottom. A graduated cable is strung across the river and velocity measurements are taken, using an instrument called a current meter, usually at one metre intervals (depending on the size of the stream) along the cable. The flow is calculated through each of these metre “panels” (velocity times the area [panel width x depth]), and then summing over all of the panels to get the total flow through the entire river section.

Over time, a number of flow measurements are done at different water levels and a relationship between flow and water level is developed. This “rating curve” or “stage – discharge (water level - flow) table” allows the observer to estimate flow from any measured water level. This is a cheap and fast way of getting reliable streamflow data. Therefore, the streamflow gauges are located in places where the rating curve remains relatively stable over time. At each of these locations, the river is geomorphologically and hydraulically stable meaning it does not change significantly with time, exhibits an unique relationship between water level and flow (such as at bridge sites or water control structures), and is not affected by downstream conditions.

The manual measurement of water level can be done by placing a measuring device or “staff gauge” in the river attached to a bridge or somewhere so that the gauge is always in the water and can be easily read by an observer. Usually, the staff gauge elevation is related to the geodetic datum by surveying from an established geodetic benchmark. This allows comparison among gauge sites.

Manual measurement of water level can be collected in an economical way and, provided there is a local observer during extreme events, they can be very useful in documenting rare events and calibrating numerical models. For long term data, electronic continuous recording units are used. A sensor reads the water levels usually at one hour intervals and that data is recorded in a “data-logger” that can be downloaded at the site or by telephone, radio or satellite communication.

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