MARINE CONDITIONS TIDE GAUGES DFO-CHS

This product has been produced by the St. Lawrence Global Observatory and includes data and services provided by the Canadian Hydrographic Service of Fisheries and Oceans Canada. The incorporation of data sourced from the Canadian Hydrographic Service within this product does NOT constitute an endorsement by the Canadian Hydrographic Service or Fisheries and Oceans Canada of this product.

Permanent water level network

The Canadian Hydrographic Service (CHS) of Fisheries and Oceans Canada (DFO) operates, across the country, a permanent water level network (PWLN) tracking the fluctuation of Canadian waters level. The CHS, is responsible among other things, of tide and water level observations for witch the given height has the chart datum for point of reference. the The goals of the PWLN is to support the hydrographic needs for the validation of tides forecast, to contribute to the safety of maritime navigation, to ensure monitoring of storm surges and tsunamis and to follow mean seas level evolution.

The “Marine Conditions” application of SLGO disseminates the tide gauges data in real time continuously since April 2014. Data prior to 2014 are available on the SLGO through the EDMS (DFO) application.

Observations

Water level observations are data measured at locations equipped with recording stations and electronic transmission systems. These measures are calculated in meters above the chart datum of the area. For more information on chart datums, visit the Vertical datums webpage on Fisheries and Oceans Canada website.

In the St. Lawrence, observations from the PWLN are provided by the “Système d’information sur les niveaux d’eaux côtières et océaniques“, known as the SINECO network, an operational system for observation and forecast of water levels that covers the whole St. Lawrence Seaway from Montréal to Cap-aux-Meules. This network supports data acquisition, validation, management and dissemination by modern means of communication.

The network is made of stations placed at strategic locations along the seaway where water levels are measured. Stations are equipped with sensors for hydrostatic pressure, atmospheric pressure, water temperature, and water salinity (salinity is only monitored at stations downstream of Île d’Orléans). The sensors are placed at depths varying between 3 and 10 metres depending on the station’s set-up and water level fluctuations. Depth and water level data are referred to chart datum.

Note: environmental data (temperature, salinity, atmospheric pressure) are available only as is and no quality control has been done.

Water level 30 day forecasts from Montreal to Saint-Joseph-de-la-Rive

The water level forecasts for the St. Lawrence River result from a one-dimensional model (Lefaivre et al. 2009) that integrates the flows from Lake Ontario, the Ottawa River basin, and other rivers to the St. Lawrence River. The model integrates the influence of tides and also the atmospheric forcing over the first 48 hours to be able to anticipate storm surges. Moreover, the model assimilates new observations in real time in order to increase its accuracy.

Water levels are shown in real time on the map; levels are colour-coded according to the legend beneath the figure. When a specific point on the map is selected (by a mouse click), a window opens showing that point’s position and the water level (in metres) relative to local Chart Datum. To see the 30 day water level forecast for the selected point, click the link “Time Series Graph.”

Forecasts

Tide forecast correspond to a precise water level calculated at a given time and space obtained from harmonic constants mainly astronomical lunisolar forces and complementary phenomena related to hydrodynamic. Predicted water levels are similar to values available in the Canadian Tide and Current Tables.

Characteristics of the Water Level

Web services from the Canadian Hydrographic Service to access tides, currents and water levels dara are available at the following address: https://www.tides.gc.ca/en/licence-agreement

Quality control

Verification and validation of raw data from the water level gauges are made by automated processes. Sensors installed on SINECO stations provide three simultaneous measures of water level in addition to the environmental data of that specific position (temperature, salinity, atmospheric pressure). This redundancy of information combined to the calculated forecast of water level are both important processes link to data quality control. So, data classified as:

• “Probably good” refers to data issued every 3 minutes that meet the first verification step. This step compares the redundant measures from the different sensors and the minimum and maximum limits determined for each station.
• “Good” refers to data issued every 15 minutes that have gone through the process of first and second steps of quality control. The second step takes into account previous measures and other criteria. Thus, in the SINECO system, acceptance limits for new observations are defined by the values of the forecasts and its standard error associated.