Water quantity in Canadian Rivers indicators: data sources and methods, chapter 3

3. Data

3.1 Data source

The Water Survey of Canada collects data for approximately 2700 active hydrometric stations across Canada through different partnerships. The daily water flow values included in the indicators were taken directly from the Water Survey of Canada's hydrological database (HYDAT).

3.2 Spatial coverage

Water quantity monitoring stations active from 1981-2013 were chosen for this analysis. To ensure an adequate number of stations with data of a sufficient time span, both natural and regulated rivers and all basin sizes were included. These criteria resulted in the selection of 866 water quantity monitoring stations across Canada for 2013.

Figure 1. Location of water quantity monitoring stations used for the Water Quantity in Canadian Rivers indicators, 2013

Map of Canada
Long description

The map shows the location of each of the 866 Canadian water quantity monitoring stations used to compile the Water Quantity in Canadian Rivers indicators for 2013.

Note: Natural stations are those where human activity upstream of the station has little impact on water quantity. 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 (2015) Water Survey of Canada.

3.3 Temporal coverage

The Water Quantity in Canadian Rivers indicators include data from 1981-2013 for both yearly and seasonal stations. At continuous stations, water flow data are collected 365 days per year. In general, seasonal stations operate six months of the year for a maximum of 217 days per year.

3.4 Data completeness

Water flow data from each monitoring station is managed by its respective Environment and Climate Change Canada regional office and stored in the federal HYDAT database. The data used in the indicators are subject to quality assurance and quality control procedures to ensure that they adhere to Environment and Climate Change Canada's national standards. There is reduced certainty in water flow data when ice cover is present.

Basic station information (e.g., name and location) and water flow data were extracted from HYDAT. The HYDAT database allows for station selection according to input parameters (e.g., record length, data type, drainage area, etc.). Environment and Climate Change Canada Data Explorer's Historical Analysis tool was used to set the parameters for running statistics calculations and to calculate the percentiles.

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 is it 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.

The Regional Water Quantity in Canadian Rivers indicator for the Maritimes is partially based on preliminary data that has not undergone the full quality assurance and quality control process.

Data for many stations in the Northern Quebec drainage region are unavailable between 1999 and 2008. To accommodate this data gap, the normal period was changed to 1971-2000, instead of 1981-2010, for the calculation of the indicator in the Northern Quebec drainage region only.

3.5 Data timeliness

There is a time lag of about two 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.

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