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Data Sources and Methods for the Water Quantity in Canadian Rivers Indicator
3.1 Data source
The Water Survey of Canada collects and publishes data for 2792 hydrometric stations across Canada through different partnerships. The daily water levels and flows included in this indicator were taken directly from the Water Survey of Canada’s hydrological database (HYDAT).
3.2 Spatial coverage
Water quantity monitoring stations active from 1981–2011 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 1132 stations across Canada. There are more stations in the more heavily populated southern portion of the country.
Water levels for the Great Lakes were not included in the analysis as they are tracked through a separate Environment Canada program.Footnote The Great Lakes drainage region data include water quantity monitoring stations on rivers draining into the Great Lakes.
Location of water quantity monitoring stations used for the Water Quantity in Canadian Rivers indicator
Note: Natural stations are those where human activity upstream of the station has little impact on water levels and 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: Water Survey of Canada, Environment Canada (2013).
3.3 Temporal coverage
The Water Quantity in Canadian Rivers indicator includes data from 1981–2011 for both continuous and seasonal stations. At continuous stations, water level or flow data are collected 365 days per year. Seasonal stations operate, in general, for six months of the year.
3.4 Data completeness
Water level and flow data from each monitoring station are managed by their respective Environment Canada regional offices and are stored in the federal HYDAT database. The data used in this report were subject to quality assurance and quality control procedures to ensure they adhere to Environment Canada’s national standards.
Basic station information (e.g., name and location) and water level or flow data were extracted from HYDAT. The HYDAT database allows for station selection according to input parameters, such as the record length, data type, drainage area, etc. The data were transferred to a Microsoft Office Access database designed to calculate the percentiles used to define reference conditions for this indicator.
There are gaps in the water level and flow datasets due to periodic instrument failure. Where possible, regional offices use standardized protocols to estimate missing flow data. Estimated flow values are considered to be reliable and are included in the water quantity indicator calculations. When missing data cannot be estimated, a complete data set 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 indicator calculation.
3.5 Data timeliness
There is a time lag of two years between 2011, the last year reported, and the publication of this indicator. This time lag is due to several factors that intertwine with each other, 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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