Data Sources and Methods for the Water Quantity Indicator

3.1 Data source

The Water Survey of Canada collects and publishes data for 2792 hydrometric stations across Canada, through different partnerships. The utilized daily water levels and flows were taken directly from the Water Survey of Canada’s hydrological database (HYDAT).

3.2 Spatial coverage

Water quantity monitoring stations active from 1978–2010 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 1196 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.^[1] The Great Lakes regional data include water quantity monitoring stations on rivers draining into the Great Lakes.

Locations of 1196 water quantity monitoring stations used in the Water Quantity 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 (2012)

3.3 Temporal coverage

The national Water Quantity indicator shows results for 2001 to 2010, while the regional and local Water Quantity indicators place emphasis on 2010 as it is the latest year for which quality-assured data are available. Normal, low or high water quantity is defined based on the amount of water observed at water quantity monitoring stations from 1978–2007. Both continuous and seasonal stations were included in the calculation of the indicator. At continuous stations, water level or flow data are collected 365 days per year. In general, seasonal stations operate 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.

Final, approved data for the North-Shore Gaspé drainage region in southern Quebec were not available in time for this publication. No results for 2008 to 2010 for this region are included in this publication.

3.5 Data timeliness

There is a time lag of two years between 2010, 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. The time period also aligns with 2008–10, the time period used to calculate the CESI Water Quality indicator.

[1] Environment Canada (2010) Great Lakes Water Levels and Related Data. Retrieved on 24 July, 2012.