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Data Sources and Methods for the Freshwater Quality Indicator

Description and rationale of the Freshwater Quality Indicator

2.1 Description

The Freshwater Quality Indicator (WQI) provides an overall measure of the ability of freshwater bodies to support aquatic life at selected monitoring sites across Canada (core sites). It is a water-quality-guideline-driven tool used to distill large amounts of water quality data at a monitoring site into a single index. Water quality at a monitoring site is considered excellent when ambient water quality never, or very rarely, exceeds guidelines for any selected parameters. When water quality is rated poor, water quality measurements usually exceed their guideline; exceedances at these sites may be large.

2.2 Rationale

Clean water is essential to sustain healthy ecosystems and the many benefits they provide us. The WQI provides a national perspective on the overall quality of untreated freshwater for aquatic life in Canada. The WQI assumes that, if measured ambient water quality does not exceed its water quality guideline, it is acceptable for aquatic plants and animals. The WQI provides information about the state of surface freshwater quality and its change through time to inform water resource management.