From the Fraser Institute

By Annika Segelhorst and Elmira Aliakbari

Canada’s rivers are vital to our environment and economy. Clean freshwater is essential to support recreation, agriculture and industry, an to sustain suitable habitat for wildlife. Conversely, degraded freshwater can make it harder to maintain safe drinking water and can harm aquatic life. So, how healthy are Canada’s rivers today?

To answer that question, Environment Canada uses an index of water quality to assess freshwater quality at monitoring stations across the country. In total, scores are available for 165 monitoring stations, jointly maintained by Environment Canada and provincial authorities, from 17 in Newfoundland and Labrador, to 8 in Saskatchewan and 20 in British Columbia.

This index works like a report card for rivers, converting water test results into scores from 0 to 100. Scientists sample river water three or more times per year at fixed locations, testing indicators such as oxygen levels, nutrients and chemical levels. These measurements are then compared against national and provincial guidelines that determine the ability of a waterway to support aquatic life.

Scores are calculated based on three factors: how many guidelines are exceeded, how often they are exceeded, and by how much they are exceeded. A score of 95-100 is “excellent,” 80-94 is “good,” 65-79 is “fair,” 45-64 is “marginal” and a score below 45 is “poor.” The most recent scores are based on data from 2021 to 2023.

Among 165 river monitoring sites across the country, the average score was 76.7. Sites along four major rivers earned a perfect score: the Northeast Magaree River (Nova Scotia), the Restigouche River (New Brunswick), the South Saskatchewan River (Saskatchewan) and the Bow River (Alberta). The Bayonne River, a tributary of the St. Lawrence River near Berthierville, Quebec, scored the lowest (33.0).

Overall, between 2021 and 2023, 83.0 per cent of monitoring sites across the country recorded fair to excellent water quality. This is a strong positive signal that most of Canada’s rivers are in generally healthy environmental condition.

A total of 13.3 per cent of stations were deemed to be marginal, that is, they received a score of 45-64 on the index. Only 3.6 per cent of monitoring sites fell into the poor category, meaning that severe degradation was limited to only a few sites (6 of 165).

Monitoring sites along waterways with relatively less development in the river’s headwaters and those with lower population density tended to earn higher scores than sites with developed land uses. However, among the 11 river monitoring sites that rated “excellent,” 8 were situated in areas facing a combination of pressures from nearby human activities that can influence water quality. This indicates the resilience of Canada’s river ecosystems, even in areas facing a combination of multiple stressors from urban runoff, agriculture, and industrial activities where waterways would otherwise be expected to be the most polluted.

Poor or marginal water quality was relatively more common in monitoring sites located along the St. Lawrence River and its major tributaries and near the Great Lakes compared to other regions. Among all sites in the marginal or poor category, 50 per cent were in this area. The Great Lakes-St. Lawrence region is one of the most population-dense and extensively developed parts of Canada, supporting a mix of urban, agricultural, and industrial land uses. These pressures can introduce harmful chemical contaminants and alter nutrient balances in waterways, impairing ecosystem health.

In general, monitoring sites categorized as marginal or poor tended to be located near intensive agriculture and industrial activities. However, it’s important to reiterate that only 28 stations representing 17.0 per cent of all monitoring stations were deemed to be marginal or poor.

Provincial results vary, as shown in the figure below. Water quality scores in Newfoundland and Labrador, Prince Edward Island, New Brunswick, Saskatchewan and Alberta were, on average, 80 points or higher during the period from 2021 to 2023, indicating that water quality rarely departed from natural or desirable levels.

Rivers sites in Nova Scotia, Ontario, Manitoba and B.C. each had average scores between 74 and 78 points, suggesting occasional departures from natural or desirable levels.

Finally, Quebec’s average river water quality score was 64.5 during the 2021 to 2023 period. This score indicates that water quality departed from ideal conditions more frequently in Quebec than in other provinces, especially compared to provinces like Alberta, Saskatchewan and P.E.I. where no sites rated below “fair.”

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Overall, these results highlight Canada’s success in maintaining a generally high quality of water in our rivers. Most waterways are in good shape, though some regions—especially near the Great Lakes and along the St. Lawrence River Valley—continue to face pressures from the combined effects of population growth and intensive land use.