About the INDICATORS

Water quality

Why it’s important

Water quality directly impacts aquatic life, drinking water safety, and recreational use. It plays a crucial role in maintaining ecosystem balance by influencing species diversity, habitat conditions, and the overall health of freshwater environments. Poor water quality can lead to harmful effects on both ecosystems and human health.

How we assess it

• We compare the results of key water quality parameters, like nutrients and heavy metals, against provincial and federal guidelines.
• We track long-term trends to detect any persistent or emerging water quality issues, as well as good news like improvements in water quality over time.

This is just a summary. You can dive deeper into water quality standards (based on regions) and more about how we calculated the scores in our tech doc.

Water Rangers assesses water quality for the Watershed Reports by evaluating the frequency of guideline exceedances across monitoring sites. Scores range from “Very Good” (5), indicating minimal exceedances and strong ecosystem support, to “Very Poor” (1), where water quality is significantly impaired and poses risks to aquatic life. This scoring system helps communicate ecosystem health and highlights areas where conservation or intervention efforts may be needed.

Water Flow

Why it’s important

The volume of water in a river and how it changes throughout the year are crucial to maintaining ecosystem health. Water flow shapes habitats by influencing the formation of riverbanks, wetlands, and floodplains. It supports species migration by providing necessary pathways and seasonal cues, and it helps maintain water quality by regulating temperature, oxygen levels, and the distribution of nutrients and sediments. Altering natural water flow by withdrawing, holding back, or diverting water disrupts these patterns. Increases in the total amount of water or the amount of water flowing at a given time can lead to flooding and stream bank erosion. Having both too much AND too little water can lead to serious ecological consequences.

How we assess it

• We evaluate the amount of water flowing in the river and the timing of these flows.
• We monitor long-term changes in natural flow patterns to identify any significant disruptions.

This is just a summary. You can dive deeper into how we calculated the scores in our tech doc.

The hydrological flow scoring process in Canada’s watershed reports evaluates long-term trends in flow magnitude and frequency using historical daily flow data from the HYDAT database. There is a large network of stations throughout Canada that regularly monitor the flow of water. For this analysis, stations with at least 50 years of consistent data were used to detect trends in the annual flow volume. The assessment uses the Mann-Kendall non-parametric trend test and linear regression analysis to detect statistically significant changes in median annual flow over time. Water Rangers also assessed whether the timing of peak and low flow was changing by comparing daily flow across multiple 30-year periods. Statistical tests like the Kruskal-Wallis and Dunn’s post-hoc test determine if differences between time periods are significant. These results are compiled into visual reports and data files, forming the basis for watershed-level flow assessments.

Benthic Invertebrates

Why they’re important

The flies, beetles, aquatic worms, snails, leeches, and other benthic macroinvertebrates that live on the riverbed play a crucial role in the aquatic food chain. Some species are highly sensitive to changes in water quality and ecological stability, making them valuable indicators of environmental health. By studying which invertebrates are present or absent in a waterbody, we gain important insights into long-term water quality and ecosystem conditions.

How we assess them

• We evaluate the abundance and diversity of species sensitive to ecological disturbances.
• A decline or absence of these species often indicates poor aquatic health, just like the increase or presence of others can be linked to good aquatic health.

This is just a summary. You can learn more about how we calculated the scores in our Tech Doc.

Benthic macroinvertebrates are vital indicators of aquatic ecosystem health due to their sensitivity to environmental disturbances and their role in freshwater food webs. The Freshwater Health Assessment uses the Hilsenhoff Biotic Index (HBI), which evaluates benthic community health based on species’ sensitivity to ecological stress. By analyzing species abundance, the HBI provides a clear measure of environmental disturbance, categorized from Very Good to Very Poor. Sub-watershed benthic scores are calculated using the median HBI score from monitoring sites in the past five years, weighted by the number of sites monitored. The Mann-Kendall test is used to detect trends and identify significant long-term changes in community health.

Fish

Why they’re important

Fish are vital to aquatic food chains and contribute to the overall biodiversity of river ecosystems. They provide food and recreation for humans, and many species hold cultural and spiritual significance.

How we assess them

• We monitor declines in native fish species richness (the number of species) over time. 
• While non-native species are not included in these assessments, their increase can signal potential threats to freshwater ecosystems.

This is just a summary. You can learn more about how we calculated the scores in our tech doc.

Due to their ecological, economic, and cultural significance, as well as their sensitivity to environmental changes, fish play a vital role in aquatic ecosystems. In Canada’s watershed reports, fish health is primarily measured through native species richness, which helps determine overall ecosystem health. Changes in species richness over time are detected using the Mann-Kendall non-parametric test, with watersheds categorized as Good, Fair, or Poor based on these trends. Data sufficiency for fish metrics is assessed by evaluating the spatial and temporal coverage of monitoring efforts, ensuring representative and up-to-date sampling. While current data often focus on species presence/absence, future assessments may adopt more advanced methodologies if sufficient data become available.