Why it’s important: The volume of water in a river and how that volume changes throughout the year are crucial to ecosystem health. Withdrawing, holding back or diverting water disrupts the natural pattern of river flows, which can have serious repercussions.
How we assess it: We examine how much water flows in the river and when it flows. We also assess whether there are significant changes in natural flow patterns over time.
Why it’s important: Water quality can have significant impacts on aquatic life. It also affects drinking water and recreation.
How we assess it: We look at the levels of certain pollutants in the river — such as chloride, phosphorus or heavy metals — and compare them to the guidelines or standards set by provincial and federal governments. We also look at long-term trends in the levels of these substances.
Why they’re important: Fish play an essential role in aquatic food chains and overall biodiversity in a river. They provide food and recreation for humans, and some species carry deep cultural and spiritual significance.
How we assess them: We look at whether the number of native fish has declined over time. Although non-invasive fish species are not included, increases in these species may indicate a threat to freshwater ecosystems.
Why they’re important: The flies, beetles, aquatic worms, snails, leeches and other benthic macro-invertebrates that live at the bottom of the river reveal a lot about the health of a freshwater system. They are also an important link in the aquatic food chain.
How we assess them: We look at whether a river contains a large number and diversity of species that are sensitive to ecological disturbance. If those species are missing, it may indicate poor aquatic health.
What it is: Harmful substances that make their way into the water due to human activities, including mining, oil and gas development, pipeline spills, wastewater treatment, pulp and paper processing, as well as runoff from agriculture.
Why it harms watersheds: Pollution can change the ecology and chemistry of rivers. Sometimes the effects are immediate: a spill may make the water unfit to drink, for example, or kill large numbers of fish. In other cases, the effects don’t become clear until the toxic substances have built up in the ecosystem for many years.
What it is: The conversion of ecosystems, including rivers, wetlands and forests, into farmland, residential areas or other built environments.
Why it harms watersheds: Losing habitat destroys the areas that fish, waterfowl and many other species use for breeding, feeding and migrating. It can also increase downstream pollution and flood risks.
What it is: The loss of connections between freshwater habitats due to the construction of roads, railways and dams across the river.
Why it harms watersheds: Dams, railways and roads can prevent species from moving from one part of the river to another. This can create dangerously small populations with limited genetic diversity. It also prevents species like salmon from reaching their upstream spawning habitats.
Overuse of water
What it is: The total amount of water removed from freshwater systems for urban, agricultural and industrial uses.
Why it harms watersheds: Withdrawing large amounts of fresh water can reduce the watershed’s ability to sustain vital ecosystem processes, species and habitats.
What it is: Species introduced intentionally or accidentally to ecosystems outside their natural range.
Why it harms watersheds: Invasive species can have serious impacts on biodiversity: for example, by out-competing native species for resources or by disrupting production and nutrient cycles. As a result, they can decrease overall biodiversity.
What it is: Shifting temperature patterns and changes in the amount of precipitation that replenishes rivers in the watershed.
Why it harms watersheds: Evidence shows that climate change is causing significant changes to water cycles globally and locally. Even small shifts in temperature and precipitation can have a relatively large impact on ecosystem dynamics. According to the Intergovernmental Panel on Climate Change, freshwater ecosystems are particularly vulnerable to the effects of climate change.
Alteration of flows
What it is: Changes in the natural flow of a river due to large dams, reservoirs and other human-made structures.
Why it harms watersheds: Dams and other water infrastructure sever connections between different parts of a river and alter flow patterns, often storing large amounts of water that would naturally flow freely downstream. These structures can disrupt the natural flooding cycles and alter shoreline habitat both upstream and downstream.