Water Quality 101

At Swim Drink Fish, we’re committed to helping communities connect with their local waters. We help facilitate this connection by providing recreational water users with the latest and most up-to-date information on water quality through our platform, the Swim Guide. 

By making this information open and easy to understand, we’re helping people make more informed choices and inspiring action to protect the waterbodies we all know and love.

Here’s a closer look at what water quality means and answers to some frequently asked questions.

What Does “Suitable for Swimming” Mean?

“Suitable for swimming” refers to the health of the water. That’s why we test the water quality using the recreational standard Guidelines for Canadian Recreational Water Quality and local health guidelines for specific communities. To be deemed suitable for swimming, bacterial levels in the water must be below levels set by local authorities.

Bacterial indicators (E. coli and Enterococci) are the most relevant measures for swimmers' health. E.coli and Enterococci are fecal “indicator” bacteria. Monitoring for fecal indicators is done to help estimate health risks from swimming in the water. When bacteria levels exceed the guideline values, beaches and other swimming locations are “posted” by the management authority as not suitable for swimming due to elevated levels of bacteria.

Fecal indicator bacteria are found in the waste of humans and other warm-blooded animals, like geese, dogs, and horses. When we find high levels of these bacteria in a water sample, we know the water is contaminated with feces. While the indicator bacteria itself isn't always the main threat, its presence indicates a higher risk that other harmful, illness-causing germs (pathogens) are also in the water. This is how we determine the risk of contracting a water-borne illness.

Health Canada establishes the Canadian Guidelines for Recreational Water Quality. The Canadian Guidelines recommend using both a maximum geometric mean (a mathematical average of the most recent 5 samples) and a single-sample maximum. In addition, Health Canada has recently introduced a third threshold limit called a Beach Action Value (BAV), which, when exceeded, triggers an action to be taken by the management authority to investigate the source of the fecal pollution.

An excess of the single sample maximum alerts management authorities to any immediate water quality issues, whereas the geometric mean highlights chronic issues that may impact a site in the long term. 

Other contaminants, such as those found in sediment, do not pose an acute risk to swimmers. We follow the accepted standard recreational water quality guidelines established at the provincial and municipal levels. You can read more about the Canadian Recreational Water Quality Guidelines below:

Guidelines for Canadian recreational water quality: Summary document - Canada.ca

The Changing Nature of Water Quality

We always say that water quality changes like the weather - this is because it’s dynamic. Water that meets government guidelines one day may fail the next day. This does not mean that the old results were wrong - they simply reflect the changing conditions. Rain, wind, and temperature can all influence levels of bacteria.

What Do We Test For?

We test for the most appropriate indicator bacteria based on water type and existing municipal, provincial and federal recommendations and guidelines. The two most common types of bacteria to test for are E.coli and Enterococci.

Our team also conducts extensive field surveys and Environmental Health and Safety Surveys so that we understand the sites we monitor. The more time we spend at a site, the more our understanding improves. However, the information in these surveys does not inform our pass/fail results.

The Importance of Bacterial Indicators

FREQUENTLY ASKED QUESTIONS

  • People should have access to water quality data so that they can make informed decisions about where, when, and how they want to connect with water. Some people will willingly accept an elevated level of risk in order to spend more time on the water or compete in an event. Others will limit exposure to contaminants because of health concerns or a compromised immune system. 

    In order to protect people’s ability to make informed choices, Swim Drink Fish developed an open data exchange standard to make data-sharing among experts and monitoring agencies easy. Swim Drink Fish also supports open government initiatives that release full water quality monitoring results to the public.

  • Bacterial indicators are the most relevant measure for swimmers' health.  To be deemed suitable for swimming, bacteria levels in the water must be below the geometric mean threshold established by the local authority. This can vary depending on the geographic location and type of water. 

    Once bacteria levels exceed government guidelines, the risk of contracting an illness increases.

  • Water quality is very localized. Test results from samples collected a few metres away from each other can be very different. Pollution tends to be highest near its source, more persistent in warmer water, and slower to flush away where water is contained by break walls and other barriers. 

    In Toronto Harbour, for example, bacteria levels tend to drop as you move away from the sewage outfalls in the harbour walls towards the open water in the middle of the harbour.

    Water quality results from one place don’t apply to other places. Every location is different, so we never make broad generalizations about water quality in an entire community or lake.

  • Water quality is like weather — it changes all the time. Water that meets government guidelines one day may fail the next day. This does not mean that the old results were wrong. It just means that conditions changed. For example, rain, changing wind conditions, or other factors may mean that test results from even one day ago may no longer be accurate. Swim Guide includes the historical pass/fail information for each beach location to help you understand how often conditions change and to better understand long-term trends at a site.

  • Government guidelines for water quality are all based on risk assessments. Health Canada estimates that there will be 10-20 illnesses for every 1,000 people who swim in waters that meet government guidelines. That rate of 1-2% is considered an acceptable level of risk by government officials. Once bacteria levels exceed government guidelines, the risk of contracting an illness increases.

  • Pass/ fail results are shared via our Swim Guide app. The free app is available for download from iTunes and Google Play. The web version is online at www.theswimguide.org.

  • E. coli are found in the intestinal tract and feces of humans and warm-blooded animals. Bacteria gets into the water in two ways. It can be dumped into the water from a sewage pipe, stormwater outfall, boat, person, or similar direct source. It can also run off the land into the water during rain, groundwater flow, or flooding. E. coli and Enterococci are the indicators for recreational water quality because there is a strong correlation between them and gastrointestinal illness. They are generally linked to human sewage, especially in urban areas, but can also come from other animal droppings, such as birds and dogs.

  • Some types of bacteria can cause illness, vomiting, diarrhea, and in rare instances, serious disease or infection. We use fecal indicator bacteria levels as an indicator of contamination, but they are not the only contaminant of concern when bacteria levels are high. High bacteria levels are also associated with other contaminants in the water that may have harmful health impacts, including cholera, typhoid, dysentery, schistosomiasis, hepatitis A, and Salmonella.

  • Swim Drink Fish gets its name from our communities’ need for swimmable, drinkable, fishable water. Our position is that all people should have access to clean water and that putting up permanent “no swimming” signs is not an appropriate response to water quality problems. In our experience, when people are banned from accessing the water, pollution and public health problems get worse and local businesses suffer. The best solution to water quality concerns is restoration and protection.