By Meetkumar Patel, Canada Summer Jobs student with Rescue Lake Simcoe Coalition
Every summer, thousands of Ontarians head to Lake Simcoe for sun and swimming, but hidden dangers lurk beneath its surface. There are growing questions about instances of bacterial contamination, erratic environmental monitoring, and changing legislation raising serious questions of public health, government responsibility, and the health of the lake itself.
How Beach Testing Works on Lake Simcoe
Ontario beach advisories are initiated when elevated Escherichia coli (E. coli) levels are detected in recreational waterways. E. coli is typically harmless, residing in the intestines of humans and animals, but its presence in surface water indicates fecal contamination that can result in acutely harmful pathogens. If E. coli levels exceed public health criteria, recreational health authorities typically issue swimming advisories or close the beach to reduce waterborne disease risks.
Public health units in the region test water quality around Lake Simcoe at recognized public beaches throughout the summer from mid-June to Labor Day. Each week during the swimming season, a public health staff visit each beach and collect five water samples from different spots along the shore. The water samples are then sent to a lab to test for E.coli growth.
Understanding Lake Simcoe’s Beach Closures
Lake Simcoe is a valued freshwater asset in Ontario, attracting millions of yearly visitors to its picturesque shoreline and welcoming beaches. While posted beach advisories for bacterial E.coli contamination are widely regarded as a sign of danger, what most people may not realize is that 2018 changes to Ontario’s recreational water quality standards shifted the definition of “safe”, a shift that may not be widely understood by the public.
The provincial Ministry of Environment, Conservation and Parks (MECP) and local health units test for E.coli bacteria levels at the public beaches within the Lake Simcoe watershed. Public testing protects against diseases such as gastrointestinal illness, skin infection and other diseases from contaminated water. But there are still lingering questions about the extent of the testing done and the level of protection the public can expect under today’s water quality standards.
Do current monitoring standards truly protect swimmers?
How reliable is E.coli testing ?
The weekly beach testing done by public health units helps catch most water quality problems, but it’s not perfect. The method they use is called a membrane filtration test that can detect around 90 to 95 % of E. coli bacteria in the water. That’s a good start, but it leaves some important holes that people may not realize.
- First off, some groups of E. coli do not appear to react with this test. Approximately 3 % of E. coli strains do not react to the chemical used in the test, and therefore you may not be able to detect E. coli in the water even if it is there.
- Secondly, if the water has been particularly sunny and warm, the bacteria could become “stressed,” and in such cases the bacteria could be so weak or deteriorated that they cannot survive the test, leading to a situation where the tests indicate that the water is cleaner than it is.
- Thirdly, there could be other things present in the water, such as benign bacteria or algae, that could affect the results. They might block E. coli from growing on the filter, which again leads to underestimates of contamination. Even floating debris or sand can clog the test filter.
- Finally, and most importantly, the standard beach test can’t detect the most dangerous types of E. coli, like the one known as E. coli O157:H7. That strain can cause serious illness, including stomach pain, vomiting, and kidney problems but it won’t be flagged by regular beach water testing.
So, while beach testing is useful and important, it’s not foolproof. That’s why it’s important for swimmers to pay attention to posted advisories and for governments to keep improving how beaches are monitored.
The 2018 Shift in E. coli Standards
Ontario used to have one of the strictest beach water standards in the world. Before 2018, beaches were considered safe only if five water samples averaged 100 or fewer E. coli bacteria colonies per 100 mL, with no single sample over 400. This helped provide strong protection for swimmers.
In 2018, the provincial government raised the geometric mean limit to 200 per 100 mL, which doubled the acceptable level of bacteria, while there remained the same single sample limit. Simply put: Ontario now allows twice as much bacteria in the water we call “safe for swimming”. What Does This Mean for Lake Simcoe’s Beaches?
Beaches that would have otherwise been closed for high bacteria are more likely to remain open, placing swimmers at a higher health risk. The shift has led to an apparent reduction in beach closure notices, which masks an actual decline in water quality.
Regrettably, the province has not provided a comprehensive and clear year-by-year overview of beach closures before or following this change, and therefore we are restricted to relying on regional reports and community insights, and a handful of important documents, including the Minister’s 10-Year Report regarding Lake Simcoe (2020).
While the province has not released consistent yearly data, available reports show a clear decline in beach advisories since the 2018 standard change. Our chart (Figure 1) offers an estimated, illustrative summary based on the limited data from health units, news coverage, and provincial documents. Before 2018, approximately 8 to 12 Lake Simcoe beaches were posted with advisories each swim season, often due to elevated E. coli levels, whether from rainfall-driven runoff or other sources. Since the standard was relaxed, that number has dropped.This decline does not necessarily reflect improved water quality, just a reduced number of official warnings.
(Figure 1: Lake Simcoe Beach Advisories by Health Units)
Here’s what we do know:
Public beaches in the watershed are typically monitored once per week during swim season, with a minimum of five water samples collected per beach per visit. Many monitored beaches in Simcoe Region (Barrie, Innisfil, Oro-Medonte), were posted fewer than 10 times in total between 2009 and 2012, often for short durations (a total of less than 16 days in a season). These beaches, located along the western and northern shores of the lake, have historically experienced few closures. However, the Minister’s Report noted that in years (2013–2017), some Simcoe beaches began to see modest increases in both the frequency and duration of postings, possibly due to storm events and runoff.
It’s also important to note that a posting doesn’t always mean a full closure; many were precautionary advisories issued after rainfall, advising swimmers to avoid the water for 24–48 hours due to potential runoff contamination.
More closures in Durham Region, especially in and around Beaverton, have tended to occur. When looking at the historical trends, it appears that these beaches have experienced steadily increasing advisory rates (since the late 1990s) which are likely a result of a variety of factors including prevailing winds from the west, population growth, aging stormwater infrastructure and runoff and other negative effects stemming from new surrounding development and farms.
In York Region, closures are often correlated to weather. When it is rainy, stormwater brings bacteria from land to the lake, and beach closures are more common. In drier years, they’re less frequent.
Unmonitored Beaches
One of the most overlooked risks for Lake Simcoe swimmers is that not all beaches are monitored for bacteria. Public health units like Simcoe Muskoka District Health, York Region, and Durham Region Health test only a limited number of official public beaches, ones that are officially listed, have certain criteria, and are funded for regular monitoring. But what about the rest? Figure 2 shows Location of monitored Lake Simcoe beaches and frequency and duration of beach postings from 2013 to 2017.
(Figure 2: From Minister’s 10 Year Report on Lake Simcoe, 2020)
Across the Lake Simcoe watershed, there are dozens of waterfront access points that see regular use in the summer by tourists, cottagers, and families but receive no official water quality monitoring. These include, but are not limited to:
- Bonnie Park (Georgina)
- Franklin Beach (Sutton)
- Virginia Wharf (Sutton)
- Claredon Beach Park (Keswick)
- Joy Marritt Parkette (Keswick)
- Ramara Beach (Ramara Township)
- Smaller public or semi-public spots in Innisfil, Oro-Medonte, and other shoreline municipalities.
- Private beaches at campgrounds, trailer parks, and cottage communities
These beaches may look just like any other public beach and in fact, they often attract large weekend crowds. But since they’re not on the official list of a health unit, they aren’t tested for E. coli or other contaminants. No test data is displayed. No beach closures are declared. No warnings are issued.
Until the local government, beach operator, or community association takes the initiative to sample the water independently (which costs money and requires lab access), people in the water are unaware of the current water quality. And this imbalance is significant. Despite sharing the same environmental hazards such as septic seepage, runoff, wildlife, and heavy boat activity, unmonitored beaches offer no alerts, leaving visitors exposed to invisible health threats.
Toward a Fairer and More Transparent Monitoring System
At the Rescue Lake Simcoe Coalition, we believe that everyone who swims in Lake Simcoe deserves equal protection, no matter which beach they visit. We are calling on the Ontario government and local municipalities to expand E. coli monitoring to include more frequently used but currently unmonitored beaches, and to make historical and real-time water quality data publicly accessible in one central location. This could be achieved through increased provincial support for health units, clear designation criteria, and partnerships with community groups. Our expectation is simple: a transparent, science-based, and equitable system that protects public health across the entire Lake Simcoe watershed, not just at a handful of designated sites.
References:
Health Canada. (2012). Guidelines for Canadian Recreational Water Quality. Link
Joint Media Release: Swim Drink Fish & Canadian Environmental Law Association (2018). Link
Minister’s 10-Year Report on Lake Simcoe (2020)
Ontario Ministry of Health Changes E. coli Measurement Standard at Beaches (2018)
Open Water Data (2025). Link
Operational Approaches for Recreational Water Guideline, 2018. Link
Rain Impacts E. Coli in Streams – GSWA
Recreational Water Protocol, 2019. Link
Recreational Water Reference Document, 2025. Link
Region of Durham, Weekly beach monitoring for the 2025
Saleem, F., Schellhorn, H. E., Simhon, A., & Edge, T. A. (2023). Same-day Enterococcus qPCR results of recreational water quality at two Toronto beaches provide added public health protection and reduced beach days lost. Canadian Journal of Public Health, 114(4), 676–687. https://doi.org/10.17269/s41997-023-00763-8
Simcoe Muskoka Health Unit (2025)
Swim Drink Fish. (2023). Swim Guide Water Quality Trends. https://www.theswimguide.org/
Test E. coli using IDEXX Quanti-Tray/2000 System.
Town of Georgina, Beach and Swimming Locations (2025)
York Region beach Water Testing (2025) Young, I., Desta, B. N., Sanchez, J. J., Majowicz, S. E., Edge, T. A., Elton, S., Pearl, D. L., Brooks, T., Nesbitt, A., Patel, M., Schwandt, M., Lyng, D., Krupa, B., Schellhorn, H. E., Montgomery, E., & Tustin, J. (2024). Canadian beach cohort study: Protocol of a prospective study to assess the burden of recreational water illness. BMC Public Health, 24, Article 2502. https://doi.org/10.1186/s12889-024-19889-6