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How experts measure beach water quality

People have heard of “water quality testing,” to be sure, but they often don’t know what it entails. So it’s a natural question: what do they really test for at my favorite watershed?

Of course, each local monitoring authority may have somewhat different standards (so long as they’re at least as good as federal guidelines), but there are general guidelines followed.

What Is Tested For – And What Isn’t?

Currently, the basis for global guidelines is to use standard bacterial indicators including E. coli, fecal coliforms, and enterococci.1 If these indicators are found at high levels in the water, human sewage is assumed to be present and risk of contracting an illness (including a virus) goes up.

Canadian guidelines don’t require that lakes (or beaches) be routinely tested for viruses, and this is similar around the developed world.


Bacterial indicators are often sufficient to point to the presence of viral contaminants. But testing for viruses is also a complicated process: there aren’t a set of standardized guidelines for testing and results can be difficult to interpret.

Should I Be Worried about Water Quality?

The most frequent negative health effects of swimming in contaminated recreational water is enteric illness, which generally leads to nausea and vomiting, abdominal pain, and diarrhea. Common illnesses caused by waterborne viruses include Rotavirus, Adenovirus, Norwalk, and Hepatitis A.

However, it’s always best to err on the side of caution. Avoid recreational water activities for at least 48 hours after a heavy rain or snowmelt. Avoid outfalls and stagnant bodies of water. Always wash with soap and water after swimming or after coming into contact with water. And check the Swim Guide before you head to the beach.

You can learn more about your local watershed by visiting your favorite beach in Swim Guide, where we show what is tested for and your local standards, or your local water quality monitoring authority’s website.

Original post appeared December 9, 2015: https://www.theswimguide.org/2015/12/09/your-beach-what-do-they-test/

By Brigitte Dreger-Smylie, Swim Guide Editor