How We Monitor Beach Water Quality
We monitor Dane County area beaches for E. coli bacteria and blue-green algae.
Our goal is to prevent harmful bacteria and toxins from making people ill while they enjoy our area lakes and beaches.
Beaches We Monitor
James Madison, Lake Mendota County Park, Maple Bluff, Marshall, Memorial Union, Spring Harbor, Tenney, Warner Park
BB Clarke, Bernies, Brittingham, Esther, Frost Woods, Hudson, Olbrich, Olin, Schluter
What we Test For
E. Coli Bacteria
- Waterborne pathogens are most commonly bacteria, viruses or parasites originating from human or animal feces and are associated with illnesses among swimmers.
- Because testing for multiple pathogens is time-consuming and expensive, scientists and beach managers use indicator organisms for monitoring. For fresh waters, Escherichia coli (E. coli) is the best indicator for the presence of pathogens that can make people sick.
Blue-Green Algae (Cyanobacteria)
- Cyanobacteria can form harmful algal blooms in freshwater that can be toxic to people and animals, causing a variety of symptoms.
- Favorable conditions, including high nutrient levels, sunshine and other factors can promote development of dense populations or blue-green algae.
When We Collect Samples
E. coli Bacteria
- We collect water for E. coli testing at least once a week at each beach.
- If bacteria levels are elevated, we close the beach. Weekday follow-up occurs until the sample meets an acceptable bacteria level, at which point the beach will be reopened.
Blue-Green Algae (Cyanobacteria)
- We conduct visual inspections for blue-green algae blooms at least once a week at each beach.
- In addition, if a lifeguard or beach user reports an algae bloom, Public Health staff will follow-up at that beach as soon as possible.
- If a blue-green algae bloom is present, water is collected daily (M-F) to test for cyanobacteria.
- The beach will remain closed until levels of cyanobacteria are acceptable.
Beach Closures for Swimming
- Beach water quality closures occur when levels of E. coli or cyanobacteria and their toxins exceed established safety limits. For E. coli this limit is 1,000 MPN/100 mL.
- For cyanobacteria, the presence of potential toxin producing algae and/or measured microcystin toxin 20 ppb or higher will prompt a closure.
- A beach water quality closure means that the water has been deemed unsafe for swimming.
- Beach goers may still enjoy the sandy area of the beach and the park's other facilities while avoiding contact with the water.
Conditions Can Change Quickly
A number of factors can influence water quality, including recent weather conditions like wind or rain, time of day, waterfowl and wildlife at the beach, number of users, as well as physical characteristics of the beach. It’s possible for conditions to vary significantly throughout the day and day-to day.
Before swimming, always take an overall look at water conditions. Conditions can change quickly, and testing results may not always reflect real-time water quality.
A few things to be aware of:
- Remember that you cannot always see or smell when water conditions are poor
- Swimming is not advisable after a heavy rainfall because bacteria levels in the water may be elevated.
- Stay away from the water and avoid contact if a cyanobacteria bloom is evident (most often blue-green in color, but can also be reddish-purple, or brown) or the water is murky. These toxins can also harm animals so keep pets away from water.
- Do not drink lake or river water and wash your hands before eating.
- Wash your pet after swimming.
- Obey beach postings.
- Report suspected cyanobacteria blooms to Public Health Madison & Dane County at (608) 266-4821.