Skip to main content

King County seasonal water quality monitoring program at popular lake swimming beaches helps protect public health


Natural Resources and Parks
Public Affairs

King County seasonal water quality monitoring program at popular lake swimming beaches helps protect public health


Sign up today to receive free alerts about the water quality at your favorite lake beaches in King County. King County’s Lake Swimming Beach Program tests water quality at 27 beaches to help protect the health of people going in the water. Sign up at


King County’s many lakes offer beautiful outdoor options as the weather warms up and people begin to gather again. To protect public health, King County monitors water quality at 27 of the most popular swimming beaches – including Green Lake, Juanita Beach and Magnuson Park – and offers free alerts when problems arise. 
King County tests the water for bacteria throughout the summer.  Bacteria is an indicator of poop in the water from people, pets, or wildlife, and germs in poop can make people sick. Select beaches are also tested for algal toxins every week, while other beaches are tested only if there is a visible algal bloom. 
When either bacteria or algal toxins exceed healthy thresholds, Public Health – Seattle & King County recommends closing the beach to swimming and wading to protect public health. If a beach is closed, closure signs are posted at the beach and on the Lake Beach Monitoring program website
The website is also where people can sign up to get King County’s alerts when beaches are closed. 
Marine beaches, such as Golden Gardens, Alki Beach or Seahurst Park, are monitored by the Washington State Department of Ecology
Poop can make its way into swimming areas in a number of ways, including from dogs, from geese and other birds, and from humans (e.g., toddlers and babies in diapers). Here are four ways to easily protect lake water quality for everyone to enjoy a safer visit: 

Only take dogs to a designated dog beach. 
Don’t feed geese and other birds at the beach. The more they hang out at the beach or on a dock, the more poop gets washed into the water. 
Use swim diapers for babies and toddlers. 
Wash off before entering the water.  
King County Lake Swimming Beach Program 
Washington State Department of Ecology Beach Environmental Assessment, Communication & Health 
Public Health Blog: As drowning deaths doubled in King County in 2020, water safety is more important than ever


Doug Williams, 206-477-4543 
About the King County Water and Land Resources Division 
The Water and Land Resources Division works to protect the health and integrity of King County’s natural resources. Employees work to reduce flood risks, monitor water quality and restore wildlife habitat; manage, and reduce the harmful impacts from stormwater, noxious weeds and hazardous waste; create sustainable forestry and agriculture; and protect open space to support all of these efforts.